Article history:Received 5 January 2011Received in revised form 29 October 2013Accepted 1 November 2013

Keywords:

commodity (Acha et al., 2004). Manufacturers make buses operators provide transport. The nature of bus operators variesof buses in a de-cale and bu

n of a bus ba supplied chassis. This manufacturing methodology is typical in countries where markets cannot support wideinvestment into chassis manufacturing capabilities. In the Australian context, the majority of chassis are manufactuEurope and shipped to the bodywork manufacturer. European chassis are considered market leaders in this area (Vuchic,

0968-090X/$ - see front matter 2013 Elsevier Ltd. All rights reserved.

Tel.: +61 3 9903 1059; fax: +61 3 9903 1440.E-mail address: robbie.napper@monash.edu

Transportation Research Part C 38 (2014) 5672

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Transportation Research Part C

journal homepage: www.elsevier .com/locate / t rchttp://dx.doi.org/10.1016/j.trc.2013.11.002from government organisations to small family businesses; they are typically responsible for the operationned geographical area to create transport service. Operators must work within the constraints of their lostrategy; reected in varied methods of operation and marked physical variations in bus vehicles.

This research investigates body-on-chassis or bus bodyworkmanufacture, characterised by the fabricatiosiness

ody onspreadred in1. Introduction

Route buses are an integral part of transportation systems. The ubiquity of roads means buses can offer an inexpensiveand versatile means of public transport (Grifn et al., 2005). Bus vehicles are capital goods, machinery used to produce aTransitBusDesignManufactureVehicleOperationSpecicationThis research examines the problem of route bus specication and vehicle manufacturabil-ity. In order for bus operators to provide transport services, a range of vehicle congura-tions must be available from bus manufacturers, generating variety which has a negativeimpact on the manufacturing process. Larger part inventories, uncontrolled labour tasksand more troublesome maintenance are known impacts of this variety. This research iden-ties the functional necessities in route bus interior design and reduces the problems inbus manufacture and operation caused by specication diversity by proposing a modular-ised system of bus design. In particular, it makes recommendations as to how bus cong-uration should be carried out, ensuring an optimum mix of operational and manufacturingneeds:

1. Determine user needs before the bus specication process.2. Designs to be developed by the manufacturer in response to user needs.3. This design should be standardised where possible, as suggested by the user needs.4. Where user needs dictate product variations, apply a mass customisation approach to

accommodate these needs.

The recommendations are communicated in design proposals for a modular bus interior,demonstrated by four cases designed to meet the present status quo of bus interior designand predictions for the future of the eld.

2013 Elsevier Ltd. All rights reserved.Modular route bus design A method of meeting transportoperation and vehicle manufacturing requirements

Robbie Napper Department of Design, MADA, Monash University, 900 Dandenong Road, Cauleld East, Victoria 3145, Australia

a r t i c l e i n f o a b s t r a c t

1981). The Australian bus market is dominated by bus bodywork manufacturers, although alternatives are available in theform of locally made complete buses.

The research problem is that specication diversity in route bus bodywork increases the costs of product development,erodes economies of scale, and increases lead times and overall production times in bus manufacture. The result is a moreexpensive and troublesome vehicle to purchase and maintain. This research sets out to determine a bus interior design pro-viding appropriate vehicles for operational purposes, while ensuring that the vehicles are also capable of efcientmanufacture.

Bus variation is manifested in several ways. Vehicle length varies as a result of road-form constraints and desired passen-ger capacity. Changing components such as doors and air conditioners allows bus operators to meet different functionalrequirements, the result being vast variation across the product range. In addition to explicit functional needs, bus operatorsmay also have a company history or culture dictating a particular specication, such as oor materials and livery. These vari-ations continue to create unique vehicles.

To the layperson and passenger, bus variation may well be invisible. Their perception is of a vehicle providing the trans-port commodity; and of being moved from origin to destination. The present aim of bus design is to facilitate manifestationof this service. The commodity-centric view of transport, and in particular bus transport is however changing by becomingattuned to the qualitative requirements of transport, particularly with reference to competition from the private car (Beiroand Sarseld Cabral, 2007) and light rail (Hensher, 1999).

Variation in bus design is necessary at present to mitigate the discrepancy between bus vehicles and operator needs; ulti-mately enabling the operator to offer the passenger consistent service. In addition, by specifying the exact nature of its cap-ital goods, the bus operator can integrate the bus into their operational strategy. For example, a bus operator might instigatea particular material specication allowing it to schedule vehicle cleaning around evening shifts, or the design of a driversarea may be more in keeping with union requirements for driver safety a factor that affects the passenger indirectly ratherthan directly. Specication is often driven by historical precedent in operator companies, which may be functionally justiedas in the case of wanting to use the same chassis marque (brand) to rationalise maintenance programmes, or culturally jus-

R. Napper / Transportation Research Part C 38 (2014) 5672 57tied by means of family company history. One example of this the bus interior shows signicant variation in congu-ration, and in the part inventory used to accommodate this variation.

In present form, bus bodywork manufacture is highly labour intensive, requiring many skilled tradespeople in variouscapacities. This is coupled with a considerable amount of engineering, sales and administrative work prior to commence-ment of build. Bus specication requires extensive negotiation between sales, engineering and the operator, supported bypreparation of contracts for delivery and payment; conditions repeated across a variety of orders from bus operators. Theseconditions have precipitated a bespoke system of manufacturing, distinguished by variety in procedures, parts and the n-ished product, despite the processes having similarities and the end product being functionally identical to the next a bus.

At present, operators specications are communicated to the manufacturer by means of the sales process and given formin the engineering department before production. While this may appear simple in its linearity, the information passedthrough this process changes at every stage. Thus, by seeking to intervene in bus design this paper also aims to addressthe process of bus specication, as shown in Fig. 1. Although the bus may appear somewhat reactionary to specications,

Fig. 1. The typical Australian bus bodywork specication, design, and manufacture process.

by analysing these specications we can improve our understanding of what drives them. Thus, the methods by which busesare brought into service are subject to research and experimentation in this research.

Diverse specications originate with the needs of bus operators. A specication can be an unclear method of communi-cating user needs, as the communiqu takes the form of a solution, rather than establishing a problem. Research into userneeds therefore forms a fundamental element of the broader research into bus specication processes, in order that the prob-lems of specication diversity may be reduced.

2. Product and literature review

The extent of variation in the bus interior was found to be signicant in a review of two years production at an Australianbodywork manufacturer (n = 495) (Napper, 2007). Interior components were found to be open to unstructured variations indesign, colour and position in the bus. For example, a handrail connecting the ceiling to a seat back may be shaped (bentfrom stainless steel tube) in a variety of curves, painted one of several colours or offered in a brushed nish, and then posi-tioned in the bus interior in only one space, or repeated in several positions. The nish paint specication is simple en-ough to accommodate in the production process, but when variations such as this are multiplied across many interiorcomponents the consequences for vehicle manufacture and consistent operation become serious. In production, large inven-

58 R. Napper / Transportation Research Part C 38 (2014) 5672Fig. 2. Seated capacity of vehicles, by bus length and number of doors.tories are required to offer all variations in components, and labour is subject to variation as the work required to fabricateand install parts is not standardised. In operation, variety in a vehicle eet has a signicant impact on maintenance and re-pair of vehicles in the same labour dimension as in manufacture. Furthermore, an inconsistent eet of buses can cause sched-uling difculties as a transport planner must accommodate differences in vehicle capability in their consideration of theavailable eet.

The review also found three key components in the conguration of a bus interior; vehicle length, number of doors, andthe number of seats. For operational reasons the need for these variations are unlikely to change due to road, dwell timeconstraints, and corridor capacity requirements respectively. Fig. 2 captures the variation in these three specications fromthe review.

This research sets out to determine how the design of buses and systems of design for route bus bodywork manufacturecan reduce the negative effects of specication diversity. The question is located across three areas of knowledge; mass cus-tomisation, design and public transport. Accordingly this section undertakes a literature review of relevant areas in publictransport and mass customisation research. The bespoke manufacturing methodology is analysed, leading to an examinationof mass customisation. Mass customisation (MC) is an umbrella term used to describe the manufacturing and managementstrategies for diverse product ranges. This section provides an introduction to MC principles and provides a critical analysisresulting in a direction for this research. The review of knowledge in public transport determines the characteristics of busfunction within the transport system, and identies knowledge gaps in this area; particularly those related to the design ofvehicles and the complex milieu of user needs.

Economies of scale in modern production systems allow less expensive manufacture and assembly of complex, identicalgoods which would otherwise be more expensive. Existing ideas of mass production were brought together in the Model TFord, in combination with the innovation of compartmentalised manual tasks in production. Henry Fords notion of stan-dardisation offered customers ...any colour that he wants so long as it is black. (Batchelor, 1994).

Fords often quoted yet reputedly never uttered phrase (Batchelor, 1994) nevertheless neatly summarises the beauty andboundaries of mass production the system will work if consumer demand is limited to the product in standardised form. Inthe Model T case, the efciency of manufacture led to such an affordable product that customers overlooked deciencies; asdespite shortcomings the Model T still represented a signicant advance from the horse. Mass production endures as thebasis of efcient manufacture, the fundamental attributes being the repetition of tasks and components. The Model T Ford

R. Napper / Transportation Research Part C 38 (2014) 5672 59successfully captured the market in personal motorised transport and through further standardisation colour choice even-tually being limited to black and larger economies of scale, the price of the vehicle dropped from its already low base of$850 in 1908 to $360 in 1916 (Batchelor, 1994).

Stan Davis suggests that manufacturers should ...mass-customise as much as necessary and as little as possible (in Gilmoreand Pine (2000)). A balance is desirable between customer satisfaction and efcient manufacture. It is important to balancecustomer needs and manufacturing capabilities, the gap between these constraints being known as customer-sacrice(Gilmore and Pine, 2000).

The notion of modularity can make MC seem a simple process, but the question remains as to which components aremodularised and which are standardised. Automotive manufacturers share both the platform for the car, and the smallercomponents which are carried by this platform. This enables the design and manufacture of a range of cars with certain sim-ilarities yet difference in the marketplace (Brewer, 2004). A similar observation can be made in bus bodywork, where similarchassis can be built into dissimilar bus vehicles.

Contemporary bus vehicle design is dominated by mechanical requirements. The task of detailing a useable, cost effectivebus capable of surviving the rigours of daily use for a lifespan of around 25 years is a signicant engineering challenge andgoes some way to justify a mechanical approach. With the added problems of product diversity and the disadvantages ofbespoke manufacturing it would appear the task is already rich with constraints. However, as has been argued elsewhere(Napper et al., 2009) the needs of the passenger are somewhat more complex than having space in which to ride the bus,and thereby form something of a bridge between the nature of the bus as a vehicle, and as a means for provision of publictransport. The review in this section is conducted to temper the quantitative operational knowledge with the qualitativeneeds of passengers to protect the integrity of the user experience in a manufacturing-dominated research question.

A great deal of information exists in the transport research eld regarding the quantitative, utilitarian needs of the pas-senger. This mature knowledge is applied in transport planning to design efcient transport systems. At the periphery oftransport system knowledge are the qualitative needs of the passenger; issues such as comfort and image which themselvesaffect passenger decision making and thus are connected with transport operations. Qualitative studies are unconventionalin the somewhat mathematical eld of transport research. Qualitative research in transport encourages an understanding ofwhy ridership gures stray from predictions, and is also particularly appropriate in the eld of public transport design.

Qualitative factors of transport are rarely the explicit subject of transport research. The resulting review is of the few di-rect sources of information, augmented by the broader transport planning literature, as there is a tendency to refer to qual-itative factors as a knownunknown of transport research. Transport planning literature refers to qualitative factors in asingular sense; this review aims to consolidate the disparate references into a cohesive body of knowledge. Design of abus interior requires this knowledge in order to understand all the constraints on the design, and to allow the design of ahigher-specication interior as a method of reducing the need for product diversity. In this review passenger needs havebeen categorised spanning from the explicit needs of transport utility to the personal, physiological, psychological and social.

The literature review on user needs is summarised in the list below with direct references. The closest works to anexhaustive list of user needs are the European Bus of the Future (UITP, 2006) and Schwartzs (1980) taxonomy of bus systemattributes, which itself lls out generic attribute categories identied by Rogers and Shoemaker (1971). Transport researchliterature tends to rely on a few key empirical studies which appear accurate and very useful but unveriable in their fullnessdescribing user needs (for example, Prioni and Hensher, 2000). The user needs literature overlaps with transport psychologyand tends to fall back on central works such as Everett and Watson (1991) and Mayr (1959). User needs across the literatureexamined in this research were elicited by means of survey work on transport modes, or derived from the psychological,ergonomic and service elds. Importantly, the list below is an un-ranked collation of attributes given that journey length,prevailing culture, expectations and price play a role in how important such needs are to passengers considering the wholejourney not just a set of separate reactions (Oborne, 1978a,b).

The incorporation of user needs into bus design is most effective when motivated by commercial means, such as contractprovision of transport services to a particular area which must uphold specied contractual standards; and in the tenders fornew bus vehicles used to full these contracts. Tenders for vehicles in the Australian metropolitan regions pertinent to thisresearch show that the literature resonates at an operational level by citing works directly in the case of UITPs European Busof the Future (New South Wales Ministry of Transport, 2007); or more generic, unreferenced but nevertheless literature-aligned calls for smooth journeys and comfortable temperatures (Government of Western Australia, 2010).

User needs are a demonstrably broad data set, increased by the inclusion of qualitative user requirements. Passengersrequire the delivery of transport services in accordance with the following review ndings:

1. Ease of cognitive and physical access. Ensuring that the transport system is accessible physically by members of the public,and also that the system of engagement with the transport network is understandable and can be effectively applied bythe user (Mayr, 1959; Oborne, 1978a,b; Schwartz, 1980; Newman and Kenworthy, 1991; Hensher, 1998; Booz Allen andHamilton, 2000; Friman et al., 2001; Friman and Grling, 2001; Ben-Akiva and Morikawa, 2002; Bus Partnership Forum,2003; Department for Transport, 2003; Litman, 2004; Howes and Rye, 2005; Nielsen et al., 2005; Beiro and Sarseld Cab-ral, 2007; Joewono and Kubota, 2007; Stradling et al., 2007a,b; Vuchic, 2007; Sweeney Research, 2008a,b).

2. Vehicular and personal safety. Users can be safe from personal attack or threat thereof, and that a driver may conduct thevehicle in operation without incident (Ben-Akiva and Morikawa, 2002; Braga, 2004; Department of Transport, 2008a,b,c;Sweeney Research, 2008a; Litman, 2011).

60 R. Napper / Transportation Research Part C 38 (2014) 56723. Physical and psychological comfort. Both contributing to comfort overall and related to physical and cognitive access. Muchof the literature speaks of comfort and a variety of denitions and attributes are relevant (Levis, 1978; Oborne, 1978a,b;Richards, 1980; Richards et al., 1980; Schwartz, 1980; Ben-Akiva and Morikawa, 2002; Howes and Rye, 2005; Stradlinget al., 2007a,b; Sweeney Research, 2008a,b; Litman, 2011).

4. Flexibility in using their transit time. That a passenger may be able to engage in work or leisure activities to their likingwhile in transit (Newman and Kenworthy, 1991; Sheller, 2004; Stradling et al., 2007a,b; Sweeney Research, 2008b).

5. An aesthetically appealing environment. Offering a space of benign pleasance to the senses in order to minimise offence(Newman and Kenworthy, 1991; Sheller, 2004; Sweeney Research, 2008b; Litman, 2011).

6. Cleanliness. A transport offering free from foreign matter from the operational environment such as dirt, dust, grafti andtheir associated odours and material consequences (Richards, 1980; Friman et al., 2001; Friman and Grling, 2001; Com-mission for Integrated Transport, 2002; Joewono and Kubota, 2007; Stradling et al., 2007a,b; Sweeney Research, 2008a;Litman, 2011).

7. Suitable space for a comfortable and useful journey. That the envelope of volume occupied by the passenger is appropriatefor use to the passenger needs (Australian Government Department of Infrastructure Transport Regional Developmentand Local Government, 2006; Beiro and Sarseld Cabral, 2007; Stradling et al., 2007a,b; Sweeney Research, 2008a).

3. Methods

This research is concerned with the qualities of designed artefacts in this case route bus bodywork as well as the pro-cess of designing them. This research offers a method for dealing with diversity in products and specications in the routebus bodywork industry. A proliferation of different specications has an adverse affect on the industry from base componentmanufacture through to the transport system used by passengers. The problem is based in the design of the product itself aswell as the process of developing bus specications. Solutions to this problem will be product proposals, complemented bytheir development process.

A route bus can be considered a compromise between the objectives of manufacturer and operator. A swing too far ineither direction could result in an operationally non-compliant vehicle or one impossible to manufacture. Reconciliationof these two constraints will allow the manufacturer to meet customer needs in a manner sympathetic to its own business.

Operators implicitly require durable, reliable buses, but as discussed above collectively have different ideas on what formthe bus might take in meeting these and other requirements. Individually, operators require their own bus. Collectively how-ever, operators require that a variety of buses can be produced, meeting the varied needs of individual companies whileupholding value for money and quality.

A third, and very important stakeholder group is passengers. The passenger requirements of the bus vehicle are closelylinked with the performance of the transport system there is a fundamental requirement for services meeting their needsas travellers. The passenger interacts with the vehicle when using transport, resulting in an important physical dimension tothe service provided (Parasuraman et al., 1985, 1988, 1991). The passenger does not require a unique bus, but the bus sup-plied to the operator must maintain attributes desirable to the passenger such as comfort, reliability and journey informa-tion. This physical relationship precipitates product development as a necessary method in a research project of this nature.

This research aims to solve a problem rooted in the design, specication, manufacture and use of a product. The problemtherefore precipitates a direction towards a physical contribution to knowledge, complemented by an aim to improve howthis product might be arrived at. In parallel with the above aim and all its constituent parts is the broader aim of combiningthe knowledge in the three elds of research locating this project: mass-customisation, design and public transport.

Design is a process of research resulting in the creation of artefacts. Design, like research, sets out to discover and createthat which does not exist (Nelson and Stolterman, 2003). Whether knowledge, products or indeed both are sought, the aimof the process is the same. As the process of designing requires that decisions are made based on existing knowledge, thedesign process encompasses information gathering, reection and synthesis into a statement of direction prior to the devel-opment of concept designs. The ideas are benchmarked against the constraints discovered early in the process and thosewhich are coming to light as part of the ideation process, and nally a conclusive position is reached where products mightbe manufactured, and the process may seek improvement through iteration.

Design, then, like Science, is not so much a discipline as a range of disciplines united by a common intellectual approach, acommon language system and a common procedure. Design, like Science, is a way of looking at the world and imposing struc-ture upon it. Design, then, can extend to any phenomenon to which we wish to pay designerly attention, just as Science canextend to any phenomenon to which we wish to pay scientic attention. (Archer, 1981)

The designerly enquiry (Archer, 1981) into the problem of specication diversity in route bus design requires that de-sign decisions are based on research. Design as a research method allows a hypothesis to be tested in an experimental set-ting. The process of design forms the test, and should a successful result be forthcoming, the material artefact provides prooffor the existence and measure for the degree of this success. The design process tests possible solutions to the problem byapplying this knowledge in the generation and application of products.

The design studio research project uses established design methods (Ulrich and Eppinger, 1995; Green and Bonollo, 2002)from task clarication and initial ideation through to nal documentation, to provide a means of hypothesis testing. Follow-ing the ideation process, the designs are taken through detailing stages, and in the case of the drivers area, prototyping and

manufacture. Following the studio experiment, it is possible to determine whether the hypothesis has been upheld, and thisinformation is then interpreted by means of discussion.

4. Design of a modular bus interior

The design of the bus interior follows on from similar work on the drivers area (Napper et al., 2010), where the problemof specication diversity was reduced in the standardisation of several key components. While signicantly improving thebus, the drivers area experiment was somewhat limited in scope as it dealt with a small part of the bus interior with notableopportunities to standardise.

The new bus drivers area shows that it is possible to design and manufacture route bus components to reduce the prob-lems caused by specication diversity. Product improvement was the main technique for meeting the conicting constraints

R. Napper / Transportation Research Part C 38 (2014) 5672 61Fig. 3. Typical seating-oriented interior layout of an 11.9M route bus.of manufacturing and customer needs. This was achieved by reducing the number of components and thus the noise gen-erated by their intersection, relocating the electrical centres to new ceiling cavities creating more passenger and driver space,and offering the driver more thermal control over their working environment. All of these features are standardised in thenew drivers area.

The principal difference between drivers area and interior experiments is that the interior needs to be a exible design inorder to t within different operational constraints doors, seating congurations, and vehicle lengths. Where the driversarea necessitated a standardised approach to components, the interior may not.

The bus operator requires that the interior accommodates passengers, however the quantity andmobility of passengers atany given time adds complexity. As illustrated above, a common feature of the bus is space for luggage and other personalitems such as prams and shopping. In addition to Australian Design Rule (ADR) constraints, the operator also requires a bussuitable for their specic purpose. Two principal operational factors which broadly dene the bus vehicle length and pas-senger capacity have a considerable effect on the interior. Desired vehicle length will determine the type and length ofchassis used for example rigid or articulated. Chassis specication determines the placement of components such aswheels, which materially intrude into the interior. The layout of seats, handrails and other items is also determined bythe desired seating capacity and door specications from the operator. The number of seats required is a balance of opera-tional requirements, a key constraint of which is the peak capacity of the bus, or any public transport system (Litman, 2004).This experiment hypothesises that it is possible to design and manufacture route bus components reducing the problemscaused by specication diversity.

4.1. Interior layouts

The status quo interior conguration in Australian route buses is seating-oriented. As shown in Figs. 39, the aim in thesecongurations is to t seating around wheel arches and doors in such a way that maximises the number of seats. Included inthese layouts is a wheelchair area towards the front of the bus which also forms passenger seating in the absence of a wheel-chair bound user. Placing as many seats as possible in the bus is a good way of ensuring the highest number of passengers arecarried in relative comfort, however when the seats are lled, the comfort for standees is severely compromised. Also, dwelltimes may be affected at large interchanges such as railway stations where many passengers are trying to alight at thesame time. Fig. 6 shows an articulated vehicle where dwell times might be mitigated by the inclusion of a third door.

Dwell times are less of an issue in ex-urban services, where passengers are likely to be carried for longer journeys withmore distance between stops. Fig. 7 shows a bus layout for this situation, where the second door is sacriced for more seats.This layout is shown on a 14.5 m chassis, which is only suitable for major roads to accommodate a large turning radius. Notethat in the analysis described in Section 3, no 14.5M buses were produced.

The difference between peak and off-peak passenger loadings can be signicant in certain service conditions. It stands toreason that in off-peak periods most, if not all passengers could nd a seat in a typical Australian urban bus setting. When thesame vehicle is used in peak periods however, the seating limits the number of passengers which may be carried, as the prin-cipal limit is one of weight, and a standee requires no seat. Furthermore, standees require less oor area than passengers inseats. An urban-oriented layout has been developed in this research as shown in Fig. 8 to test the proposition of

Fig. 4. Typical seating-oriented interior layout of a 12.5M route bus.

Fig. 5. Typical seating-oriented interior layout of a 14.5M route bus.

Fig. 6. Typical seating-oriented interior layout of an articulated route bus.

Fig. 7. Typical seating-oriented interior layout of a 14.5M route bus for ex-urban use, sacricing some dwell-time by substituting the rear door for anadditional row of seats.

Fig. 8. Urban-oriented layout providing more passenger accommodation by sacricing seats, in an 11.9M bus.

Fig. 9. Urban-oriented layout providing more passenger accommodation by sacricing seats, in an articulated bus.

62 R. Napper / Transportation Research Part C 38 (2014) 5672

accommodating more passengers as standees. Seats are available in the rear of the vehicle, but the low-oor area is givenover to standee and wheelchair space. The combination of standee and wheelchair space is a new development for this lay-

Product diversity has been reduced from a purpose-fabricated system of near innite variation, to nine key componentsas shown in Fig. 10. Two types of model were created, at the mechanical level and the whole-interior level. The mechanicallevel model was concerned with the mechanical detailing of extrusions and handrails shown in Figs. 11 and 12. A second set

R. Napper / Transportation Research Part C 38 (2014) 5672 63of models at the interior level determines the effectiveness of the components in creating a complete bus interior. Modelswere developed around the Volvo B12BLE family and represent present and possible future interior specications. The inte-rior level models created four proof cases.

Figs. 13 and 14 represent a typical 12.5M, 43 seat metropolitan route bus, demonstrating that the modular interior systemmeets present market requirements; the functional characteristics of the interior from an operators perspective are quan-titatively unchanged. This case, as with the following cases, also illustrates the aesthetic benets of a unied family of inte-rior components, with continuity of form creating a unied interior whole.

Figs. 15 and 16 show an 11.9M conguration with 41 seats. This further illustrates the ability of the modular system toaccommodate congurations in the present market. This conguration shows that the modular system is exible in accom-modating a different seat pattern, including six longitudinal seats (shown in yellow1) minimising the shorter vehicle length onthe seated capacity.

Figs. 17 and 18 are based on an articulated bus for high-density urban service the New South Wales State TransitAuthority (NSW STA) metrobus (New South Wales Ministry of Transport, 2007). This specication may point towardsthe future of bus interior designs, away from a strict focus on seated-capacity. The specication is characterised by a seatingconguration maximising passenger capacity in light of a specic inner-urban and CBD route. It also aims to minimise theimpact of loading and unloading on dwell time. This case illustrates the ability of the modular interior to meet unusualspecications.

Figs. 19 and 20 illustrate a completely conceptual specication for a route bus, and aims to show the extent to which themodular interior can depart from current trends. This case serves to illustrate the capabilities of the modular system withinthe same envelope as the rst three cases. The present suite of components can be used to create a range of interior spec-ications, of which this is one; and the modular system can also be augmented with further components to accommodatesignicant change in bus interiors into the future the buses prospective service life of 25 years is re-emphasised at thispoint. This specication shows an articulated bus congured for metro service, and as such the provision of standing roomfor short trips, reminiscent of streetcars, highlighted by the green colouring in Fig. 19.

1 For interpretation of colour in Figs. 15, 16 and 19, the reader is referred to the web version of this article.out, as wheelchair spaces are typically paired with fold-away seats in a normal layout such as Fig. 4. This layout proposalmay have the benet of maximising passenger capacity in peak periods, and also of minimising dwell times through easyaccess to doors. The same principle is demonstrated in Fig. 9 for an articulated bus. The layout is not intended to determinewhether this type of interior conguration is operationally necessary, but to ensure versatility of interior components.

Following the study of present and potential layouts, the design moved into concept generation of product moduleswhich would be used to construct the interiors. These modules will subsequently be tested by conguring them into testcases. In order to design a functioning Product Family Architecture (PFA), the modules are designed concurrently with themodule interfaces (Ulrich and Tung, 1991). The spatial interfaces of the product how it ts into the bus are separate fromthe technical interfaces, with the former being typical of industrial design work, and the latter engineering (Sanchez, 2002);although the design process in this experiment is mindful of the signicant overlap in skills between these two areas (Bon-ollo, 2001). MC literature recommends the complete design of modular interfaces prior to designing the modules themselves(Sanchez, 2002) however in this instance this was found to pre-empt the design of a successful solution.

A system of components is used in existing bus interiors to create a functional interior space. In this research, the interiorcomponents are developed as a modular system through the iterative and exploratory design studio process. The standingand wheelchair space was designed to contain a perch-style seat, providing the short-distance or peak-period passenger withan additional point of contact. The perch seat does not interfere with the carriage of passengers in wheelchairs.

The modular interfaces as well as the modules themselves demonstrated a simple customisation structure in conceptform. Several modular interfaces were created using empty space which would be utilised in the bus by passenger accom-modation; thus introducing a sense of purpose to the interface itself. Other interfaces shared purposes too, such as modestypanels and handrails. Modesty panels are also functionally necessary as the difference in head height between seated andstanding passengers can lead to psychologically uncomfortable postures in this situation.

Following concept development and renement, the project was taken into a detailing phase, which is concerned with themechanical details of modules, in particular how they fasten to the envelope in a manner conducive to modularity of thesystem as a whole.

4.2. Concept modular bus interior

64 R. Napper / Transportation Research Part C 38 (2014) 56725. Results and discussion

The modular bus interior demonstrates that an MC approach to bus design can be applied where standardisation issought, with product diversity being reduced from a bespoke system to nine key components in a modular system as shownin Fig. 21. Fig. 21 also estimates the work saving in hours of the modular interior compared to the bespoke interior. TheMC approach allows the specication process to t within a narrower range of components, without limiting function. Forexample, the handrail is a component of the modesty panel, and the two components share mounting hardware. The mod-ular interior suggests a less laborious specication process and smaller component inventories because of fewer componentsand a more controlled system. This component reduction also serves to reduce labour and increase opportunities for higherquality in manufacturing. Finally, more streamlined bus maintenance is possible for operators through the use of commoncomponents, xtures and fastening hardware. The bus design task has also been changed; generating a complete interior isnow a matter of component conguration rather than component design. Thus, it is determined that the hypothesis has beenupheld in the route bus interior, and indeed it is possible to design and manufacture route bus components reducing theproblems caused by specication diversity, as suggested by Fig. 22.

Evidence from commercial tenders and the current specication process suggests that the two key decisions affectinginterior specication are vehicle length and number of doors. The requirement for the maximum number of seats is a tacitrequirement of bus specication, save for exceptional cases such as case three above. In creating the interior t out to meetspecications, the modular system has fewer variables, allowing the specication process to focus on desired functionalcharacteristics of the bus, rather than in re-engineering the components to t within an ever-changing envelope. The spec-ication process is thereby made less labour intensive. Paint and fabric colours and material types are intended to be part ofthe modularity of the system, affording the operator cosmetic customisation to augment mechanical function with little orno impact on the production system. Cosmetic choices complete the interior specication process.

Fig. 10. The nine key components of the modular bus interior.

R. Napper / Transportation Research Part C 38 (2014) 5672 65The specication process benets from the reduction of variables. The PFA sets out parameters for interior specicationinstead of redesigning each time, resulting in less interaction between the bus operator, sales personnel and engineering. Acongurator system could further reduce the interaction improving the experience of specication and the end result

Fig. 11. Seat assembly attached via nearside stanchion to the overhead handrail.

Fig. 12. Modesty panel assembly.

66 R. Napper / Transportation Research Part C 38 (2014) 5672(Blecker et al., 2004b; Cross et al., 2009). Professional, or expert consumers such as bus operators are noted for their abilityto specify complex products and their increased likelihood of reaching a desirable end product, without the usual negativeexperiences of ordinary consumers (Dellaert and Stremersch, 2005).

Reduction in the number of components will save inventory cost, and likely reduce the cost of components used as theyare subject to economies of scale in production. Part reduction will ow onto reduce the number of processes necessary inthe manufacture of the interior, making quality control a more nite task. Overall the benets to manufacturing of the mod-ular interior will be of better product quality and reduced manufacturing time, in line with the expected outcomes of an MCapproach.

Results of the bus interior project demonstrate that modular design is an appropriate strategy to reduce components anddesigns, where a broader functional scope necessitates exibility, and manufacturing constraints require standardisation.This was achieved by sharing components across products and by creating a modular system of interfaces between them.The cases also illustrate the ability of the modular interior to meet unusual specications.

Fig. 13. Typical route bus layout - 12.5m.

Fig. 14. Typical route bus layout - 12.5m.

R. Napper / Transportation Research Part C 38 (2014) 5672 67In reference to the user needs discovered in the literature review, the implementation of a design process generically andthe MC process more specically, give an alternative view to creating transport more in tune with user needs. The basic pre-mise of improvement is the notion that the mere presence of an element, for example passenger amenity for a productivejourney, is not sufcient to meet passenger needs. The passenger-centric viewpoint taken in the design described above re-sults in a process of design whereby specic passenger behaviours are identied and incorporated as design requirements.More specically, the modular design described in this paper offers the following advantages:

1. Ease of cognitive and physical access component reduction through modular interface design, as distinct from moduledesign, leading to a reduction in components and simplication of the vehicle interior.

2. Vehicular and personal safety the incorporation of functional features such as grab-rails as modular interfaces offersincreased function for personal safety.

3. Physical and psychological comfort psychological comfort increased in the offer of more appropriate interiors to partic-ular bus applications, disentangling the pervasive relationship between passenger capacity and seat provision.

Fig. 15. Typical route bus layout - 11.9m.

Fig. 16. Typical route bus layout - 11.9m.

68 R. Napper / Transportation Research Part C 38 (2014) 56724. Flexibility in using their transit time as impacted through comfort, and the provision of interior modules given to partic-ular work or leisure pursuits, for example computer use.

5. An aesthetically appealing environment reduced visual clutter and an integration of fastening features to modules andmodular interfaces.

6. Cleanliness the vehicle is more easily cleaned if the number of surfaces and the existence of acute angles between thesesurfaces is reduced.

7. Suitable space for a comfortable and useful journey as with 3 and 4.

The reduction of components is concurrent with improvements in product function which is, in turn improved by main-taining mechanical properties and improving their aesthetic delivery and the likelihood of correct, useable specication. Thisadvantage exists in addition to the demonstrated outcome of a rationalised specication process, simplifying generation ofthe bus interior, with subsequent reductions in engineering labour.

Fig. 17. Typical route bus layout - Articulated.

Fig. 18. Typical route bus layout - Articulated.

R. Napper / Transportation Research Part C 38 (2014) 5672 69User requirements necessitate signicant scope for variation in the bus interior and as such, the reliance on a modularsystem is higher in the interior than in the drivers area. This result serves to strengthen the conclusions from a previousexperiment conducted through to manufacture and eld implementation in the bus drivers area (Napper, 2011), both doc-umented as four interventions:

1. Determine user needs before the bus specication process.2. Designs to be developed by the manufacturer in response to user needs.3. This design should be standardised where possible, as suggested by the user needs.4. Where user needs dictate product variations, apply a mass customisation approach to accommodate these needs.

The critical difference in these results is that the generation of a standardised design represented by intervention three is severely limited by the user needs being so diverse in the bus interior. Despite this, intervention three was interpreted to

Fig. 19. Non-typical route bus layout - Conceptual articulated layout.

Fig. 20. Non-typical route bus layout - Conceptual articulated layout.

70 R. Napper / Transportation Research Part C 38 (2014) 5672dictate the generation of a standardised suite of products, enabling the manufacturer to maintain control over the productsand therefore reduce the negative effects of product diversity. This system was carried out in line with intervention four, bydeveloping a controlled modular system of components.

The increase in variation is driven indirectly by chassis selection and directly through interior needs. The functional objec-tives of manufacture were met in the modular interior by standardising the components and operations within a denedproduct architecture. By employing a design process the manufacturer, operator and passenger objectives were represented.Better manufacturing will benet the operator with regards to cost and quality. A bus which meets operator needs is a ben-et to the business of the manufacturer.

Fig. 21. Comparison of components in the old and new interiors.

Fig. 22. Interventions into, and the resulting new bus specication, design and manufacture process.

This test determined the repeatability of previous research in the drivers area by examining the same problem in a dif-ferent experimental setting. While the rst two interventions were applied in the same way, the modular interior has shown

Archer, B., 1981. A view of the nature of design research. In: Design, Science, Method: Proceedings of the 1980 Design Research Society Conference:

R. Napper / Transportation Research Part C 38 (2014) 5672 71[Conference Organized by the Design Research Society in collaboration with Portsmouth Polytechnic], Westbury House, Guildford.Australian Government Department of Infrastructure Transport Regional Development and Local Government, 2006. Vehicle Standard (Australian Design

Rule 58/00 Requirements for Omnibuses Designed for Hire and Reward) 2006, Federal Register of Legislative Instruments. 58/00.Batchelor, R., 1994. Henry Ford, Mass Production, Modernism, and Design. Manchester University Press, Manchester.Beiro, G., Sarseld Cabral, J.A., 2007. Understanding attitudes towards public transport and private car: a qualitative study. Transport Policy 14 (6), 478

489.Ben-Akiva, M., Morikawa, T., 2002. Comparing ridership attraction of rail and bus. Transport Policy 9 (2), 107116.Blecker, T., Abdelka, N., et al., 2004b. Product conguration systems: State-of-the-art, conceptualization and extensions. In: Hamadou, A.B., Gargouri, F.,

Jmaiel, M. (Eds.), Intelligence Articielle. Genie Logiciel & Soussee, Tunisia.that interventions three and four are implemented in a slightly different manner.Intervention one in the modular interior required an understanding of passenger needs. The literature review serving this

purpose concluded that the qualitative elements of public transport have a signicant effect on public transport perfor-mance. This conclusion is signicant for the successful design of route buses as it claries and broadens the notion of productfunction.

In applying intervention two, the modular interior seeks to rationalise components without reduction of function. Theproject was carried out in a different context of variation, as the interior of the bus is comprised of many functional elementsover a larger physical envelope. Signicantly, interior variations are found in the envelope and in the interior conguration both dictated by the functional requirements of bus operation. This means that the generation of a standardised design wasnot strictly possible; the standardised design is itself a modular system which is strictly controlled by the manufacturer.

Intervention four has been most expedient in the development of an interior to reduce the negative effects of productdiversity, as it is on the whole a modular system.

The holistic view of product function was a critical element in reducing product diversity; including an awareness of thecommodity the bus is used to create public transport. Design of public transport must account for the whole stakeholderchain, as opposed to one-up or one-down as is currently the case, with some stakeholders separated from the commodity ofpublic transport. Design of capital goods must be carried out in light of end use. This forms part of the argument above inwhich knowledge of product function makes the design of a higher-specication product more likely, and thus more freelyallows accommodation of specication diversity. The modular interior reduces the time necessary to generate an interiorconguration for a bus. Using standardised parts from a set modular system changes the interior conguration task fromone of bespoke, individualised design to one of component specication. This is possible because the interfaces betweenthe modules have been determined to allow the exible deployment of components. At present, interior specication takesseveral weeks of engineering time depending on the nature of the specication and to what extent precedents can be re-used. The modular interior can be congured in only a few hours and is constructed from a limited inventory of standardisedcomponents.

The interventions full the aim of this research by reducing the negative impacts of specication diversity in route busbodywork design through both design methods and designed artefacts. An understanding of user needs (1) will allow thedetermination of whether and to what extent product variation is necessary. The understanding of user needs allows themanufacturer to develop (2) a standardised product if such an outcome is possible within the scope of those needs (3). Whenneeds dictate functional differences in the product, a modular system can satisfy these needs and minimise the negative im-pact on the machinations of manufacture, customer specication and use (4).

The experiments have shown that the interventions into bespoke route bus bodywork manufacturing have benetted thecomplete user cross-section and manufacturer by offering a more cost effective product closely aligned with user needs, con-ducive to efcient quality manufacture.

This research has identied a new method for balancing the needs of manufacturers with end users in the area of vehicledesign for public transport. The paper shows that although the eld exhibits a thorough understanding of the end user inparticular passenger needs, further work towards a typology of user needs is required to offer a more complete under-standing and practical grounding into how they may be incorporated into the public transport user experience.

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Modular route bus design A method of meeting transport operation and vehicle manufacturing requirements1 Introduction2 Product and literature review3 Methods4 Design of a modular bus interior4.1 Interior layouts4.2 Concept modular bus interior

5 Results and discussion6 ConclusionsReferences