Ergonomics; Impact of science on society; Vol.:165;...

Ergonomics

Impact N o . 165

3 Ergonomics—the design of work Stephen Pheasant

13 Occupational ergonomics and health

Choon-Nam Ong

23 Ergonomics of the home fj o

Yang Gongxia

35 Ergonomics and road safety

Karel Brookhuis and Ivan Brown

41 Ergonomics of job and equipment design tr&

Colin G. Drury

53 Ecological ergonomics: the study of human work environments

Alan Hedge

65 Ergonomics of human-computer interaction

Martin G. Helander and Thiagarajan Palanivel

75 The relationship between humans and industrial robots Waldemar Karwowski

87 Ergonomics of large-scale technological systems Najmedin Meshkati

99 Ergonomics and industrial development Houshang Shahnavaz

Reminder to readers

Impact of science on society is also published in Arabic, Chinese, French, Portuguese and Russian. Information about these editions can be obtained by writing to the following:

Arabic: Unesco Publications Centre in Cairo, 1 Talaat Harb Street, Cairo (Arab Republic of Egypt).

Chinese: Institute of Policy and Management , Chinese A c a d e m y of Sciences, P . O . Box

8712, Beijing (People's Republic of China). French: Editions Eres, 19 rue Gustave Courbet, 31400 Toulouse (France). Portuguese: Publicaçôes Europa-América Lda, Est. Lisboa Sintra k m 14, 2726 M e m

Martins Codex (Portugal). Russian: Progress Publishing Group , 17 Zubovsky Boulevard, 119847 M o s c o w

(Russia).

Authors are responsible for the choice and the presentation of the facts contained in signed articles and for the opinions expressed therein, which are not necessarily those of U N E S C O and do not commit the organization.

Published texts may be reproduced and translated free of charge (except when reproduction or translation rights are reserved), provided that mention is made of the author and source. A n entire issue may not be reproduced as a whole without the authorization of U N E S C O .

Ergonomics—the design of work

Stephen Pheasant

The science of ergonomics is concerned with the design of human work. An ergonomie injury is one which results from the nature of the person's working task—most commonly when the demands of that task exceed the person s capacities. This article is concerned with the causation and socio-economic impact of two common types of ergonomie injuries: back injury and the range of musculoskeletal problems affecting the neck, shoulder and upper limb which are known as repetitive strain injuries (RSI).

Ergonomics is the scientific study of work: the people w h o do it and the ways in which it is done. It is concerned (for example) with the tools people use, the places that they work in and the procedures and practices that they follow. In other words, ergonomics is concerned with the design of working systems.

W o r k is both a social and an economic process. The nature of work must necessarily therefore be shaped by social and economic forces. It is these social and economic aspects of ergonomics that I wish to discuss in this article; and I shall discuss them with reference to a number of problems which currently interest m e , as a practising ergonomist concerned with the prevention of musculoskeletal injury in the workplace—and as one w h o is increasingly involved in the process of litigation that ensues when preventitive measures have been neglected and the work-injured employee seeks redress at law against his (or more commonly her) erstwhile employers.

In general, ergonomics sets out to find the best possible match between the physical and mental demands of work and the capacities of the individual members of the workforce—in order to optimize both the productivity of the organization or enterprise and the health, safety and well-being of its people. It is more or less an article of faith a m o n g ergonomists that these two objectives will generally tend to go together. Before w e examine the evidence for this belief, w e shall first consider some of the deleterious effects of the failure to take due account of the ' h u m a n factor' in the design of work.

Stephen Pheasant is a freelance consulting ergonomist, living and working in London. His current work is principally concerned with the prevention of back injuries and other work related musculoskeletal disorders. He is an Honorary Consultant at the Robens Institute of Health and Safety of the University of Surrey and an Honorary Lecturer at University College London. He has written four books on ergonomics and related subjects including Bodyspace—anthropometry, ergonomics and design (Taylor & Francis, 1986) and Ergonomics, Work and Health (Macmillan, 1991).

Dr Pheasant may be contacted at the following address: 81, Arlington Road, Southgate, London N 1 4 5BA, U K .

3 Impact of science on society, no. 165, 3-12

S. Pheasant

Ergonomie injuries

In Sweden, the legal definition of an 'occupational disease' is drawn up a good deal more widely than in m a n y other countries (including the U K for example) to include almost any form of ill-health that can be shown to be work-related (other than the effects of an accident as such). Figure 1 shows a breakdown by cause of occupational diseases in Sweden for the year 1983. Ergonomie problems accounted for more than half the total.

In discussing the effects of work on health, I should like to introduce the concept of an ergonomie injury which I propose to define as follows:

A n ergonomie injury is one which results from the nature of a person's working task—most commonly, when the demands ofthat task exceed the person's working capacities.

The best known and most widely recognized examples are the work-related musculoskeletal disorders: such as back pain, neck and shoulder pain, and the range of conditions affecting the upper limb which are collectively referred to as repetitive strain injuries. In part, conditions of this sort are the consequence of physical riskfactors in the person's work—working posture, repetitive or awkward patterns of movement , forceful exertion, lifting and handling loads, and so on. But it is becoming increasingly clear that these conditions have a complex and multifactorial aetiology in which psychological riskfactors m a y also play a role. Thus in coming to understand these conditions, the mental demands of the working task and the psychosocial context in which it is performed cannot be ignored.

The term 'ergonomie injury' would not normally, in m y view, be applied to conditions resulting from exposure to hazards which are not strictly speaking inherent in the task itself—environmental contaminants, unsafe machinery or structures, and so on. There are grey areas, however—for example environmental conditions such as heat or cold m a y diminish a person's working capacities and thus be contributory factors in an ergonomie injury.

A n accident is an unplanned, unforeseen or uncontrolled event—generally one which has unhappy consequences. (At least, this is the way in which safety practitioners commonly define an accident. In other contexts the word m a y have a somewhat different meaning.) S o m e ergonomie injuries are accidents in this sense of the word—for example a person m a y stumble and fall while attempting to handle a difficult load, m a y

Figure I.

Occupational diseases in Sweden in 1983, by causative agent. Data from N B O S H (1987); reproduced from Pheasant (1991).

Other 3%

Psychosocial 1% -

Biological agents 2%

Vibration 3%

Noise 15%

Chemical agent 20%

Ergonomics 56%

4


drop the load on his foot, etc. But most ergonomie injuries are not accidents in the strict sense, in that they occur in the course of doing the normal working task in what appears to be the normal way. That is, they do not involve any specific intervening unforeseen event other than the injury itself. Most lifting injuries are like this, for example.

S o m e ergonomie injuries have an acute onset—that is, they seem (at least in the injured person's account of the matter) to occur at a particular point in time. But m a n y do not—in that the symptoms of the condition concerned have a gradual, progressive or insidious onset. Although this onset m a y be accelerated, or the condition m a y be exacerbated, at a time when the demands of work are unusually heavy—for example due to changes in working practices, peaks in workload or the need to meet a particularly tight deadline.

Back pain

Back pain is an extremely c o m m o n condition—so c o m m o n in fact that m a n y people (mistakenly in m y view) regard it as 'part of the h u m a n condition' or 'the price w e have to pay for standing upright'. According to official sources, about 60 million working days were lost, in the U K last year, due to back pain sickness absence. (This figure is almost certainly a considerable underestimate since it includes only registered sickness absence.) T o put this figure into context, it is as if, each day, a city the size of Coventry (pop. approx. 300,000) stopped work. T o get some quantitative estimate of what this represents in lost productive capacity, you can multiply the figure for the number of days by the national average daily wage. The sum of money you end up with is in the order of £3 billion (US $ 5 2 billion)—which is equivalent to the annual turnover of G E C , Ferranti and K o d a k combined ( N B P A , 1991).

Not only is back pain a major cause of sickness absence, but the problem is getting steadily worse by the year. Figure 2 shows U K data for days of sickness absence due to back pain and for back pain sickness absence expressed as a percentage of sickness absence due to all causes. ( M y thanks are due to the National Back Pain Association for providing m e with these data.) T w o principal conclusions m a y be drawn: firstly that the overall figures are on an upwardly accelerating curve; secondly that the rate of increase in the relative figures is greater in w o m e n than it is in m e n .

Back pain is a condition of complex multifactorial aetiology. So the social forces which are driving this process of change must of themselves necessarily be complex. Perhaps our best chance of understanding this process lies in asking, in a statistical sense, what sorts of people are most likely to have trouble with their backs.

Figure 3 is based on a survey of a sizeable sample of m e n and w o m e n , from m a n y walks of life, reported by Magora (1972). The people w h o took part in this survey answered a series of questions about the nature of their working lives, on the basis of which I have grouped them into three categories (see Pheasant 1991 for further details). The principal conclusion to be drawn is that people w h o spend most of their lives in a sitting position and do very little physical work have a high prevalence of back trouble; but so do people w h o mainly stand at work and have physically very demanding jobs; whereas people w h o have jobs imposing moderate physical demands and w h o are free to alternate between standing and sitting at work are relatively unlikely to have trouble with their backs.

5

S. Pheasant

Daysx 10e

60 r

Women

Men

(b)

1970 1980 1990 1970 1980 1990

Figure . Back pain sickness absence in the U K , expressed (a) in millions of days absent from work, and (h) as a percentage of sickness absence due to all causes. The breaks in the graphs indicate a change in reporting procedures. Data kindly supplied by the National Back Pain Association.

In fact, there is something like a 10 to 1 difference between the prevalence of back

pain in the middle category, as compared with the two end categories: 2 % of people at

any point in time as against about 2 0 % of people. In the middle category back pain is

really quite rare. Supposing this middle category represents back pain due to 'the

h u m a n condition'—that is, the prevalence in a population which is not exposed to any

work-related risk factors. (As I see it, the true figure for the non-work-related

prevalence could not logically be higher than this, although it could in principle be

lower.) A n y prevalence over and above this level must be due to work-related risk

factors. Simple arithmetic leads us to the conclusion that back pain is a work-related

condition in about 85% of cases. In other words, mos t cases of back pain (or to be m o r e

precise most of those cases occurring in a working population, since only working

people took part in Magora ' s survey) m a y be regarded as ergonomie injuries.

Ergonomie factors which have been shown to lead to an increased risk of back pain are

summarized in Table 1.

Although s o m e occupational categories are clearly at a very m u c h higher level of

risk than others, it must also be the case that in any given working population s o m e

individuals are m o r e at risk than others. (If this were not so then w e should expect to

find all the m e m b e r s of a high-risk occupation like nursing affected, whereas in reality

only a proportion are affected, albeit a relatively large one.) There has of course been

considerable interest, over the years, in attempting to identify those personal

characteristics which place the individual in a high-risk category. If these could be

identified in a reliable way , it should in principle be possible to reduce the incidence of

back pain by preventing high-risk people from going into high-risk jobs. (This

6


Figure 3.

Prevalence of back pain as a function of physical workload. Based on data from Magora (1972); reproduced from Pheasant (1991).

Medium High

Physical workload

Overall prevalence = 14%

85% cases are work-related

12% work-related

2 % non work-related

approach continues to c o m m e n d itself to m a n y people on the grounds that, if it were

effective, it would be considerably cheaper than eliminating the features of working life

which lead to increased risk.) T h e epidemiological literature points to the conclusion

however that, on the whole, such personal risk factors as can be identified have

relatively weak predictive value compared with the ergonomie risk factors discussed

above. The exceptions seem to be things to do with the person's lifestyle rather than his

or her constitutional make-up—general fitness, smoking, motherhood, etc. (see

Pheasant 1991 for a further discussion).

The inference to be drawn therefore is that back pain is a consequence of what w e do

rather than what w e are. There is a curious irony in this state of affairs: overall, the

productive capacity of our society—that is, its capacity for the performance of

economically productive work—is being significantly compromised by the nature of

that work itself. O r to look at it another w a y , the cost of ill health resulting from back

pain (and indeed from other ergonomie and work-related injuries) is a production cost

which has to be carried: either by the organization, or by the injured person, or by

society as a whole—or by s o m e combination of these.

It is, however, more complicated than this. There is evidence that a disproportion

ate amoun t of the economic loss associated with back pain is attributable to a

relatively small proportion of long-term chronic cases. It is widely believed, fur

thermore, that as back pain progresses to its chronic forms it is increasingly dominated

Table 1.

Back pain—ergonomie risk factors, from Pheasant (1991).

Heavy work—lifting and handling, forceful exertions, bending, twisting, etc.

Prolonged sedentary work Prolonged work in a stooped position Vibration Psychological stress

7

S. Pheasant

by the psychogenic component in its aetiology. In a comparison between acute and chronic cases, Vallfors (1985) was unable to demonstrate objective physical signs in 70% of chronic cases as against 40% of acute cases. The chronic cases, however, showed more evidence of psychiatric illness, more signs of alcohol abuse and reported lower degrees of job satisfaction, although the nature of this study (and indeed m a n y others) is such that it would not permit us to distinguish cause from effect in these psychological findings.

The interaction between mind and body in the aetiology of these conditions presents a number of very difficult questions. T o see these matters a little more clearly w e shall turn our attention to a superficially different, but in m y view extremely closely related, set of problems.

Repetitive strain injuries

The term repetitive strain injury (RSI) is applied to a set of work-related musculoskeletal disorders affecting the hand, wrist and forearm—and, to a lesser extent, the upper arm, shoulder and neck. RSI is really a collective term; it is not a diagnosis in the strict sense of the word. S o m e of the conditions which fall under the RSI rubric are relatively well understood medically, in that they have a relatively consistent clinical presentation and a generally recognized underlying pathology (tenosynovitis and carpal tunnel syndrome both fall into this category). But m a n y cases of RSI (in some contexts the majority) are very m u c h more obscure, in that they present themselves with relatively diffuse patterns of pain and dysfunction, often at multiple sites, and with a relative paucity of objective clinical findings, such as would enable the physician to infer the precise nature of the underlying pathology involved. Furthermore, a patient m a y present with the objective signs of tenosynovitis per se at an early stage in his or her history: and then go on to develop one of the more obscure forms of RSI when the acute signs of tenosynovitis have subsided.

It has been k n o w n for 50 years or more that people w h o do hand-intensive work, often of a repetitive nature on industrial assembly lines, are prone to tenosynovitis and related conditions. Agricultural workers and traditional craft workers like net-makers are also affected. Sometimes the onset of the condition is associated with some unaccustomed physical activity: for example, the people from London's East E n d w h o used to go hop picking in Kent in the summer, were prone to a form of tenosynovitis (or something similar) which was k n o w n locally as 'hopper's gout'.

It has also been k n o w n for m a n y years that typists and other keyboard workers are likely to suffer from these conditions—but as far as one can tell they were never really very c o m m o n . It is widely believed, however, that with the computerization of office work and the advent of the electronic keyboard, the incidence of these conditions in office workers has become very m u c h greater.

S o m e occupational groups w h o are widely recognized as being likely to suffer from these disorders are summarized in Figure 4, together with the possible 'risk indicators' present in each case. The most striking thing about this picture is the inconstancy of the pattern of associations involved.

In Australia in the 1980s there was something of an 'epidemic' of these conditions; Figure 5 shows the annual number of cases for N e w South Wales for the period in question. The epidemic hit the headlines in a big way: comparisons were drawn with A I D S and the press used emotive terms like 'keyboard cripples'.

8


Figure 4.

Repetitive strain injury risk markers.

Fixed Posture

Static Loading

Forceful Gripping

Repetitive Motions

Deviated Wrist

Pertormance Stress

Boredom

Alienation

•

O

•

•

o

•

•

•

•

•

•

o o

•

o •

o o o

# = Present to a marked extent

O = Present to a limited extent

Although the greatest rates of increase did indeed occur in office workers (mainly w o m e n ) , the highest incidence rates continued to occur in blue-collar trades. In other words, there was an epidemic in office workers, superimposed over an endemic condition in blue-collar workers.

T h e Australian epidemic is not the first of its kind k n o w n to history. In Britain in the 1830s there was an epidemic of'writer's cramp' a m o n g (male) civil service clerks, which was attributed at the time to the introduction of the steel pen nib. Another epidemic occurred a m o n g telegraph operators (using the old Morse key) in the years preceding the First World W a r which some people believe was initiated by the introduction of workman ' s compensation payments (Luciré, 1986). Furthermore, on a smaller scale, RSI cases m a y occur in clusters which peak and fall away; Buckle (1990) has documented the time-course of such an outbreak at a London newspaper.

Three principal explanations m a y be offered for this epidemiological picture:

(i) the outbreak is caused by a change in working practices; (ii) the outbreak is due to hysteria; (iii) the 'outbreak' is a statistical artefact resulting from the increased reporting of

an endemic condition.

M a n y keyboard workers w h o develop RSI attribute their condition to some adverse feature of the keyboard itself. (This particularly seems to be the case with journalists.) I do not believe that this explanation can be ruled out. For example, the lighter touch of the electronic keyboard m a y cause the user to 'hold back', so that the light ripple of dynamic muscular activity is superimposed over a sustained muscle tension. But it is equally possible that the more intensive keyboard use which c o m m o n l y follows computerization is to blame. In the case of journalists, for example, computerization m a y permit deadlines to be moved later into the night, thus increasing the pressure of work in the final stages of preparing the next day's edition.

9

S. Pheasant

Casesx103

7

6

5

4

3

2

1

0

Figure 5.

I I L J L J I L J L 1975 1980 1985

The Australian RSI epidemic. Data kindly supplied by Mike Stevenson; reproduced from Pheasant (1991).

The case for the Australian epidemic having been spread by 'hysterical contagion'

has been forcefully m a d e by Luciré (1986). The paucity of objective clinical signs to be

found in the majority of cases occurring at the time obviously lends weight to this

explanation. This argument has in m y view been effectively refuted by the findings of

Dennet and Fry (1988), w h o discovered clear signs of physical damage in microscopical

specimens of muscle tissue taken from the hands of R S I victims. The extent of this

damage was proportional to the severity of the person's symptoms. This would seem to

m e to give the condition a clear foundation in organic pathology. The psychogenic

component in its aetiology cannot be ignored, however. R y a n and B a m p t o n (1988)

found that data-processing workers w h o had upper limb symptoms reported more

stress and boredom at work than those w h o did not, although the physical features of

their working conditions (posture, workspace layout, etc.) seemed to be similar. (The

people with symptoms did report missing rest-breaks m o r e often, however.)

D o the psychological states cause the musculoskeletal symptoms or vice versal O r

are people w h o find their working lives stressful or unsatisfying, more likely to report

the everyday aches and pains which afflict us all from time to time? In a comparative

investigation of workplaces doing similar sorts of work but having high and low

prevalences of RSI, Hopkins (1990) studied symptom-free workers only—and found

that those in the high prevalence workplaces reported m o r e stress and boredom and

lower degrees of autonomy, job variety and job satisfaction. It seems therefore that the

quality of working life in those organizations where RSI was prevalent was truly lower,

and by inference, that the association between RSI and stress and boredom is due to

adverse features of the working situation, rather than the individual's inner mental

turmoil, lack of social adjustment or other (hypothetical) personal idiosyncracies.

10


Ergonomics and economics

The economist defines the productivity of an organization or enterprise (like the engineer defines the efficiency of a machine) as a ratio of output to input—that is, as the ratio of the value of the goods or services produced to some appropriate measure of the costs of producing them.

Ergonomie improvements in the design of work have the potential to increase productivity: both by increasing the per capita output of the workforce and by reducing indirect labour costs incurred through sickness absence, labour turnover and so on. For example, a number of studies of people w h o work with V D U s have shown that ergonomie improvements in workstation layout, etc. m a y result in an increase in output of something in the order of 20-25%, as measured in terms of transactions per unit time (Dressel and Francis 1987) or keystrokes per hour (Dainoff and Dainoff 1986; O n g 1984). In the study by O n g , there was also a dramatic decrease in error rate and a reduction of about 50% in the number of people reporting work-related aches and pains.

It would seem reasonable to propose that these 'ordinary' or 'everyday' aches and pains (which most of us experience from time to time) are the precursors of more serious problems (which only arise in a small minority of cases). If this is so, then we should expect that by reducing the prevalence of the former w e should also reduce the prevalence of the latter. I a m not aware that this has ever been demonstrated directly; but it is of interest that in a study of the epidemiology of RSI in Telecom Australia, Hocking (1987) found a negative correlation between symptom prevalence and keying rate. (I take this to mean that people in well designed jobs have both high outputs and low sickness rates.)

In a now-classic follow-up study of ergonomie improvements at the S T K electrical assembly plant at Kongsvinger, Norway, Spilling et al. (1986) were able to show that reduced sickness absence and labour turnover resulted in a net gain to the company over a twelve-year period of 2-9 million N K r (approx. l ! N K r = £l sterling or 6NKr=US$l).

T o what extent can findings of this kind be generalized? The studies cited above all involved sedentary work tasks, in which the musculoskeletal stresses to which the workers were exposed were principally ones of static muscle loading due to unsatisfactory working posture. As such they could be eliminated relatively easily, without the need for radical changes in the nature of working practices.

But what of the highly repetitive manipulative tasks of the industrial assembly line where RSI is endemic? Here, I suspect, the position is less optimistic. Supposing that you are the owner of a company which manufactures a certain product on such an assembly line. After due consideration you conclude that it is cheaper to carry the costs of overmanning, which result from a high sickness absence rate, than it would be to make the radical changes in production methods required to eliminate the problem. Y o u m a y perhaps argue that to make these changes would raise the price of your product beyond the level which the market would stand. The law only requires you to take such steps to ensure the well-being of your workforce 'as are reasonably practical'. So you opt for the status quo—and when an employee becomes unfit for work you 'let him/her go'.

F r o m the limited standpoint of the employer this is a perfectly sensible policy—and one which is widely adopted. F rom a broader perspective it is less satisfactory. If you do

11


not continue to support your work-injured employees then somebody else mus t— unless of course their disabilities are to force them into destitution. In other words, s o m e of your production costs are being borne, either by the injured person in particular or by the communi ty at large. This is effectively a hidden subsidy on the manufacture of your product; that is, those people w h o do not care to buy your product are subsidizing those w h o do. W h y should they? •

References

B U C K L E , P. (1990) Upper limb disorders among newspaper personnel. Occupational Disorders of the Upper Extremities, University of Michigan, pp. 1-6.

D A I N O F F , M . J. and D A I N O F F , M . H . (1986) People and Productivity—A Manager's Guide to Ergonomics in the Modern Office. Holt, Reinhardt and Winston, Toronto.

D E N N E T , X . and F R Y , H . J. H . (1988) Overuse syndrome: a muscle biopsy study. Lancet, i, 905-908.

D R E S S E L , D . L . and F R A N C I S , J. (1987) Office productivity: contributions of the workstation. Behaviour and Information Technology, 6, 279-284.

H O C K I N G , B. (1987) Epidemiological aspects of'repetition strain injury' in Telecom Australia. Medical Journal of Australia, 147, 218-222.

H O P K I N S , A . (1990) Stress, the quality of work, and repetition strain injury in Australia. Work and Stress, 4, 129-138.

L U C I R É , Y . (1986) Neurosis in the workplace. Medical Journal of Australia, 145, 323-330. M A G O R A , A . (1972) Investigations into the relation between low back pain and occupation. III.

Physical requirements: sitting, standing and weight lifting. Industrial Medicine, 41 (12), 5-9. N B P A (1991) Annual Report 1990-1991. National Back Pain Association, 31-33, Park Road,

Teddington, Middlesex T W 1 1 0 A B , U K . N B O S H (1987) Occupational Injuries in Sweden. National Board of Occupational Safety and

Health, Swedish Work Environment Fund, Sweden. O N G , C . N . (1984) V D T workplace design and physical fatigue—a case study in Singapore. In

Grandjean, E . (ed.) Ergonomics and Health in Modern Offices, pp. 484-9. Taylor & Francis, London.

P H E A S A N T , S. T . (1991) Ergonomics, Work and Health. Macmillan, London. R Y A N , G . A . and B A M P T O N , M . (1988) Comparison of data processing operators with and without

symptoms. Community Health Studies, 12, 63-8. SPILLING, S., E I T E R H E I M , J. and A R A S , A . (1986) Cost-benefit analysis of work environment

investment at S T K ' s telephone plant at Kongsvinger. In Corlett, E . N . , Wilson, J. and Manenica, I. (eds.) The Ergonomics of Working Postures, pp. 380-397. Taylor & Francis, London.

V A L L F O R S , B . (1985) Acute, subacute and chronic low back pain—clinical symptoms, absenteeism and work environment. Scandinavian Journal of Rehabilitation Medicine, Suppl 11,1-98.

12

Occupational ergonomics and health

Choon-Nam Ong

Ergonomics encompasses both the prevention of occupational disease and the promotion of health. Recent studies have suggested that many of the occupational diseases are connected to poor design of tools, machines and workplace. To prevent unnecessary error and overt and cumulative injuries, ergonomics has an essential role to play in increasing work efficiency and productivity by making the tool or machine fit the users and the worker's capability.

The International Labour Organization (ILO) defines ergonomics as 'the application of h u m a n biological sciences in conjunction with engineering sciences to the worker and his working environment, so as to obtain m a x i m u m satisfaction for the worker which, at the same time, enhances productivity'. Ergonomics can perhaps therefore be regarded as a science which is primarily concerned with the adaptation of work to the physical and psychological capabilities and limitations of m a n .

Ergonomics is a multi-disciplinary science comprising subjects like anatomy, physiology, psychology, sociology, physics, engineering and medicine. The application of all these sciences is necessary in order to identify and optimise all the factors which m a y affect the worker in his working environment.

Ergonomics aims to promote efficiency, safety and comfort at work situation in industry through better relationship between m a n , his tools and the work environment. The task of ergonomics is to develop the optimal conditions for the workers, to reduce physical workload, to improve working postures and to facilitate psycho-sensorial functions in instrument handling, to avoid unnecessary information recalls, to assist in job placement of workers, and so on. M a n y of the principles of ergonomics can be readily applied to factories in industrializing countries to improve the quality of working life, maximize the efficiency of production operators, and to minimize h u m a n error.

Dr C h o o n - N a m O n g is an Associate Professor with the Department of Community, Occupational and Family Medicine at the National University of Singapore. His research has covered a wide range of topics, with many publications in the field of Occupational Health. H e has served as an I L O and W H O expert on Environmental Health and on Occupational Health. H e is currently the Editor of Ergonomics and the Journal of Human Ergotogy.

Dr O n g m a y be contacted at the following address: Dept. of Community Medicine, National University of Singapore, Kent Ridge, Singapore 0511.


Choon-Nam Ong

The World Health Organization defined health as 'not merely the absence of disease, but a state of complete physical, mental and social well-being'; a healthy and well organized workplace is therefore one which promotes the complete well-being of its workforce. F rom the occupational health standpoint, the objective of ergonomics is to study the nature of tasks so that disease or ill effects are prevented.

The scope for the application of ergonomics in our working environment is tremendous. The correct matching of m a n , technology, task and organization to form a total entity capable of higher job performance is n o w an important function of management, and the ergonomie approach can go a long way to help meet this objective.

Man-machine-environment interaction

As technology becomes more complex, so ergonomics is undoubtedly destined to play an increasingly important role in industrial production and industrial health and safety. The aircraft pilot needs to know h o w his engines are behaving, the factory worker has to look after a particular machine, the factory foreman must keep track of all the changes in the processes, and the maintenance engineer must make regular checks on the automatic devices. Instruments communicate with people, yet the communication is two way: the user or operator often has to respond to the machine or the tools, turning a switch or a knob to obtain or to react to the information.

At the workplace, ergonomics places equal emphasis upon greater system efficiency and improved health of the individual. Ergonomics must be involved in fitting the tool and machine to the worker by design, fitting the worker to the machine by selection and training, and the optimization of the ambient environment to suit the m a n or the adaptation of the m a n to tough environmental conditions.

T o fulfill the general aim of ergonomics in integrating m a n machine and m a n -environment relations, the interaction between these elements must be optimized. This approach has to consider (1) the operator's interaction with the tool, (2) the immediate workplace around him, and (3) the work environment in which he has to work (Figure 1).

Man-machine interaction

The efficient operation of any apparatus depends on a close interface of man-machine (tool) interaction, and since w e can only modify the capacities of the h u m a n being to a limited extent, it is axiomatic the apparatus suitable for a job should also fit the user as well. Most machines in use today are reasonably well designed for optimum performance, but the physical capacity of the worker assigned to the machine is frequently exceeded. This results in the operator unable to handle the machine efficiently because of unnecessary mental and physical strain. The job takes longer to complete and the risk of errors increases. T o prevent this, the designer should from the very beginning look at the instrument and the user not separately, but as a combined production unit.

W h e n considering man-machine interaction, it is also useful to consider them as a complete information flow loop (Figure 2). If efficient work is to be achieved, all parts must function properly.

14


Figure I.

Relationship of job factors, the operator, the tool, the work-station and the environment.

N e w technology Training Job satisfaction Support systems Rest breaks Management system Shiftwork

Biomechanics Anthropometric Lighting Work surfaces Furniture Climate

Figure 2.

Man-machine interaction.

Man-environment interaction

T h e interaction of the operator with the immediate workspace around him/her is influenced by m a n y factors. They include items such as the seat design, the working desk, the controlling consoles and adjacent machines. These immediate work-tools m a y affect the position and postures of the users, and thus their comfort and efficiency.

T h e physical and psycho-social aspects of the work environment are crucial factors that affect the comfort and consequently the job performance of the operator. The physical factors at the workplace include lighting, noise and ventilation. T h e psychosocial aspect is concerned with w o r k organization in order to create a more

15

Choon-Nam Ong

motivational work environment for the working population. Working hours, rest

pauses, shift system, health and safety, and supervisory practice are important aspects

affecting the interest, morale, motivation and well-being of the worker.

Workplace and anthropometry

Backaches, neckaches and other muscular strains due to bad seating and incorrect working posture are c o m m o n in industry, where m a n y jobs require people to remain sitting or standing in a fixed posture for a long period of time. It is c o m m o n to find in m a n y industries and offices glaring examples of poor work design. Chairs, tables, work benches, tools and machines are introduced without any consideration of their relationship to one another. Incorrect and awkward postures associated with either the level of working height or with the poor design of the machine could result in discomfort and fatigue. In addition, neglect of ethnic and anthropological differences through the unthinking importation of foreign technology developed in a different cultural and social framework, can have a generally negative effect.

Ergonomics has been focused on fitting the machine to operator in such a w a y that the operator will be able to function efficiently. Tools and machines designed to accommodate operators of one country m a y not be suitable for operators in another. The size of the driver's cab and the placement of gearshift, brake pedals etc. are generally designed to suit the bigger and taller truck drivers in the industrially developed nations, and not the more diminutive Asians, for example. A s a result, transportation workers readily succumb to fatigue, through straining to reach the brakes, gears and other controls. Modifications to suit the size of the users as well as a modification in the layout of the driver's cab have been found to lead to a significant improvement in health and a drop in accident rates, especially with respect to longdistance driving. There are numerous other examples to demonstrate that unnatural body positions and musculoskeletal complaints are the direct result of differences in anthropometric dimensions or poor workplace design (Figures 3 and 4).

Designing workplace, equipment and the physical environment to fit the characteristics and capabilities of the majority of people is a complex task.

In order to adapt the workplace to h u m a n dimensions the measurement of the physical features of the body will be needed. It is not enough, as a rule, to design a work

Figure 3.

Bad workplace design. A good example is found in cases where the worker has to manoeuvre a badly positioned foot pedal. Pressure on the joints when they are stretched to uncomfortable extremes can cause considerable wear.

16


Figure 4.

The working posture should be as comfortable as possible. However, sitting all day long is not good for the body, even though the working posture may be comfortable. There should be some variation in the jobs performed.

place to suit an average individual. In the case of furniture design allowance has to be m a d e for the larger person; however, it is also necessary to take account of the body dimensions of the smaller users. Abnormal desk heights reduce efficiency and hasten fatigue. Thus for workbench design the 95th percentile value must be considered in order to ensure that the visual and musculoskeletal strain will be at a min imum. As far as machinery is concerned, allowance should be m a d e for the smaller person w h o m a y need to reach the handles and/or the controls.

W e are all physically unique. People are of different heights; they are built differently; some people are stronger than others, and able to withstand physical stress and strains during work. Anthropometric studies suggest that males and females from different geographical regions and of different ethnic origins are significantly different in their body dimensions. A good example of this is the size of the openings in machine guards. Those designed for European use are sufficiently small to prevent access by Caucasians to dangerous parts of the machine. But recent studies in H o n g K o n g have revealed that Chinese females have much smaller hands than their United Kingdom counterparts or those of American w o m e n . They are, however, larger than those of Japanese w o m e n . Furthermore, Chinese have shorter, narrower hands with longer fingers than Europeans and Indians (Courtney and N g , 1984). Such findings suggest that caution should be exercised when applying standards from one region to another.

Studies on the anthropometric dimensions of male industrial operators and female office workers have indicated little differences for Malays, Indians and Chinese in Singapore. However, when compared to data from Germany and the U S A , the three Asian cohorts are smaller in body size. Owing to their smaller body build, the Asian operators naturally prefer to have seating and working heights lower than those used by European operators (Ong and Phoon, 1988).

Ergonomics and the prevention of musculoskeletal strain

Occupational disorders of the musculoskeletal system are not new. Musculoskeletal complaints have probably been around since m a n first undertook repetitive tasks. Early examples of musculoskeletal injury include the various craft palsies or cramps, such as threader's wrist and brewer's arm.

Musculoskeletal problems have been reported as occurring in a wide range of industries. The National Institute for Occupational Safety and Health ( N I O S H ) in the

17

Choon-Nam Ong

U S A reported that 15-20% of workers employed in construction, food preparation, the electronic industry, clothing and bag manufacturing, and clerical work are at risk for cumulative trauma disorders.

Despite increased mechanization, cumulative musculoskeletal disorders or repetition strain injuries (RSI) have increased dramatically in recent years. The increase can be linked to the changes in technology which have been taking place. A study in Sweden has suggested that 50% of reported cases of this occupational disease are caused by ergonomie factors such as physically heavy work, manual material handling, repetitive work and unsuitable work posture. Employees w h o had this problem took 20 to 26 days of sick leave per year more than others (Kilbolm, 1983).

Cumulative musculoskeletal problems are not the result of single events; they stem from (a) the repeated performance of certain tasks, (b) bad working posture, (c) application of force, and (d) inadequate rest. There are two major factors that can affect the health and performance of industrial operators through their musculoskeletal system: static load and awkward posture.

(1) Static muscle load W h e n tools or equipment are used in situations where the arms have to be held for extended periods, such as during grinding operations, muscle of the shoulders, arms and hand m a y be loaded statically. This loading can result in fatigue and reduced capacity to continue the work, and it m a y produce soreness in the muscles. The most severe manifestations of these complaints m a y be tendonitis, tenosynovitis or carpal tunnel syndrome. T h e causes of these problems are not fully understood. W h a t is k n o w n is that forceful, highly repetitive exertions at awkward hand, wrist, or arm postures are associated with increased complaints in susceptible people. It is believed that the main cause is the constant repetitive movement of the wrists, causing the tendons to swell (tenosynovitis) and eventually putting pressure on the median nerve inside the carpal tunnel. T h e nerve itself is stretched by repeated exertions and compressed between the walls of the carpal tunnel.

The primary strategy to prevent musculoskeletal trauma is the use of ergonomie principles to modify hand tools and to improve workstation design and work practices. Workload should be distributed between hands and feet wherever feasible. Precision control should be delegated to the dominant hand. The emergency control should be operable with either hand. Commercially available hand tools are normally designed for occasional or intermittent use, but not for repetitive manual effort. The following ergonomie rules are suggested for repetitive use:

• The tool should be designed for operation with a straight wrist—bend the tool handle, not the wrist.

• Use power tools whenever feasible. • M a k e tool light—heavy tools should be suspended or otherwise

counterbalanced. • Handle surfaces should be so shaped as to contact the largest possible surface of

the inner hand and fingers, distributing the forces evenly and not creating power points.

Ergonomie interventions have been remarkably successful where they have been instituted (Office of Technology Assessment, 1986; V a n Wely, 1970).

18


Figure 5.

Examples of bad working postures.

*

(2) Awkward posture The necessity to adopt one posture, or a very limited range of awkward work positions (Figure 5), m a y result in wrist and hand fatigue, and difficulty in sustaining a proper work position. A n earlier study by V a n Wely (1970) demonstrated h o w industrial surgery data could reveal postural problems arising from the job and h o w they could be used as evidence to support the modifiction of tasks in the interest of both the health and performance of workers.

The multidisciplinary approach of ergonomics can be applied to prevent both overt and cumulative musculoskeletal traumas. The primary strategy to prevent cumulative trauma disorders is the use of ergonomie principles (a) to modify hand tools, (b) to improve work-station design, and (c) to improve work practices. This has proved to be particularly useful when applied at the design stage, such that the relevant h u m a n factor information can be incorporated. Redesigning of hand tools (Figure 6), workstations or equipment can significantly reduce the awkward, forceful movements c o m m o n to m a n y jobs on assembly lines in manufacturing industry and in offices.

The main areas of ergonomics which have a part to play in preventing illness and fatigue are task design, workplace design and work organization.

Task design

Task design involves the nature of job and the design of equipment, machinery and tools in accordance with ergonomie concepts. This will ensure that the jobs are within the physical and mental capacities of the workforce. Whenever possible, the job should include a mixture of repetitive and non-repetitive work in which recovery from the effects of the former is possible. The task should not require the muscles to be used repetitively in a forceful manner. Abnormal work postures caused by poor task or workplace design are to be avoided, since these m a y increase the static load on a specific muscle group.

Workplace design

Workplace design and layout should conform to ergonomie principles, while both physical and physiological aspects of the working environment should be considered. The use of ergonomics is essential in such areas as working posture, tool design and workplace layout, together with environmental factors such as ventilation and lighting. Temperature and humidity should be kept at a comfortable level through the use of

19

Choon-Nam Ong

Figure 6.

The design of hand tools influences the position and motions of the hand.

1. Avoid short tool handles that press into the palm of the hand. The palm is very sott and easily damaged.

2. Avoid narrow tool handles that concentrate large forces onto small areas of the hand.

3. Tools and jobs should be designed so that they can be performed with straight wrists. Hands are stronger and less vulnerable to injury when the wrists are kept straight.

proper ventilation systems. The noise level should be low enough not to cause interference with communication and distraction from work. Lighting has to be adequate and glare should be minimized.

Work organization

W o r k organization is an important factor to be considered for reducing musculoskeletal strain at the workplace. Measures such as reducing the work rate in paced operations, reducing shift length, and the provision of extra rest breaks have proved helpful in repetitive operations.

Tasks consisting of lifting, pushing, or pulling objects without the assistance of mechanical devices are referred to as 'manual material handling'. Manual material handling tasks carry a high risk of injury not only because of the interaction between the worker and the object itself (sharp edges, dropping the object, slipping, or falling while carrying it, and so on) but also because there is a potential for overloading the body's supporting structure, the musculoskeletal system. Lifting of heavy objects presents a high risk of over-exertion injuries and cumulative damage to the soft tissues around the spine. These injuries to the back constitute the largest single category of workers' compensation claims in m a n y developed countries, amounting to 25% of all disability cases (Office of Technology Assessment, 1986). Lower back injuries can be extremely painful and significantly diminish the quality of life of the workers so afflicted. Again, m a n y of these problems can be prevented by job and equipment redesign.

Applications of ergonomics in new technology

With the rapid computerization of industry and business Visual Display Units ( V D U s ) are getting to be c o m m o n . In m a n y large organizations, such as airlines and banks, the operation of V D U s has become a full-time job in which operators are required to sit in front of computer terminals entering data or carrying out word processing for eight or more hours daily.

20


Conventional office furniture and lighting is designed for sedentary staff to read a manuscript placed flat on the desk. With V D U work, there is a need to read characters on a reflecting, vertical glass screen; thus the traditional office-work desk design is not suitable for V D U work. In addition, V D U s have usually been placed at workplaces without sufficient attention to ergonomie principles. Numerous studies have suggested that a poorly designed work place incorporating a V D U can cause a variety of health problems, including visual fatigue, stress, and repetitive strain injuries of the muscles.

Visual fatigue and musculoskeletal disorders at the V D U workplace are usually caused by: (1) factors at the work-station itself, i.e. the design of the work-station, screen or the keyboard; (2) environmental factors, such as lighting conditions at the workplace; (3) personal factors such as defective vision, uncorrected eyesight or age; or (4) long working periods.

F r o m the ergonomics point of view these factors can be changed. The keyboards and screens of m a n y early V D U work-stations were fixed to each other and the height of the work station was not adjustable. Today, most equipment has been redesigned and can be adjusted to fit the various sizes of user. Recent ergonomie studies have also demonstrated that unwanted glare on the V D U screen can be significantly reduced and character legibility can be increased on a positive-display screen. Job redesign to reduce repetitiveness and alleviate constrained posture is also possible. Rest breaks can be instituted to reduce fatigue from working in one position for a long period of time. Well designed rest breaks often result in increased productivity, as well as fewer musculoskeletal complaints (Ong, 1990).

In order to minimize the above-mentioned stresses arising from the use of visual display units, attempts have been made by various health authorities and standards institutions to develop design and usage guidelines taking ergonomie principles into consideration.

Conclusion

Occupational ergonomics is a part of industrial medicine, and is essentially applied to reduce work injuries and discomfort. The discipline deals with the body size of the workers, strength and stress while at work. W h e n faced with a problem at the workplace, ergonomists need also to take into account biomechanical, physiological, psychological and epidemiological factors. Changing work practices, tools, machine design and plant layout are a m o n g the principal ergonomie solutions. T o prevent unnecessary errors and overt and cumulative trauma injuries, ergonomie design has been shown to increase work efficiency and productivity by making the machine or tool fit the user and the worker's capabilities. •

References

C O U R T N E Y , A . J. and N G , M . K . (1984). H o n g Kong female hand dimensions and machine guarding. Ergonomics, 27, 187-93.

K I L B O L M , A . (1983). Occupational disorders of the musculoskeletal system. National Board of Occupational Safety and Health, Sweden.

21


O F F I C E O F T E C H N O L O G Y A S S E S S M E N T (1986). Preventing illness and injury in the workplace. Congress of the United States, Washington, D C .

O N G , C . N . (1990). Ergonomie intervention for better health and productivity: two case studies. In: Sauter, S. (ed.) Promoting Health and Productivity in the Computerised Office, pp. 17-27. Taylor and Francis, London.

O N G , C . N . , K O H , D . and P H O O N , W . O . (1988). Anthropometrics and display station preferences of V D U operators. Ergonomics, 31, 337-47.

V A N W E L Y , P. (1970). Design and disease. Appl. Ergonomics, 1, 262-9.

22

Ergonomics of the home

Yang Gongxia

Ergonomics of the home investigates the habits and reactions of people in their domestic

life. Its objective is to work out a scientific basis by which buildings and rooms and their

fittings can be matched to human requirements. The space needs in relation to furniture

and fitments and the requirements of ambient conditions (lighting, noise and indoor

climate) are discussed here, and some appropriate recommendations given.

H o m e is a word having m a n y connotations, but for most people at least it denotes

security, comfort, companionship and leisure. There is a tendency to forget that

domestic work is one of the world's major occupations, and that there are more

accidents within the h o m e than outside. M o d e r n housework involves the use of m u c h

sophisticated machinery.

The modern science of ergonomics is concerned with relationships between m a n ,

machines and the environment which he has created, and serves to m a k e man-machine

systems more efficient and more safe. The problems of efficiency and fatigue also exist in

the domestic environment. A poor environment can lead to m a n y social problems. U p

to the present, most ergonomists have been concerned more with industrial situations

than with the h o m e , and the wide application of ergonomie principles to the domestic

situation is long overdue. In order to reduce work intensity and to enhance work

efficiency, not only must w e develop highly efficient h o m e facilities and ones with low

energy consumption, but the design and arrangement of these h o m e facilities must also

be in accordance with ergonomie principles.

Ergonomics of the h o m e investigates the habits and reactions of people in their

domestic life. Its objective is to work out a scientific basis by which buildings and rooms

and their fitments can be matched to h u m a n requirements. People's domestic needs can

be classified into physiological, psychological and social. The ergonomist is mainly

concerned with the physiological needs, but also takes account of psychological and

social needs as far as possible. Since the h u m a n being is an integrated whole, the

Yang Gongxia is the Professor of Building Science at the College of Architecture and Urban Planning of Tongji University. His research work also deals with visual ergonomics and visual environment design. H e is the President of the Shanghai Illumination Engineering Society.

Professor Y a n g m a y be contacted at the following address: College of Architecture and Urban Planning, Tongji University, 1239 Siping Road, Shanghai 200092, People's Republic of China.


Yang Gongxia

definition of his or her needs from the one-sided viewpoint of any one scientific discipline risks giving a rather incomplete picture (Grandjean, 1971).

Housework seriously influences the well-being of the housewife. The problem of household duties is further complicated in most countries by the ever-increasing number of housewives w h o go out to work. In China m a n and wife are typically both out at work: the working couple will tend to share the housework. Kitchens are no longer dominated by w o m e n ; n o w the 'apron husbands' are increasingly assuming the duties of food preparation, etc., so that the ergonomics of the h o m e needs to take account of the needs of both sexes.

The intensity of housework

Housework represents the major part of the physical output of a family. Past studies have shown that, in an average day, the overall consumption of energy by a housewife fluctuates between 2600 and 2700 kilocalories, and on washing days or cleaning days it rises to 2800-3000 kilocalories. Domestic energy consumption is thus comparable with a moderately hard occupation outside the home , particularly heavy calls upon energy being made when making beds, scrubbing and washing floors, cleaning windows, ironing and going up and d o w n stairs. Kraut et al. verified these conclusions in 1956, and found that for about 100 days per year a housewife running a household of five people does a job which is as hard as that of a postman, stone-mason, or production-line operative. O n the remaining working days of the year her energy consumption is equivalent to the light to moderate work of a bus driver. During housework, the heart rate increases by 20-30 beats per minute, because housework involves much static activity and this is reflected more in heart rate change than in energy consumption.

Static muscular efforts, which are both heavy and tiring, occur commonly in household activities, many of the jobs requiring unnatural postures such as a stooped back, and m a n y having to be done in one fixed position. A c o m m o n problem is backache, often caused by some damage to the intervertebral discs; much backache could be prevented by avoiding stooped positions as much as possible, and by not pushing or pulling clumsily at heavy loads. A n improvement in working posture should cause a reduction in postural load on the most affected muscles, and thereby reduce the occurrence of musculoskeletal illness.

The basic working week of a housewife w h o does not go out to work is about 50-55 hours. A housewife w h o also has a job spends m u c h less time working in the home, but her total working hours for the week m a y be very high. S o m e surveys (Table 1) on the time spent by housewives on various tasks have shown that work in the kitchen occupied the most time. W a r d (1971) calculated the time which people spend at various work-places in the kitchen. H e found that the time spent by housewives in the kitchen was over three hours on weekdays and at weekends, of which the majority was spent at the sink, and the remainder at the work surface and cooker. W e carried out an investigation at the staff residential quarters of Tongji University. The samples included various occupations, incomes and family compositions. The results of investigation show that the amount of time spent in the kitchen was similar to Ward 's findings, 307 hours on average, the m a x i m u m being 6 hours. This means that w e should pay more attention to the ergonomics of the kitchen.

24


Table 1.

Average working week for housewives in Switzerland (from Grandjean, 1971).

Activity Working time, hours per week

Cooking, washing up, tidying kitchen General housework Washing and ironing Mending, sewing, knitting Caring for children Shopping Other household tasks

16 11

7 4 6 4 5

Space needed for sitting and standing

It is customary nowadays not only to quote the average body measurements but also to indicate the limits of size for groups of people. It is usual to indicate the 9 5 % confidence limits (the 95 percentile) and use them as a measure of variation from the m e a n measurement. This confidence zone indicates that, for the measurement in question, 9 5 % of the population sampled fall inside the given limits. Table 2 gives the heights of m e n and w o m e n from several countries.

T h e principal dimensions of people w h e n standing and sitting are collated in Table 3. T o avoid unnatural bodily attitudes which are tiring and damaging to health, any furniture or equipment needs to be suited to the vertical and horizontal reach of the operative.

T h e vertical and horizontal distances that people can reach are of considerable importance. T h e following vertical and horizontal reaches of m e n and w o m e n are given by Grandjean and Burandt.

W o m e n : x = 55cm T = 95%: 47-63 cm

Men: x = 62cm

T = 95%: 54-70 cm

The horizontal reach for grasping and for working on a surface 3 5 cm below the level

of the elbows are as follows:

Men W o m e n Working field with the elbows lowered x 40 cm 36 cm

T = 95% 36-44 cm 32^10 cm Grasping-circle from shoulder joint x 55 cm 50 cm

T = 95% 47-63 cm 42-58 cm

Table 2. Height of men and women in different countries.

Men W o m e n

Country

Germany USA France UK Switzerland China*

Average height (cm)

172 175-5 170-2 170-7 172-0 167-8

T = 95%(cm)

158-186 163-188

158-6 181-8 157-3-184-1

158-186 158-3-177-5

Average height (cm)

161 162-6 157-8 162-5 160 157-0

T = 95% (cm)

148-174 —

149-9-167 1491 175-9

148-172 148-4-165-9

* For the Chinese data T = 90% confidence limits for normal distribution (5-95%) were used.

25

Yang Gongxia

Table 3. Body measurements when standing and sitting.

Men W o m e n

Measurement

Height of shoulders w h e n standing

Breadth of shoulders

Span of arms

Elbow-ground, standing

Height above seat, sitting

Back of knee to floor, seated

Front edge of knee to back (seated length to knee)

Elbow height above seat

Country

Germany China* USA

Germany China* USA

Germany

Germany China* USA

Germany China* USA

Germany China* USA

Germany China* USA

Germany China* USA

Average (cm)

142 136-7

45 431

175

106 102-4

90 90-8

45 41-3

59 55-4

24 26-3

T = 95%(cm)

129-155 128-1-145-5

40-50 38-8-46-9

155-195

96^116 95-4-109-6

83-97 85-8-95-8

41^19 38-3^4-8

53-65 51-5-59-5

19-29 22-8-29-8

Average (cm)

131 1271 133

41 39-7 36

155

97 960

100

85 85-5 84-7

43 38-2 37-8

57 52-9 59-4

24 251 22-9

T = 95%(cm)

118-164 119-5 1350

36-46 36-3^3-8

135-175

87-170 89-9-102-3

78-92 80-9-90-1

39-47 34-2-40-5

51-63 49-5-57-0

19-29 21-5-28-4

' For the Chinese data T = 90% confidence limits for normal distribution (5-95%) was used.

Space needs in relation to household furniture

The physical need for space is determined by the size of person, the space needed to m o v e round the equipment and the space necessary for passage to and fro, and also the space for their psychological peace of mind.

Working heights when seated

W h e n seated, the hands are at their best in terms of both power and precision if the elbows are at the sides and bent at right angles. If w e take account of the height of seat, the elbow height and the knee room beneath the table, it is recommended that tables for manual work (assembly work or typewriting) have an opt imum height for m e n of 68 c m and that for w o m e n 65 c m ; tables for skilled work (such as drawing, reading, writing, pen in hand) have an opt imum height for m e n of 74-78 c m , and for w o m e n of 70-74 c m . According to our studies the recommended height for reading is 72 c m , for typewriting is 66 c m and for the general office work is 69 c m .

26


Table 4. Preferred heights for working surfaces when standing (from Ward and Kirk, 1970).

Working Activity

Above working surface O n working surface Using force on working surface

The spnrp rpnuirpd fnr stooping, squatting and M e n resting on one knee W o m e n (in cm).

surface above floor Elbow-height to working surface (cm) (cm)

88 91 87-5

Stooping

97-117 92-112

Squatting

90-110 85-105

+ 11-9 + 8-8

+ 12-2

Resting on one knee

102-117 97-117

Working heights when standing

The working height for standing activities should be suited to the height of the elbows above the floor and to the requirements of the manual operations being carried out. W a r d and Kirk (1970), with the help of 56 female subjects, studied the most convenient heights for three kinds of activity. Table 4 sets out the results.

Elbow room when stooping or bending the body

M a n y household activities call for the body to be held in an unnatural position, such as

stooping, squatting and resting on one knee. This can be roughly estimated by the

measurement from head to buttock, with the addition of a certain amount of space to

allow for movement . Table 5 gives the space requirements for all the three postures.

Working heights for kitchen facilities

Table 6 shows the heights of the kitchen work surface as recommended by W a r d (1971). Table 7 sets out the results of Y a n g and Y u (1991) for Chinese kitchens; these heights agree fully with Japanese data.

Space in relation to cupboards and shelves

The following factors should be taken into consideration in the design of cupboards, shelves and all kinds of storage-surfaces: the vertical reach; the most comfortable, and the m a x i m u m height that can be reached w h e n standing free or hindered; and access in relation to the depth of the storage surfaces and their height above ground. Table 8 collates a few of the most comfortable and the m a x i m u m heights that can be reached as revealed by earlier studies.

27

Yang G

on

gxia

•a

t'

co

a -2

ON

I -a c

-c •S

5

S -c ta

-c

-o

u

00

e

et!

60

C

CS

•*

O

O

un

O

un

ig ig

oo

o

©

X

>í

ON

O

N

Os

ON

~

~

OS

OS I

M7

\

O

O

OS

Os

O

O

-S" ON

O

ON

O

N ON

—

O

N I

ON

ON

ON

3"

ON

j"

ON

ON

Tj-

OO

00

TH

mm

O

N oo

oo

toei

es

o

a

00

.e eel

cu

O

CS

O

a.

euo

OÙ

S -S 'S a

O

3

¿3

U

|\s >

N:3

J-

PQ

•c

3

M O

O

O

U

28


5th percentile 50th percentile 95th percentile (short) (medium) (tall)

Sink 80 85 90 W o r k surface 80 85 90 Cooking table 65 70 75

Table 8. Comfortable and maximum heights of reach for women (cm). Summarized from various sources.

Country

Germany USA U K Netherlands

Source

Wenke McCullough Ministry of Housing Woningbouw Houses

Height

Comfortable

65-140 66-137

170 up to 170

s of reach above floor level

M a x i m u m with M a x i m u m without lower cupboard lower cupboard

195 — 168 193 195 200 185 —

The design of household furniture

The stress of work can be offset by sufficient rest and sleep. The furniture of a h o m e must be suited to the physiological needs of rest and sleep as well as to those of certain forms of work and leisure activities.

Sitting is a natural attitude for the body which reduces the static muscular effort of the legs, hips and back. F r o m an orthopaedic point of view seats should promote a seated attitude that reduces bending strain on the back and prevents the development of curvature of the spine. For young people they should permit a combination of a forward and a backward sitting position on the one hand and active straightening of the spine, with slight lordosis of the lower spine on the other. W h e n sitting normally the pelvis is pushed back and the sacrum held in a position almost at right angles to the ground. Orthopaedic considerations require that backwards rotation of the pelvis should be minimized by suitable support for the loins and the lower back to counteract curvature of the spine. In this way strain on the back musculature is reduced.

Ergonomists have analysed sitting attitudes in relation to habits, comfort and anthropometric data. Research into appropriate forms of seating and orthopaedic measurements of bending forces in the spine have produced similar results: sitting attitudes that are comfortable also meet orthopaedic requirements.

Armchairs for leisure

Armchairs for leisure should permit complete relaxation of the muscles of the back, while holding the spine in a natural attitude. So the back-rest must consist of a convex support for the loins at the height where the sacrum joins the lumbar vertebrae, and have a slightly concave shape at the height of the thoracic vertebrae. The slope of seat

Table 7.

The recommended height (in cm) of three kinds of kitchen facility (from Yang and Yu, 1991).

29

Yang Gongxia

should be 10-23°, and the angle between the back-rest and the seat should be 110-127°. The seat height is 39-41 c m , its depth around 47-48 cm. Chairs for leisure should be well padded.

Working seats

Seats which are used for work should be suitable for a forward and an upright attitude, with occasional periods of leaning back on the back-rest or lumbar support. The height of the seat must be below the desk top, at 27-30 c m . The height of seat and lumbar support should be adjustable as far as possible.

W h e n smaller people use working seats they should be able to adjust themselves to a given working height, and a foot rest should be provided with a height range of 0-18 cm. Working seats need to be lightly padded on both seat and back-rest.

Multipurpose seating

Multipurpose seats should be suitable both for sitting forward and for reclining. The back-rest should have slight padding at the small of the back and a slight concavity at chest height: it must extend at least 85 c m above the floor, as long as the seat is not higher than 43 c m . W h e n compressed, the seat cushions should be not less than 43 c m from the floor. The height of the seat should be 43-46 cm.

The bed

The bed essentially consists of bedstead and mattress, and must provide good retention of warmth, comfort when lying down, and provide absorption and permeability to allow ventilation. In hot and humid zones, the latter feature is of great importance, and we recommend the use of a wooden bed frame strung with criss-cross coir ropes and covered with a straw or b a m b o o mat in place of the mattress.

The dimensions of bed are as follows:

length: 210 c m breadth (single bed): 100-120 c m

(double bed): 180 c m height above floor (with mattress): 60-70 c m

(with wooden bed frame strung with criss-cross coir ropes supporting a straw or b a m b o o mat): 50-60 c m

space for movement round bed: 60-100 c m

The bed springs and mattress must conform to every change in sleeping attitude, so that the spine keeps its natural shape while all the musculature is relaxed.

Ambient conditions

Lighting

The visual environment should be such that essential task details are made easy to see and that adverse factors which m a y cause visual discomfort are either excluded or

30


appropriately controlled. The traditional functional division of a h o m e into rooms of specific purpose such as bedroom, dining room, etc. has become rather obsolete in m a n y cases. H o m e lighting should be planned on the basis of activities, rather than on the basis of rooms.

M a n y visual tasks can be performed in almost any part of the h o m e . In one room w e m a y work, play and also rest. For activities which are so different in nature and based on different emotional states, a flexible lighting system is required. In most circumstances, a combination of local lighting and general lighting is preferable. For reading, an illuminance of 200 to 300 lux is recommended. For older people higher illuminance m a y be necessary. For occasional sewing the illuminance should be between 300 and 500 lux.

Illuminance has a considerable influence on the atmosphere in an interior. Higher values usually cause an incitement to action; a low illuminance creates a pleasant atmosphere for relaxation, conversation, watching T V , or listening to music. Uniformity of illuminance is not needed; moderate variations create a pattern of light which is more attractive. Dimming facilities are useful for changing atmosphere.

A good solution for lighting the dining area is to use a pendant lamp with a predominantly downward component over the centre of the table, creating an illuminance on the table of 100 to 200 lux. In the kitchen a general lighting system can be designed with ceiling-mounted lights to supply the illumination of 300 to 500 lux. The illuminance for reading in bed should be 150 to 200 lux. In bathrooms, the general lighting can be combined with mirror lighting. The illuminance should be 100 to 200 lux. All lamps used in homes should have good colour rendering.

Indoor daylighting depends on the direction of the sun, and on the amount of reflection from internal and external surfaces. The use of daylight as an illuminant can save energy used for electric lights, but this must be balanced against the energy required to compensate the heat gains and losses through glazing. Sunlight in living quarters has the following effects: it dries out the walls, kills micro-organisms, helps children to grow, reduces heating expenses and has a pleasing psychological effect. The duration of sunlight should not be less than 60 minutes for living room and children's room in winter.

Noise in the home

Noise is any disturbing sound that the subject finds inappropriate for his activity at the relevant time. The most important effects of noise are: damage to the hearing mechanism (not to be expected from domestic noises); interference with verbal communication; interference with thought and concentration; annoyance; disturbed sleep; psychological stress; and injury to health.

Street noise predominates in external noise. In a study of noise in London, the following noise-levels were recorded during 80% of the time (S80):

In daytime At night

O n main arterial roads 68-80 dB(A) 50-70 dB(A) O n main roads in a residential area 60-70 dB(A) 44-55 dB(A) O n residential roads with local traffic 56^65 dB(A) 45-53 dB(A) In parks, far away from the street 50-55 dB(A) 4 1 ^ 6 dB(A)

Table 9 summarizes limiting noise levels for the interior of rooms.

31

Yang Gongxia

Table 9.

Minimal requirements for sound insulation in apartments (from Grandjean, 1971).

Rooms, all with window open

Living-room Bedroom Children's room

Background level, S 5 0

Day Night

48

48 38 38

Frequent peaks, S 9 9

Day Night

58 — — 48 58 48

level of sound not exceeded for 50% and 99% of the time respectively.

T h e basic layout of an apartment is of the highest importance in keeping out noise. M o s t experts agree that the b e d r o o m is the r o o m most sensitive to noise. Hence w e should distinguish between a 'noise zone' and a 'quiet zone', and that the latter should contain the bedrooms and living rooms. T h e noise zone would include kitchen, bathroom and entrance hall. T w o adjacent apartments should have their quiet zones next to each other, with either two bedrooms or two living r o o m s together. T h e boundary between a rest zone and a quiet zone should fall entirely within one and the same flat. Furrer (1961) proposed the following guidelines for the sound insulation of party walls between apartments, and between apartments and entrance hall:

M i n i m u m sound insulation 52dB(A) Desirable sound insulation 57dB(A)

T h e noise of footsteps is the c o m m o n e s t cause of complaint. T h e most important sources of noise in kitchens, bathrooms and toilets are the

noises associated with water installation, and the highest of these is the sound of water flushing. K a m b e r (1968) measured the noise of running water in adjoining living r o o m s and obtained the following values:

water running into the bath 35-44 d B ( A ) water running into the w a s h basin 26-42 d B ( A ) water flushing w .c . 33-40 d B ( A ) water running out of bath or wash basin 32 40dB(A)

Indoor climate

A comfortable indoor climate is essential for the well-being and efficient working of the occupants. T h e principal recommendations for a favourable micro-climate in the h o m e are as follows:

— in winter the temperature of living rooms whould be within one degree of 21°C, and should be capable of being regulated between 20°C and 23°C. In other rooms lower temperatures are suggested. Temperatures between 20°C and 24°C are comfortable in s u m m e r .

— the temperatures at the surface of the surrounding walls, etc. should be of the same order as the air temperature. Differences from the m e a n temperature should not exceed 2 - 3 ° C , and differences in surface temperatures should not exceed 3 - 4 ° C .

32


Table 10. Guidelines for the ventilation of dwellings (from Grandjean, 1971).

Number of changes per hour

Room

Living room Bedroom Children's room Small kitchen, less than 20 cubic metres Medium kitchen, 20-30 cubic metres Large kitchen, more than 30 cubic metres External and internal bathrooms

(12-15 cubic metres) External w.c. (4-6 cubic metres) Internal w.c. (4-6 cubic metres)

Corridor Entrance hall

Minimal

2 2 2

10 8 6

4 2 2

1 1

Desirable

2-3 2-3 2-4

20-30] 15-25 \ 10-20 J

5-8 4-6 4-6

2 1 2 1

Type of ventilation

Windows Windows Windows Preferably windows

plus mechanical ventilation

W i n d o w plus ventilator fan

W i n d o w Window plus

ventilator fan Doors and

possibly air-shaft

— air with a relative humidity of 40-45% is comfortable in winter: below 30% the air is too dry, and m a y cause discomfort from desiccation of the respiratory tract.

— air movement past a seated person should not exceed 02metres/second.

If a heating system is used, the temperature must vary as little as possible, both in the vertical and the horizontal plane. In all rooms where people are likely to remain for any time, temperatures must be kept within the limits of comfort. Using large heating surfaces keeps the temperature of the heating surface relatively low, so ensuring a good distribution between radiation and convection. The heating units must not scorch dust-particles, and they must be easy cleaning and simple to regulate.

Windows are important for the indoor atmosphere. They present cooling surfaces in winter and admit radiant heat from the sun in summer, and this m a y cause overheating of the room. All experts agree that external sunshades over the windows give the most effective protection against this.

The atmosphere inside buildings is affected by the pollution of the outside air, by h u m a n emissions and by smells from the kitchen, bathroom and w . c , and especially by smoking. In living rooms h u m a n odour is the determining factor in h o w much fresh air is needed, and as a rough rule there should be 30 cubic metres per person per hour. Table 10 gives general rules for regulating air changes in dwellings. •

References

CIE (1973) Guide on Interior Lighting, Publication no. 29, 2. Commission Internationale de l'Eclairage, Vienna.

C O R L E T T , E . N . , W I L S O N , J. and M A N E N I C A , I. (eds) (1985) The Ergonomics of Working Postures.

Taylor & Francis, London. F U R R E R , W . (1961) Raum- und Bauakustik, Lärmabwehr. Birkhäuser, Basel. G R A N D J E A N , E . (1971) Ergonomics of the Home. Taylor & Francis, London. K A M B E R , F. (1968) Schallschutzmassnahmen bie Sanitär- und Heizungs-installationen, Gesund

heitstechnik, 7, 15-22.

33


K R A U T , H . , S C H N E I D E R H Ö H N , R . and W I L D E M A N N , L . (1956) Die Arbeitsbelastung der Hausfrau, Internationale Zeitschrift für angewandte Physiologie, einschliesslich Arbeitsphysiologie, 16, 175-302.

National Standard of the P R China (1988) G B 10000-88, H u m a n dimensions of Chinese adults. Beijing.

O K I T A , F. and K A M B A Y A S H I , H . (1980) Optimum height for the base cabinet counter of the kitchen, Proceedings of Architectural Institution of Japan, no. 295, 9.

W A R D , J. S. (1971) Ergonomics technique in the determination of optimum work surface heights, Applied Ergonomics, 9.

W A R D , J. S. and K I R K , N . S. (1970) The relation between some anthropometric dimensions and preferred working surface heights in the kitchen, Ergonomics, 13, 783-797.

Y A N G , G . and Y u , L . (1991) The determination of optimum heights for Chinese kitchen facilities, Ergonomics, 7, 945-957.

34

Ergonomics and road safety

Karel Brookhuis and Ivan Brown

Modifications to the design of vehicles and road infrastructures have improved road safety significantly over the past decades, but all such developments depend upon user acceptance and institutional backing for their success. New R & D programmes combining ergonomie and engineering approaches are attempting to improve safety on our roads, transport efficiency and environmental quality whilst at the same time preserving individual driver freedoms.

Transport safety is largely a matter of ergonomics, of h u m a n factors. A growing number of traffic safety studies shows that h u m a n error is a major cause in the majority of traffic accidents. It follows, therefore, that prevention or reduction of traffic accidents requires behavioural changes a m o n g responsible road users. For this to occur, first the mechanisms of accident causation have to be understood and the specific behaviour contributing to accidents has to be identified; then, countermeasures have to be devised and introduced to prevent such behaviour, but without eliciting undesirable side-effects, i.e. unwanted displacement behaviour.

O n e problem in this respect is the lack of a suitable database for analysing the causes of traffic accidents (see Brown, 1990, 1991). The main source of information on road accidents stems, from police records of injury accidents (for example in the United Kingdom) , or the registration of traffic accidents involving injuries by police, physicians and hospitals (as in the Netherlands). However useful these sources of information might be for s o m e purposes, they contribute little to our understanding of the real causes of accidents. First of all, they include no reliable information about the intentions of traffic participants involved in accidents reported. Secondly, the behaviour prior to accidents, as reported by the people themselves, is not likely to be very reliable, for obvious reasons. Thirdly, damage-only accidents are usually not recorded, let alone conflict-provoking behaviour that did not lead to accidents at all.

Karel A . Brookhuis works at the Traffic Research Centre of the University of Groningen in the Netherlands, and his co-author, Ivan B . Brown , is at the Applied Psychology Unit of the United K i n g d o m Medical Research Council in Cambridge.

They m a y be contacted at the following address: University of Groningen Traffic Research Centre, P . O . Box 69, 9750 A B Haren, The Netherlands.


K. Brookhuis and I. Brown

In the absence of reliable information on the extent to which different traffic participant behaviour is associated with road accidents, it is difficult if not impossible to identify with any validity the most appropriate and acceptable measures to prevent the behaviour contributing to accidents. Hence, it is difficult to justify the introduction of safety measures that restrain certain forms of road-user behaviour. In the immediate past, there seems to have been a lack of political will to tackle certain road safety problems because of a reluctance to restrict freedom of choice a m o n g road users. M o r e recently, however, an increasing political determination to substantially reduce road accidents has been developing. S o m e European countries have actually set targets for the reduction of casualties. For instance, in The Netherlands the government has formulated a tangible objective of a 25% reduction by the year 2000. T o boost activities in support of this challenging goal, local authorities are being stimulated to play an active role in the drive for traffic safety by putting a premium on results.

Safety measures

A fruitful w a y of improving road safety, in the sense of reducing or preventing injuries, has been achieved by so-called 'secondary' safety measures (see Brown , 1991). Once a collision becomes inevitable the impact m a y be minimized by a number of measures in the form of modifications to the design of vehicles and road infrastructure, so as to prevent or reduce the severity of collisions between road user and hardware. For instance, vehicle manufacturers install crumple zones and safety cages in vehicles to dissipate the energy from collisions, in this way reducing the probability and/or severity of injuries. Recently, the introduction of retracting steering wheels has shown that further developments are still feasible, though at increasing cost. Exterior vehicle changes, such as special zones in the car-front to reduce pedestrian injury, or by the fitting of under-run guards to heavy goods vehicles are also recent developments. However, such modifications sometimes produce conflicts between safety on the one hand and styling, aerodynamics, cost or social acceptance on the other. The increased wearing of helmets by motorcyclists is another example of secondary safety producing demonstrable reduction of casualties. However, in spite of such positive evidence, the wearing of helmets is not universally mandatory. N o doubt some authorities have their o w n manner of weighing the h u m a n and financial costs in terms of death and brain injury against individual freedom a m o n g motorcyclists. The widespread introduction and acceptance of seat belts should be included here, as another measure that has resulted in substantial and lasting effects on injury patterns. Although introduced tentatively and with at least s o m e initial controversy, the compulsory wearing of seat belts seems to have gained acceptance and compliance.

Whilst not all the injury-prevention initiatives are unanimously considered successful, empirical evidence generally supports the view that secondary safety measures have improved road safety substantially over the past decades. It is for this reason that traffic authorities have given precedence to this type of measure over those designed to change behaviour on the part of road users. Political decisions needed to introduce m a n y secondary safety measures are relatively easy to take since, apart from some personal restraint and protective features, personal freedom is not unduly constrained. S o m e drivers m a y have the feeling that secondary safety measures are redundant because of their o w n personal driving skills, although the strength of feeling

36


against the introduction of modifications to m a k e vehicles safer is certainly less of a threat to the political future of policy-makers than legislative attempts to constrain road-user behaviour.

A well-known and illustrative example of the latter type of measure, meant to directly change road-user behaviour, is the imposition of speed limits. Although speed limits, both general depending on average traffic flow and variable with traffic flow, have proven to be statistically associated with casualty reduction, the beneficial effects are not directly apparent to the road user—certainly not outside the conditions that implicated them in the first place. Hence, drivers show a tendency to be motivated towards higher speeds and the acceptance of objectively higher, but subjectively unlikely levels of risk. The retention of fixed speed limits, therefore, is based on the argument that drivers should be prevented from unperceived hazardous traffic manoeuvres.

A better accepted legislative constraint these days is the establishment of legal limits on blood-alcohol concentration while driving, although this is not uniformly done across countries. Traffic authorities and the road-user population generally agree on the necessity of detecting and convicting offenders whose blood or breath alcohol level exceeds the legal limit.

Ergonomie solutions

Existing technology would certainly enable the introduction of acceptably safe, automatic vehicle control systems. However, drivers would be understandably reluctant to give up the independent and flexible mobility afforded by a private vehicle under their personal control. Neither would they be inclined to pay for expensive technological systems which deprived them of the pleasure to be gained from exercising their decision making and vehicle control skills on the road. For a number of reasons governments would also be resistant to the spending of huge amounts of state funds on the required road and traffic infrastructure. O n e of these reasons is the issue of product liability raised by automatic traffic control systems, in cases where failure results in property damage, injury or death. Vehicle manufacturers have similar objections to the overhasty introduction of automatic vehicle control systems.

History teaches us that technological improvements in vehicle safety generally require over ten years to be adopted by the majority of vehicles on the road. It follows that, at least until around the year 2000, h u m a n drivers will continue to exercise principal control over their vehicles and behave largely in a self-paced manner. Hence, traffic safety will continue to be dependent on the decisions and actions of drivers w h o either initiate manoeuvres themselves for personal reasons, or respond to the demands m a d e by the other road users and the traffic environment. H o w , then, could traffic safety be improved substantially, if final control remains with the driver? Teaching drivers h o w to detect, identify and evaluate road and traffic hazards more effectively is clearly desirable (see Brown, 1989), but it is not the ultimate answer to the question. Research shows that the (often misplaced) feeling of 'being in control' is a major determinant of driver behaviour. Hence, there is a need to teach drivers the limits of their performance capabilities and h o w to more or less continually adapt their behaviour to changes in these limits. However , the results of such training would

37

K. Brookhuis and I. Brown

probably not persist, become less effective as a consequence of fatigue or lack of motivation, and be occasionally overruled by alternative demands such as time pressure.

Recently, combined ergonomie and engineering approaches to both hazard assessment and the indication of drivers' performance limits have developed into the research and development ( R & D ) of new and relevant (primary) safety measures. The Commission of the European Communities ( C E C ) proposed a R & D programme in the field of road transport informatics and telecommunications. The objectives of this programme were defined as the improvement of road safety, transport efficiency and environmental quality. In 1988 a research programme, Dedicated Road Infrastructure for Vehicle safety in Europe ( D R I V E ) , was formally adopted by the C E C for an initial period of three years. D R I V E envisages a complete general European road transport environment in which individual drivers are better informed and monitored; and in which 'intelligent' vehicles communicate and cooperate with each other, the road users and the road infrastructure itself. D R I V E seeks to create favourable conditions for the development of this integrated road transport environment through collaborative R & D in the field of information technology and telecommunications applied to road transport. It seems likely that this comprehensive concept reduces the political objections to the introduction of m a n y safety measures that include constraints on individual drivers' freedom. A n y measure that marginally constrains individual road-user behaviour in order to improve safety is m u c h more acceptable if it can be shown incidentally also to reduce traffic congestion and air pollution.

Certain projects within the D R I V E programme aim at sustaining adequate vehicle control under conditions where the driver's cognitive, perceptual and motor abilities m a y become impaired (i.e. accident risk is increased). O n e of these projects (Driver Related Evaluation A n d Monitoring, or D R E A M ) is concerned with the development of a device for the continuous unobtrusive monitoring of driver status and abilities, in and by the vehicle itself. This ' D R E A M ' device should function as a detector of insidious deteriorations in driving performance, such as decreasing alertness that accompanies fatigue or the use of alcohol, which are frequently difficult for the driver to recognize because they impair perception and judgement as well, and hence the ability to monitor and assess one's o w n state of competence.

Another, and the biggest project within D R I V E , is G I D S (or Generic Intelligent Driver Support System). This project has the overall objective of 'determining the requirements and design standards for a class of intelligent driver support systems which will conform with the information requirements and performance capabilities of the individual h u m a n driver'. Its aim is to develop a 'knowledge refinery' which will 'accept information from vehicle sensors and dedicated driver support applications and filter, integrate and present this information in ways which are consistent with the intentions and capabilities of individual drivers'. Figure 1 illustrates this point (Kuiken, 1991).

O n the one hand G I D S systems will aid the driver's detection and assessment of road and traffic hazards. O n the other, since such systems are supposed to have warning and tutoring functions as well, they will provide guidance, on-line and off-line, on the driver's ability to deal with specific hazards. G I D S represents a combined ergonomie and engineering solution to the problems and pitfalls which affect an individual driver's traffic safety. Although its aim is not directly to change behaviour, the potential for intervention and assumption of full vehicle control is there, if needed.

38


Figure 1. Application of the Generic Intelligent Driver Support (GIDS) system.

Conclusion

Since there exist no valid data on which estimates of the risks of particular traffic behaviour can be based, it is very difficult if not impossible to forecast the savings of death and disability that might result from the introduction of risk-reducing driving aid systems. However , as long as road users are allowed to participate in traffic in an independent and virtually self-paced manner, road safety is essentially determined by individual road users' perceptions of the risks associated with their o w n driving behaviour, and misperception of risk m a y very well be mediated by such technological support systems.

The C E C ' s D R I V E programme favours an ergonomie approach to behavioural change via engineering measures, in the form of 'road transport informatics'. Various projects within the programme aim implicitly at improving road users' risk acceptance by aiding detection, identification and evaluation of traffic hazards and by guiding individuals' assessments of their o w n ability to deal with such hazards. Contributions to this guidance will come from projects which aim to keep road-user behaviour within legal limits, hopefully resulting in more homogeneous and hence safer performance.

At the time of writing, the D R I V E p rogramme has reached the end of its initial three-year phase. N e w project teams are starting work on the next phase, 'Advanced Road Transport Telematics' (ATT) , shifting the objectives of this R & D cooperation from exploring the options to preparing for implementation. T h e next few years should mark the beginning of a n e w phase in the impact of (primary) safety measures against road traffic accidents. •

39


References

B R O W N , I. D . (1989). H o w can we train safe driving? Traffic Research Centre, University of Groningen, Haren, The Netherlands.

B R O W N , I. D . (1990). Drivers' margins of safety considered as a focus for research on error. Ergonomics, 10/11, 1307-1314.

B R O W N , I. D . (1991). Prospects for improving road safety during the 1990s, pp. 315-34 in: Singleton, W . T . & Dirkx, J. (eds.) Ergonomics, health and safety. Leuven University Press, Leuven.

K U I K E N , M . J. and M I L T E N B U R G , P . G . M . (1990) Adaptability in driver support, in: Proceedings of the 24th ISATA international symposium on automotive technology and automation, pp. 733^0, Florence.

40

Ergonomics of job and equipment design

Colin G . Drury

The systematic application of ergonomics in industry can contribute to higher quality, more efficient production and a safer working environment. This can best be achieved through deduction of systems functions from system objectives, detailed analysis of human tasks, and true operator involvement throughout the design process. Examples from manufacturing industry serve to show how different aspects of the human can be critical to design under different circumstances.

Although ergonomics can be used in the design of things as diverse as consumer products, agricultural tools, and military hardware, this article will deal mainly with its application in industry.

Throughout the world, manufacturing and service sections of industry are being subjected to severe changes in their operating environment, and thus being forced to find new methods of operation. Most of the changes stem from increased competition from worldwide sources. As an example, the number of products m a d e in the U S A which face foreign competition in their h o m e market has increased from 20% to 80% in a generation. Companies are less and less protected by national tariff barriers, and transportation of goods and information is n o w relatively rapid and inexpensive. The implication is that companies must use every means available to remain competitive. This means higher quality products, delivered on time, at competitive prices.

At the same time countries throughout the world are enacting more stringent environmental and safety laws to protect both the population and the workforce. Industry must n o w operate efficiently and safely at the same time. The cost of major disasters, such as Bhopal, Three-Mile Island or Chernobyl, is beyond contemplation for most companies (and most societies), but it is often the smaller h u m a n errors, accidents and injuries whose increasing costs force action through safer workplaces.

Dr Colin G . Drury is Executive Director of The Center for Industrial Effectiveness (TCIE) at the University at Buffalo, where he is also a Professor of Engineering. His main work has been in manufacturing and other industrial applications of ergonomics. Technical interests include h u m a n factors in inspection, h u m a n control of complex processes, and implementation procedures for industrial ergonomics. In 1982 he was awarded the Bartlett Medal by the Ergonomics Society.

Dr Drury m a y be contacted at the following address: Department of Industrial Engineering, 342 Bell Hall, State University of N e w York at Buffalo, Buffalo, N Y 14260, U S A .


C. G. Drury

Thus, any discipline which can contribute to higher quality, more efficient production, and a safer working environment at the same time is receiving serious consideration on purely financial terms. W h e n it is learned that ergonomics is at least equally concerned with worker satisfaction (and even fulfillment), then the current interest in industrial ergonomics can be understood.

In order to effectively utilize the ergonomics data and techniques presented elsewhere in this issue, a systematic procedure for the design of the workplace and the job is required. This m a y be an initial design, for example of a n e w tool or a new seated workstation, or it m a y be a redesign of an existing workplace. Ergonomics requires explicit consideration of the h u m a n operators' abilities, characteristics, and even limitations. However, humans are complex 'components' with m a n y different aspects to their performance and their needs, so that without a design (or redesign) procedure it is easy to be overwhelmed by the complexity of the design choices. This article presents a systematic way of combining the analysis of the task requirements with the data available on the h u m a n body and brain, so as to achieve a better human/system fit. It is this improved fit which allows performance (quality, efficiency) to be achieved at the same time as operator well-being (safety, satisfaction).

A design/redesign procedure

Since its earliest inception, mainly in military hardware design, ergonomics has had a systems orientation (e.g., Singleton, 1974), due in part to the complexity noted above. In a complex system, such as air traffic control or the control room of a warship, m a n y humans must interact with m a n y pieces of equipment to m a k e the whole system successful. However, the techniques developed in those environments have been successfully applied to the design of such simple items as toothbrushes, agricultural tools, computer workstations and sewing machines. Systems orientation forces the designers to consider the ultimate goals of the system, and then progressively smaller sub-goals, before considering alternative designs of hardware. It is this 'planned procrastination' of putting hardware decisions aside until the goals and functions have all been determined which is so powerful both in initial design and in redesign.

The other powerful concept behind design ergonomics is that of user involvement. T o o often in modern society the user of a system is not the purchaser. Forklift trucks are bought by engineers, but used by drivers. Office chairs are bought by purchasing agents but used by clerks and secretaries. Even toys are bought by parents but used by children. The voice of the user in design can easily be overlooked. In redesign, for example installing a new chair at a sewing workstation, it is less easy to overlook the user, though it is still possible to give the user only a cursory role in design, for example, by showing an already-purchased chair to the operator and 'asking' whether he/she thinks it is an improvement. True user involvement means that the user is part of the design team from the m o m e n t the need for a n e w design is first articulated. A user's input, whether into the purchase of a tool or into major organizational change, should have a weight equal to that of other interested parties, such as management , engineers or safety professionals.

42


Initial design

Design begins by analysis. A typical design conception is shown in Figure 1. The overall objective of the system is found, followed by sub-goals called functions. Each function is then, in theory, assigned to a h u m a n or a machine, although the distinction is blurring somewhat n o w that machines and humans have m a n y tasks in c o m m o n . For example, an airliner might have as its objective the completion of the mission (deliver 250 people, over stage lengths of 1500 k m , with fuel consumption less than 12,000 kg) within certain tolerances. Beneath this objective is a function of 'perform landing approach'. With modern computers for navigation and piloting, 'perform landing approach' m a y not be assigned exclusively to h u m a n or machine, but m a y have a flexible assignment depending upon circumstances (e.g., weather, malfunctions, congestion at the airport, etc.). This assignment of a function to a device (human or machine) is a central part of the ergonomie design process, where it is k n o w n as allocation of function. Because of this centrality, it is an issue dealt with at some length in ergonomics texts (e.g., Kantowitz and Sorkin, in Salvendy, 1987).

Having allocated the function, we must n o w design for that function. Hardware must be designed to perform correctly; so must the h u m a n operator through selection

Figure 1.

The process of ergonomics in systems design.

Hardware design

System objectives

' 1

Function separation

i ' Function allocation

i ' Interface design

X . ' ' Jf

System integration

' ' System

evaluation

Personnel design

43

C. G. Drury

and training. Perhaps the major design impact of h u m a n factors engineering (the U S term for ergonomics) has been in the design of the interface between h u m a n and machine. Interface can mean something as grandiose as the control panel for a chemical plant, or something as mundane as the handle on a power tool. Both need designing to fit the operator, and the consequence of mis-design is error in each case. Errors can be revealed as reduced quality, reduced safety or avoidable delay. It is in interface design that the ergonomist uses anthropometric data to fit the mechanical components of workplace and tools to the operator, and also uses knowledge of h u m a n cognitive functioning to fit the operator's needs for controls, displays and software.

After the hardware, interface and operator are designed they must be integrated so as to fulfill the overall system objective, rather than just fulfilling each function in isolation. It is here that the ergonomist must ensure that design solutions for each function are compatible, and also that the overall jobs formed from the functions build into meaningful, satisfying wholes for the operators. Finally, of course, comes test and evaluation. Even though our models of the h u m a n (biomechanical, physiological, cognitive) m a y show that the system should work as planned, this must still be proven. Prototypes can be built, or even computer simulations used, but at some point the user and the hardware must be brought together for evaluation under realistic conditions.

While all of the steps shown in Figure 1 are usually presented as proceeding in a linear manner, in practice there is much back-tracking, with checking and partial evaluation at each step. Perhaps some functions are just not presently possible, suggesting that the overall objective must be modified. Perhaps a function assigned to the human causes overload when combined with other functions, and has to be reassigned to the machine. Perhaps the initial assumptions about the user population are incorrect, as with the breakdown of gender-specific occupational stereotypes, in which case new interfaces or new training m a y be required. Perhaps, even, some functions can be eliminated without affecting the overall system objective. The art of design is hardly as cold and rigid as Figure 1 suggests, but this does not invalidate the general design framework.

Redesign

In many ways, redesign is simpler than design, though it is m u c h more expensive. The design team has a working system to observe, interrogate and test, which makes design faults clearer. However, the cost of change is m u c h larger. It is no longer merely moving a line on a design drawing, or of redefining a subroutine in a computer program, but n o w involves physically changing equipment, training schemes and working software. However, in most industrial environments, the ergonomist only gets invited on to an initial design team after a track record of successful redesigns has been established. Thus, as a practical matter, most ergonomists spend considerable effort on redesign, even if it is disguised as 'system upgrading'.

Redesign starts from an existing allocation of functions: machines perform functions 2,5 and 7, while humans perform functions 1, 3,4 and 6 in the current system. It m a y not always be possible to re-allocate functions—as an extreme example consider adding a h u m a n crew to a robotic spacecraft! Usually, however, some re-allocation will be possible. M o r e frequently it is in the redesign of the interface that the ergonomics team can have an impact. Examples will be given later of typical redesigned systems.

44


O n e constant in all of these examples is the early and deep involvement of the operators in the design process. A n y working system will have an incumbent in each h u m a n job, often more than one where shift work is practised. This incumbent will not only provide insights into the skills inherent in the job, but will also have worthwhile insights into the frustrations or likely errors. M o r e importantly, the operator will have a considerable interest in any changes to be m a d e to the job—it is, after all, her (or his) job where the largest single fraction of her (or his) working life is spent. Involving the operator means not just asking for opinions, or even eliciting knowledge, but empowering him (or her) so that ergonomics is no longer just the province of the ergonomist, but a shared responsibility of the redesign team. Designs produced with the help of an empowered operator have a way of becoming implemented more quickly, and producing the desired results more effectively than design solutions imposed from the outside (e.g., Shipley in Wilson & Corlett, 1990).

Task analysis in design/redesign

Analysis of the activities of the operator when performing a function is a necessary step in ergonomics design. Only when the effects of each activity on each sub-system of the h u m a n are understood can the designers be sure of function, and hence system, performance. Task analysis is a standard procedure in systems design which does this by systematically comparing task demands with h u m a n capabilities to determine possible errors. For initial design, tasks are derived logically from each function by listing the steps necessary to perform that function successfully. For redesign, the tasks can be listed directly by observing the operator. There are m a n y techniques for task analysis (e.g. Stammers et al, in Wilson & Corlett, 1990) but all start from such a list of tasks, called a task description.

Task analysis is then the comparison of the demands placed on the operator (task demands) with the operator's ability to meet those demands (human capabilities). As there are m a n y demands in each task, it is usually necessary to form a matrix with the tasks listed as rows and the h u m a n sub-stystems listed as columns. Sub-systems are those parts of the body, or mind, with unique limitations. Thus colour vision is limited to objects with a luminance above about 0 3 cd m " 2 , while reach to an object across a workbench is limited to 380 m m for 95% of adults. M a n y sets of sub-systems are available, but they often have a similar structure based on h o w a h u m a n processes information to respond to an input event. A n example would be those sub-systems listed in Table 1.

The output from a task analysis is thus the comparison of task demands with h u m a n capabilities for each cell in such a matrix. While it m a y seem a laborious procedure, and indeed the database of ergonomics is not extensive enough to give a numerical analysis in every cell, it does focus the design team on which tasks are likely to cause problems for which sub-systems. Thus is might highlight excessive spinal forces during lifting tasks, or glare from a computer screen when reading text, or excessive repetition of an assembly movement in an awkward posture. Such highlighting gives the design team the data it needs to justify design or redesign solutions, particularly for problems which m a y not be obvious to those outside the team. It is also a useful w a y in which to involve the operator at sufficient depth. The

45

C. G. Drury

Table 1. Human subsystems for task analysis.

Sensing Information input to the human, through vision, hearing, kinesthesis, taste, smell and touch

Attention The concentration of the human information processing system on one of the many sources of input information

Perception Information transformation used by the human to simplify processing using learned mental models

Memory H u m a n sub-systems for sensory storage ( < 1 s), short-term rehearsal (1 —20s), and long-term storage

Decision Active choice of possible responses, based on inputs received and memory , including social factors

Action Use of the musculoskeletal system to execute a movement, exert a force, or maintain a posture

discipline of analysing each step in the job from the point of view of each h u m a n subsystem helps operators understand the complexity of their o w n skill, as well as demonstrating this complexity to outsiders. Additionally, task analysis provides a framework of honesty in design: any solution which does not address the 'problem' cells will not necessarily provide benefits.

Finally, task analysis can be applied as a recursive procedure. W h e n the job, tool or workplace has been redesigned, it is time for another task analysis as part of the evaluation procedure. Did the solution work? W e r e the excessive spinal forces reduced? W a s the screen glare removed? W a s the posture in a repetitive task more neutral? Again, the discipline of task analysis forces honesty—the solution can be seen to work, or not to, by the whole design team.

Examples of ergonomie change

The following examples have been chosen to demonstrate where different h u m a n subsystems were critical to the design. It should be appreciated, however, that just because one sub-system was critical did not allow the neglect of others. In practice, no design or redesign is as simple as these examples might suggest. Note also that in all cases, the redesign effort involved the operators from its earliest inception: these were team designs.

Example 1. Critical input: vision lighting

A production line for computer disk drives was transferred from one factory within a corporation to another. Hasslequist (1981) describes h o w ergonomie changes were m a d e to the workplaces, the seating, the air tools and the lighting. Because the tasks involved the assembly of complex components, shadow-free lighting was a requirement. N e w ambient lighting was provided using lowered fluorescent fixtures. Moreover, to ensure freedom from shadows, workplace components (conveyor, bench top) were of a light, neutral beige colour. Perhaps the most useful innovation was to replace the concrete floor by light beige floor tiles, which increased the illuminance at

46


Figure 2. Example of an ergonomie workplace redesigned to improve lighting, seating and layout (after Hasslequist, 1981).

the working surface by 80%. Figure 2 shows a workplace, with a box placed on the work surface to demonstrate the lack of shadows. Overall, there were energy savings, rather than energy costs, in changing the lighting system, despite the n e w system providing an illuminance of 1000 lux at the work surface.

Across the whole production line, time utilization increased by 6%, assembly time reduced by 5% and absenteeism was 5 0 % less than in other areas of the plant. Continuing evaluation in the lj years following Hasslequist's paper showed that musculo-skeletal injuries had been eliminated, and defect rate had decreased from 4 % to 2 % . Job satisfaction, measured regularly in this plant, increased from 50% to 80% satisfied. The management calculated that the increased costs of ergonomie design were paid back in improved productivity in less than six months.

Example 2. Critical perception/decision: control panel layout

In a factory making sheet-steel stampings, each production line consists of a sequence of presses separated by mechanical loaders and extractors. Between any two presses the extractor for the upstream press is followed by the loader for the downstream press. W h e n an ergonomics team was formed to recommend improvements, the operators indicated that the control panel between each pair of presses was not well laid out. A task analysis gave the sequence required to re-start the line, and is depicted graphically as a sequence of movements in the upper half of Figure 3 (from Drury, in Wilson & Corlett, 1990).

47

C. G. Drury

Figure 3. Before (a) and after (b) designs of a control panel in a stamping plant.

T w o problems were noted. First the panel was laterally reversed with respect to the physical locations of the extractor and loader. This was not true on some other lines in the plant, causing confusion and control errors w h e n operators m o v e d between lines. Second, there were only four buttons on each side panel required for start-up, but these buttons were scattered across the panel.

The ergonomics team suggested interchanging the loader and extractor panels, and bringing the four buttons required to start each machine together into sub-panels. This

48


also had the side-benefit of clearly separating the functions of the line operator, w h o could only control start-up and shut-down, and the maintenance mechanic, w h o needed all of the other controls to perform set-up changes. The lower half of Figure 3 shows the revised panel.

Analysis of the new panel used data on h u m a n reliability in the face of good and poor panel layouts to show that the probability of correct operation (i.e. no errors) in the fourteen-button start-up sequence would increase from 91-9% to 98-6% for operators under some degree of time stress. In addition, the information processing requirements for choosing the fourteen-button sequence were decreased, hence saving time. Total choice time was calculated at 16 seconds on the original panel and only eight seconds on the new panel, due to the reduced number of buttons within the new sub-panels.

These changes were implemented by the ergonomics team, and control panel vendors were contacted to ensure that similar changes would be made on all new panels ordered.

Example 3. Critical anthropometry: workplace layout

Garment and shoe manufacture are worldwide activities, with severe competitive pressures, usually resulting in highly repetitive tasks. The workplaces for these tasks are often ill-designed for such high repetition rates, resulting in the potential for repetitive motion injuries to the arms, shoulders and trunk. Analysis of jobs in a shoe plant (Drury and Wick, 1984) by an ergonomics team composed of operators, staff and ergonomists, showed that sewing workstations typically had a bent-over (flexed) posture, with non-neutral wrists, raised hands and poor leg/foot posture. Figure 4 (a) shows one of the less extreme examples before modification.

A detailed task analysis concentrating on the body angles at each task step, showed that the posture was caused in part by the chair, in part by the sewing machine being mounted in a flat position, and in part by the operator needing to see the work clearly. This latter caused her to raise her hands and flex her neck.

Modifications to the workplace included tilting the sewing maching, adding a curved work surface in line with the sewing point, adding better task lighting to improve vision, fitting and folding arm rests to the work bench, and purchasing a new chair. A second task analysis of the new workplace shown in Figure 4 (b) found a reduction in potentially-injurious wrist motions from 7495 to 0 per day for the left hand and from 5996 to 1449 per day for the right hand. Measured postural discomfort was decreased significantly, while productivity increased by 5-2%. The workplace was both safer and more productive, and the operator became an advocate for ergonomics redesign throughout the plant.

Example 4. Critical work organization: cellular manufacturing

Ergonomie design is not j ust of the workplace and tools: it can involve the design of the job itself. As part of a drive towards just-in-time manufacturing, a plant making alternators for trucks sought help in designing a new organization based on self-contained work cells. The first demonstration project redesigned the machining

49

C. G. Drury

Figure 4.

Before (a) and after (b) designs of a sewing workstation (after Drury & Wick, 1984).

50

(b)


Table 2.

Results of manufacturing cell implementation

Criterion

Cycle time, days Travel distance, miles W o r k in process, inventory Changeover time, hours Cost/part Inventory turns/year Quality (number of defects) Space required, m 2

Before

7 209

> 2,500 10 $1-71 30 ? X

After

0-3 130

< 1,000 1-5

$0-81 >100

0 X-37

operations on alternator end-caps into a manufacturing cell (Drury, 1991). Again, a team of company personnel, operators and ergonomists were responsible for the analysis and design. Ergonomics input included the detailed task analysis, re-layout, job aids, training in multiple skills and organizational redesign. T w o operators n o w ran the cell autonomously, using a telephone to maintain rapid contact with other departments w h o were their 'suppliers' and 'customers'.

Evaluation was on m a n y criteria (Table 2) and was most encouraging. Note that ergonomists were part of the team responsible for introducing cellular manufacturing, rather than being the leaders of an ergonomie redesign project as such. Thus ergonomics enabled the change to be m a d e in organizational structure, so that the improvements were not the direct result of physical ergonomie changes. Perhaps more important than the physical measures of effectiveness shown in Table 2 was the enthusiastic attitude of the operators to the change. While both workload and responsibility (e.g. for quality control, scheduling and preventive maintenance) had been augmented, the new autonomy which came with this was m u c h appreciated.

Conclusions

Ergonomics can apply to any system involving humans and their machines, although the aspect of ergonomics which applies m a y be different in each application. The four examples described here have shown measurable improvements where four different aspects (sub-systems) of the h u m a n were critical. All were chosen from manufacturing industry, but the results are applicable across m a n y sectors: service industry, agriculture or consumer products. Equally, ergonomie techniques for systematic design or redesign apply at any level of technology. Manual systems using hand tools have as m u c h scope for ergonomics as do the traditional machine-aided industrial processes, or even highly automated systems. The keys remain as detailed analysis of the system requirements, detailed task analysis, and operator involvement throughout the design process. •

References

D R U R Y , C . G . (1991). Ergonomics practice in manufacturing. Ergonomics, 34, 825-839. D R U R Y , C . G . and W I C K , J. (1984). Ergonomie applications in the shoe industry. Proceedings of

the 1984 International Conference on Occupational Ergonomics, Toronto, Canada, 489^193.

51


H A S S L E Q U I S T , R . J. ( 1981 ). Increasing manufacturing productivity using human factors principles. Proceedings of the H u m a n Factors Society 25th Annual Meeting, Santa Monica, California, U S A , 204-206.

S A L V E N D Y , G . (1987). Handbook of Human Factors, Wiley, N e w York, U S A . S I N G L E T O N , W . T . (1974). Man-Machine Systems, Penguin, Harmondsworth, U K . W I L S O N , J. R . and C O R L E T T , E . N . (1990). Evaluation of Human Work, Taylor & Francis,

London, UK.

52

Ecological ergonomics: the study of human work environments

Alan Hedge

Ecological ergonomics investigates the principles for creating and maintaining habitable and healthy work environments. This overview illustrates the multidisciplinar y nature of ecological ergonomics. The field covers a diverse array of work environment factors that influence worker health, satisfaction and productivity. These factors include the effects of thermal conditions, indoor air quality, office lighting, acoustics, office technology and workplace design.

Ecological ergonomics describes the study of the processes and conditions essential for creating and maintaining habitable and healthy work environments for people. The combination of ecology (i.e. the study of organisms in relation to their environment), and ergonomics (i.e. the science of work) is timely because w e spend about 90% of our lives inside buildings, and the conditions created by the built environment are crucial to our well-being.

The complexity of modern settings requires that ecological ergonomics has a multidisciplinary orientation, and that it integrate research from the h u m a n sciences, medicine, industrial hygiene, chemistry, computer science, engineering and design. Figure 1 illustrates some of the research topics involved in ecological ergonomics. This broad perspective subsumes the study of environmental ergonomics, a field more narrowly concerned with topics such as the impact of the design of clothing on h u m a n thermoregulation in extreme climates or the creation of habitable environmental conditions inside aeroplanes, spacecraft, submarines, and so on. Ecological ergonomics focuses on the biological and psychological processes by which w e regulate a harmonious relationship with our environment, both natural and artificial, hospitable

Alan Hedge is an Associate Professor in the Department of Design and Environmental Analysis at Cornell University in Ithaca, N e w York. His research and teaching focus on workplace ergonomics issues which influence the health, comfort and productivity of workers, such as indoor air quality, office lighting and workplace design, and has published widely on these topics. H e chairs the Ecological Ergonomics Technical Subcommittee of the International Ergonomics Association, and an American Standards for Testing and Materials ( A S T M ) task group on the development of behavioral tools for assessing the performance of facilities. H e was President of the Division of Environmental Psychology of the International Association of Applied Psychology from 1982 to 1986. H e has served as an expert to the House of Representatives in connection with the Indoor Air Quality Act 1991, to the N e w York State Assembly in connection with indoor air quality policy, and to the U K House of C o m m o n s Environment Committee on Indoor Pollution.

Dr. Hedge m a y be contacted at the following address: Department of Design and Environmental Analysis, N Y S College of H u m a n Ecology, Cornell University, Ithaca, N Y 14853-440, U S A .


A. Hedge

Figure 1.

Example of the kinds of workplace design issues addressed by ecological ergonomics.

^ j ^ O N M E N r c p ^

°^RATCCUtf^

and hazardous, and applies this knowledge to improve the fit between people, products and places.

H u m a n responses to the ambient environment

Since the d a w n of civilization humankind has sought protection against the unpredictable ravages of Nature by creating ingenious barriers to the elements. Clothing is the primary barrier that, besides its adornment value, functions as a second skin to protect us from adverse meteorological conditions (heat, cold, wetness, wind, etc.). Vehicles and buildings are secondary barriers which in turn function as a third skin. They keep us dry and comfortable, and provide us with sustainable conditions even in the most inhospitable places. Understanding h u m a n responses to ambient environmental conditions holds the key to the successful design of these barriers.

Thermoregulation

The thermoregulatory processes that keep us in thermal balance with our environment are well understood. Muscular activity is an important w a y by which the body regulates its temperature. At rest, the muscles produce about 20-30% of our body heat. During strenuous exercise for about one minute the heat output from muscles can increase to 40 times that from all other tissues.

Effects of heat and cold on the body

Thermoregulatory processes work differently for two body compartments: the shell

(the skin), and the core (the internal organs, etc.). The skin acts as the outer body shell,

54

Human work environments

and copes with a wide range of different thermal conditions. The core maintains the integrity of the body's internal organs within a m u c h narrower range of temperatures.

W h e n we get too w a r m , blood flows from the central core of the body to the skin and sensible perspiration starts, which dissipates body heat by the evaporation of sweat. If body heating continues beyond our ability to lose heat through perspiration (i.e. the upper critical temperature) we will collapse from heat stroke (hyperthermia). If overheating continues w e will eventually die. W h e n w e get cold, peripheral blood vessels constrict and blood shunts from the skin to the body core, piloerection occurs (i.e. the hairs of the skin stand up to better trap an insulating layer of air over the skin), and shivering (spasmodic muscular activity that generates heat) starts. If body cooling continues beyond our ability to generate and conserve heat (i.e. the lower critical temperature) w e will suffer hypothermia, become lethargic, then comatose. If cooling continues beyond this point we will die. While we keep within these two extremes of thermal conditions our body can thermoregulate with the environment.

Severe thermal situations can pose problems for workers in hot industries, such as steel-making or glassworks, where workers can be exposed to high radiant temperatures (e.g. 60°C in glassworks, steelworks, etc.), or in cold industries, such as refrigerated cold storage work, Arctic or Antarctic deep-sea fishing, oil rig work, deep-sea diving, etc. Severe thermal conditions challenge the body in extreme habitats: cold stress poses problems for people in polar regions, both on land and at sea; and heat stress poses problems for people in desert and tropical regions. Within the shelter of our buildings most of us never encounter such extremes, although we m a y experience discomfort from inappropriate thermal conditions. Considerable research has been conducted to determine appropriate thermal comfort conditions for everyday indoor settings.

Thermal comfort

Research has shown that six variables influence our perception of thermal comfort. Four of these are environmental variables:

• air temperature the temperature of the air around the body; • air speed the velocity of the air past the body; • humidity the percentage relative humidity of the air (i.e. the ratio of the amount

of moisture in the air divided by the m a x i m u m amount of moisture that the air could hold at the same air temperature and barometric pressure multiplied by 100);

• mean radiant temperature the average temperature of the radiant sources.

A n d two are individual variables:

• activity muscular activity generates heat, so the more active w e are the warmer w e can become, even in cold conditions. This factor becomes particularly important when looking at people doing heavy work in hot conditions.

• clothing isulation different clothing materials have different thermal insulation properties. W i n d or body movements disrupt the air layer between the skin and the clothing and reduces clothing insulation. W h e n clothes get wet they lose their insulation value.

55

A. Hedge

Thermal comfort standards

Over the years several thermal comfort indices have been developed, two of which n o w dominate modern envionmental design practice.

Thermal comfort zone (ASHRAE 55-1981) The American Society of Heating, Refrigerating and Air-conditioning Engineers ( A S H R A E ) defines a comfort zone (i.e. a region on a psychrometric chart in which people will be comfortable). A S H R A E gives a series of charts for winter and summer, for different clothing ensembles, and different air velocities. Air temperature and m e a n radiant temperature are assumed to be equivalent and activity levels are assumed to be typical for indoor settings. The comfort zone defines the combinations of air temperature and relative humidity at which 80% or more of the people with a given clothing ensemble at a given activity level will not report dissatisfaction with thermal conditions ( A S H R A E , 1981).

Fanger's comfort equation (ISO 7730) In Fanger's approach thermal comfort is defined in terms of the physical state of the body rather than environmental conditions, because what w e perceive is skin temperature and not air temperature (ISO, 1984; Fänger, 1970). Fanger has derived comfort equations from the experimental literature that use the four environmental variables and the two individual variables to predict comfort temperature, the average thermal comfort votes for any group of people (predicted m e a n vo te—PMV) , and the percentage of people w h o will be dissatisfied with the thermal environment (predicted percentage dissatisfied—PPD).

Experiments show that for sedentary work and light clothing the preferred temperature is close to the 25-6°C predicted by Fanger's equation. Research has not found effects of age, sex, race, or individual differences in preferred temperatures. Field studies show that the P M V gives good results for standard conditions of sedentary activity and light clothing, although it has yet to be validated across a range of clothing and activity. The general application of Fanger's equation is increasing n o w that computer programs and portable thermal comfort instruments are available. In everyday indoor situations, differences in preferred temperatures are often due to clothing and activity differences between people.

Temperature and performance

Hot and cold conditions can impair the performance of a variety of activities because they decrease arousal, and several studies of heat stress conducted in tin and munitions factories have confirmed this effect. Studies in office buildings, where conditions usually are never so extreme, also have shown that changes in thermal conditions affect worker performance. People w h o are typing with no incentive or knowledge of results produce more work at 20°C than at 24°C. Thermal conditions also affect student learning and test performance. Results show that test scores are generally better at temperatures of 22-23°C than at more than 26°C (Mclntyre, 1980).

56


Ventilation and indoor air quality

Indoor air quality refers to the range and concentrations of air pollutants, either particles or gases, found in the air inside buildings. In the U S A the current A S H R A E standard sets m i n i m u m levels for these air pollutants and corresponding exposures to protect occupants' health. It defines acceptable indoor air quality as 'air in which there are no k n o w n contaminants at harmful concentrations as determined by cognizant authorities and with which a substantial majority (80% or more) of the people exposed do not express dissatisfaction' ( A S H R A E , 1989).

Since the 1970s buildings are constructed to be more energy efficient, and m a n y older buildings have been renovated to improve their energy efficiency. Workers in modern, sealed, air conditioned offices, m a y experience symptoms of the sick building syndrome* that m a y be caused by poor indoor air quality (Hedge, 1987, 1989).

Indoor air quality is influenced by m a n y factors, including outdoor air quality, ventilation system performance, building materials, technology, workers, and their activities. Indoor air pollutants can cause chronic and fatal illnesses, provoke allergic reactions, and produce eye, nose, throat and lower respiratory tract irritation.

Microbiological hazards—bioaerosols

In the U S A respiratory tract infections (mainly viral illnesses) annually account for 75 million visits to physicians, 1-25 million hospitalizations, $15 billion in direct medical costs, 150 million lost workdays, and $59 billion in indirect costs (lost income, absenteeism). But w e have a scant understanding of the relationship between the risk of respiratory tract infections and the spatial design of buildings and ventilation system performance. Three groups of microorganisms are repsonsible for most of these illnesses: viruses, bacteria and fungi.

Viruses Although they die when outside the body, respiratory tract viruses (e.g. those causing colds, influenza) are responsible for a tremendous amount of lost work time each year. People are the main source of viruses in indoor air. Recent Finnish research has found that workers in air-conditioned buildings w h o share offices are over 30% more likely to catch colds at work compared with those in private offices. Similarly, army recruits in modern air conditioned barracks are more likely to develop acute respiratory infections than those in older barracks with opening windows and mechanical air extraction only.

Bacteria People are also the main source of indoor air bacteria. These can pose two types of problem for occupants: allergy—hypersensitivity to inhaled matter of microbiological origin—and infection—an invasive growth of microorganisms in the respiratory tract. Hypersensitivity symptoms of malaise, cough and shortness of breath can be caused by contaminated humidifiers. The risks of contamination are greatest in places where there is plentiful organic dust (e.g. wood , paper or textiles). Humidifier fever is an allergic response to aero-allergens (e.g. viable cells, spores, dead cellular

* Sick building syndrome describes complaints of non-specific symptoms among building occupants, such as headaches, sore and irritated eyes, sore throats and flu-like symptoms.

57

A. Hedge

contents, and endotoxin-proteins and polysaccharides from bacterial cell walls); the symptoms are similar to influenza and they occur at the start of a week when a worker returns to work.

Legionnaires' disease is perhaps the best k n o w n bacterial problem in buildings because it can be fatal. Legionella pneumophila causes the infection, and symptoms are similar to those of pneumonia. The disease was so named because the first well documented outbreak affected a Conference of the American Legion in Philadelphia in 1976. Since 1978, there have been over 60 outbreaks worldwide of legionnaires' disease, and it kills up to 45,000 people annually in the U S A .

Fungi (moulds) There are up to 200,000 species of fungi in the world, and at least 45 species are k n o w n to cause illness. Fungi are plants that range from single cell organisms (e.g. yeast) to multicellular forms that have a body mass (mycelium), tubular filaments (hyphae), and m a n y spore fruiting bodies (sporangia). Fungi can tolerate wide climatic ranges (temperatures from — 10°C to 65°C), but only thrive when the relative humidity is around or above 75%. U p to 30% of people show allergic reactions to fungal spores, such as itchy eyes, sneezing, coughing, wheezing and shortness of breath. People can become sensitized to fungi after one large exposure, and subsequently they m a y show reactions to very low exposures. S o m e fungi (Aspergillus, Stachybotrys) produce volatile toxic metabolites (mycotoxins) that can also cause kidney and liver damage.

Dust mites

A gram of indoor dust m a y contain over 10,000 microscopic insects known as dust mites. These mites feast on the 50 million dead skin scales that each of us sheds each day. Some 10-15% of people in the U S A are allergic to dust mites, especially their faeces that are to be found in carpets and other material surfaces. Mite faeces have a tough membrane and their allergy-causing potential can remain in a carpet or other material surfaces for months. O n e square metre of material in a building can contain between 1000 and 10,000 mites. Mites cannot survive at humidities below 50%. Keeping air to 21 °C and maintaining humidity below 50% will control them, but as the temperature rises so the relative humidity has to be lowered to prevent mite growth.

Respirable particulates/fibres

M a n y building materials and furniture products shed mineral fibres and particulates into the indoor environment. S o m e of these mineral fibres, such as asbestos, can cause lung disease, both a type of pneumoconiosis (asbestosis), and mesothelioma (lung cancer). In the U S A an estimated 733,000 commercial buildings and 30,000 schools built before 1970 have asbestos in them. Major programmes for its controlled removal are currently underway. Other mineral fibres of interest include fibreglass and 'slag wool', which are mucous membrane irritants (of eye, nose and throat). They also can cause skin rashes and itching, especially among computer workers, because electrically charged visual display units ( V D U s ) tend to attract these irritants. Irritating fibres can be present in acoustic ceiling tiles and moveable office partitions, and m a y be the cause of some cases of the sick building syndrome.

58


Volatile organic chemicals

Buildings can contain m a n y volatile organic chemicals (VOCs) emitted from construction materials, furniture products, office technology, cleaning agents, smoking, etc. The health effects of m a n y of these V O C s are unknown. Studies of emissions from building products report that over 80% of V O C s are eye irritants, and about 30% are suspected carcinogens. Considerable research on the effects of prolonged exposure to low levels of V O C s on health and performance is being conducted in several countries.

Formaldehyde is perhaps the best studied V O C in indoor air. It is a colourless gas with a pungent odour. People can become sensitized to formaldehyde, and toxicity occurs through contact with skin and mucous membranes (eyes, nose and throat). Exposure can induce fatigue, m e m o r y lapse, headache, difficulty in sleeping, respiratory problems (including asthma), eventually chronic respiratory disease and possibly nasal and respiratory tract cancers.

Radon and radon decay products

Radon is a colourless, odourless gas that is radioactive. As it decays it emits radiation. Inhalation of radon can lead to lung cancer; after cigarette smoking, it is the greatest cause of lung cancer in the U S A , accounting for some 20,000 deaths per year.

Recent developments in building ventilation

Office workers rank ventilation as being very important. Current standards propose stepping up the ventilation rate as a means of increasing the dilution of pollutants. T w o other strategies also work with dilution ventilation: source control and breathing-zone iillration. Source control means restricting, removing or encapsulating pollution sources. Breathing-zone filtration (BZF) recirculates air wilhin a person's breathing zone (the air layer 0-75-2-0 m above floor level). This air passes through mechanical filters to remove particulates, and a sorbent filter to remove V O C s . B Z F systems deliver localized air filtration in each worker, providing a continuous supply of clean air (Hedge, Martin and McCarthy, 1991).

Light, vision and glare

The development of electric lighting has forever freed us from the restraints of daylight and the limitations of candles and oil lamps. Electric lighting allows us to continue daytime activities well into and sometimes even through the night hours without adversely affecting our visual abilities. Six factors are important in the creation of lighting that is appropriate for the visual demands of the work (Boyce, 1981):

• Contrast the relationship between the luminance (brightness) of an object and the luminance of the background. These luminances can be affected by location of light sources and reflectance of room surfaces.

• Size the larger an object, the easier it is to see. The size of the image on the retina is important, not the size of the object. W h e n w e bring smaller objects into closer focus w e can see finer details.

59

A. Hedge

• Time there is a time lag in the photochemical processes of the retina, therefore the time available for viewing is important. W h e n objects are briefly seen w e need bright light. W h e n ample time is available fine details can be seen at lower illumination levels.

• Luminance the amount of incident light available for seeing. Illuminance levels (i.e. the amount of light falling over a unit area) affects the luminance of the task.

• Colour this is not really a factor by itself, but it relates both to contrast and luminance because the eye is not equally sensitive to all wavelengths.

• Visual acuity the structural anatomy of our eyes. The cornea is the major refracting (i.e. light bending) component, giving the eye about 70% of its resolving power. The crystalline lens provides the remaining 30% resolving power. This lens changes in curvature (accommodation) to alter refraction and focus light onto the photoreceptive retina. T h e fluid-filled compartments of the eye, the aqueous humour and vitreous humour , serve to provide nutrients to the nonvascular structures within the eye and to maintain its shape.

Visual processes

The retina has two types of visual receptor: about 130,000,000 rods and about 7,000,000 cones, only the latter being concentrated in the fovea, which is our region of greatest sensitivity and acuity. These receptors operate under different lighting conditions: photopic conditions (cone vision)—when light is plentiful our visual acuity is high and w e can see colours; and scotopic conditions (rod vision)—when light is scarce our visual acuity is low and w e cannot discern colours. Because of this there is an adaptative delay in moving from light to dark (slow) or vice versa (fast). Partial adaptation occurs if the visual field contains bright or dark areas. Placing a V D U screen either facing or backed up against a bright background, such as a window, is not recommended because of partial adaptation. This increases the chance of visual fatigue over the work day. For visual information displays all surfaces within visual field should be of same order of brightness, and the general level of illumination should not fluctuate rapidly because full adaptation is a slow process.

Effects of ageing on visual performance

The transmittance of the various components of the eye (i.e. the amount of light transmitted at various wavelengths) varies with age. In young eyes 70-85% of white light reaches the retina. The cornea absorbs most of the radiation less than 300 n m . The lens filters out wavelengths of less than 380 n m . The retina responds to wavelengths between 380 n m and 950 n m . In the visible range (380-770 n m ) the eye transmits more red light (longer wavelength) than blue light. In old eyes there is reduced transmittance of the crystalline lens to all wavelengths, especially shorter blue wavelengths. Other effects of ageing on visual abilities include a decreased ability to focus on close objects, and to adapt to dark and light. Sensitivity of the retina, especially at low luminances, also decreases, and scattering of light within the eye increases. There is a narrowing of spectral (colour) range of sensitivity due to yellowing of the lens. Most Western countries have ageing workforces, and urgently need to attend to the changing lighting provisions in our workplaces to better support the visual abilities of older workers.

60


Lighting, VDU work and eyestrain

Workers, particularly those using computers, m a y experience two types of glare. Disability glare is direct glare from a bright light source, such as direct sunlight through a window. Discomfort glare is indirect glare from uncomfortably bright reflections, such as specular reflections of ceiling light fixtures in a computer screen. Such screen reflections can be a source of distraction, discomfort and eyestrain. Computer use in offices has increased greatly over the past decade, as have concerns about the effects of inadequate office lighting for computer work. A recent national survey found that 85% of U S office workers use a personal computer at work. Ninety-two percent of workers rated proper lighting as being very important, but only 6 4 % said that they had proper lighting. Forty-seven percent reported that eyestrain was a serious problem (Harris and Associates Inc. 1991). Several lighting solutions are available for computerized offices. Field studies have found that computer workers report fewer complaints of eyestrain and eye focussing problems, greater satisfaction, and express strong preferences for lensed-indirect uplighting compared with parabolic-lensed downlighting (Hedge, 1991). The effectiveness of other lighting systems and glare solutions on eyestrain complaints remain to be tested.

Acoustics: our noisy world

Every element of building design and construction affects the acoustic environment. Acoustic principles should influence the choice of finish materials in rooms, the location of these materials in a building and the building design, though they seldom do.

Noise

Noise is 'unwanted sound'. Noisiness is the subjective impression of h o w annoying the sound is. Generally w e distinguish two types of noisiness: unwanted sound that carries information about the sound source that signifies unpleasantness (e.g. crying baby), and unwanted sound that is annoying because of its sheer loudness, not its meaning (e.g. machine noise). Higher-frequency sounds are more annoying than low-frequency sounds of the same loudness (Kryter, 1985).

Occupational noise

Like other types of noise (e.g. that of traffic or aircraft), occupational noise has increased in intensity in the last 30 years. Sources of industrial noise include vibration of structures, machines or their components, as well as aerodynamic turbulence (e.g. sound produced by the contact of a high-speed, high-pressure air jet with surrounding air). Industrial plants typically transmit noise to the external environment via certain sources or routes (e.g. open windows, roof ventilators, steam injectors, compressors and diesel engines). Planning regulations have reduced the impact of noise-generating industries on m a n y residential areas. However, indoors in manufacturing industries

61

A. Hedge

80% of noise levels exceed 80dB(A) and 20% exceed 95dB(A). Exposure to noise this loud can cause hearing loss (i.e. physiological deterioration of hearing due to destruction of hair cells in the Organ of Corti, and decreased number of associated nerve fibres). Exposure to uncontrollable and unpredictable noises can also have stressful after-effects on behaviour.

Acoustics and privacy of speech

A major problem in the design of m a n y modern office buildings is the lack of adequate speech privacy. This is particularly acute in open-plan offices, where noise sources include telephones, typewriters, printers/photocopiers, environmental services (e.g. air conditioning) and conversation. The problem of speech privacy concerns the intelligibility of the encroaching sound. Intelligible speech occurs in the 2,000-4,000 H z range (the full speech range being 100-8000 Hz) , irrespective of gender, although w o m e n tend to have voices one octave higher than m e n . There are two ways of overcoming the privacy problem. Asking workers to speak more quietly or increasing the sound absorbance of room surfaces reduces signal strength. Installing a sound masking system adds background 'white' noise to the setting which lowers the signal-to-noise ratio.

Electromagnetic fields

Recent evidence suggests that there m a y be a link between health and electromagnetic fields (EMFs) . Such fields emanate from power lines and from appliances such as electric blankets, microwaves and T V s , and have been implicated in increased risk of nervous system cancers and leukemia (Nair, Morgan and Florig, 1989). E M F s m a y affect the electrical potential at cell membranes, which in turn influences biochemical processes that m a y indirectly stimulate cancer growth. Research findings on the effects of E M F s from household appliances on h u m a n health are conflicting. However, there is a growing concern over the possible health effects of exposure to E M F s emanating from computers. Placing a computer on a non-conducting surface, such as a wooden table, and keeping the screen and systems unit at least at arm's length away from the body will lower the field strength to a level that m a y not pose a risk. Placing a computer on metal or metal-frame furniture m a y amplify the field strength because of induction. Whether E M F s really pose a serious health risk in these situations needs to be tested in carefully controlled studies.

Workplace design: the need for integration

In the past decade the office has become the workplace for most people. The widespread use of computers and the growth in the white-collar workforce has stimulated research on office design (Hedge, 1986). Office buildings are costly to rent, buy or construct, and maximizing the efficiency of space use is an economic necessity. In addition to traditional private offices, several alternative space layouts have become increasingly popular, including group offices, shared offices, and open-plan systems offices.

62


Poorly designed open-plan offices can create problems with visual and aural privacy, noise and other disturbances, and these problems reduce productivity and job satisfaction. Poorly designed office environments are more stressful for workers. Well designed offices have efficient, flexible layouts, provide good ambient conditions and satisfy the personal requirements of workers.

In modern design practice, architects, interior designers, engineers (ventilation, illumination, acoustics) and ergonomists all separately contribute to workplace design. Unfortunately, this piecemeal approach to workplace design often fails to produce a better environment. The result of this lack of coordination and integration of knowledge is the epidemic of health problems caused by poor workplace design that are n o w afflicting m a n y workers.

Ergonomists are skilled at developing and applying systems models which depict the interactions between users, technology and the user-technology interface, and the ways in which these determine overall system performance. The same logic has been applied to formulating a holistic systems approach to the interactions between people, organizations and the built environment (Hedge, 1989), but further development of this approach is needed.

Conclusions: the decade of the environment

W e are living in the decade of the environment, and ecological ergononics has an important contribution to m a k e to improving the design of work environments. A comprehensive systems approach to work settings can integrate diverse research, and help predict h o w best to create healthy and productive conditions for workers in a variety of settings. The development of this approach should have a high priority, but it is not an easy undertaking because historically there are no well established communication channels between the m a n y different disciplines involved in environmental design. This limitation, coupled with the complexity of the factors affecting worker's health, comfort and productivity, m a y be the most daunting obstacle to the maturation of this field. Although in its infancy, ecological ergonomics will play an increasingly important role as organizations strive to improve the quality of work environments, and as societies aspire to spread the mark of h u m a n influnece into ever more remote and hazardous places on and beyond the earth. •

References A S H R A E (1981). Standard 55-1981: Thermal environmental conditions for human occupancy,

American Society of Heating, Refrigerating and Air-conditioning Engineers, Inc., Atlanta, USA.

A S H R A E (1989) Standard 62-1989: Standard for Ventilation for Acceptable Indoor Air Quality. American Society of Heating, Refrigerating and Air-conditioning Engineers, Inc., Atlanta, USA.

B O Y C E , P. R. (1981) Human factors in lighting, Applied Science Publishers, London. F Ä N G E R , P. O . (1970). Thermal comfort. McGraw-Hill, N e w York. H A R R I S , L. and ASSOCIATES, I N C . (1991). The Office Environment Index, Steelcase, Inc., Grand

Rapids, U S A . H E D G E , A . (1986) Open versus enclosed workspaces: the impact of design on employee reactions

to their offices. In Wineman, J. Behavioral issues in office design. Van Nostrand Reinhold, N e w York.

63


H E D G E , A . (1987). Office health hazards: an annotated bibliography, Ergonomics, 30, 733-72. H E D G E , A . (1989). Environmental conditions and health in offices, International Reviews of

Ergonomics, 3, 87-110. H E D G E , A . (1991). Healthy office lighting for computer workers: a comparison of lensed-indirect

and direct systems, Healthy Buildings—IAQ '91, A S H R A E , Atlanta, U S A , pp. 61-6. H E D G E , A . , M A R T I N , M . G . , and M C C A R T H Y , J. F. (1991). Breathing-zone filtration effects on

indoor air quality and sick building syndrome complaints, Healthy Buildings—IAQ '91, A S H R A E , Atlanta, U S A , pp. 351-7.

ISO (1984). International Standard 7730. Moderate Thermal Environments—Determination of PMV and PPD indices and specification of the conditions for thermal comfort, International Standards Organization, Geneva, Switzerland.

K R Y T E R , K . D . (1985). The effects of noise on man, Academic Press, N e w York. M C I N T Y R E , D . A . (1980). Indoor climate, Applied Science Publishers, London. N A I R , I., M O R G A N , M . G . and F L O R I G , H . K . , (1989). Biological effects of power frequency electric

and magnetic fields—background paper, U S Congress, Office of Technology Assessment, O T A - B P - E - 5 3 , U S Government Printing Office, Washington D C .

64

Ergonomics of human-computer interaction

Martin G . Helander and Thiagarajan Palanivel

Whereas ergonomists have traditionally concerned themselves with anthropometric design, work posture and visual performance, the introduction of computers into the work situation has led to increasing emphasis being put on human information processing and cognition. It is in this context that the subjects of workstation, hardware, interface and software design are addressed.

Since the beginning of the 1970s, a large volume of research has been published on ergonomics design of computer systems (Helander, 1988). At first, research focused on computer programming: h o w can programming be m a d e easier, h o w can the task be structured, and what are the characteristics of programming languages that are easy to use? This primarily addressed sophisticated users. During the later part of the 1970s research focused on hardware design aspects such as workstation design and screen image quality. During the eighties, with the increasing proliferation of personal computers, the focus has been on less sophisticated, casual users; h o w to design a computer interface that is easy to use, h o w to present information on the screen and format the language used for computer input. According to the U S Bureau of Census in 1989,46% of children and 28% of adults regularly used computers, and almost 15% of American households had a computer. T h e challenge for software and computer companies is to design a human-computer interface that can be used by a variety of individuals, including computer specialists, P h D s , high-school dropouts, and housewives. Changes in the age-pyramid have also prompted interest in the older user in order to understand whether possible changes in abilities to process information affect

Dr. Martin Helander is an Associate Professor at the Department of Industrial Engineering at the State University of N e w York at Buffalo, U S A . H e has dual degrees in Engineering and Psychology, and his research interests include human-computer interaction, ergonomics in manufacturing, and safety. H e is a Fellow of the H u m a n Factors Society and the Ergonomics Society. In addition, he is a m e m b e r of the Executive Committee of the International Ergonomics Association and he is the Chair of the U S Technical Advisory G r o u p to ISO/Technical Committee 159 (Ergonomics). H e is an editor of Ergonomics.

M r . Thiagarajan Palanivel is a P h D candidate at the same department. H e has a Bachelor's degree in Engineering and an M S degree in Operations Research. His interests include human-computer interaction, occupational safety, and industrial ergonomics. H e currently serves as an ergonomics consultant to several companies.

The authors' address is: Department of Industrial Engineering, State University of N e w York at Buffalo, 342 Bell Hall, Buffalo, N Y 14260, U S A .


M . G . Helander and T. Palanivel

computer usage. T o summarize, hardware design dominated research at first but the focus is n o w on interface design and ease-of-use of software. This is also a selling argument for manufacturers. However, research has not been very helpful for innovations. The Direct Manipulation Interface, used by Apple, (originally developed by Xerox) or Microsoft Windows , were based on assumptions of what is easy to use, although there was no supporting research. M u c h of the research in the cognitive area (human information processing) has had a flavour towards traditional experimental psychology rather than computer-oriented psychology, which has made it difficult to formulate valid design principles (Carroll, 1991).

In this article w e will review the development of ergonomics standards, and research on design of visual display terminal workstations and the human-computer interface.

Development of standards

This interest in standards started in Europe around 1970 and later spread to the U S A and Japan (Helander and Rupp, 1984). Early standards primarily addressed the physical attributes of workstations, including glare on the screen, image quality and appropriate work posture. Unfortunately, the ambitions to standardize were often governed by political ambitions rather than available research. As a result different standards were produced in different countries. S o m e interesting controversies centred on the amount of allowable luminance contrast between darker and lighter areas at a workstation. A n early G e r m a n standard specified an allowable contrast ratio of 1:3, which had the (perhaps unfortunate) implications of making all terminals light grey, since black, white and saturated colours would not fit into the allowable range. Scientists consider this too strict—a ratio of 1:20 is more reasonable. Equally contested was the G e r m a n assumption that typists prefer to type with a 90-degree elbow angle and with the forearms horizontal. This led to the development of the thin profile keyboard, and limitation of the thickness of the table top to 3 cm. Later research has proven that 90^70-degree elbow angle is more reasonable, implying that keyboards can be thicker. Nonetheless, the thin keyboard is a good feature, because it allows more freedom in anthropometric design, although the original argument was misleading.

V D T workstation design has also been a topic of union-management negotiations. O n e company in the U K , negotiated a standard for 'refresh-rate' of the screen to avoid visible flicker. Union leaders advocated 60 H z and management 50 H z and they compromised at 57-5 H z , obviously unaware of the restrictions in technology (Helander and Rupp , 1984).

O n e important issue for standardization has been screen radiation. Most ergono-mists would agree that the amount of X - , infra- and other radiation is well below allowable limits. Yet the concerns keep cropping up in different countries, and they re-emerge. For example, in Sweden the issues of radiation were put to bed jointly by the government and union leaders around 1980. Around 1982 the issue exploded in the U S and as a result re-emerged in Sweden around 1984. The discussion today focuses on electromagnetic radiation. The main problem is that there m a y indeed be a fair amount of electromagnetic radiation, but the physiological effects, if any, are unknown.

In the United States there have been two recent standards for V D T workstations, the San Francisco Ordinance and the N e w Jersey P E O S H Guidelines. Both deal

66


primarily with the physical anthropometric design of workstations and chairs. Several of the recommendations are based on myths about desirable design features, rather than research. The benefits of a lumbar support rests on the assumption that users generally sit straight up in the chair (which is doubtful) and that sitting up straight is the preferred posture (which it probably is not). However, even more basic is the fact that there are no measurements of lumbar height published in the open literature. It is important that ergonomics standards and guidelines rest on research of good quality. There are m a n y holes in our knowledge and m a n y standards are yet premature.

The International Standardization Organization (ISO) and the European c o m munity have organized an impressive schedule for standards development to unify regulations throughout the European Communi ty by 1992. The I S O 9241 standards series will be published in 20 parts covering V D T workstation design as well as interface design. The quality of the I S O 9241 standards that have been published so far is high, as judged by international consensus.

D u e to the proliferation of computers and the simultaneous change in working procedures, several governmental agencies have taken an interest in the development of guidelines. In Europe, computer integrated manufacturing has been supported through the E S P R I T project, and in the United States m u c h activity is sponsored through the Department of Defense and the Nuclear Regulatory Commission. The European efforts have centred more on operator job satisfaction and in the United States the focus has been on operator performance and error. Both approaches fall back to the same basic concern; ease-of-use of computer systems, user acceptability of innovations, and ease of training are paramount.

Research on hardware and software

There are three primary interests in human-computer research: workstation design and computer hardware, interface and software design, and organizational design including job satisfaction (see Table 1). This article is limited to the first two issues, which have been dealt with by ergonomists.

Workstation design

There are three main features of computer workstations that make them potentially different from regular work: static work posture, use of computer input devices and poor visibility of the screen.

Table 1.

Three main research areas in human-computer interaction.

Area

Workstation design and computer hardware

Interface and software design

Organizational design and job satisfaction

Research disciplines

Anthropometry Biomechanics Perception and vision Cognition Perception Organizational psychology Motivation Anthropology

67

M. G. Helander and T. Palanivel

With regular paperwork, the location of papers on the desk change continually and so does the work posture. Visual display terminals (VDTs) force a static work posture which m a y impose biomechanical strain resulting in aches and pains. M a n y studies have been performed with the objective of identifying biomechanical stressors, but the results have not been clear-cut, primarily due to methodological difficulties.

Typically, researchers have compared operators at V D T workstations to a control group of operators at regular workstations. Questionnaires are used to identify body pain syndromes. The main difficulty has been to identify control groups that are equal in all other (i.e. n o n - V D T ) respects, including the task and operator characteristics, such as educational background. Only a few studies have managed to obtain unbiased comparisons. Starr (1984) at Bell Laboratories compared telephone directory assistance operators working either at V D T s or with telephone books. There were surprisingly no differences in the frequency of muscular pain, visual fatigue or headaches. S o m e researchers have implied that the greater amount of complaints associated with V D T work m a y be due to psychological strain rather than the task itself. Thus the introduction of V D T s m a y be taken as a legitimate outlet to voice complaints that in reality m a y be unrelated to V D T s .

With the improvement of computer technology, the physical design of the workstation has also become increasingly sophisticated. In the last ten years 'ergonomie' chairs and height-adjustable workstations have become standard items. O n e should note that 'ergonomie' chairs are not necessarily better; it has not (yet) been proven that they reduce back injuries, shoulder pain and repetitive motion trauma. They are primarily high-tech, and usually afford adjustability of seat height, back-rest angle, seat-pan angle, lumbar support height, and back-rest spring tension. These features m a y be difficult to use, since most operators have little knowledge of what constitutes a desirable working posture. 'Sit up straight'—a c o m m o n parental exhortation—is not necessarily good. In fact, leaning the back-rest to 30 degrees from the vertical will reduce the pressure on the spine by about 30%, but m a y not be considered good manners. In the future, chairs and conventions will probably change to allow a more reclined posture.

The natural (relaxed) viewing angle is about 25 degrees below the horizontal (see Figure 1). This recommendation is particularly important for older workers w h o use bifocals. The lower part of bifocals are typically ground for a viewing distance of 50 c m (20 in.) and the upper part for 500 c m (200 in.). A high location of the screen will then force the operator to bend his/her head backwards to view the screen. This causes discomfort and pain in the neck and shoulders.

Height-adjustability of chairs and desks are desirable features, and they are particularly important for workstations used by operators of different body sizes, such as in shift work (see Figure 1).

Screen visibility depends on several factors: image quality, the type and location of illumination sources, and the use of anti-glare filters. The image quality is primarily a function of character luminance, the luminance contrast ratio of characters against the background, and character resolution. T h e character luminance should be greater than 35 cd m ~2. This specification is difficult to measure, since a photometer with a micro-slit is required. However, most modern screens are well above 35 cd m " 2 unless a very dark screen filter is used. Screen filters, such as polaroids and neutral density filters enhance the character-to-background contrast. The light from luminaries and windows is filtered twice—first before it falls on the screen and later after it has been

68


Figure 1.

Adjustability mechanisms in computer furniture. Adapted from Kroemer (see Helander, 1988)

fâji^àzjijx.

reflected from the screen. The light from the character, however, is filtered only once. This increases the contrast between characters and screen background and enhances visibility.

In general, illumination washes out the contrast on the screen. The best viewing condition (contrast) would be a pitch dark room. However, this is not socially acceptable nor practical. M a n y standards specify an ambient illumination level of 300^500 lux as a compromise to retain image contrast while at the same time enhancing visibility of printed source documents. The ambient illumination m a y be complemented by task illumination, which is directed at the source documents.

In the early days of personal computers, regular T V sets with poor resolution were often used. The American A N S I standard for V D T workstations specifies a m i n i m u m resolution of 7 x 9 dots for generating characters ( H u m a n Factors Society, 1988). T o enhance readability there should be no visible empty spaces between the dots; the characters should resemble regular stroke fonts.

Computer operators frequently complain about visual fatigue, a concept that for the scientific community has been impossible to define and measure. Poor image quality m a y , of course, be annoying and distracting, but m a y not necessarily fatigue the visual system (National Academy of Science, 1983). Several studies have compared visual fatigue for V D T operators performing different types of tasks; those w h o perform data input complain the most. However, these are the operators that view the screen the least—they mostly look at the source document. Complaints of visual fatigue m a y therefore be taken as an indication of general fatigue. Data input is indeed a demanding task; m a n y operators input more than 100,000 characters per day.

Input devices

A variety of input devices m a y be used to control the cursor on the computer screen; mouse, joystick, trackball, keyboard cursor control keys, touch pen, touch screen and graphic tablets are all well established. S o m e novel devices include the foot mouse, eye-controlled input, and gesture-based input using a data glove. The efficiency and practicality of input devices depend on what task they are used for and the environment in which they are used. A large number of scientific studies have been performed to compare the effectiveness of input devices (Greenstein and Arnaut, see Helander, 1988). Tasks that focus primarily on pointing at or selecting from stationary targets on the screen, such as m e n u and text selection, are best performed with direct pointing devices such as touch screen or light pen. This is due to 'directness' of pointing with a high degree of eye-hand coordination.

69

M . G. Helander and T. Palanivel

If a separate confirmation action is required, a mouse m a y be more effective than the direct devices. A confirmation button can be located underneath the fingertips resting on the mouse, so that little additional movement is required.

A m o n g the indirect pointing devices, the mouse , the trackball and the graphic tablet do not differ greatly in positioning speed or accuracy. For stationary targets, these devices are faster than the joystick. The principal advantage of the graphic tablet is its flexibility. It can emulate the functionality of other devices and it is used most effectively for drawing and tracing tasks. W h e n choosing a m o n g these three devices for a particular application, it is likely that the overall fit to the task and the environment is more relevant than differences in speed and accuracy.

For targets that m o v e rapidly and change direction frequently, such as military targets, a spring-loaded joystick or a trackball m a y be faster than other devices since they only require movements of the fingers.

Computer interface design

W e consider performance on computers to be the result of interaction between the h u m a n operator and the processing apparatus of the computer. The primary factor affecting performance is the efficiency of the communication between the user and the computer's processor. This role is filled by the computer interface. If the user can consistently convey his or her intentions in a form that the computer can understand, and if the computer can always present information to the user in a format that he or she can understand, there is total, unambiguous communication, and the system as a whole is operating at m a x i m u m performance.

Typically, this is not the case; computer software is difficult to design and difficult to use, Figure 2 illustrates that software programs m a y be viewed as abstract representations of the real world. The use of a spreadsheet program such as Lotus 1-2-3 is not obvious, and to those w h o implement and use the system it m a y be difficult to justify, since it is far removed from the real world. This makes it difficult for the operator to validate results and initiate action. It m a y also lead to dissatisfaction with the job, since operators m a y not understand the implications of their work.

Traditionally, in interface design, w e are mostly concerned with the last stage in Figure 2, the human-computer interface. T h e guidelines of Smith and Mosier (1986) offer m a n y practical suggestions. There are several important design principles for interface design: understandability of dialogue, formatting and layout of information

C o m p a n y Translation Accounting Translation Spreadsheet Translation Computer Lotus 1-2-3

Representation of The real world Representation of Representation spreadsheet

state ol company of accounting Assumptions about input and output

Figure 2. The computer operator is three times removed from the real world. Several abstract representations accumulate to m a k e it difficult to initiate actions and validate results.

70


o n the screen, consistency in dialogue, user feedback and tolerance to errors in operator input (see Figure 3).

T h e understandability of the dialogue has to d o with clarity of language, symbols, icons and so forth. M u c h research has been devoted to choice of c o m m a n d names and abbreviation of c o m m a n d names . O n e of the m o s t consistent research findings has been that people n a m e functions or operations differently. O n e study found that an individual m a y use over 15 different strategies for naming a computer file. Meaningful c o m m a n d n a m e s are helpful. Howeve r , the effect on operator performance is fairly minor, at least for a small set of c o m m a n d n a m e s .

There are several strategies for abbreviation of c o m m a n d n a m e s :

(a) Phonetic strategy: A P N D would be the abbreviation of A P P E N D . (b) Contraction—retaining first and last letters: E X T E w o u l d imply E X E C U T E . (c) Vowel deletion: R M V stands for R E M O V E . (d) Truncation—using the m i n i m u m number of letters in the beginning of the

word: O P would m e a n O P E R A T E .

Although some research studies seem to favour truncation, the most important issue is consistency: use only one method.

The best formatting and layout of information on the screen depends on task characteristics. A good start is to perform a task analysis to understand what type of information users need, in what sequence the information should be given, and what information the user must input. T o carry out a task analysis, direct observation of the operator is useful, as are questionnaires a n d interviews. Estimates of frequency of use of different subtasks and criticality of use are also helpful. A study performed by Tullis at Bell Laboratories (see Helander, 1988) investigated the effects of redesigning a screen used for fault-diagnosis of telephone lines. T h e n e w screen reduced the time for fault identification from 8-3 to 5-0 seconds, which saved A T & T about t w o man-years of w o r k per year.

Other important design issues include the definition of standard screen areas a n d typography such as message areas, m e n u areas a n d status areas, standard use of icons, text fonts a n d colours. Several r ecommenda t ions are available (see Smith and Mosie r , 1986). Again , consistency in screen design is p a r a m o u n t .

These principles can be implemented at a n early stage of system development b y using rapid prototyping. This is a technique where the intended system can be simulated (on a computer) without full computational functionality. User interaction is

Memory limitation Cognitive style Previous experiences Formation of mental model

Evaluation Decision-making

Figure 3.

Design principles for the human-computer interface.

Understandability Formatting and layout Consistency in dialogue User feedback Error tolerance

Required action

71

Ai. G. Helander and T. Palanivel

observed and the effect of design changes can be explored. Typically the design is then modified in an iterative fashion to minimize performance time and operator errors.

Consistency in dialogue design has already been mentioned. The cost for failing to provide consistency can be very high. O n e study at the I B M Corporation showed that inconsistencies in the position of m e n u resulted in a 73% increase in search time. The consistency principle strongly suggests that previous experience with similar systems should simplify use rather than m a k e it difficult to learn a new system.

Feedback should be provided to the user, with respect to both the user's performance and status of the computer. Users should at all times be aware of where they are, what they have done and whether or not their action was successful. With feedback users can correct errors and it will take less time to learn the system and develop a mental model of the system.

S o m e recent developments have explored the possibility of intelligent help systems. This implies that the computer keeps track of frequent errors of individual users. It is then possible to tailor the help information to fit the level of expertise. A very experienced user m a y be helped by short abbreviated error messages and codes, while the inexperienced user requires complete explanation.

Error tolerance is somewhat related to intelligent help. The principle here is that computers should not require any specific format without good reasons. For example, upper or lower case characters, punctuation, or spaces in c o m m a n d language m a y seem arbitrary to the casual user— and should be avoided. Likewise, computers should tolerate spelling mistakes of c o m m a n d names and suggest most likely alternatives.

O n e helpful feature is the U N D O c o m m a n d , whereby operators can step back to the previous screen. This encourages users to explore options without penalty and they learn the system faster and with less stress.

There are several limitations in h u m a n information processing which must be considered when formulating design principles: limitations in short-term m e m o r y , cognitive style, previous training, and formation of mental models (see Figure 3).

The short-term memory is limited to about seven chunks of information. Chunks m a y be words, concepts or characters depending upon h o w the information is presented. Thus, for example, IBM, UPS, and N R C are three corporations well k n o w n in the U S A and hence constitute three chunks; presented as C R N S P U M B I they represent nine chunks, which just about exceeds the short-term m e m o r y capacity. The challenge is hence to form large chunks in the design of screens and dialogue sequences. This can be done by bringing together entities that belong together, or by using symbols, concepts or metaphors. The desk-top metaphor touted by Apple Computers simplifies chunking, since it relies (partly) on a familiar scenario.

Cognitive style implies that users are different. In fact, there are vast differences in performance between different computer operators. Eagan (see Helander, 1988) noted that for manual tasks such as factory assembly, performance differences between a fast and a slow operator are usually not greater than 50%. In operation of computers there m a y be differences of 500%. Thus intellectual capabilities are very critical to task performance. T w o aspects seem to be particularly important: spatial m e m o r y (measured by the ability to memorize items on a m a p ) and logical reasoning. The challenge is then to design computer systems which do not require spatial m e m o r y or logical reasoning.

T o some extent the direct manipulation interface, first implemented by Xerox and later by Apple, m a y fill the ticket. Direct manipulation interfaces use large size, high-

72


resolution, bit-mapped displays which m a k e it possible to visualize m a n y features at the same time. The principle is that all objects (icons or c o m m a n d names) are visible on the screen and can be directly manipulated by pointing and dragging. In reality there are usually several indirect (non-visible) features present, for example c o m m a n d words hidden in pull-down menus.

Previous experiences and training are helpful in understanding new systems, particularly if the new system is similar to previously used systems. Software designers can then capitalize on 'transfer-of-training' effects from one system to another.

Related to this issue is the formation of mental models. A n interface that is consistent with user expectations will simplify the formation of a mental model. A mental model need not be elaborate or complete as long as it is helpful to the user. In fact, it is advantageous to let users form simplified models that can expand with increasing experience. In the 'training-wheels' approach advocated by John Carroll at I B M , sophisticated features of a word processing program are hidden until the user can manage the fundamentals (see Helander, 1988).

O n e major concern in the formation of mental models is that the programmer responsible for development of the software must resist the temptation to impose his/her o w n mental model or assumptions of what the users mental models m a y be. Such issues should be left to the expert—the ergonomist, w h o can observe real users with the system.

Conclusion

As ergonomists, our goal is to influence the design of man-machine systems so that h u m a n capabilities and limitations are considered from the early stages of the design process, and are accounted for in the final design. O u r knowledge, and our experience, show us that a design that considers such issues will result in an optimal system than enhances productivity, safety and job satisfaction. The rapid development of technology has had a great impact on the role of humans in systems. F r o m our perspective, this has meant an increasing emphasis on h u m a n information processing and cognition. W h e r e w e once concerned ourselves almost exclusively with issues such as anthropometric design, work posture and visual performance, w e are n o w forced to consider issues such as information-processing capacity and problem-solving abilities. This article has pointed to some of the important research results and controversies in ergonomie design of computer systems.

References

C A R R O L L , J. M . (1991) Designing Interaction. Psychology at the Human-Computer Interface. Cambridge University Press, Cambridge & N e w York.

H E L A N D E R , M . G . (1988) Handbook of Human-Computer Interaction. North-Holland, Amsterdam, Netherlands.

H E L A N D E R , M . G . and R U P P , B . (1984) An Overview of Standards and Guidelines for Visual Display Terminals. Applied Ergonomics, 15, 185-95.

H U M A N F A C T O R S S O C I E T Y (1988) ANSI/HFS 100. Standard for Design of Visual Display Terminal Workstations. The H u m a n Factors Society, Santa Monica, C A .

73


N A T I O N A L A C A D E M Y O F S C I E N C E (1983) Video Displays, Work and Vision. National Academy Press, Washington, D C .

P A L A N I V E L , T . and H E L A N D E R , M . (1991) H u m a n Factors Issues in Dialog Design. In M . Yovitz (ed.), Advances in Computers, vol. 33. Academic Press, Boston, M A .

S M I T H , S. L. and M O S I E R , J. N . (1986) Guidelines for Designing User Interface Software. M I T R E , Bedford, M A .

S T A R R , S. J. (1984) Effect of Video Display Terminals in a Business Office. Human Factors, 26, 347-56.

74

The relationship between humans and industrial robots

Waldemar Karwowski

In the pursuit of greater productivity and higher quality standards many manufacturing industries are turning to automated machines and in particular robotic workstations. Safety and health professionals are increasingly concerned over the hazards associated with these complex, non-traditional sytems, and whilst in the past robot design was studied from the purely mechanical standpoint, the need now is for more research on human-robot interaction in the workplace.

Over the last twenty years there has been a significant increase in the development and implementation of both industrial- and service-oriented robot systems. A robot has been defined by the Robot Institute of America (1982) as 'a reprogrammable, multifunctional manipulator designed to m o v e materials, parts, tools, or special devices through variable programmed motions for the performance of a variety of tasks'. The application of robots has had a phenomenal growth of almost 40% since they were first commercially installed by the Planet Corporation in 1959. The U S A had witnessed the installation of some 100,000 robots by 1990, and there is likely to be an acceleration in the trend with the improvement of robot technology. By comparison, it had been expected that more than 550,000 robots would be introduced by the same year in Japan.

In m a n y cases, the application of industrial robots can lead to improvements in working conditions, reduction of hard physical work, and the liberation of workers from monotonous and environmentally stressful jobs. Robots, however, constitute complex systems which are potentially hazardous to humans, not only in faulty operation, but also in the normal operating m o d e . Therefore, even though robotics is a

Waldemar Karwowski is an Associate Professor of Industrial Engineering and Director of the Center for Industrial Ergonomics at the University of Louisville. H e holds an M . S . (1978) in Production Engineering and Management from the Technical University of Wroclaw, Poland, and a P h . D . (1982) in Industrial Engineering from Texas Tech University. H e is a senior m e m b e r of the Institute of Industrial Engineering and Society of Manufacturing Engineers, and a m e m b e r of the H u m a n Factors Society, Ergonomics Society, American Industrial Hygiene Association, and Tau Beta Pi. H e is the author or co-author of over 100 publications, including editorship of 15 books. D r Karwowski serves as Editor of the newly established International Journal of Human Factors in Manufacturing and is the Founder and General Chairman of the biennial International Conference on Human Aspects of Advanced Manufacturing and Hybrid Automation. H e was a Fulbright Scholar and Visiting Professor at Tampere University of Technology in Tampere, Finland during 1990/91.

The author m a y be contacted at the following address: Center for Industrial Ergonomics, Department of Industrial Engineering, University of Louisville, Louisville, K Y 40292, U S A .


W. Karwowski

technology that can be used for the benefit of humankind, there are potential dangers involved, and adequate safeguards must be instituted to reduce its potentially harmful effects on people. This need arises especially due to the fact that today's robots are high-velocity, multifunctional, sophisticated machines capable of extremely diversified motions with high payload capacities. A m o n g other factors, robots differ from traditional machinery in that they have m a n y degrees of freedom and are capable of a wide range of movements which are often unpredictable. Indeed, the introduction of robotics has led to whole n e w categories of work-related accidents and injuries.

The futuristic laws of robotics, proposed by Asimov in 1950, state the following: (a) a robot must not harm a h u m a n being, nor through inaction allow one to come to harm; (b) a robot must always obey h u m a n beings, unless it conflicts with the first law; (c) a robot must protect itself from harm, unless it conflicts with the first or second laws. Unfortunately, the first law is violated today, in the sense that robot manufacturers and users are aware of the fact that a robot might collide with a worker or some other equipment, causing personal injury or material damage. Parsons and Kearsley (1982), and Noro and Okada (1983) stressed that industrial robots are built to work with humans, and therefore their design and operation call for ergonomie considerations. In order to prevent robot-related accidents in industry it is imperative to understand h o w humans perceive and respond to robots in the workplace, and evaluate the hazards associated with the operation and maintenance of robotic workstations.

H u m a n factors engineering in robot implementation

At present, very little is k n o w n about h o w humans react in the computerized workplaces surrounded by robots, where the mobility of machines with risks of accident is a new characteristic feature. Sheridan (1984) suggested that it is necessary to set up a man-robot system to determine experimentally the effective distribution of roles between a robot and a m a n . Noro and O k a d a (1983) stressed that h u m a n factors can play an important role in optimizing allocation of functions between m a n and robots, and in relaxation of physical and mental loads created when humans work alongside the robots.

Ergonomics of robotics considers h o w robots and those w h o work with them interact in the workplace, with emphasis on the design of robot systems, procedures for using them, protection of their users, and the division of labour between robots and h u m a n workers. Unfortunately, h u m a n factors research on robot systems, and their effects on the safety and well-being of industrial workers, is lagging considerably behind robotics hardware developments. T o date, only limited research has been conducted on h o w workers themselves perceive robots with respect to potential hazards and the job stress they create. Argote et al. (1982) performed a prototype study aimed at investigating h o w employees, as individuals, perceive and accept the introduction of robotic technology. The results indicated that, with experience, workers increase their understanding of what a robot really is. However, workers' beliefs about the potential hazards associated with such machines become more complex and pessimistic. There was also a significant increase in the psychological stress a m o n g the workers w h o interact directly with the robot systems.

Because of a tendency to anthropomorphize robots, both workers and managers are more sensitive to their introduction into the workplace than they are to the

76

Human-robot relationship

introduction of other technologies. Introduction of robots into one part of the plant m a y have a detrimental effect on other places. According to Reader (1986) 'all too often as part of a system is automated and production rates are increased, workers in other parts of the system are overloaded'. Consequently, serious accidents and low-quality production m a y result if the above problems are not corrected. Scarborough (1981) observed that when working with robots, employees m a y find that their jobs are actually more difficult, since they must n o w devote more attention to monitoring the robot's performance as well as accomplishing their o w n jobs. A s system monitoring clearly becomes one of the most important tasks for the robot operator, m a n y of the components of boredom and stress are due to the fact that robot systems m a y require minimal operator intervention. However, smooth operation depends on the operator's altertness and intelligent response to unexpected difficulties that develop.

The effects of industrial robotization

Industry worldwide is rapidly changing from the use of traditional machines to that of automated systems, with the emphasis being on robotic workstations. Safety and health professionals are becoming concerned with hazards associated with these non-traditional and complex systems. Providing safe robotic workstations is clearly one of the requirements for effective utilization of the very automation technology designed to improve industrial productivity. Although in the past robot design has been studied from the standpoints of mechanics and kinematics, it must today be considered from the h u m a n perspective.

Causes of robot-related accidents

A robot system consists of three elements: (a) the h u m a n operator, (b) the industrial robot, and (c) a communication system. Hazards, which can lead to an accident, can occur in any of the three modes of operation, i.e: (1) normal operation, (2) maintenance, and (3) teaching (i.e. programming the robot). Studies conducted in Sweden and Japan (Backstrom and Harms-Ringdahl, 1983; Sugimoto and Kawaguchi, 1983) have shown that most of the robot-related accidents occurred during maintenance, testing and teaching of the robot. About 30% of the accidents involved the operator's finger, hand or arm, indicating the proximity of the operator to the point of operation (Linger, 1988). Another category of injury occurring frequently was related to head and neck.

Initial studies on robot-related accidents have served to identify several causes and to classify these into two categories: (a) engineering (or system design) factors, and (b) behavioural and administrative (or organizational system) factors (Backstrom and Harms-Ringdahl, 1983). F r o m the h u m a n point of view, the factors of interest here are:

1. Inadvertent robot movement . 2. Failure to stop. 3. Expected and unexpected halts and starts of robots. 4. Inadvertent contact with the start button and other switches. 5. High-speed motion of the robot arm. 6. A n individual entering the danger zone of a halted robot for troubleshooting,

repair, testing, maintenance, or teaching.

77

W. Karwowski

1. A curious non-operator approaching the robot to take a look. 8. Unauthorized entry into the general robot work area. 9. A n operator performing workpiece adjustments and positioning.

10. A n operator performing a tool change. 11. A n operator unfamiliar with a robot's programmed movements. 12. Intentional disabling of safety devices. 13. A robot's work function unknown to the operator. 14. Improper motion path for operator manual tasks.

T o date, Japan has had the highest number of fatal accidents due to industrial robots or manipulators. As reported by the U S Department of Commerce, Japan has also 62-3% of the robotic world market. According to Nagamachi (1988), the first robot-induced fatal accident occurred in 1978, when the auto loaders crushed the human operator working with a variable sequence robot. Between 1978 and 1987 Japan reported a total of ten fatal accidents (Nagamachi, 1986, 1988). The first fatal accident reported in the United States occurred in 1984 (Sanderson et al. 1986), when an experienced worker entered a robot's working area, and was pinned between the safety barrier and the moving robot's arm. Commenting on the robot-related accident rate in Japan, Laudesbaugh and Montgomery (1986) considered that the high incidence m a y be attributed to two factors. Firstly, the Japanese definition of robot includes many more classes of industrial equipment than that adopted in the United

Figure 1. Physical size of a typical industrial robot (in this case a P50 from General Electric Co.) .

78


Figure 2.

Robots are dangerous: demonstration of a robot-related accident in a laboratory environment.

States. Secondly, Japan has a m u c h longer experience of using industrial robots for a variety of applications.

Jiang and Gainer (1987) conducted a cause-effect analysis on thirty-two robot-related accidents reported in the U S A , F R Germany, Sweden and Japan. Grouping the accidents according to personnel injured, type of injury and cause of injury, they found that line workers were at the greatest risk of injury, followed by maintenance personnel. Pinch-point accidents, caused by a part of the individual's body being pinched between moving parts of the robot, or between a moving part of the robot and a non-moving external fixture, accounted for 56% of all accidents. A n impact-related injury caused by the robot projecting a tool or workpiece in its end effector and striking the individual, accounted for 44% of accidents. The main root cause of injury turned out to be poor workplace design (62%), followed by h u m a n error (41%).

The studies reported above indicate that robot-related accidents can happen when workers are present inside, or in close proximity to, the robot's work envelope, and indicate that a c o m m o n cause of accident can be ascribed to h u m a n perceptual and judgmental processes. In m a n y production environments, the close physical interaction between robot and h u m a n operator that is needed for task completion, m a y result

79

W. Karwowski

in a high risk of accidents. F o r example , according to S u g i m o t o (1985) 'unnatural' and 'unexpected' m o v e m e n t s of robots were responsible for about 7 3 % of robot-related injuries and fatalities. In the reported cases the operators incorrectly a s s u m e d that the robot had stopped d u e to a system malfunction. These accidents involved a person entering the w o r k area w h e n the robot stopped (or w a s work ing very slowly) a n d then unexpectedly started to m o v e again.

H u m a n factors in robot-related accidents

A recent survey of 1 0 2 7 robot operators w a s designed to investigate the hazards operators feel working a round robots (Goto , 1987). T h e survey s h o w e d that 4 6 % of respondents felt robots to be hazardous in their jobs. Accident analysis for injuries caused by industrial robots indicate that tasks of set-up p r o g r a m m i n g , trouble shooting, maintenance, a n d clean-up are the m o s t dangerous (Jiang a n d Gainer, 1987). Ironically, these are a m o n g the m o s t difficult tasks to automate . Published data o n death a n d injuries caused by industrial robots are primarily from Japanese and E u r o p e a n industry.

Exposure to hazardous mot ion is m o s t evident during maintenance procedures. Etherton (1988) s h o w e d that the m e a n activity time for a large robotic assembly line w a s calculated to be 115-3 minutes (for 120 manually logged items in 102 workdays) . In 7 6 % of these maintenance activities the robots h a d full p o w e r available to them. A n d 4 3 % of these activities required h u m a n intrusion into the robots' w o r k zones with the p o w e r source available to the robots. D a t a were also collected for trouble-shooting, adjustment, and repair ( m e a n time with available power : 240-2,108-6, a n d 8 7 0 minutes respectively). T h e results were 5-4 minutes /workday/robot , as average maintenance exposure time, during w h i c h an injury could occur. Considering the 25 robots in the 19 cells studied, a maintenance worker is therefore exposed to 135 minutes of potentially hazardous enivironment, hence a claim that robots are a m o n g the m o s t dangerous of industrial machines.

A study of K a r w o w s k i et al. (1988b) c o m p a r e d safety performance of a manufacturing plant pre- and post-computer automation (i.e. robotization). Using the A N S I injury code classifications, it w a s found that, overall, the change to manufacturing processes resulted in a lower incidence of cuts, lacerations, and punctures for the factory floor as a whole . H o w e v e r , further analysis s h o w e d that this reduction w a s primarily due to changes in the manufacturing process itself, rather than safer h u m a n interaction with the robotic w o r k cells. In other w o r d s , improvemen t in safety w a s mostly obtained through the elimination of dangerous processes, for example by replacing sharp metal parts with plastics, thus reducing potential risk exposure.

Studies conducted b y the Swedish W o r k Env i ronment F u n d (1988) revealed that the majority of robot-related accidents occurred as follows:

(a) after a workpiece h a d been correctly repositioned, (b) during observation of the operating cycle, (c) during adjustments of peripheral equipment, (d ) w h e n the robot started in spite of a safety device having been actuated (resulting

in 15% head, 15% back, 30% finger, 34% hands, 3% arm and 3% leg injuries), (e) machines not being safety stopped before the operator intervened to deal with a

stoppage,

80


(f) the absence of safety devices, (g) safety devices having been incorrectly wired into the machine control, (h) the absence of an indicating system to inform the operator that the fault had

been rectified, (i) the operator believing he could evade dangerous movement of the machine, ( j) work being done that should never be done with the machines running.

The analysis of five fatuities due to industrial robots performed by Laudesbaugh and Montgomery (1986) revealed the following:

(a) In almost all cases, the worker entered the robot's w o r k zone to correct a minor problem in interfacing equ ipmen t such as conveyors or metal-working machines, but not in the robot itself.

(b) Whi le in each case the worke r w a s experienced, he did not follow safety procedures, w a s complacent, took unnecessary risks, or w a s in error.

(c) T h e robot struck the worker f rom behind without warning. (d) The worker was pinned by the robot against another machine or a structure in

the workspace, and the worker was killed by the other machine or by crushing.

These results indicate that in m a n y cases h u m a n error is one of the main causes of robot-related accidents, and therefore that adequate system design and safety measures as well as h u m a n behaviour at robotic workstations need to be addressed.

Technological provisions for robot safety

N u m e r o u s safety features have been proposed and implemented to ensure the safe operation of industrial robots. These include protection against software a n d hardware failures, fail-safe designs, intrusion monitoring, introduction of d e a d m a n switches and panic buttons, workplace design considerations, restriction of a r m motions, warnings, and operator training (Bonney and Y o u n g , 1985). M o s t of these features a n d devices (i.e. fences, enclosures, guards, sensing devices, etc.) are hardware-centered, a n d attempt to physically separate the robot from the h u m a n , or w a r n operators about the potential danger.

A s evidenced by several robot-related accidents, m a n y safety devices such as safety mats , light curtains and metal enclosures have not proved 1 0 0 % effective in accident prevention, since: (1) m o s t accidents occur during the periods of teaching, troubleshooting, testing, or maintenance, and (2) hybrid production systems d o require the cooperative interaction of both operators a n d robots in close proximity, such as the loading of parts into a magazine feeder, hybrid assembly, or periodic visual inspection by the operator. Linger (1988) indicated that it is a c o m m o n practice today that s o m e w o r k is carried out inside the hazardous space while robots are performing potentially dangerous operations, for example during installation, p r o g r a m m i n g a n d maintenance tasks.

According to R a h i m i (1987), state-of-the-art technologies in sensing capabilities using microwaves , ultrasonics, or infrared-based techniques for the detection of h u m a n intrusion into the robot's working space, have addressed the safety of robotic workstations from the robot side, but not from the h u m a n . R y a n (1988) concluded that h u m a n error is one of the primary causes of personal injury and deaths related to accidents involving industrial robots. In this regard, it has been suggested that

81

W. Karwowski

knowledge of h u m a n errors due to limitations in h u m a n perception, cognition, and decision-response processes should be integrated into the robotic workstations at the initial design stage (Nagamachi and Anayama, 1983; A d a m s , 1988; Helander and D o m a s , 1987; Karwowski et al. 1988a).

Human perception of hazardous robot workstations

C o x and Butler (1986) observe that the robot 'thinks' with its computer, makes 'decisions' through its programs, performs curiously human-like manoeuvers with its 'arms' and 'hands', and does all this with great precision and indefatigability. A h u m a n w h o miscalculates a robot's path and gets inside the painted lines (the working envelope), or someone w h o inadvertently wanders there, stands a good chance of being injured or killed. Such a possibility is enhanced if the person is working in a manufacturing facility where the work envelope of the robot m a y quickly change.

Previous experience with robots also influences the safety behaviour of h u m a n observers. There m a y be quite lengthy pauses to allow for processes to take place, and these could lead operators to think that it is safe to approach the robot. Since the robot m a y simply stop as a programmed step in the sequence of the program, and could accelerate again with great force a m o m e n t later, such a situation poses considerable danger to inexperienced operators. Even experienced individuals m a y have difficulty in understanding w h y the robot stopped; whether it is safe to approach it; if the cause of stoppage is a malfunction due to abnormality, a runaway halt for machine failure, or a condition halt for machinery cycling (Sugimoto and Kawaguchi, 1983). As pointed out by Irwin (1986) 'robots are fascinating and people love to get closer. They will walk to a stopped robot and touch it, but the robot m a y be simply in a pause of an automatic cycle. It could take off at any time at high rate'.

Slow robot operating speeds allow minimization of such hazards. For example, it is recommended that teach pendants should have an automatic slow-speed facility. In the Japanese and Soviet standards such speeds have been set at 14 and 30 cm/sec, respectively, while the German and U S drafts point to 25 cm/sec. These speeds appear to be based on current practice rather than any criterion which implies that speeds below these figures are safe for all operations requiring close interaction between the operator and the moving robot.

Intrinsic safety design and human limitations

The U S National Bureau of Standards (Robinson, 1985) identified three 'zones of safeguarding vigilance' around robots: (1) the perimeter, (2) the zone within the perimeter, and (3) the contact zone immediately adjacent to the robot arm. But even then, the majority of accidents still occurred to fully authorized personnel within the perimeter, in spite of the presence of detectors, collision sensors and a combination of traditional devices.

A n intrinsic safety system is essentially an in-built safety device in a robot for safe operation. Laudesbaugh and Montgomery (1986) state that designing for intrinsic safety is important for two reasons: (1) the safe operation of a robot that is not intrinsically safe additionally taxes the robot operator's skill, and (2) operator error causes a significant percentage of industrial accidents. Several traditional safety

82


measures such as perimeter guards, floor marks, photoelectric guards, the use of micro switches, light beams, pressure pads, protection locks, collision and trap sensors, area intrusion sensors, training and familiarization techniques, have been implemented to ensure the protection of workers from dangerous robotic workstations. Since the majority of robotic accidents occur during the programming/teach m o d e or during the troubleshooting/maintenance mode , m a n y of these safety features fail to ensure protection, since the operator has to bypass the safety devices in order to enter the robot's work envelope.

Conclusions

In the distant future w e m a y look forward to robots that are intrinsically safe, though for the present the prospects of eliminating hazards altogether or of providing totally secure fencing to prevent injury to persons w h o serve robots seem unlikely. According to Bellino (1985), 'most engineers will probably agree that aboslute safety cannot be achieved with robots; therefore, a blend of safety with efficiency of operations should be used in forming realistic goals. As reliability decreases with complex design, the trend towards robots with the ability to detect the presence of humans will increase. However, the safety of programmers/teachers and maintenance personnel must still be addressed.'

According to the Request for Assistance in Preventing the Injury of Workers by Robots ( N I O S H Alert, U S Department of Health and H u m a n Services, December 1984) both safety training and supervision of workers w h o are involved with programming, operating or maintaining robots should be provided. The training should be specific to the particular robot, and include 'refresher courses which re-emphasize safety' and discussions of 'new technological developments'. The N I O S H (1984) document also outlines the following safety procedures for any personnel interacting with industrial robots:

1. Workers must be familiar with all working aspects of the robot, including full range of motion, k n o w n hazards, h o w the robot is programmed, emergency stop buttons, and safety barriers, before operating or performing maintenance work at robotic work stations.

2. Operators should never be in reach of the robot while it is operating. 3. Programmers, operators, and maintenance workers should operate robots at

reduced speeds consistent with adequate worker response to avoid hazards during programming and be aware of all conceivable pinch points, such as poles, walls, and other equipment, in the robots' operational areas.

With respect to supervision of workers, the N I O S H (1984) document requires that plant supervisors should adhere to the following:

1. Assure that no one is allowed to enter the operational area of a robot without first putting the robot on 'hold,' in a 'power d o w n ' condition, or at a reduced operating speed m o d e .

2. Recognize that with the passage of time, experienced workers doing automated tasks m a y become complacent, overconfident, or inattentive to the hazards inherent in complex automated equipment.

83

W. Karwowski

The above conclusions can be further supported by a new set of rules for the design and use of robotic systems proposed by Yokomizo et al. (1987), which point out to the importance of h u m a n factors considerations. These new rules are as follows: Rule 1. Robots must be m a d e and used for the well-being and development of people. Rule 2. Robots must not replace people on jobs people want to do themselves, but

must replace people on jobs that they do not wish to do or believe to be hazardous.

Rule 3. Robots must be built to such specifications that they do not psychologically and physically oppress people.

Rule 4. Robots must follow the c o m m a n d of people so that they do not harm other people, only damaging themselves.

Rule 5. If robots replace people on certain jobs, the prior approval of the people affected must be obtained.

Rule 6. Robots must be m a d e so that they can be easily operated by people and they can readily perform the role of assistants to people.

Rule 7. As soon as robots finish their assigned tasks, they must depart from the place so they do not interfere with people and other robots.

As we have indicated, m a n y c o m m o n causes of robot-related accidents can be attributed to h u m a n physical, perceptual and psychological limitations. It is widely recognized today that the terms safe and safety are not absolutes, and that the ultimate link in a robot-safeguarding system is a person. Personnel training and attitude are therefore important factors that must be taken into consideration in the design for safety of robot systems. •

References

A D A M S , S. K . (1988) Anticipating and controlling human error in nuclear power plants, pp. 231 54. in: Blache (ed.), Success Factor for Implementing Change, S M E Publications, Michigan.

A R G O T E , L., G O O D M A N , P. S. and S C H K A D E , D . (1982). The Human Side of Robotics: How Workers React to a Robot, Technical Report 38-8182, Graduate School of Industrial Administration, Carnegie-Mellon University, Pittsburgh, P A .

A S I M O V , I. (1950) Robot, Doubleday, Page and Co. , N e w York. B A C K S T R O M , T . and H A R M S - R I N G D A H L , L. (1983) A statistical study on control system and

accidents at work, in: Proceedings of International Seminar on Occupational Accidents, Stockholm, Sweden.

BELLINO, J. P . (1985) Design for safeguarding, pp. 127-32. in: Bonney, M . C . and Young, Y . F. (eds.), Robot Safety, Springer-Verlag, IFS Ltd., Berlin.

B O N N E Y , M . C . and Y O U N G , Y . F. (eds) (1985) Robot Safety, IFS Publications Ltd., Springer-Verlag, Berlin.

Cox, J. L. and B U T L E R , J. K . (1986) H u m a n factors issues in robotics: physical, mental, safety, legal, pp. 34—45 in: Strubhar, P. M . (ed.), Working Safely with Industrial Robots, Robotics International of S M E , Dearborn, M I .

E T H E R T O N , J. (1988) Safe maintenance guidelines for robotic workstations, NIOSH Technical Report (March).

G O T O , M . (1987) Occupational safety and health measures taken for the introduction of robots in the automobile industry, pp. 399-417 in: Noro, K . (ed.) Occupational Health and Safety in Automation and Robotics. Taylor & Francis; London.

G R O O V E R , M . , W E I S S , M . , N A G E L , R . and O D R E Y , N . G . (1986) Industrial Robotics, M c G r a w Hill, N e w York.

H E L A N D E R , M . G . and D O M A S , K . (1987) The effect of product design on task allocation between humans and automation in manufacturing, pp. 368-76. in: Noro, K . (ed.), Occupational Health and Safety in Automation and Robotics, Taylor & Francis, London.

84


I R W I N , R . D . (1986) Get the most from the computerized steel-collar workers, pp. 23-7. in: Strubhar, P. M . (ed.), Working Safely with Industrial Robots, Robotics International of S M E , Dearborn, M I .

J IANG, B . C . and G A I N E R , C . A . (1987) A cause-and-effect analysis of robot accidents. Journal of Occupational Accidents, 9 (1); 27—46.

K A R W O W S K I , W . and R A H I M I , M . (1991) Worker selection of safe speed and idle condition in simulated monitoring of two industrial robots. Ergonomics, 34 (5), 531-46.

K A R W O W S K I , W . , P A R S A E I , H . and W I L H E L M , M . R . (1988a). Ergonomics of Hybrid Automated Systems-I, Elsevier Science Publishers, Amsterdam, Netherlands.

K A R W O W S K I , W . , R A H I M I , M . and M I H A L Y , T . (19886) Effects of computerized automation and robotics on safety performance of a manufacturing plant. Journal of Occupational Accidents, 10(3), 217-35.

L A U D E S B A U G H , L . K . and M O N T G O M E R Y , D . (1986) Robot safety: industrial experience, pp. 7-12. in: Andary, J. (Tech. Officer), Critical Issues in Robot-Human Operations During the Early Phases of the Space Station Program, Consortium for Space/Terrestrial Automation and Robotics (Feb.).

L I N G E R , M . (1988) Robot Safety—Are Robots Safe? Swedish Institute of Production Engineering Research, Göteborg, Sweden.

N A G A M A C H I , M . and A N A Y A M A , Y . (1983) An ergonomie study of industrial robot (1); The experiment of unsafe behavior on robot manipulation. Japan Journal of Ergonomics, 5, (1- 1), 259-64 (in Japanese).

N A G A M A C H I , M . (1986) H u m a n factor of industrial robots and robot safety management in Japan. Applied Ergonomics, 17 (1), 9-18.

N A G A M A C H I , M . (1988) Ten fatal accidents due to robots in Japan, pp. 391-6, in: Karwowski, W . et al. (eds.), Ergonomics of Hybrid Automated System, Elsevier Science Publishers, Amsterdam, Netherlands.

N I O S H (1984) Request for Assistance in Preventing Injury of Workers by Robots, D H H S , N I O S H Publication 85-103, U S Department of Health and H u m a n Services, Washington, D . C .

N O R O , K . and O K A D A , Y . (1983) Robotization and human factors. Ergonomics 26, 985-1000. P A R S O N S , H . M . and K E A R S E L Y , G . P. (1982) Robotics and human factors: current status and

future prospects, Human Factors, 24, 535-52. R A H I M I , M . (1987) Design of automated hybrid work stations: an evaluation of robot sensory for

safety. International Journal of Industrial Ergonomics, pp. 293 303. R E A D E R , D . E . (1986) H u m a n factors in automation, pp. 46^8, Strubhar, P. M . (ed.), Working

Safely with Industrial Robots, Robotics International of S M E , Dearborn, M I . R O B I N S O N , O . F . (1985) Robot guarding—the neglected zones, pp. 181-8, in: Bonney, M . C . and

Young, Y . F. (eds.), Robot Safety, IFS Publications Ltd., Springer-Verlag, Berlin. Robot Institute of America (1982) Robot Institute of America Worldwide Robotics Survey and

Directory, Society of Manufacturing Engineers, Dearborn, M I . R Y A N , J. P. (1988) Safety considerations in robot design, pp. 483-90, in: Karwowski, W . et al.

(eds.), Ergonomics of Hybrid Automated Systems-I, Elsevier Science Publishers, Amsterdam, Netherlands.

S A N D E R S O N , L . M . , C O L L I N S , J. N . and M C G L O T H L I N , J. D . (1986) Robot-related fatality involving a U . S . manufacturing plant employee: case report and recommendations. Journal of Occupational Accidents, 8, 13-23.

S C A R B O R O U G H , H . (1981) Working with robots is a bore. New Scientist, p. 555. S H E R I D A N , T . G . (1984) Supervisory control of remote manipulators, vehicles and dynamic

processes: experiments in c o m m o n and display aiding. In: Rouse W . B . (ed.), Advances in Man-Machine Systems Research, vol. 1, JAI Press, Greenwich.

S U G I M O T O , N . (1985) Safety measures for automated machines. Safety Staff, 12, 4-18. S U G I M O T O , N . and K A W A G U C H I , K . (1983) Fault tree analysis of hazards created by robots,

pp. 83-98, in: Bonney, M . C . and Young, Y . F. (eds.), Robot Safety, IFS Ltd., Springer-Verlag, Berlin.

Swedish W o r k Environment Fund (1988) Robot Safety, Arbetsmiljofonden, Stockholm, Sweden. Y O K O M I Z O , Y . , H A S E G A W A , Y . and K O M A T S U B A R A , A . (1987) Problems of and industrial medicine

measures for the introduction of robots, pp. 167-74, in: Noro, K . (ed.), Occupational Health and Safety in Automation and Robotics, Taylor & Francis, London.

85

Ergonomics of large-scale technological systems

Najmedin Meshkati

Many serious accidents at large-scale technological systems in developed and developing countries have been primarily attributed to operator error. However, further investigations have revealed that a majority of these incidents were caused by a combination of many factors whose roots can be found in the lack of (micro- and macro-) ergonomie considerations at the design and operating stages.

A c o m m o n characteristic of m a n y large-scale technological systems such as nuclear power plants and chemical processing installations, are the large amounts of potentially hazardous materials that are concentrated in single sites and under the centralized control of few operators. Catastrophic breakdowns of these systems pose serious threats, not only for those within the plant, but also for the neighbouring public, and even the whole region and the country. Attesting to this are the accidents at the Bhopal chemical plant in India and at the Chernobyl nuclear power plant in the Soviet Union, in 1984 and 1986 respectively. Chernobyl demonstrated, for the first time, that the effects of any such nuclear accident would not be localized, but rather would spill over into neighbouring countries and have global consequences. The radioactive fallout resulting from Chernobyl was detected all over the world, from Finland to South Africa. Specifically, the Europeans, in addition to serious health concerns, have had to deal with significant economic losses and serious, long-lasting environmental consequences. This phenomenon has been summarized most succinctly as a nuclear accident anywhere is a nuclear accident everywhere. The critical role of (the lack of) ergonomics, or in other terms, h u m a n factors-related causes in the Chernobyl accident is encapsulated in the following statement which appeared in the concluding section of

Najmedin Meshkati is an Associate Professor of H u m a n Factors at the Institute of Safety and Systems Management, and lectures at the Department of Industrial Systems Engineering at the University of Southern California. H e was born in Iran in 1954, and educated in Iran and the U S A . H e received the Presidential Young Investigator Award from the U S National Science Foundation in 1989, primarily for his research on the roles of h u m a n and organizational factors in the operation and safety of complex, large-scale technological systems.

Dr Meshkati m a y be contacted at the following address: Institute of Safety and Systems Management, University of Southern California, Los Angeles, California 90089-0021, U S A .


N. Meshkati

the International Atomic Energy Agency's (IAEA) Summary Report on the Post-Accident Review Meeting on the Chernobyl Accident (1986, p. 76):

'The root cause of the Chernobyl accident, it is concluded, is to be found in the so-called h u m a n element... The lessons drawn from the Chernobyl accident are valuable for all reactor types.'

The underlying rationale and the major objective of this article is to highlight and demonstrate the critical effects of ergonomie considerations in the safety of hazardous, large-scale technological systems. This is done by briefly analysing the c o m m o n causes of the three well-known accidents at such systems: Three Mile Island (TMI) nuclear power plant in the U S A in 1979; the Bhopal chemical plant in India, in 1984; and the Chernobyl nuclear power plant in the Soviet Union, in 1986. Moreover, by integrating the c o m m o n causes of these three accidents, a policy framework and/or guideline facilitating adherence to those identified, safety-ensuring, ergonomie factors is suggested. The specific needs of the developing countries in the context of technology transfer, are also suggested.

Ergonomics

The present complex, large-scale technological systems pose additional demands and new requirements on h u m a n operators. These systems require operators to constantly adapt to new and unforeseeable system and environmental demands. Furthermore, there is no clear-cut distinction between system design and operation, since the operator will have to match system properties to the changing demands and operational conditions. In other words, according to Reason (1990), operators must be able to handle the 'non-design' emergencies, because the system designers cannot foresee all the possible scenarios of failure and are not able to provide automatic safety devices for every contingency. Therefore, it is highly important that the operator's job, which involves effortful and error-prone activities of problem-solving and decisionmaking at the workstation level, be facilitated by the proper interface devices and be supported by the required organizational structure.

Thus, the role of the h u m a n operator responsible for such systems has changed from a manual or man-in-the-loop controller to a supervisory controller w h o is responsible for overseeing one or more computer controllers, w h o perform the routine, frequently occurring control functions. In supervisory control systems, the h u m a n operator's role is primarily passive, a monitor of the change in the system state (Mitchell, 1987). The operator's passive role, however, changes to one of active involvement in cases of unexpected systems events, emergencies, alerts, and/or system failures (Rasmussen and Rouse, 1981). Moreover, operators of these systems, faced with the system's inherent opacity and decision uncertainty, are usually working in a centralized location (e.g. control room), sharing and exchanging data, collectively analysing information and making decisions.

Micro- and macroergonomics

Ergonomics, also called h u m a n factors, is a scientific field which is concerned with improving the productivity, health, safety and comfort of people, as well as the effective interaction between people, the technology they are using and the environment in

88


which both must operate. Ergonomics specialists call these collective sets ' h u m a n -machine-environment systems'. Ergonomics at the micro level, microergonomics, is focused on the human-machine system level and is concerned with the design of individual workstations, work methods, tools, control panels, displays, etc. Micro-ergonomics includes studies of h u m a n body sizes, k n o w n as anthropometrics, physical and psychological abilities and limitations, h u m a n decision-making and error, etc. Ergonomics at the macro level, macroergonomics, is focused on the overall people-technology system level and is concerned with the impact of technological systems on organizational, managerial and personnel (sub-)systems (Hendrick, 1987).

It is a k n o w n fact that the two major building blocks of any large-scale technological system are: (i) the physical, engineered components, and (ii) the (human) operators. Even though not one of the fundamental building blocks, the role of organization (and its structure) is equally important, being perhaps analogous to the mortar—facilitating the interface, connecting and joining the blocks together. Thus, output, performance, stability and the survival of technological systems, as well as their ability to tolerate environmental disturbances, are dependent upon the nature, formation and interaction of their H u m a n , Organizational, and engineered (Technological) [ H O T ] subsystems. The connection of three ( H O T ) subsystems, in the context of the total system, is represented in Figure 1. This simplified and symbolic demonstration only depicts one critical system's reality—the role of each subsystem as a link in a chain—in the integrity of the whole system. It does not, of course, show all the required subsystems' interactions and interrelationships.

The chain metaphor also is helpful in understanding the effects of output or production load, produced by the system, on its individual subsystems. A n y increase in the output level or the 'capacity utilization rate', as it is k n o w n in process plants and

Figure 1.

Major subsystems of a large-scale technological system.

89

N. Meshkati

refineries, imposes strain on all subsystems. Obviously, the chain (system) could break d o w n if any link breaks d o w n . This m a y occur if either all the links (subsystems) are not equally strong and designed for handling the additional load, or if they are not adequately prepared and reinforced to carry the extra load in a sustainable fashion. According to the author's studies, a majority of the large-scale technological systems' accidents have been caused by breakdowns of the weakest links in this chain, most often the h u m a n or organizational subsystems (Meshkati, 1991 a). A n important ramification of this fact, in addition to the need for microergonomic considerations in technological system design and operation, is the requirement for a thorough macroergonomic analysis, which will further be delineated in this article.

At Bhopal, macroergonomics would have been concerned with the performance of the poorly trained Third World operators operating advanced technological systems designed by other humans with m u c h different educational backgrounds, as well as cultural and psycho-social attributes (Meshkati, 1989 a). Micro- and macroergonomic approaches build upon each other and concentrate on the introduction, integration and utilization of technology, and its interface with the end-user population. Their overall objective is to optimize the functions (i.e. safety and efficiency) of the intended technological system. This issue is eloquently stated by Rasmussen (1989, p. 1) as:

'The h u m a n factors (ergonomics) problems of industrial safety in (the operation of large-scale systems) not only includes the classical interface problems, but also problems such as the ability of designers to predict and supply the means to control the relevant disturbances to an acceptable degree of completeness, the ability of the operating staff to cope with the unforeseen and rare disturbances, and the ability of the organization in charge of operation to maintain an acceptable quality of risk management. The h u m a n factors problems of industrial safety have become a true cross-disciplinary issue.' (Parenthetical statements are added.)

The payoffs of the proactive incorporation of, and the on-line compliance with ergonomie considerations in large-scale technological systems are reflected in economic and non-economic gains. They include the improvement of functional effectiveness, higher equipment utilization a m d maintainability, the enhancement of h u m a n welfare through reduction of accident potential, which could otherwise result in loss of life and property, and the minimization of adverse environmental effects (e.g. discharge of hazardous material into the environment) due to haphazard and sub-optimal human-machine-environment interactions (Meshkati, 1988).

Additional ergonomie considerations for developing countries

It is contended that the safety and operation of large-scale technological systems become even more important for developing countries because of the transferred nature of the required technologies. Additionally, a good majority of developing countries do not have the resources to build infrastructures that m a k e industries safe. The consequence is that major technological accidents in developing countries lead to far more deaths and injuries than in industrialized countries (Shrivastava, 1987; Smets, 1985). In the last ten years, the accidents with the most fatalities have all occurred in the technological systems located in developing countries (Shrivastava, Mitroff, Miller and Miglani, 1988). Incidently, the most catastrophic industrial accident in history—the

90


Bhopal disaster—occurred at a chemical plant using transferred technology in a developing country.

The need for extra attention to the safety-related issues of hazardous technological systems for developing countries is also raised by Peter Thacher, the former Deputy Executive Director of the United Nations Environmental Programme ( U N E P ) . H e has stated, in the context of Bhopal, 'it is obvious that some manufacturing processes are more dangerous in a developing country than a developed one . . . Y o u have to assume that in a developing country people will not be as careful in terms of inspection, quality control and maintenance. And you must assume that if a problem occurs, it will be more difficult to cope with it.' (Cited in Bordewich, 1987, p. 30.)

Moreover, beside the serious and disastrous effects of the major accidents at these facilities, the importance of this study and others of this nature is further heightened by the proliferation of nuclear power plants in m a n y (developing) countries. According to the International Atomic Energy Agency (IAEA), as of 31 December 1990, there are some 423 nuclear power plants operating in 24 countries, with 83 new reactors under construction (IAEA Bulletin, 3/1991). Furthermore, an increasing number of developing countries are embracing nuclear power to gain greater economic independence and to achieve permanent relief from their worrisome balance of payment and foreign debt burdens, which are aggravated by their continuously increasing need for imported energy and their growing demand for electricity. According to the most recent I A E A forecast, by the coming decades up to the year 2010, the electricity consumption of developing countries will be up to 200% above their 1990 level (Mueller, 1991). Nuclear power in these countries is expected to continue to gain an increasing share of electricity generation from a 4 % share in 1990, to 6% by 2010. In capacity terms, 22% of all new nuclear generating capacity to be placed in commercial operation in the world by 2010, is expected to be in developing countries (Semenov, Guthrie and Tatsuta, 1991 ). According to a study by the Division of Nuclear Power of the I A E A , a total of 21 developing countries either have nuclear power plant(s) in operation, or have plants in the construction or planning stages (Csik and Schenk, 1987). This number will certainly increase at a 'modest rate' in the future. Based on a recent estimate by the I A E A , nuclear energy production will grow an average of 2-8 to 3 9 % per year, worldwide from 1989 2005; whereas the estimated average range of annual growth rates of nuclear power production for developing countries in the Middle East and South Asia (combined), and Latin America are 19-5 24-2% and 12-8 16-5% respectively (IAEA Newsbriefs, August/September, 1990).

Human^>rganization technology interactions in developing countries require additional ergonomie considerations that are not necessarily needed when the intended technology is used in the country of origin. Primary micro- and macroergonomics-related considerations affecting large-scale technological systems in developing countries include the local operator populations' needs, capabilities and limitations. They also cover, for instance, physical and psychological characteristics and cultural and religious norms. Examples of ergonomics considerations in technology transfer to and utilization by developing countries would include (Meshkati, 1989 b and c):

• Considering the local user population's attributes, e.g. anthropometric and perceptual characteristics, psychomotor skills, and mental models which affect task performance, error and the determination of efficient h u m a n workstation interaction;

91

N. Meshkati

• Considering physical environmental conditions affecting operators' safety and performance, e.g. adjusting ventilation requirements based on the installation site's down-draught wind, heat exchange characteristics and climatical conditions;

• Considering the effects of cultural and religious variables, e.g. adopting separate production schedules, quality control (QC) , machine requirement planning ( M R P ) and adjusting shift duration for the holy month of R a m a d a n due to d a w n to dusk fasting for the production facilities operating in Islamic countries;

• Employing more adaptive managerial and organizational factors, e.g. deciding the rigidity and flatness of the organizational structure; and

• Determining the appropriate level of needed 'requisite variety' (Meshkati, 1989 d; 1991 b), finding the optimum span of control, designing feedback mechanisms and determining the proper supervisory style based upon the identification of the local operators' background, understanding, expectations and tolerance for uncertainty.

H u m a n error and technological systems' accidents

It is said that h u m a n performance factors are the 'guts of every accident', or, according to Cherns (1962), an accident is 'an error with sad consequences' (p. 162). B y declaring that operators must have failed, it always helps to avoid a lot of'undesirable' problems. A s suggested by Perrow (1986), 'finding that faulty designs were responsible would entail enormous shutdown and retrofitting costs, finding that management was responsible would threaten those in charge; but finding that operators were responsible preserves the system, with some soporific injunctions about better training' (p. 146).

Operators' errors should be seen as the result of h u m a n variability, which is an integral element in h u m a n learning and adaptation (Rasmussen, 1985). This approach considers the human-task or h u m a n machine mismatches, instead of solely tasks or machines, as a basis for analysis and classification of h u m a n errors (Rasmussen, D u n c a n and Leplat, 1987). Thus h u m a n error occurrences are defined by the behaviour of the total human-task system. Frequently, the human-system mismatch will not be due to spontaneous, inherent h u m a n variability, but to events in the environment which act as precursors. Furthermore, in m a n y instances, the working environment can also aggravate the situation. Rasmussen (1986) has characterized this phenomenon as the 'unkind work environment'. Once the error is committed, it is not possible for the person to correct the effects of inappropriate variations in performance before they lead to unacceptable consequences, because the effects of the 'errors' are neither observable nor reversible. Finally, according to m a n y case studies, a good portion of errors in complex human-machine systems, so called design-induced errors, are forced upon the h u m a n operators and can be eliminated by the adoption of the ergonomie considerations.

Major causes of human error and the resulting accidents in large-scale technological systems

Performance, as well as the inherent accident potential of complex technological systems, is a function of the interactions of their engineered and human (i.e.

92


workstation, personnel and organizational) subsystems. Traditionally, m a n y (technological) systems' failures implicated in serious accidents have been attributed to operators and their errors (e.g. Three Mile Island and Bhopal). However, this a great over-simplification. Perrow (1984) has reckoned that while 60-80% of all accidents are officially attributed to operators, the real figure might be closer to only 30-40%.

O n m a n y occasions, the error and the resultant failures are both the attribute and the effect of a multitude of factors such as poor workstation and workplace designs, complicated operational processes, unbalanced workload, unsafe working conditions, faulty maintenance, disproportionate attention to production, ineffective training, lack of motivation and experimental knowledge, non-responsive managerial systems, poor planning, non-adaptive organizational structures, rigid job-based pay systems, haphazard response systems, and sudden environmental disturbances, rather than being their cause (Baldissera, 1988; Meshkati, 1988; 1989 a, 1990, 1991a; Reason 1988). Generally, the solution to the problem of technological systems safety has been defined as an engineering one (Perrow, 1986). Nowadays , however, through m a n y rigorous scientific and multidisciplinary investigations, it is k n o w n that system accidents are caused by the way the (system) parts—engineered and human—fit together and interact.

Moreover, the 'system's environment', which includes different operational milieux and their peculiar h u m a n subsystem-related factors, could exacerbate the vulnerability of such interactive subsystems, and if not proactively dealt with, could activate a chain reaction resulting in low system performance and efficiency, unsafe operations, higher accident potential, and even disasters. The Bhopal tragedy, for instance, was a typical example of such a vicious circle causing total system failure—an inherently faulty and unprepared human-organizational-technological system aggravated by a developing country's (India) contextual factors (Shrivastava, 1987).

Commonalities of ergonomics problems in large-scale technological system accidents

There were two main categories of ergonomie causes of the three most devastating large-scale system accidents—Three Mile Island, Bhopal and Chernobyl— investigated by the author (Meshkati, 1991 a): (a) a lack of ergonomie considerations at the (system) design stage; and (b) a lack of ergonomie considerations at the (system) operating stage. Notwithstanding the overlapping domains and intertwined nature of these two stages, the former, using Reason's (1990) characterization, refers primarily to the 'latent errors'—adverse consequences that m a y lie dormant within the system for a long time, only becoming evident when they combine with other factors to breach the system's defences. In the context of this study, they include control room, workstation and display/control panel design flaws causing confusion and leading to design-induced errors; problems associated with lack of foresight in operators' workload estimation, leading to overload (and stress); inadequate training; organizational rigidity and disarrayed managerial practices. The latter, which is associated with the performance of the front-line operators immediately before and during the accident, includes sources and variations of 'active errors', such as misjudgements, mistakes and wrong-doings.

The comparison of T M I , Bhopal and Chernobyl is not unprecedented. In the case of the former two, m a n y authoritative analogies have already been made . In 1984, the

93

N. Meshkati

President of the World Resources Institute, James Speth (1984), in his statement at the hearing on the 'Implications of the Industrial Disaster in Bhopal' before the Subcommittee on Asian and Pacific Affairs of the U S House of Representatives, argued that 'it is likely that Bhopal will become the chemical industry's Three Mile Island, an international symbol deeply imprinted on public consciousness'.

Regardless of the nature of the utilized technology, there are striking similarities and commonalities in the nature and magnitude of the causes of complex, large-scale technological system failures, such as Three Mile Island, Bhopal and Chernobyl. Furthermore, it would not be spurious to state that the causes of these accidents are reminiscent of the causes of another past nuclear power plant accident—the accident in January 1961 at the SL1 (Stationary L o w - P o w e r Reactor N o . 1), located at the National Reactor Testing Station, Idaho Falls, Idaho. A quotation from the general conclusions as to the causes of this accident could, as well and almost exactly, be applied to the T M I and Chernobyl cases. [As such, one m a y argue that, had it been heeded, these accidents could have been prevented.]:

'Most accidents involve design errors, intrumentation errors, and operator or supervisor errors... The SL1 accident is an object lesson on all of these... There has been m u c h discussion of this accident, its causes, and its lessons, but little attention has been paid to the h u m a n aspects of its causes... There is a tendency to look only at what happened, and to point out deficiencies in the system without understanding w h y they happened; w h y certain decisions were made as they were. . . Post-accident reviews should consider the situation and the pressures on personnel which existed before the accident' (Thompson, 1964, p. 681).

Conclusions

A s demonstrated by Shrivastava et al. (1988), technological system crises, e.g. accidents, are caused by two sets of failure (and their interactions); (a) failure in the system's components (or subsystems) and their interactions; and (b) failure in the system's environmental factors. The former refers to a complex set of H u m a n , Organizational, and Technological ( H O T ) factors (and their interactions), which lead to the triggering event for the accident. The latter, according to the authors, includes Regulatory, Infrastructural and Preparedness (RIP) failures in the systems' environments. Although RIP is equally important, the emphasis of this article has been on H O T factors. As such, the following conclusions and recommendations address only the HOT-related issues.

As also suggested by Shrivastava et al. (1988), technological 'organizations are simultaneously systems of production and of destruction' (p. 297). This face becomes even more critical for the hazardous large-scale systems, such as the ones discussed in this article. These are risky systems, and risky systems are full of failures. Inevitably, these failures will interact in unexpected ways, defeat the system's safety devices and bring down the system. This is what Perrow (1984) has called a 'normal accident'. Using Perrow's characterization of these types of industrial accident, the Bhopal catastrophe, as well as T M I and Chernobyl, could each well be called a 'normal accident'. Normal in the sense that the accident emerged from the inherent characteristics of the respective system itself and, because of the existing serious micro- and macroergonomics

94


problems at both the design and operating stages, it could neither have been prevented nor avoided.

M a n y scholars such as Goldman (1986), Wilson (1987), Oberg (1988), particularly Munipov (1990) and Medvedev (1991) have implicated the pre-glasnost Soviet secrecy and the ignorance of T M I ' s lessons as root causes of the Chernobyl accident. T M I , Bhopal, Chernobyl, previously mentioned S L 1 , and numerous other accidents will always remind us of George Santayana's dictum that 'those w h o ignore history are forced to relive it'. The continued operation of hazardous systems with secrecy, complacency, or ignorance; not heeding the occasional warnings (incidents); and without change to a proactive, integrated and total systems approach to design, operations, safety control, and risk management in complex technological systems, will force us to relive horrors like Chernobyl and tragedies like Bhopal. These accidents were not isolated cases, but were only manifestations—the tip of the iceberg—of the negative effects resulting from the unfortunate and c o m m o n practice: lack of ergonomie considerations in the design and operation of major industrial facilities and process plants throughout the world.

Another excuse for not considering ergonomics in industrial plants has traditionally been that it is too costly, particularly for systems operating in developing countries. However, in his latest seminal book, Porter (1990 a) has debunked the old myth that greater safety, health and environmental considerations and additional regulations erode the competitivenes of a firm. According to Porter, 'such thinking is based on an incomplete view of h o w competitive advantage is created and sustained' (p. 648). A manufacturing firm, by providing safer working conditions for its employees and maintaining higher environmental standards, can also be profitable and competitive. Also, 'stringent standards for products, safety, environmental quality, and the like not only serve the public good but are vital to economic success' [emphasis added] (Porter, 1990 b, p. 108).

Finally, m a n y industrial accidents can be prevented if the critical issue of large-scale technology utilization is not plagued by sheer political, economic, bureaucratic and/or technical tunnel vision. N o matter what the nature or level of the technology and regardless of the plant's location—in industrialized or developing countries—the ergonomie considerations are still universally important and their absence invariably cause inefficiencies, problems, accidents and the loss of property and lives. •

Acknowledgements

This work is supported partially by the Faculty Research and Innovation Fund of the University of Southern California and partly by the National Science Foundation through the Presidential Young Investigator Award. A n y opinions, findings and conclusions or recommendations expressed in this work are those of the author and do not necessarily reflect the views of the sponsoring organizations.

References

B A L D I S S E R A , A . (1988). Incidenti anormali: una critica della teoría degli incidenti tecnologici di C. Perrow (Abnormal incident: a critique of Perrow's theory of technological incidents),

95

N. Meshkati

reference paper presented at the International Conference on Joint Design of Technology, Organization and People Growth, 'Scuola Grande di San Rocco' Venice, 12-14 October.

B O R D E W I C H , F. (1987). The lessons of Bhopal. The Atlantic, March issue, 30-3. C H E R N S , A . B . (1962). In Welford, A . T . (ed.). Society: problems and methods of study. Routledge

and Kegan Paul, London. C S I K , B . J. and S C H E N K , K . (1987). Nuclear power in developing countries: requirements &

constraints. IAEA Bulletin, 29 (2), 3 9 ^ 2 . G O L D M A N , M . L . (1986). Keeping the cold war out of Chernobyl. Technology Review, July, 18-19. H E N D R I C K , H . W . (1987). Macroergonomics: a concept whose time has come. Human Factors

Society Bulletin, 30 (2), 1-3. M E D V E D E V , G . (1991). The truth about Chernobyl. Basic Books, N e w York. M E S H K A T I , N . (1988). An integrative model for designing reliable technological organizations: the

role of cultural variables. Invited position paper for the World Bank Workshop on Safety Control and Risk management in Large-Scale Technological Operations, 18-20 October, World Bank, Washington, D C .

M E S H K A T I , N . (1989 a). A n etiological investigation of micro- and macroergonomic factors in the Bhopal disaster: lessons for industries of both industrialized and developing countries. International Journal of Industrial Ergonomics, 4 , 161-75.

M E S H K A T I , N . (1989 b). Critical issues in the safe transfer oflarge-scale technological systems to the third world: an analysis and agenda for research. Invited position paper for the World Bank Workshop in Risk Management (in Large-Scale Technological Operations), 6-11 N o v e m ber, organized by the World Bank and the Swedish Rescue Services Board, Karlstad, Sweden.

M E S H K A T I , N . (1989 C). Technology transfer to developing countries: a tripartite micro- and macroergonomic analysis of human-organization-technology interfaces. International Journal of Industrial Ergonomics, 4 , 101-15.

M E S H K A T I , N . ( 1989 d). Self-organization, requisite variety and cultural environment: three links of a safety chain to harness complex technological systems. Invited position paper for the World Bank Workshop in Risk Management (in Large-Scale Technological Operations), 6-11 November, organized by the World Bank and the Swedish Rescue Services Board, Karlstad, Sweden.

M E S H K A T I , N . (1990). Preventing accidents at oil and chemical plants. Professional Safety, 35 (11), 15-18.

M E S H K A T I , N . (1991 a). H u m a n Factors in large-scale technological systems' accidents: Three Mile Island, Bhopal, Chernobyl. Industrial Crisis Quarterly, 5, 133-54.

M E S H K A T I , N . (1991 b) Integration of workstation, job, and team structure design in complex human-machine systems: a framework. International Journal of Industrial Ergonomics, 7 , 111-22.

M I T C H E L L , C . M . (1987). G T - M S O C C : A domain for research on human-computer interaction and decision aiding in supervisory control systems. IEEE Transactions on Systems, Man and Cybernetics, 17 (1), 553-72.

M U E L L E R , T . (1991). Energy and electricity supply and demand: implications for the global environment. IAEA Bulletin, 33 (3), 9-13.

M U N I P O V , V . M . (1990). H u m a n engineering analysis of the Chernobyl accident. Unpublished manuscript. U S S R Scientific and Research Institute of Industrial Design (VNIITE), Moscow.

O B E R G , J. E . (1988). Uncovering Soviet disasters: exploring the limits ofglasnost. R a n d o m House, N e w York.

P E R R O W , C . (1984). Normal accidents. Basic Books, Inc., N e w York. P E R R O W , C . (1986). Complex organizations: a critical essay (3rd ed.). Random House, N e w York. P O R T E R , M . E . (1990 a). The competitive advantage of nations. The Free Press, N e w York. P O R T E R , M . E . (1990 b). W h y nations triumph. Fortune, 12 March, 94-108. R A S M U S S E N , J. (1985). Trends in human reliability analysis. Ergonomics, 28 (8), 1185-95. R A S M U S S E N , J. (1986). Information processing and human-machine interaction: an approach to

cognitive engineering. North-Holland, N e w York. R A S M U S S E N , J. (1989). Human error and the problem of causality in analysis of accidents. Invited

paper for Royal Society meeting on H u m a n Factors in High Risk Situations, 28-29 June, London.

96


R A S M U S S E N , J., D U N C A N , K . and L E P L A T , J. (eds) (1987). New Technology and human error. John Wiley & Sons, N e w York.

R A S M U S S E N , J. and R O U S E , W . B . (eds) (1981). Human detection and diagnosis of system failures. Plenum Press, N e w York.

R E A S O N , J. (1988). Resident pathogens and risk management. Invited position statement presented at the World Bank Workshop on Safety Control and Risk Management, 18-21 October, Washington, D C .

R E A S O N , J. (1990). Human error. Cambridge University Press, Cambridge and N e w York. S E M E N O V , B . A . , G U T H R I E , D . and T A T S U T A , Y . (1991). The future role of nuclear power in the

global energy balance. IAEA Bulletin, 33 (3), 20-4. S H R I V A S T A V A , P. (1987). Bhopal: anatomy of a crisis. Ballinger Publishing Company, Cambridge,

M A , USA. S H R I V A S T A V A , P., M I T R O F F , 1.1., M I L L E R , D . and M I G L A N I , A . (1988). Understanding industrial

crises. Journal of Management Studies, 25 (4), 285-303. S M E T S , H . (1985). Compensation for exceptional environmental damage caused by industrial

activities. Paper presented at the Conference on Transportation, Storage and Disposal of Hazardous Materials, 1-5 July. IIASA, Laxenburg, Austria.

S P E T H , J. G . (1984). Statement published in The Implications of the Industrial Disaster in Bhopal, India. Transcripts of the Hearing before the Subcommittee on Asian and Pacific Affairs of the Committee on Foreign Affairs House of Representatives, Ninety-Eighth Congress, 12 December. U S Government Printing Office, Washington, D C .

Summary Report on the Post-Accident Review Meeting on the Chernobyl Accident (1986). International Atomic Energy Agency Safety Series #75- INSAG- l . IAEA, Vienna, Austria.

T H O M P S O N , T . (1964). Accidents and destructive tests. In Thompson, T . J. and J. G . (eds). The technology of nuclear reactor safety. M I T Press, Cambridge, M A .

W I L S O N , R. (1987). A visit to Chernobyl. Science, 236, 1636-40.

97

Ergonomics and industrial development

Houshang Shahnavaz

The ergonomics intervention programme can be a means of guaranteeing the most efficient use of the labour force of an industrially developing country by creating safe and appropriate working environments, and has an important role to play in the choice and optimal application of new or transferred technology.

During the course of this last century, and especially since the Second World W a r , technological development has contributed enormously to economic growth and social progress in the industrialized countries. The wealth in today's world is mainly of applied technological origin and is primarily the product of applied sciences and technological knowledge. This notion underlines the importance of adapting technology to its users and the operating environment.

At places of work, technological development has contributed greatly to the reduction of m a n y sources of occupational accident, injury and disease and has in particular improved physical working conditions. However, the pattern of stress at work has changed with the technological changes. Advanced technology has introduced new sources of work stress and injuries. The total work demand (physical and mental) has sometimes increased, resulting in increased sick leave, absenteeism and loss of production in m a n y industrialized (ICs) and industrially developing countries (IDCs).

Ergonomics has been used traditionally in ICs for optimizing h u m a n performance and well-being and enhancing the effectiveness of facilities that people use for achieving higher productivity, improved worker health and job satisfaction. Ergonomics is used both in the design and introduction of new technology to workplaces and for the improvement of the existing technology through ergonomics intervention programmes.

With regard to IDCs , ergonomics is an essential means of assuring the efficient use of the labour force (which is, after all, a country's basic resource) and can help to m a k e best use of technical resources through optimizing the application of existing and the

Houshang Shahnavaz trained in mechanical engineering at the Technical University Darmstadt, in the Federal Republic of Germany. H e obtained his M S c and P h D in the field of industrial ergonomics at the University of Birmingham, United K i n g d o m in 1974 and 1976 respectively. In 1983 he became Head of the Centre for Ergonomics of Developing Countries ( C E D C ) at Luleâ University, Sweden, and one year later Professor of Industrial Ergonomics at the same university. H e m a y be contacted at the following address: Department of H u m a n W o r k Sciences, Luleâ University, S-951 87 Luleâ, Sweden.


H. Shahnavaz

new or transferred technology to the benefit of the local user population and the operating environment.

Ergonomics is also a useful tool for evaluating the choice of technology, and its implementation. It can contribute to the safe and productive transfer of technology and reduces the number and scale of accidents and catastrophes in industrial operations.

Appropriate technology

Technology, defined in terms of physical products, techniques, knowledge and organization, is an integral part of a country's structure. Any change in technology has an impact on the social, political and economic system. The solution to m a n y of the problems associated with industrialization in the I D C s lies in their cause. By adapting better development policies, choice of appropriate technology and more efficient control with regard to its implementation, Third World countries could solve m a n y of their current problems and provide acceptable living and working conditions for their population.

A n appropriate technology is a technology which is suited to its user population and to the environment in which it is used: technology which is appropriate to the needs and means of the population. Technology should therefore not be regarded as the objective of development, but rather the principal means for its attainment.

The large variety of circumstances that exist in the various countries of the world (with regard to economic climate, demography, culture and social customs, religious tradition, political system, social conditions, etc.) highlight the need for cautious development strategies and selection of alternative technologies. The development strategy of each country has to be based upon its o w n resources, skills, culture, h u m a n and environmental factors and also its social objectives. Therefore, there exists no uniform prescription or single system that one can regard as the relevant or appropriate technology for all developing countries at all times. Each country should define and develop its o w n technology fully appropriate to its special needs and resources.

The crucial issue which needs to be fully considered before any decision on transferring n e w technology is an examination of the existing technology and consideration of what can be done to improve it. However, as far as new technology is concerned, it is important to identify which technology to acquire, h o w to transfer it, h o w to adapt it to the future users and its operating environment, h o w to maintain it and h o w to build upon it in order to achieve the goal of strengthening the autonomous capacity of the country.

The appropriateness of technology

Industrially developing countries have tended to try to achieve the same level of development as industrialized countries by importing technology designed for the latter nations. However, because of several complex historical and socio-economic factors, this policy has not led to any significant improvements, either in relative or absolute terms, in the living conditions of the majority of the poor ( U N C T A D , 1978). Technology from ICs has often been designed with a view to the minimization of labour costs and according to the availability of capital skills and a well-developed infrastructure that are very different from those available in the I D C s .

100


The criteria of what is considered to be appropriate technology differs according to the place and stage of development. Concepts, ideas and policies of appropriate technology are also dependent on local conditions. There are no universals and permanently applicable 'appropriate technologies' in the world, and there are varying views as to what should be considered as appropriate technology.

However, from the various views of what should be considered as an appropriate technology it is possible to identify certain characteristics.

Local needs

Innovation and development of technology is closely oriented to the demands and needs of the user, i.e. the h u m a n being. However, the needs of humans are changeable. At different social and economic levels the needs will not be exactly the same. H u m a n needs also change with time. For example, for m a n y Asian families fifteen years ago it would have been a wishful thought to o w n a colour television set, a refrigerator or a washing machine. Today it is quite usual to possess such goods.

The priority of development of technology should be to give the majority of people a basic standard of living, provide good working conditions and offer possibilities for improvement over time.

Local resources

The successful application and implementation of a certain type of technology will depend on its environment. The environment is m a d e up of both 'hard' and 'soft' elements. The hard environment includes factors such as natural resources, e.g. water, energy, raw and processed materials, and the physical materials that are essential for a certain kind of technology. The soft environment includes level of knowledge and skills, and the educational, organizational, social, cultural, economic and political infrastructure. M a n y examples have shown that the inappropriate application of certain technologies has been due to incompatibility with the operating environment.

Unemployment

The issues of unemployment and under-employment have been the object of m u c h concern when considering the question of appropriate technology.

Technologies from ICs have on the whole been designed to reduce labour costs and are usually large-scale, complex and capital-intensive. However, shortage of labour is not a problem in IDCs and it has been k n o w n that one of the most serious and most immediate causes of poverty in the Third World is the shortage of productive employment.

Environmental considerations

The use of inappropriate technology has led to m a n y environmental problems. A n extreme example is that of the disaster at the Union Carbide Chemical Plant in Bhopal, India. Lanza (1985), writing about the incident, stated that: 'The real cause of the Bhopal tragedy is blind technology transfer...'. In many cases the destruction of the environment is a direct result of the manner in which productive resources are

101

H. Shahnavaz

combined and used. Particularly in the case of industrialized economies, the leading cause of environmental damage is to be found in the way technologies are employed. In other cases, careless application of inappropriate technologies contribute to the environmental problem. T o o m a n y development projects focus only on the immediate economic benefit, and neglect the detrimental side-effects on the environment.

Evolutionary capacity

Technology should not be immutable and static, but should have some evolutionary capacity. As the needs of h u m a n beings are continually increasing and changing, so technology needs to be able to keep up with them. Furthermore, it is not only the h o m e market that is changing, but also the international market. Again, technology needs to be able to keep up with these changes in order to be competitive within an international context, otherwise, products from IDCs will end up with second-class status.

The evolutionary capacity of technology is also dependent on the company's environmental conditions and policy. For example, although a large amount of sophisticated equipment from ICs has been imported into I D C s the latter m a y not be using this equipment to its full capacity and cannot usually contribute either to its future development or improvement. This is because the educational background, the organizational structure and the social and political conditions, in conjunction with the lack of k n o w - h o w , hinder the process of innovation and lead to I D C s remaining in the position of buyer as opposed to seller.

Social-cultural considerations

The relationship between technology transfer and technology change and the influence of social and cultural factors is becoming more and more important and is particularly relevant in choosing appropriate technology. Cultural variables and cross-national considerations in relation to various types of work are significant issues. M a n y studies highlight the cultural parameters of h u m a n performance (Kaplan, 1991).

The failure to employ a certain type of technology optimally is often due to the differences in social and cultural factors that exist between the transferor and the transferee. Generally, designers of technology in ICs are unaware of the complexities of the cultural context of the country to which their technology is going. Furthermore, the acquiring country usually has little opportunity to choose or specially request the technology which is best adapted to their cultural environment (Shahnavaz, 1991).

Ergonomie considerations

M a n y cases have shown that if there is not a 'good fit' between technology, technology users and the operating environment there results low productivity, poor quality of work, and a high rate of injury and accident. Fundamental physical, social and mental differences exist between the populations of the I D C s and those of the ICs. It follows that technology designed specifically for one population is not going to be ideal or adequate for others.

In the technology transfer process, emphasis is usually laid on economic progress. It is, of course, necessary that the economic situation and the general standard of living should improve, but the method by which this is achieved is also important.

102


According to Wisner (1984), technology can be inappropriately transferred in three ways:

Incomplete transfer: not considering all aspects of the technology in the transfer process, e.g. leaving out (neglecting) the transfer of the maintenance capability.

Imperfect transfer: not considering the user's characteristics in the transfer process, e.g. not translating maintenance manuals and instruction books into the local language.

Inadequate transfer: not considering the environmental conditions of the recipient country such as the climate, infrastructure of society, finance, technology and culture etc., e.g. transferring products such as protective clothing m a d e for cold countries to tropical ones.

Fundamental differences that exist and need to be considered from an ergonomie point of view in the process of industrialization are as follows:

Anthropometry Differences in body size of different populations m a y mean that m a n y products and machines imported from ICs do not fit the size or shape of the user population in the I D C . The wide diversity in size and shape of people living in different parts of the world can be attributed to factors such as genetics, climate, standard of living and type of activity.

Workplaces, equipment and tools must fit the physical characteristics of the user population. M a n y accidents, injuries and low productivity in workplaces have been shown to be the result of misfit. For example, poor working posture has been regarded as one of the major risk factors causing musculoskeletal disorders, which represent the most serious problem at workplaces both in ICs and IDCs .

Areas where these differences apply and need to be considered are in the design of equipment, workstations, lay-out of work-space and protective equipment.

Physical working capacity This is the capacity of people to perform prolonged physical (i.e. manual) work and is related to individual health, age, weight, sex, fitness, level of nutrition, as well as environmental conditions. In I D C s manual work is the main type of employment.

Considering the high workloads in I D C s , and the lower physical work capacity of the workers because of their poor health standard, lower weight, inadequate nutrition and harsher working conditions, it is not difficult to find that the work d e m a n d is in m a n y cases too high, which leads not only to higher accident and injury rates but also lower productivity. Apart from differences in physical work capacity between people in I D C s and ICs there also exists differences in functional ability such as differences in generation of force and muscular function. Several studies have shown that on average the m a x i m u m force generated by the worker in an I D C can be as little as a quarter of that of someone from an I C (Shahnavaz, 1988). These differences need to be considered when designing manual work, work rest schedules, selection and placement of workers in different physically demanding jobs.

The various factors which affect an operator's physical performance and well-being in an I D C , (e.g. longer working hours, improper shift-work schedules, hazardous uncontrolled working environment, nutritional inadequacies and the effects of tropical disease) are often not taken into account when technology is transferred.

103

H. Shahnavaz

Time spent at work The amount of time spent at work includes not only the actual time spent working at the official place of work but also the time spent in getting there (which can be very long and highly stressful) and the time spent at the secondary place of work, such as h o m e . This is particularly relevant for people of an I D C , especially w o m e n , as the amount of time they spend working can be up to 14-16 hours per day. Consequently, the work-force can become excessively fatigued and this is detrimental to both its health and to productivity.

Physical working environment T h e physical environment of an I D C is generally that of a tropical or sub-tropical climate, and consequently there are problems of heat and ventilation to be encountered. The introduction of manufacturing and its associated processes has served to exacerbate these difficulties. Furthermore, there is the additional heat produced by the hard physical work being performed. Subsequently, if the working environment is such that this excess heat is not removed and the workforce is unable to retain normal body temperatures, then it can be very uncomfortable and indeed dangerous (e.g. causing heat collapse) both for the individual and for those working in the same environment.

Problems regarding working conditions need to be taken into consideration when organizing jobs, working methods, work-rest schedules and plant and work-place design.

Protective equipment The high temperatures and high humidity levels generally found in I D C work-places lead to a decrease in performance and discourage the worker from using personal protective wear. A s a result only a few percent of people w h o should wear such materials are actually doing so (Abeysekera and Shahnavaz, 1988).

Ideally, the use of protective equipment should be avoided by the improvement of working conditions through engineering measures. However, if this is not completely achievable, then the protective wear should be matched to the condition and size of the user population in the I D C , so as to not add further to existing problems.

Psychology The factors which can be classified as psychological include cognitive differences, variation in skills and differences in perception and cognitive procedure. It has been observed that people from developing countries have a different internal model, have different operational images and population stereotypes and that there is a difference in their pictorial perception and information processing behaviour. These differences will affect the operator's performance in areas such as communication (verbal and written), display design, software design, training programmes, organization of work and skills, system design (particularly complex systems) and system operation.

Consequently, it can be seen that the question of choosing appropriate technology is not as straightforward as it might at first appear. This fact becomes all the more apparent when it concerns transferring technology to an I D C which has completely different requirements and needs from those of the transferor.

However, industrialization still proceeds in m a n y IDCs with low or no priority for the more important aspects of technology, apart from the short-term economic benefits. The transfer of technology without consideration of the h u m a n factors from the very early stages of the technology life-cycle has not only resulted in economic

104


losses but has also proved to be expensive in terms of h u m a n suffering and social tension in m a n y IDCs .

This general discussion highlights the need for an active and on-going intervention system at company level to take care of the ergonomie issues related to the introduction of new technology or improving the existing one for the better well-being and productivity of the work force.

Ergonomie intervention

M a n y organizations in the industrial world are using ergonomics to tackle some of the problems encountered in the work-place. Initiatives for such intervention have been developed in response to a range of problems, but mainly those arising from the introduction of new technology, low productivity, and health and safety problems amongst the workforce. These problems have become of significant concern for the industries involved, because of the increase in absenteeism, early retirement, loss in productivity, work-related injuries and high compensation claims, which apart from the financial loss can cause a nasty dent in the corporate public image.

M a n y ergonomics intervention programmes have been directly initiated in response to health and safety problems in the work-place. C o m m o n problems are posed by poor physical working conditions, for example, high noise levels, presence of toxic chemicals, heavy load handling, repetitive muscular activities, excessive bending and twisting and bad working posture because of inappropriate design of work-places, machinery and tools. In some cases the organization of work and its content, as well as the managerial structure of the company, have been the cause of m a n y labour problems.

The ultimate objective of an ergonomics intervention should be to design ajob which is possible for people to do, is worth doing and gives the worker job satisfaction and a sense of identity with the company (Corlett, 1991). However, the success or failure of an intervention programme depends on the effectiveness of the technique used: that is, whether the intervention leads to the expected changes and whether the changes are sufficient to eliminate the initial problems which the intervention was aimed at, as judged by all parties concerned in the long term.

The intervention should be viewed by the companies as a dynamic process. Adopting a continuous and on-going programme with the participation of all parties concerned is a prerequisite for successful development. This is because with time and technological development, new problems arise in company work-places, and these require fresh and collective action.

Factors affecting ergonomics intervention

There are several factors that influence the success of an intervention programme. A multi-disciplinary approach considering all the influencing factors is essential, as is good planning and appropriate training of the people concerned. The main factors are as follows:

Worker participation A number of studies have emphasized the importance of worker participation in the introduction of new technology into the organization or the

105

H. Shahnavaz

improvement of the existing technological system (Lenior and Verhoven, 1990; Wilson, 1991; Levi et al. 1990; Algera et al. 1990; Fröhlich and Krieger, 1990). The most important factors cited for successful ergonomics implementation were management support and involvement of the operators. This is because the resulting ergonomics intervention needs to be legitimized by both management and workers, the procedure should stimulate the expression of different views on existing problems and finally all the participants have the opportunity to check out findings and suggest changes (Algera et al. 1990).

In m a n y cases the major objection to worker participation in the process of ergonomics intervention is, from the management point of view, the fear that vital decisions might be delayed. However, survey data from several studies clearly show that this fear has no scientific grounds and that the opposite is more likely to be the case. Worker participation has in most cases improved the quality of the decision, and minimized the total time taken to reach it and to implement the technology to the full (Fröhlich and Krieger, 1990; Eason, 1990).

Worker participation is essential both for the correct identification of the various work-related problems and for defining the appropriate solution. Workers involved in doing a job for many years can often come up with excellent ideas and simple and feasible solutions to problems. They represent a resource which should be used to the full. In addition, the worker will accept an intervention more readily if she or he has been involved in suggesting it.

Ergonomics awareness and know-how M a n y problems at work-places can be resolved quite easily with an ergonomics approach, but they persist due to lack of relevant k n o w - h o w . Training courses in ergonomics both for employees and management would help to bring about such awareness to the organization. This would help those involved to be aware of various risk factors and encourage them to work in a safer way and help avoid problems.

Sometimes the necessary ergonomics knowledge does not exist within the organization for the proper carrying out of the various stages of intervention. These include the diagnosis and identification of the problems, followed by collection of subjective and objective data for detailed analysis of the problems, proposing of feasible recommendations and solutions, practical intervention and final long-term evaluation. In such cases assistance needs to be sought from an ergonomics consultancy or research organization. A well established support system at country level would ensure successful function of any intervention programme for the provision of a safe and satisfactory working environment.

Legislation and inspection Legislation has a significant role in the improvement of conditions in the working environment and the encouragement of ergonomics intervention. It is an important way of ensuring a healthy, safe and ergonomically sound workplace. It contributes towards national aims and has a significant impact on companies in the maintenance of standards. However, periodic and systematic inspections are vital to identify problems in time and develop preventive measures in the work-place for their alleviation.

Cost It is suspected by some managers that ergonomics interventions at the workplaces have financial implications. However, m a n y studies show that despite such

106


reluctance at first attitudes of managemen t change as the work progresses. This is mainly due to the fact that m a n y improvements can be carried out immediately at little expense, and that the benefit gained from these outweigh the cost of improvement. Benefits usually include increased productivity and product quality, as well as improved working conditions resulting in greater worker well-being and satisfaction, cost-saving for the c o m p a n y through reduced absenteeism, reduced accident and compensation claims, reduced work stoppages and loss of production.

Structure and culture T h e cause of m a n y problems m a y be also related to inappropriate

organizational structure and culture and the existing operational climate of rapidly

changing and difficult-to-predict environmental forces on the enterprise.

Narrow, tightly controlled and fragmented jobs usually lead to low motivation amongst the workforce, and this has an adverse effect on individual and organizational performance, as well as product quality (Burnes, 1990). Such organizational environments also lead to increased labour turnover, absenteeism and poor industrial relations, which in turn increase overall costs and reduce organizational flexibility.

The cultural identity of the organization is an important feature of all companies, but as H a n d y (1986) has commented , 'No t all cultures suit all purposes or people... W h a t suits them and the organization at one stage is not necessarily appropriate for ever—strong though that culture m a y be.' So, culture can m o v e from being an asset to the organization to being a hindrance, if not fitted to the needs and preferences of the employees.

Top management

support

Workers1

representatives

INTERVENTION TEAM

Inspection and

enforcement

Figure 1. Model of an ergonomics intervention.

107


Conclusion

It is worth mentioning that it is not possible to propose a general and detailed intervention programme applicable to all countries or enterprises. The unique situation and characteristics of each company and the prevailing conditions within the country demand a specially designed intervention programme for that environment. Nevertheless, the above-mentioned principles do need to be applied for a successful ergonomics intervention programme.

A proposed model for ergonomics intervention is presented in Figure 1, showing the composition of the 'Intervention team' at workshop level and the types of support required for the group to function successfully within an organization.

References

A B E Y S E K E R A , J. D . and S H A H N A V A Z , H . (1988). Ergonomics aspects of personal protective equipment: its use in industrially developing countries. Journal of Human Ergology, 17, 67-79.

A L G E R A , J. A . , REITSMA, W . D . , S C H O L T E N S , S., VRINS, A. A . and W U N E N , C . J. D . (1990).

Ingredients of ergonomie intervention: how to get ergonomics applied. Ergonomics, 33, 557-8.

B Ö R N E S , B . (1990). Barriers to employee involvement in technical change: 'more than a case of the good guys and the bad guys'. Advanced Manufacturing Engineering, 2, 69-75.

C O R L E T T , E . N . (1991). Ergonomics fieldwork: an action programme and some methods, in Kumashiro, M . and M e g a w , E. D . , Towards Human work—solutions to problems in occupational health and safety, pp. 179-86. Taylor & Francis, London.

E A S O N , K . D . , (1990). N e w systems implementation, in Wilson, J. R . and Corlett, E . N . , Evaluation of human work: a practical ergonomics methodology, pp. 835-49. Taylor & Francis, London.

F R Ö L I C H , D . and K R E I G E R , H . (1990). Technological change and worker participation in Europe. New technology, work and employment, 5 (2), 94-106.

H A N D Y , C . B . (1986). Understanding organisations, Penguin, Harmondsworth, U K . K A P L A N D , M . (1991) Cultural ergonomics: an evolving focus for military human factors, in

G O L , R . and M A N G E L S D O R F F , A . D . , Handbook of military psychology, pp. 155-167. L A N Z A , G . R . (1985). Blind technology transfer: the Bhopal example. Environment Science

Technology, 19 (7), 581-2. L E N I O R , T . M . J. and V E R H O E V E N , J. H . M . (1990). Implementation of human factors in the

management of large-scale industrial investment projects: a management point of view and ergonomics practice, Ergonomics, 33, 643-53.

LEVI, D . J., S L E M , C . M . and Y O U N G , A . (1990). Technology versus team-driven approaches to implementing advanced manufacturing technology, in Noro, K . and Brown, O . , in Human factors in organizational design and management: III. pp. 129-132. Elsevier Science Publications, Amsterdam, N e w York.

S H A H N A V A Z , H . (1988). Lecture notes on human factors and technology transfer. Luleâ University, Sweden.

S H A H N A V A Z , H . (1991). Transfer of technology to industrial developing countries and human factors considerations, TULEA 1991: 22, Luleâ University, Sweden.

U N I T E D N A T I O N S C O N F E R E N C E O N T R A D E A N D D E V E L O P M E N T ( U N C T A D ) (1978). Transfer of technology: its implications for development and environment. United Nations, N e w York.

W I L S O N , J. R . (1991). Design decision groups—a participative process for developing workplaces (unpublished paper), Institute for Occupational Ergonomics, University of Nottingham, UK.

W I S N E R , A . (1984). Organization transfer toward industrially developing countries, in O . Brown and H . W . Hendrick (eds.), Human factors in organizational design and management. North-Holland, Amsterdam.

108

Did you know that

educators, research workers and

students can use Unesco coupons to purchase

books, periodicals, films

art work, sheet music

radio and television sets

typewriters

scientific equipment

tape-recorders machine tools

musical instruments

measuring instruments

U N E S C O C O U P O N S can also be used to pay for subscriptions to educational, scientific or cultural publications, for university registration fees a n d copyright dues

U N E S C O C O U P O N S are siooo Unesco coupon Siooo issued in the following ,„«„.,.„, I. ScunlrtK und lukur«! úrfanin

denominations:

US Dollars

1,000 A n 100 30 10 1

• ; I K ? W fficThousand dollars -V.IL:

(Blank coupons which can be made out for the sum of 1 to 99 cents also available)

H o w do they work?

In every user country there is a body—often the National C o m m i s s i o n for Unesco—which is responsible for the sale of the coupons.

Write to Unesco C o u p o n s Office, Unesco , 7 place de Fontenoy, 75700 Paris, France, for list of main suppliers participating in the p r o g r a m m e , as well as for the n a m e and address of your country's Unesco C o u p o n Sales Office.

Y o u pay for the coupons in your own currency and enclose the coupons with your order to the supplying c o m p a n y of the material you want .

http://-v.il

Linguistics & Language Behavior Abstracts

ELBA N o w entering our 26th year (135,000 abstracts to date) of service to linguists and language researchers worldwide. LLBA is available in print and also online from BRS and Dialog.

Linguistics & Language Behavior Abstracts

P.O. Box 22206 San Diego, C A 92192-0206

Phone (619) 695-8803 FAX (619) 695-0416

Fast, economical document delivery available.

An official journal of the Ergonomics Society and the International Ergonomics Association

Ergonomics General Editor R. Goldsmith

Editors P. J. Barber, A Grieco, E. J. Harnley, M . Helander, E. Hof fmann, H . Luczak, J. B. Morrison, K. Noro, C. N. O n g , C. O'Brien, J. Patrick, R. Ortengren, Y. Queinnec, Z. M . W a n g , F. G . J. Witt, S. K o n z and W . Kurwowski

Editorial Office do 4 John Street, London, WC1N2ET

Scope E R G O N O M I C S is an international multidisciplinary journal concerned with all aspects of the interactions of human beings and their work and leisure. The contents of the journal report research results on the psychological, physiological, anatomical, and engineering design aspects of human beings at work, being particularly concerned with optimizing performance. Research data from developed and developing countries is reported. Special issues, containing collections of papers on important contemporary themes, are published from time to time; recent special issues have covered areas as diverse as advances in visual ergonomics in Japan, the contemporary ergonomie scene in China, the ergonomics of sport, risk decision-making, and cognitive ergonomics. As well as the peer-received scientific papers, the journal publishes a regular news section, Ergonomics International, in conjunction with the International Ergonomics Association. This section of the journal covers ergonomie activity worldwide. The journal also features book reviews, and regularly publishes the contents and abstracts of ergonomie journals from France, Germany, Poland, and Yugoslavia.

Recent Contents SHAPA: an interactive software environment for protocol analysis, P.M. Sanderson et al. (USA) I Video analysis in cognitive ergonomics: a methodological perspective, 1. V. Laws and P.J. Barber (UK) I Fault management in process control, N. Moray and I. Rotenberg (USA) I Multivariate analysis of mental and physical load components in sinus arrhythmia, D.H. Lee and K.S. Park (Korea) I Neck and shoulder muscle activity during work with different cash-register systems, L. Lannerstan and K. Harms-Ringdahl (Sweden) I Resultant clothing insulation: a function of body movement , posture, wind, clothing fit and ensemble thickness, G . Havenith etal. (The Netherlands) I Perceived relationship between elements of a complex display, G.J. Armstrong and E.R. Hoffmann (Australia) I Predicting the transmissibility of a suspension seat, I.E. Fairley (France) I Dynamic analysis of isoinertial lifting technique, J.M. Stevenson et al. (Canada) I H o w display polarity and lighting conditions affect the pupil size of V D T operators, 5. Taptagaporn and S. Saito (Japan).

Publisher: Taylor & Francis Ltd Subscription Information Volume 35 (1992) Monthly ISSN 0014-0139 Institutional: U S $ 4 7 0 / £ 2 7 2 Personal: U S $ 1 3 8 / £ 8 1

ALERE IFLAMMAM

Published in association with the Ergonomics Information Analysis Centre

Taylor

Francis Group

Send for a free

sample copy to:

TAYLOR & FRANCIS UK: Rankine Road, Basingstoke, Hants RG24 OPR

USA: 1900 Frost Road, Suite 101, Bristol, PA, 19007-1598

Ergonomics Abstracts

Ergonomics Abstracts

?»

Editor Christine Stapleton Ergonomics Information Analysis Centre, University of Birmingham, Edgbaston, Birmingham, B15 2TT, UK

Scope E R G O N O M I C S A B S T R A C T S ¡s a bimonthly journal providing an international abstracting service for all areas of ergonomics and human factors. Because of the changing frames of reference in modern scientific research and application, E R G O N O M I C S A B S T R A C T S has become an invaluable source of information for everyone w h o needs the most up-to-date literature in psychology, physiology, biomechanics and work design. Over 3 0 % of the content relates to the increasingly important area of human-computer interaction. E R G O N O M I C S A B S T R A C T S publishes a selection of over 4500 abstracts from over 350 journals, books, reports and conference proceedings per annum. Full bibliographic details and a summary of the abstracted article are presented in a clear and concise format. In addition to the unique classification scheme, each issue contains an index by application and a comprehensive book reviews section.

Recent Contents Each article is classified within 600 headings and located under that heading considered to reflect its primary interest, with extensive cross referencing to indicate other areas of interest. The 600 headings are grouped into 12 sections with three levels of subdivision. The section headings shown in bold, and a selection of first levels of subdivision are listed / Ergonomics / H u m a n Characteristics / Psychological Aspects / Physiological and Anatomical Aspects / Performance Related Factors / Individual Differences / Task Related Factors / Information Presentation and Communication / Visual Communication / Software Design, Maintenance and Reliability / Display and Control Design / Input Devices and Controls / Visual Displays / Workplace and Equipment Design / Workstation Design / General Workplace Design and Buildings / Environment / Illumination / Noise / System Characteristics / System Usability / Work Design and Organization / Hours of Work / Payment Systems / Health and Safety / Etiology / Prevention / Social and Economic Impact of the System / Trade Unions / Quality of Working Life / Methods and Techniques / Measures / Approaches and Methods.

Publisher: Taylor & Francis Ltd Subscription Information

Volume 24 (1992) Bimonthly ISSN 0046-2446 Institutional: U S $ 5 9 9 / £ 3 4 8

Date post:	06-Sep-2018
Category:	Documents
Upload:	dinhdien
View:	228 times
Download:	0 times

Ergonomics; Impact of science on society; Vol.:165;...

Documents