Nordic Road and Transport Research 2-2003

Fatigue Catchesyou Unawares

page 8

Fatigue Catchesyou Unawares

page 8

2 NORDIC ROAD & TRANSPORT RESEARCH NO. 2 2003 3NORDIC ROAD & TRANSPORT RESEARCH NO. 2 2003

Cover photo: Johan Knutsson

Volume 15•No.2•September2003


Long Span Bridges with Lightweight Concrete in Norway. . . . . . . . . . . . . 4Norwegian Public Roads Administration (NPRA)

HVS-Nordic in Poland . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7Swedish National Road and Transport Research Institute (VTI)

Fatigue Catches you Unawares . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8Swedish National Road and Transport Research Institute (VTI)

Prewetted Salt versus Brine on Motorway . . . . . . . . . . . . . . . . . . . . . . . . . 10Danish Road Directorate (DRD)

Danish Road Institute Is 75 Years Old . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12Danish Road Directorate (DRD)

Image Processing for Analysis of the Effectiveness of a Reconstruction . .14Technical Research Centre of Finland (VTT), Building and Transport

Public Transport: Travellers’ Valuation of Time in the Oslo Region . . . . . . . . 16Institute of Transport Economics (TØI)

A N N O TAT E D R E P O R T S . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

C O N T E N T S

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NORWEGIAN PUBLIC ROADS ADMINISTRATION (NPRA)

Long Span Bridges with Lightweight Concrete in Norway

completed in 2003, it will be, together with the Raftsund bridge, the next longest cantilever bridge in the world.

Background

When the Romans built their impressive roads and bridges over 2000 years ago, hardly more than a simple track had been built in Norway. Boats were the normal means of transport along the coast in the North, and by 800 AD it had been devel-oped to an effective tool both in war and peace. Norwegian long-ships sailed as far as the Black Sea, the Mediterranean, and even crossed the Atlantic to Greenland and America.

The old Vikings almost certainly took home knowledge of road building and wheeled transport. One of the oldest bridges in Norway, the Hjallar bridge at Rennesøy in Rogaland, was, according to

tradition, built about 900 AD. The bridge has been demolished, and only old photo-graphic records of the bridge remain. The bridge was built of local rock, the central span being a large rock slab. The weight of the slabs determined the bridge-span.

After 1960 about 115 concrete canti-lever bridges have been built in Norway. As the length of span increased in Norwe-gian cantilever bridges, so did the interest for using lightweight concrete.

Lightweight concrete bridges had been built in several contries prior to 1980. However, in the course of the 1980s two things occurred which had decisive influ-ence on the use of lightweight concrete in Norway. These were:• a new manual for design of concretestructures (1987)• a desire to use lightweight concrete inproduction platforms for oil and gas inthe North Sea.

Investigations are currently being made to find out the behaviour of light concrete in certain bridges in order to provide a better verification of light concrete’s durability.

High-strength, lightweight concrete has been used in a number of bridges in Norway. Lightweight concrete has been used in floa-ting bridges (pontoons), cable-stayed brid-ges and cantilever bridges. This is a result of close co-operation between the public road authorities, research laboratories, consul-ting engineers and contractors.

The co-operation began when Norwegian Contractor AS who was contemplating the use of low weight concrete in North Sea oil platforms, and the Norwegian Public Road Administration who wanted to build low weight cantilever bridges with long spans, pooled their efforts. As a result, several oil platforms have been built with lightweight concrete for the North Sea oil-fields, e.g. Troll and Heidrun.

The two longest cantilever bridges in Norway have also been built with light-weight concrete – the Raftsundet and Stolma bridges, both with spans of about 300 metres. Several other cantilever bridges of LWA-concrete (lightweight aggregate concrete) are also in the proc-ess of being built or are on the drawing board. At present, there is not sufficient data available concerning durability of reinforcement due to corrosion in light concrete, for any reliable conclusions to be drawn.

Sundøy bridge

Work is almost completed on the building of Sundøy bridge in Nordland county. The bridge is a typical result of the techno-logy that has been developed in Norway over the course of several years. The bridge has a main span of 298 metres and two side-spans of 120 metres. To ensure the balance of weight in the main span, light concrete will be used in 224 metres of the central span. When the bridge is

The article is written by Dr. Ing. Karl Melby, Norwegian Directorate of Public Roadse-mail: [email protected]

Hjallar bridge, construction method. After 1960 about 115 concrete cantilever bridges have been built in Norway. As the length of span increaseNorwegian cantilever bridges, so did the interest for using lightweight concrete. Lightweight concrete bridges had been built in several lands prior to 1980. However, in the course of the 1980s twthings occurred which had decisive influence on the use of lightweight concrete in Norway. These were: • A new manual for design of concrete structures (1987) • A desire to use lightweight concrete in production platforms for oil and gas in the North Sea. Investigations are currently being made to find out the behaviour of light concrete in certain bridges in ordea better verification of light concrete’s durability.

NORWEGIAN CONCRETE BRIDGES WITH LIGHT AGGREGATES

After the construction of Endrestø bridge in 1987, eleven other bridges have been built with lightweight concrete. Below is a list of lightweight concrete bridges in Norway. Endrestø bridge 1987, Rogaland county (pilot project) Concrete slab with 15 m span Concrete: LC60 (28 days cube strength min 60 MPa) Lightweight aggregate: Liapor 8. Sandhornøya bridge 1989, Nordland county Concrete cantilever bridge with a main span of 154 m + two side spans of 110 m Concrete: Normal weight concrete C45 in the main span, LC55 in both side spans Lightweight aggregate: Liapor 8. Boknasund bridge 1991, Rogaland county Concrete cantilever bridge with a main span of 190 m + two side spans of 97.5 m Concrete: LC60 in the main span and 62.5 m of both side spans. Normal concrete C55 in 3o buttresses in both side spans Lightweight aggregate: Liapor 8.

Hjallar bridge, built about 900 AD.

Hjallar bridge, construction method. After 1960 about 115 concrete cantilever bridges have been built in Norway. As the length of span increaseNorwegian cantilever bridges, so did the interest for using lightweight concrete. Lightweight concrete bridges had been built in several lands prior to 1980. However, in the course of the 1980s twthings occurred which had decisive influence on the use of lightweight concrete in Norway. These were: • A new manual for design of concrete structures (1987) • A desire to use lightweight concrete in production platforms for oil and gas in the North Sea. Investigations are currently being made to find out the behaviour of light concrete in certain bridges in ordea better verification of light concrete’s durability.

NORWEGIAN CONCRETE BRIDGES WITH LIGHT AGGREGATES

After the construction of Endrestø bridge in 1987, eleven other bridges have been built with lightweight concrete. Below is a list of lightweight concrete bridges in Norway. Endrestø bridge 1987, Rogaland county (pilot project) Concrete slab with 15 m span Concrete: LC60 (28 days cube strength min 60 MPa) Lightweight aggregate: Liapor 8. Sandhornøya bridge 1989, Nordland county Concrete cantilever bridge with a main span of 154 m + two side spans of 110 m Concrete: Normal weight concrete C45 in the main span, LC55 in both side spans Lightweight aggregate: Liapor 8. Boknasund bridge 1991, Rogaland county Concrete cantilever bridge with a main span of 190 m + two side spans of 97.5 m Concrete: LC60 in the main span and 62.5 m of both side spans. Normal concrete C55 in 3o buttresses in both side spans Lightweight aggregate: Liapor 8.

Hjallar bridge, construction method.

Cantilever bridges

The first Norwegian cantilever bridge built of lightweight concrete was Sand-hornøya bridge.

Sandhornøya bridge connects the island of Sandhornøya to the mainland. The bridge is situated just north of the Arctic

Sundøy bridge

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Norwegian Concrete Bridges with Light Aggregates

After the construction of Endrestø bridge in 1987, eleven other bridges have been built with lightweight concrete. Below is a list of light-weight concrete bridges in Norway:

Endrestø bridge 1987, Rogaland county (pilot project)Concrete slab with 15 m spanConcrete: LC60 (28 days cube strength min 60 MPa)Lightweight aggregate: Liapor 8.

Sandhornøya bridge 1989, Nordland countyConcrete cantilever bridge with a main span of 154 m + two side spans of 110 mConcrete: Normal weight concrete C45 in the main span, LC55 in both side spansLightweight aggregate: Liapor 8.

Boknasund bridge 1991, Rogaland countyConcrete cantilever bridge with a main span of 190 m + two side spans of 97.5 mConcrete: LC60 in the main span and 62.5 m of both side spans. Normal concrete C55 in 35 m adjacent to buttresses in both side spansLightweight aggregate: Liapor 8.

Bergsøysundet bridge 1992, Møre and Romsdal countyFloating bridge with 8 steelframe spans of 104.4 m built on pontoonsConcrete: The pontoons are of LC55Lightweight aggregate: Liapor 8.

Sund bridge 1992, (Eidsvoll) Akershus countyBeam and concrete slab with 8 spans of 40 mConcrete: LC55 throughout superstructureLightweight aggregate: Leca 750.

Støvset bridge 1993, Nordland countyConcrete cantilever bridge with a main span of 220 m + two side spans of 100 mConcrete: Normal weight concrete C45 in the superstructure, apart from the central 146 m of the main span where LC55 is usedLightweight aggregate: Liapor 8 (pre-mois-tened).

Nordhordland bridge 1994, Hordaland countyCable-stayed and floating bridgeConcrete: LC55 is used in the cable-stayed bridge’s main span and the floating bridgeLightweight aggregate: Respectively Leca (high-strength) and Liapor 8.

Grenland bridge 1996, Telemark countyCable-stayed bridge with a steel box-girder main span of 305 m and a total length of 608 mConcrete: The pavement is LC55Lightweight aggregate: Leca 750.

Raftsundet bridge 1998, Nordland countyConcrete cantilever bridge with a main span of 298 m and a total length of 711 mConcrete: Normal concrete C65 was used in the superstructure apart from the central 224 m of the main span where LC60 was employedLightweight aggregate: Stalite 2-16 mm (pre-moistened).

Stolma bridge 1998, Hordaland countyConcrete cantilever bridge with a main span of 301 m and a total length of 467 mConcrete: Normal concrete C65 was used in the superstructure apart from the central 184 m of the main span where LC60 was employedLightweight aggregate: Leca 800 (dry).Rugsund bridge 2000, Sogn and Fjordane countyConcrete cantilever bridge with a main span of 190 m and a total length of 302 mConcrete: Normal concrete C55 was used in the side spans and ballast section, LC60 was employed in the main spanLightweight aggregate: Stalite.

Sundøy bridge 2003, Nordland countyConcrete cantilever bridge with a main span of 298 m and a total length of 538 mConcrete: Normal concrete, C65, is used in the superstructure. In the central 224 m of the main span LC60 is employedLightweight aggregate: Stalite.

Raftsundet

Sandhornøya

Støvset

Bergøysundet

Rugsund

Stolma

Bokna-sundetEndrestø

Sund

Grenland

Nordhordland-brua

Sundøy


No. Project Country Span in m Construction year1 Stolma, Hordaland county Norway 301 19982 Raftsund, Nordland county Norway 298 19983 Humen, Pearl River China 270 19974 Varodd, Vest Agder county Norway 260 19945 Gateway Bridge, Brisbane Australia 260 19866 Skye Bridge Scotland 250 19957 Ponte San Joao, Porto Portugal 250 19918 Talübvergang Schottwien Austria 250 19899 Northumberland Strait

CrossingCanada 250 1997

10 Jialing River China 250 199915 Norddalsfjord, Sogn and

Fjordane countyNorway 231 1987

20 Støvset, Nordland county Norway 220 1993


Circle, not far from the city of Bodø.The bridge consists of three spans,

110–154–110 m, total length 374 m, see figure. The total length of the bridge was determined by the wish to keep the open-ing between the embankments as wide as possible. Low circulation of seawater in the vicinity might have caused environ-mental problems. The location of the main piers was virtually pre-determined by the longitudinal profile of the seabed. When due consideration was made in relation to these two factors, the length of the bridge and the spans were given.

This presented a challenge to the bridge designers, as the length of the spans was unbalanced. To rectify this, it was decided to use lightweight concrete, grade LC55 with a density of 1850-1900 kg/m³ (fresh concrete) in the side spans, and normal concrete, grade C45 in the mid span.

The bridge beam rests on sliding bear-ings in axis 1, 2 and 4, with a maximum capacity of 10,000 kN each.

The cross-section of the bridge beam is the standard common for free cantilever bridges constructed in Norway since 1970. The cantilevers from axis 3 were built between August and December 1988, and from axis 2 between January and June 1989.

Four of the world’s ten longest con-crete cantilever bridges have been built in Norway. LWA-concrete has been used in the central spans of the bridges Stolma, Raftsund and Sundøy.

An analysis of the costs shows that the bridges cost on average rather more than NOK 230,000 per metre. Local condi-tions for foundations and side spans are decisive factors in bridge prices – not the use of LWA-concrete.

The world’s 10 longest free cantilever concrete bridges (2001).

Visit our web site: www.vti.se/nordic

Visit our web site: www.vti.se/nordic

Sandhornøya bridge

5.4 m

7.8 m

2.3 m

7.7 m

LC55 LC55C45

30 x12 m

110 m 110 m154 m

374 m

5.4 m

7.8 m

2.3 m

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LC55 LC55C45

30 x12 m

110 m 110 m154 m

374 m


Last year the mobile Heavy Vehicle Simulator, HVS-Nordic, was in Poland for some months. It was used there for tests on two road structures prior to the construction of 100 km of motorway between Warsaw and Berlin.

In the beginning of December 2001, Leif G. Wiman at VTI received an enquiry from NCC in Poland if it was possible to use HVS to test some road structures in situ in Poland. VTI owns HVS jointly with the Finnish VTT, and just then the simulator was in Finland.

– The Finnish engineers were in the middle of a research programme, but they said they could break off their tests and resume them at a later date.

A wish was realised

It had long been the wish of both VTI and VTT to make tests with HVS for others, and not only in Sweden and Finland. The vehicle is expensive to run and it makes no economic sense to let it stand idle for either short or long periods.

HVS can simulate several years’ heavy traffic in just a few months. It is the only one of its type in Europe (there are six more simulators of this type in other places in the world – four in USA and two in South Africa). Although there are machines which carry out approximately the same tests as HVS, the critical differ-

ence is that HVS is mobile while other equipment of this type is stationary. It is easy to transport HVS from one project to another. It has the same driving character-istics as any other large lorry.

– When HVS was taken to Poland, it was taken by sea from Helsinki to Gdynia and then driven over about 300 km to the test site outside Poznan, tells Leif G. Wiman.

The Polish test

The project coordinator for the motorway construction in Poland was a company called A2 Bau Development. The actual construction was carried out by the compa-nies Strabag and NCC Polska. They were responsible for half the motorway each.

The contract with the Polish State guar-anteed that the road should stand up to a certain traffic volume – 6 million vehicle passages with an axle load of 11.5 tonnes – before it would be damaged to such an extent that it would be in need of repair.

– A2 Bau Development proposed a type of road construction that was slightly thinner than what the code specified. The authorities were doubtful about this, but said that if A2 Bau Development could demonstrate in some way that the thin-ner construction would stand up to the agreed traffic volume they would be pre-pared to agree to this. And this was where HVS came into the picture, says Leif G. Wiman.

Two test roads were built in Poland, one complying with the current code, and one

HVS-Nordic in Poland Article written by Catarina Gisby/redakta. thinner version according to the A2 Bau

Development design.6 million vehicle passages take quite a

long time to simulate, and therefore it was decided at an early stage to simulate this traffic volume with a smaller number of vehicle passages but at a higher load.

– HVS loaded each test construction with 600,000 vehicle passages at a wheel load of 8 tonnes (corresponding to axle load of 16 tonnes) which, according to calculations by experts, was considered equivalent to 6 million passages at an axle load of 11.5 tonnes, explains Leif G. Wiman.

All’s well that ends well

After the test the results were analysed by different members of a verification project. One study from Technical Uni-versity of Vienna showed that the thinner structure should comply with the speci-fied requirements, but a study at IBDiM in Warsaw came to the conclusion that the thinner structure was too weak and could not be considered.

Even if the thinner structure was not approved the leader of the verification project was of the opinion that “the field test has had a very positive psychological influence on the acceptance of the pave-ment design by Polish Road Authorities and by “public road opinion”. Unfortu-nately for A2 Bau Development without change of thickness, but the acceptance itself is of high benefit, too.”

SWEDISH NATIONAL ROAD AND TRANSPORT RESEARCH INSTITUTE (VTI)

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In 3 per cent of the total number of reported single vehicle accidents in Sweden over the period 1994–2001, the police suspected the driver to have been drowsy or to have gone to sleep.

– It is highly probable that this is a gross underestimate, says Anna Anund.

In the focus groups she and Göran Kecklund have worked with in this study, the participants were asked to estimate the number of single vehicle accidents that were caused by tiredness. The answer was “over 50 per cent”.

– I imagine that the truth is somewhere between the estimates of the police and the study participants.

An example that may be mentioned is that in a questionnaire study based on the statistics of Norwegian insurance compa-nies, it was found that ca 19 per cent of the accidents during the night were caused by tiredness. As regards injury accidents, ca 7 per cent were reported to have been due to tiredness.

If the single vehicle accidents in Sweden where tiredness is given as the cause of accident are analysed, it is found that accidents due to fatigue are over-rep-resented on roads outside built-up areas

– on roads where speeds of 90 and 110 km per hour are permitted – i.e. on motor-ways and wide two-lane roads.

– What can also be seen is that the con-sequences of an accident are more severe in these accidents than in other types of single vehicle accidents.

Rumble strips

In the US, it was found that grooved rumble strips along the marginal strip had an enormously positive effect in reduc-ing the number of accidents and injured. The number of single vehicle accidents dropped by as much as 70 per cent.

– We have experimented with grooved rumble strips on a 70 km long section of the E4 motorway, and there is nothing to indicate that the strips would not have the same effect in Sweden as in the US.

Unfortunately, the experiment was discontinued too early. It was intended to last for five years but was stopped after two years.

– The results we obtained were similar to the American ones. Our fund provider, the Swedish National Road Administra-tion, therefore decided it was unnecessary

What makes a driver develop fatigue? Is it possible to recognise and to be aware of the feeling of tiredness? Do accidents due to fatigue occur more often on certain roads than on others? Research-ers Anna Anund and Jörgen Larsson, VTI, and Göran Kecklund, Swedish National Institute for Psychosocial Medicine, put the spotlight on fatigue in a VTI report.

It may seem strange, but fatigue in con-junction with traffic and traffic accidents is a phenomenon that has received rela-tively little attention over the years.

But something may at last be happen-ing now. There is much to indicate that measures directed at fatigue in traffic could reduce the number of accidents, especially the number of single vehicle accidents and head-on collisions. In USA, for instance, the National Transportation and Safety Board claims that fatigue is one of the foremost causes of accidents in traffic.

At European level there is e.g. the AWAKE project which deals with the way in which driver fatigue can be predicted – and with developing methods of keep-ing the drivers awake. (VTI is taking part in this work). And here in Sweden, Anna Anund and Jörgen Larsson, together with Göran Kecklund, have carried out a study financed by the Swedish National Road Administration. A report has now been completed. Its title is “Fatigue in Focus”.

Traffic accident statistics

The aim of the Swedish study has been to gain increased knowledge of where acci-dents due to fatigue occur, and to formu-late hypotheses on what it is that causes a driver to develop fatigue. The emphasis has been on hypotheses regarding the information that a driver needs to• “recognise” and be aware of the feeling of tiredness• refrain from driving when tired• understand more fully the danger of driving when tired.

Fatigue Catches you Unawares Article written by Catarina Gisby/redakta.

In USA and Australia, fatigue is an issue that has been highlighted; it is stated that many acci-dents in traffic can be related to fatigue.

– In Sweden we have not got to that stage – as yet. But I think it will come. It is not possible to aim for no fatalities in traffic without discussing fatigue, says Anna Anund.

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by everybody in this group as extremely frightening.

– What presumably happens is that the driver falls asleep, says Anna Anund.

In the long distance commuter group people also talk of hallucinations. It is not unusual to see moose that are not there.

The professional drivers believe that driving deteriorates even when one is only moderately tired. They realise the impor-tance of stopping and having a sleep.

– They take fatigue seriously. On the other hand, long distance commuters do not have this attitude. They would rather not stop. They are convinced that they can overcome tiredness. And, finally, the young drivers agree with professional drivers that their driving deteriorates even when they are only moderately tired, but they do not recognise tiredness when it comes. So they do not stop either.

Fatigue due to stress

The drivers who want to stop complain that there are few places where they can stop. Some have read in the papers of vehicles being hijacked and robbed, and quite simply dare not stop at the side of the road. Professional drivers also say that they have no time to stop. They are under so much stress.

– Here we could note that their driving schedules are not geared to road condi-tions, Anna Anund points out. They have the same times laid down, summer or winter. They say that almost all the time they must drive in the left-hand lane. They must get on.

The word stress is heard a lot. It is also something that is felt to cause fatigue.

– Stress is a subject that I would like to highlight in fatigue research. I believe that stress is worth looking into for its own sake. People are in much greater hurry now than before, and stress makes them more tired. Stress can also impair performance.

Other things that make people tired are monotony, the lights of passing vehicles and heat.

– Long distance commuters know that they are tired when they start feeling cold, and they do not turn up the heating. Young drivers, on the contrary, turn up the heat when they begin to shiver.

Sleeping passengers can also be tiring.

Of the focus groups, it is the long dis-tance commuters who are most in favour of systems in the car that “tell them” when they show signs of tiredness. For instance, systems that measure eye movements and begin to signal when the driver blinks his eyes far too often. Or even systems that stop the vehicle if the driver falls asleep.

Young drivers are negative to such systems.

– They say that they would not bother about these, says Anna Anund.

As big a problem as alcohol

On the whole, young drivers are a group where “there is a lot to be done”, to quote Anna Anund.

– They are a difficult group. Lack of experience is a serious problem. For instance, none of the participants in our focus group had driving in the dark included in their driving licence training. Nor do they recognise tiredness when it creeps up on them, and if they do, they are both frightened to stop and think it is silly to stop to have a sleep.

When the different groups had to answer the question “who do you think is the most tired on the roads”, the unani-mous answer was that it is young drivers and shift workers. The young drivers were more specific and said it was young men who are most tired. Professional drivers think that long distance commuters and people with chronic sleep disturbances are most tired, and the long distance com-muters say that it is older, near sighted lorry drivers who are most tired….

– Statistically, it is young male drivers who have the most accidents.

– I am convinced that tiredness is just as big a problem as alcohol, but people in general unfortunately do not understand how dangerous it is to drive when they are tired, says Anna Anund.

to continue the Swedish study. Results would instead be purchased from the US. In any case, this is an extremely inexpensive traffic safety measure. Cut-ting grooves in the marginal strip costs no more than SEK 11–12 per metre run.

Focus groups

Apart from the accident analysis, the report Fatigue in Focus is based on the discussions held in three different focus groups. One group comprised long-dis-tance commuters (7 people), the second group young drivers (10 people) and the third and last group comprised profes-sional drivers (7 people).

Anna Anund emphasises that work-ing with discussions in focus groups is a qualitative method. It is not possible to generalise from what the participants have said. The discussions are instead regarded as providing a basis for further work. (For instance, 3000 vehicle owners are just now answering a questionnaire in which the questions have been formulated on the basis of the discussions in the focus groups).

– However, what must not be disre-garded is that discussions in the focus groups provide a lot of knowledge.

The same interview guide has been used in the discussions in the focus groups. The basic questions were roughly as follows:• what happens when you get tired?• when do you get tired?• what significance do other drivers have?• what combinations are the worst?• what action must be taken?• what type of information do you think you should have?

Tiredness catches you unawares, say the participants. It is insidious. You become drowsy and you gradually lose judgment.

Long distance commuters, young drivers and professional drivers

Professional drivers are very specific. They divide fatigue into three stages.

First you have memory gaps. “Where actually am I”? Then your driving starts to deteriorate. You weave from side to side. The third stage is described as “when everything becomes quiet” and is seen

Title: Fatigue in Focus Authors: Anna Anund, Göran Kecklund and Jörgen Larsson Series: VTI meddelande 933Language: Swedish with English summaryThe report is also available as a pdf file on www.vti.se under Reports.



Prewetted Salt versus Brine on Motorway

Article written by: Freddy Knudsen, Danish Road Directorate ([email protected]),Jens Kr. Fonnesbech, County of Funen ([email protected]) and Jørn Christensen, Epoke A/S ([email protected]).

This article is an extract of the report issued in connection with the formal completion of studies concerning liquid salt spreading carried out in the County of Funen during the winters of 2000–2002.

The primary material used for slippery roads’ control on the superior road net-work in Denmark is salt (NaCl). Increased

the County of Funen had carried out stud-ies of brine spreading and compared the results with traditional spreading using prewetted salt.

The studies showed, among other things, that the relative quantity of resid-ual salt on the road was higher when using brine than when using prewetted salt. For example, two hours after spreading prewetted salt, the residual salt quantity was measured at 68 per cent compared with 89 per cent when spreading brine. All results were measured on county roads. In time, increased attention has been directed to the fact that most salt spreadings take place at temperatures down to minimum –3oC. In order to perform slippery roads’ control in these

attention to the ill effect of salt on the environment and the major development within the field of winter road mainte-nance equipment and methods have made significant reductions of the average salt consumption per turn-out possible.

Introduction

This report deals with winter road main-tenance methods using NaCl in the form of brine (22% salt solution) and prewetted salt (70% dry salt + 30% brine).

In 1998, it was decided to appoint a working committee with the purpose of comparing the effects of the above-mentioned salt spreading methods. One of the reasons for this decision was that

Prewetted Salt versus Brine on Motorway

DANISH ROAD DIRECTORATE (DRD)


open road surfaces is less suitable, as it causes an over-consumption of liquid, because the liquid runs into the pores. As a result, the distribution of a significantly larger amount of ml/m² is required.

Advantages of liquid spreading:• the liquid is active immediately after application• the liquid does not blow off the road surface• liquid distribution is possible at higher speeds, i.e. faster completion of a salt-ing route and thus less inconvenience to traffic. However, this requires the use of nozzle spreaders• a predefined liquid distribution across the road lanes is possible by means of the liquid system• suitable for preventive spreading due to the long-term effect• less salt results in less road damage and fewer rust problems• reduced environmental impact• whenever possible, the liquid must be distributed preventively – also when the weather forecast predicts snow or freez-ing rain• in case of snowfall the use of a snow plough is required, which must be able to clear snow all the way down to the road surface• during continuous snowfall the salt spreading must take place immediately after snow clearing in order to prevent the snow from freezing into the road surface.

Results – Prewetting spreading versus liquid spreading

Hoar frost situations: Hoar frost forma-tion is conditioned on the road tempera-ture being below 0ºC as well as lower than the air dew point temperature. Often, more than 50 per cent of all turn-outs for winter road maintenance take place during hoar frost.

Based on observations from the two winter seasons of the study period, the following conclusion may be drawn: In hoar frost situations 5.2 g of NaCl/m² was distributed in the form of brine, and 7.7 g of NaCl/m² in the form of prewetted salt. Nothing in the studies indicates a difference in efficiency of the winter road maintenance.

Snow situation: When the weather forecast predicts snow, it is extremely

important to spread salt on the roads prior to the snowfall. If the salt spreading takes place too late, the snow will compact and subsequently be very difficult to remove. If the snowfall lasts a long time, ploughs must be brought into action. In order to minimize the salt consumption in this process, it is highly important that the snow ploughs used are capable of clearing all the way down to the road surface.

The present study made use of the same procedure and plough type for all four lanes. Snow clearing was initiated when 3–5 cm of snow had fallen. After each run-through with the snow plough, salt spreading was repeated.

The use of the stationary cameras turned out to be extremely illustrative, because it was possible to closely follow the development and the effect of the two spreading methods in either road direc-tion from the start of the snowfall. These pictures are enclosed on a CD in the final report, which is available upon request from the Danish Road Directorate.

Going through the pictorial material and personal observations of the testing area, it is the opinion of the work committee that the “overdosing” by the prewetting spreader in the fast lane is more expedi-ent in a snow situation than the uniform distribution by the liquid (brine) spreader. This study shows that spreading of brine does not have the same positive effect as spreading with prewetted salt, however, keeping the above in mind, the study will continue.

Future and further developments

The “Liquid Group” agrees that a close cooperation between the Danish Road Directorate, the County of Funen and Epoke® A/S must continue in the future with the purpose of refining the spread rate and the spreading pattern, in order to spread only the minimum amount required to ensure maximum level of traf-fic safety and passable roads.

situations, it is only necessary to spread approximately 4.6 g of salt/m2 in the form of brine, when approximately 7.7 g/m2 is the typical amount spread today in the form of prewetted salt.

A reduction of the salt consumption – without lowering the service level and the traffic safety – is possible by adding more liquid to the dry salt or by spread-ing the salt in the form of a concentrated saline solution.

In order to further examine the possibil-ity of saving salt, a project was carried out from 2000–2002. The research test-ing area was the motorway across Funen in both directions between the cities of Nyborg and Middelfart (Route E20).

The project was carried out with a subsidy for development programs from the Danish Environmental Protection Agency.

Project objectives

The major objective of the project was to find methods and document activities, which enable a cutback of salt quantities used for winter road maintenance without decreasing efficiency, and reduce the environmental impact compared to the currently used methods.

The work committee decided to carry out this study by comparing the spreading of salt by means of a traditional prewet-ting spreader and a liquid spreader (both spreaders of the EPOKE brand). The comparison was based on the following parameters:• sensors built into the traffic lane for measurements of residual salt• photos and video recordings• inspection – by means of four perma-nently installed video cameras in the center strip, by means of mobile video cameras, as well as by direct visual obser-vations made by the committee members themselves.

Salt spreading – using liquid (brine)

The distribution of a liquid saline solu-tion, called brine, on the road surface is done by means of NaCl in a 22 per cent solution.

Porous asphalt: It is the opinion of the Danish Road Directorate that the use of brine on porous asphalt and other similar



Danish Road Institute Is 75 Years Old

The first Deflectograph, known as ”The Grashopper”, developed by the Danish Road Institute around 1970.

Article specially written for Nordic Road & Transport Research by Jørgen Christensen, Director, Danish Road Institute.

would be used in the best possible way.”The Danish Road Laboratory was

renamed National Road Laboratory after the Second World War and was integrated into the Danish Road Directorate when the national road authorities were reor-ganised in 1972.

In 1983, all the functions of the National Road Laboratory were collected in one place, when the two asphalt groups, working with road asphalt and bridge asphalt, moved from Copenhagen to new laboratory facilities in Roskilde.

New requirements – new answers

In 1998, Denmark carried through a major change in road legislation. One of the consequences was that 3,000 km of the main road network was handed over to the Danish counties, while the Road Directorate and thus also the Danish Road Institute got the responsibility for the run-ning of the 1,600 km of main roads. The change in legislation also meant that the Road Directorate got greater responsibil-ity for the entire Danish road sector.

In order to live up to the new demands, the Danish Road Institute restructured and created two departments, both of which deal with research and testing. The one department, called Asphalt Department, takes care of research, development, test-

In 2003, the Danish Road Institute has its 75th jubilee. In this article, a short overview of the history of the institute and some of the milestones in research and development of the institute are given. Finally, the author of the article looks ahead at some of the challenges facing Danish road research in the coming years.

The Danish Road Institute has its origin in the “Danish Road Laboratory”, which was founded in 1928. The main task of the laboratory was to undertake the neces-sary examinations, which were required in order to make use of new maintenance methods of roads. The background was the increase in Danish road traffic. In 1928, there were 89,000 registered vehicles in Denmark and therefore requirements for the quality of roads had been drawn up. When the Danish Parliament discussed the necessary legislation in 1927, it was pointed out that the new laboratory should give its users “the greatest possible secu-rity that the money spent on maintenance

ing and consultancy regarding asphalt pavements for roads and bridges and their surface properties. The other department, called Research and Testing Department, takes care of research, development, test-ing and consultancy regarding unbound and hydraulically bound surfaces and materials, including recycled materials and the bearing capacity of pavements.

The Consultancy and Measuring Department, which already had existed for a number of years, takes care of all sorts of technical measurements and advice to road administrations regarding planning, tendering and functional control of maintenance and repair of pavements.

Technical landmarks

The use of measurement equipment for roads began in the early 20th century. From simple methods with slide rules and clocks, the development in road traf-fic demanded increasingly sophisticated techniques. Over the years, the Danish Road Institute has especially focused on bearing capacity, evenness, friction and rutting on roads.

Problems with correctly measuring the bearing capacity of roads led to the invention of the Falling Weight Deflec-tometer, FWD, in the early 70s. The FWD measures the effect of a falling weight,



determining the necessary thickness of the layer, according to prognoses on the amount of traffic on the given road. After initial adjustments, the FWD became a very popular instrument for measur-ing bearing capacity in large parts of the world. A recent breakthrough of the Danish Road Insitute on bearing capac-ity is the development of the High Speed Deflectograph (HSD), which consists of a towing truck and a trailer on which laser sensors are mounted. The HSD can per-form continuous bearing capacity meas-urements at driving speeds in the range 20–70 km/h.

The evenness of roads has always been an important issue for road builders and road users. The Danish Viagraph was introduced in 1943, built as a sleigh on wheels, pulled by manpower. In 1959, 10 viagraphs were built to be used in Denmark and in1967, the British invented Bump Intergrator was added to this equip-ment. The two types of equipment worked well together, determining the even-ness of the road surface – the Viagraph being the slow, but thorough one, while the Bump Intergrator was quick to use, producing acceptable results to evaluate the general evenness of the road. In the 1990s a new equipment, the Profilograph, was taken into use. The Profilograph uses laser technology, enabling the tests to be executed at up to 100 km/h, determining not only the evenness of the road, but also giving valid data on wheel noise, rutting and friction.

Friction was one of the earliest issues to be adressed by road engineers. In the early 50s, the Danish Road Institute con-ducted its first test on friction, using the so-called Stradograph, built according to inspiration from France. After using sev-eral similar models, a brand-new Strado-graph was introduced in 1976. The Stra-dograph was able to measure friction on roads at highway speed, but was difficult to handle, and was replaced in 1998 by the ROAR, which is a lighter equipment. Both measuring vehicles are now used to find road sections with poor friction.

Next to the climate and the ageing of the road, axle loads have the biggest influ-ence on the condition of the road. Flow rutting, due to heavy traffic is a general problem that has been adressed by the Danish Road Insitute in various ways

• accelerated testing of rutting of asphalt pavements in the special equipment of the Danish Road Institute, DART (Danish Asphalt Rut Tester)• analysis of the connection between road surface texture and friction, which is of utmost importance for vehicle safety and the ability to brake, etc.

Dissemination of knowledge is a central pillar in the activities of the Danish Road Institute and is supported by the following groups of tasks:• the technical library of the road sector• the internet• internal sharing of knowledge• technical networking• publications in technical journals• teaching and consultancy• participation in publication of Road Standards and work in CEN.

Apart from this, there are a number of varying tasks for the Construction Unit and the Operation and Maintenance Unit of the Road Directorate, as well as the servicing of the many customers of the institute, incl. county administrations, and local administrations, the asphalt indus-try, construction contractors, consultancy companies and the EU Commission. The market of the Danish Road Institute is dominated by the public sector, which stands for about 80 per cent of the turno-ver.

The future

The present focus areas, which will influ-ence research and development in the future, are:• Perpetual pavements (Long-life pave-ments) – new pavement types, which have a lifetime of 20 – 35 years• Asset Management – Contribution to the development of common planning systems in the road sector• Total reuse of the road – Life cycle evaluations for all materials.

These research areas have been described in an article in Nordic Road and Transport Research No. 1/2003.

over the years. In order to test the resist-ance to rutting in Danish asphalt layers, the Danish Road Institute decided to build equipment for accelerated load testing, the so-called DART (Danish Asphalt Rut Tester). Research with the DART, in combination with laboratory tests, makes it possible to assess the resistance to per-manent deformation of different types of asphalt pavements.

Road management systems

In order to determine the overall condi-tion of roads, the Danish Road Institute has since the mid-seventies provided informaton to Danish and foreign road administrators, using Bridge Manage-ment Systems (BMS), Construction Management and Supervision (CMS) and Pavement Management Systems (PMS). The systems ensure correct plan-ning of maintenance of roads and gather experiences used for constructing new roads. The Danish Road Institute is cur-rently working on the development of PAVEMAN – a system design for road constructors, ensuring consensus in data-processing between owner, constructor and authorities.

Central contributions today

The Danish Road Institute has since its creation 75 years ago, carried out research and dissemination of knowledge as an integral part of its work.

Research is directed towards the proper-ties and use of materials for construction and maintenance of the road infrastruc-ture. The fundamental problems, which require research are connected to the strength, durability and functional proper-ties of roads and the development of these properties with time due to the influ-ence of traffic and weather. The Danish Road Institute has obtained international specialist status because of its research results in a number of areas:• the use of crushed building materials in road construction • description of shortcomings in asphalt materials through microscopy in thin sec-tions of asphalt• instrumentation of test stretches for accelerated deterioration experiments in road testing machines



Image Processing for Analysis of the Effectiveness of a Reconstruction

The lack of recorded crashes often means that we need less blunt instruments than crash data for designing or evaluating treatment. Until now the focus has been on working with trained observers in con-flict and behavioural studies. Usually the Swedish Traffic Conflicts Technique is used. However, recently also image pro-cessing tools have been developed.

How to get started

The intersections are filmed with one or more video cameras. Sony’s Hi8 system and SuperVHS cameras can be used. The quality of the picture is very important, and the conventional VHS system does not meet a high enough standard. When filming traffic situations it is most impor-tant that road users do not easily detect the cameras as this may influence their behaviour. The cameras are therefore placed on posts and walls of buildings, hopefully invisible to drivers as well as pedestrians and cyclists. The angle of the video shoot is very important for the quality of the results. A flat camera angle creates a strong distortion of perspective, which is undesirable. The real plane and picture-plane are set in a mathematical relationship to make it possible for the program to do the measurements. Every point in the real plane corresponds to exactly one point in the picture-plane, as shown in Figure 1.

An important factor for the kind of anal-ysis made in a study of a traffic conflict is the length of time in relation to how valu-able the obtained results are. Working with this specific program, speed, acceleration, distance, Time to Accident (TA), Time to Collision (TTC), Post Encroachment Time (PET) and Deceleration to Safety Time (DST) can easily be gathered over a given distance (covered by the camera). Compared for example to conventional radar measurements, which typically only

ViVAtraffic

In Germany, a semiautomatic video based computer program ViVAtraffic has been developed as a tool for image processing. It was developed by a team of computer specialists and traffic engineers from the University of Kaiserslautern. It is supplied by GVA (Gesellschaft für VerkehrsAnalyse) mbH. The program offers two different methods of meas-urement; interactive measurements and automatic survey.

The interactive measurements include:• distance measurements• speed measurements• acceleration measurements• motion-line measurements.The motion-line measurement tool is used for the analyses in this article. This tool makes it possible to track all movements of road users in an image sequence and relate them to each other.

The program can also make automatic observations by automatically tracing road users in video sequences and col-lecting relevant data such as number of vehicles, average speed and the projected 2-dimensional length of the vehicles. However, this method was developed for rural conditions. Our task was to check the applicability of the interactive meas-urement device in more complex urban conditions. Therefore the results of inter-active measurements in ViVAtraffic were included and compared with the results of three observers.

Article specially written for NR&TR by Kristin Nilsson (FB Engineering AB, Sweden) and Lars Leden (VTT, Finland).

Concepts

High Severity SituationInteraction when at least one of the road users takes an evasive action to avoid a collision or encounter with a small PET value. Does not have to be a collision course.

Time to Accident, TAThe time remaining to collision between two road users, from that the first road user to take evasive action starts a manoeuvre till the col-lision would have occurred if the road users had continued with unchanged directions and velocities.

Time to Collision, TTCThe time remaining to collision between two road users, if the road users had continued with unchanged directions and velocities.

Post Encroachment Time, PETTime measured from the moment the first road user leaves the potential collision point to the moment the other road user enters the conflict-ing point.

Deceleration to Safety Time, DSTThe necessary deceleration to reach a last PET ≥ 0.

Figure 1. Relationship between the real plane and picture-plane, expressed graphically and mathematically. (http://transport.arubi.uni-kl.de, 1999).

TECHNICAL RESEARCH CENTRE OF FINLAND (VTT), BUILDING AND TRANSPORT

The fact that there are no crashes during every three-year period on every spot of a road network does not mean that the long-term safety level is exactly zero crashes. However, what the lack of recorded crashes does mean is that we need less blunt instruments than crash data for evaluating, for example, the effectiveness of a reconstruction.


detail. These encounter situations, when at least one of the road users takes an eva-sive action to avoid a collision, or encoun-ters with a small PET value are here called High Severity Situations. They are most often less severe than serious conflicts. Even if conflicting road users are not on a collision course, some encounters can be defined as Situations. Dr. Åse Svensson from Lund University in Sweden raises the possibility of a threshold in the seve-rity hierarchy above which there is a high probability of an accident, while encoun-ters below this level are safe interactions. Occurrence of conflicts situated low in the severity hierarchy can therefore be a good sign, according to Åse Svensson. This threshold might be different if a child is involved. Adults are most often capable of making safe judgements in the traffic environment and can interact with other road users with lower safety margins. When errors are made, adults typically learn from their mistakes. Children are not capable of this and therefore often act unpredictably.

Reliability tests

The first reliability test of observers’ esti-mates were based on one hour of video filming in Malmö, Sweden, October1999. Nineteen situations were detected. The average differences between by the observers estimated speeds of pedes-trians, cyclists, motor vehicles and TA values are shown in Table 1. Estimates from Observer 1 and 2 were more uniform than those from Observer 3. If the results

measure speed at one specific point, this is an obvious advantage. However, radar guns can be modified to send speed data to a laptop computer, which makes it a cost-effective way of gathering speed data over a given distance. Radar meas-urements normally have a very small range of measurement fault of ± 1 km/h. If there are many metal objects or a low motor vehicle speed, a laser gun might be needed, as this identifies the car being measured with a red spot.

An advantage working with an image processing method is the possibility to go back and check things like prerequisites and important details, which might other-wise be missed or forgotten. However, it can be more difficult to identify a hazard or unpleasant situation by just looking at a screen, without the live experience of field studies. Some other less pleasant problems experienced when working with a computer program are software prob-lems and low-resolution video films. For example, poor quality video does not only create problems with calibration and pin-pointing precise positions of road users; the time needed is also much longer than with good quality. It may also be difficult to find good positions for video cameras. The optimal position is at about 10–25 m above the area of interest.

Situations can be analysed in detail

An important advantage with the image-processing tool is that encounters, e.g. when a car gets in close proximity to a pedestrian or cyclist, can be analysed in

Key reference: Application of ViVAtraf-fic to study the interaction between vul-nerable road users and motor vehicle drivers. Case studies in Sweden and GermanyAuthor: Kristin NilssonSeries: Luleå University of Technology, Master’s thesis 2000:116 CIVLanguage: English

from Observer 3 are excluded the average difference in estimation of TA values was –0.2, compared with the average TA value of 1.8, which is quite a small deviation of 11 per cent. The corresponding deviation for speeds of pedestrians, cyclists and motor vehicles were 40, 15 and 5 per cent respectively.

For the second reliability test 60 Situ-ations were selected from a video film from Malmö, March 1999. To make the intended conflicts less obvious, the three observers were given 60 film sequences to study and identify situations for them-selves. A total of 133 different Situations, with no consideration as to severity level, were detected. Of these 133 situations only 19 were found to be comparable, since those were the Situations when all three observers had detected the same road users involved, the same evasive action being taken at approximately the same time and estimated a TA value. It should be noted that ViVAtraffic only calculated TA values for four of the Situations. All four were among the most serious. The deviance between the four estimates of the observers and ViVAtraffic was -0.8 (st dev 0.8). For most of the Situations ViVAtraffic suggested that there was no collision course, but a PET value.

The agreement between the three observers was good, as seen in Table 2. The maximum average deviation was 3 per cent (between Observers 1 and 2).

All observers Observer 1-Observer 2

Observer 1-Observer 3

Observer2 – Observer 3

Pedestrian speed 2.6 (1.0) -1.0 (0.9) -1.7 (1.1) -0.7 (0.6)Cyclists speed 8.4 (3.1) 1.3 (1.3) -3.3 (1.7) -4.5 (2.9)Motor vehicle speed 41.0 (9.2) -2.0 (6.1) -5.2 (5.0) -3.1 (4.9)TA 1.75 (0.52) -0.20 (0.64) 0.32 (0.49) 0.52 (0.53)

Table 1. Mean and mean differences between by the observers estimated speeds (km/h) of pedes-trians, cyclists, motor vehicles and Time to Accident, TA values (s). St dev in brackets (n=19).

All observers Observer 1-Observer 2

Observer 1-Observer 3

Observer2 – Observer 3

TA 1.79 (0.55) -0.05 (0.61) -0.03 (1.14) 0.02 (1.11)

Table 2. Mean and mean differences betweenby the observers estimated speeds (km/h) of pedestri-ans, cyclists, motor vehicles and Time to Accident, TA values (s). St dev in brackets (n=19).

TECHNICAL RESEARCH CENTRE OF FINLAND (VTT), BUILDING AND TRANSPORT


INSTITUTE OF TRANSPORT ECONOMICS (TØI)

Passengers on public transport in the Oslo region in Norway are willing to pay a higher fare if they can use rail rather than bus, can get a direct service and be sure the service is on time.

The purpose of this study was to analyse passenger preferences and evaluations of the quality of public transport in the capi-tal Oslo and the nearby county Akershus, as well as to find out whether passenger evaluations have changed over time. A similar study was carried out in 1993 (Norheim and Stangeby 1993).

Method

The sample has been chosen at random from the population register. Those selected were aged 14 years or above, all with addresses in Oslo or Akershus. Everyone who was selected received a letter by post with an internet address and a user name/password to log into the survey. Those who did not have access to Internet were given the opportunity to fill out a form on paper. The response rate was 29.4 per cent.

The method which was used to chart preferences is called Stated Preference Analysis. Stated preference analyses are based on hypothetical choices, and in order to make the situation as realistic as

possible, we based this on the first jour-ney, the last day the respondent travelled with public transport.

Those interviewed were asked to choose between different ”packages”. Each ”package” describes different characteristics of a journey. The choice of ”package” forms the starting point for charting the factors which are given the

greatest weight. From these choices we calculate how much price, journey time, frequency and departure time mean for the choice of public transport.

Journey time

The total journey time by public transport consists of the time taken to get to or from bus-stop, the waiting time (actual and hidden) and the time on board the vehicle. If it is necessary to change buses, the waiting time between the two buses is also included. In total, the average jour-ney time is 42 minutes in Oslo and 62.5 minutes in Akershus (table 1).

The passengers’ evaluation of the jour-ney time on board public transport does not only depend on the length of journey but also whether they have to stand or whether they get a seat. About 80 per cent of those involved in the study state that they have a seat for the whole journey. The disadvantage of standing is associ-ated with so much discomfort that the dis-

Public Transport: Travellers’ Valuation of Time in the Oslo Region

Akershus2002

Oslo2002

Oslo1992

Walking time to bus stop 8 6 10Actual waiting time at bus stop 5 5 5Hidden journey time 17.5 8 7,5Journey time on board public transport 32 23 20Total 62.5 42 42,5

Table 1: Average journey time on the first form of transport. Minutes. Source: Stated preference analysis for Oslo and Akershus 2002 and Better Public transport 1992.

There is a willingness among public transport users in Oslo and Akershus to pay 12 per cent higher fares if they have the possibility to use rail transport rather than bus.


advantage of a journey without a seat is valued almost twice as much as a journey time with a seat in Akershus.

The evaluation of reduced journey time without a seat is about twice as high in Akershus as in Oslo. On average, journeys in Akershus are longer and the disadvantage of standing is thus greater. In addition public transport in Akershus is less suitable for passengers who have to stand than public transport in Oslo.

In Oslo, the disadvantage of departure times is regarded as greater than the disadvantage of the journey time on board public transport, even if one has a seat. In Akershus, the disadvantage of walking to the bus stop is almost the same as the disadvantage of the journey time on board public transport with a seat.

Delays

About 1/3 of the passengers said that they experienced delays in relation to

the timetable on the journey itself. 58 per cent of the delays in Oslo and 49 per cent of delays in Akershus are five minutes or less.

An average delay is eight minutes in Oslo and nine minutes in Akershus. Bearing in mind that the average journey time is longer in Akershus compared with Oslo, the relative delay is shorter in Aker-shus than in Oslo

Passengers regard delays as a major dis-advantage. If the frequency of the delays

is reduced from 20 per cent of departures to 10 per cent of departures, this is valued at NOK 2 per journey in Oslo and NOK 4.30 per journey in Akershus (figure 2).

When a delay actually occurs, one minute reduction in the delay is valued at NOK 4.60 in Oslo and NOK 7.90 in Akershus (effective time).

Based on this, it can be seen that pas-sengers evaluate the disadvantage of an incurred delay of 20 minutes at NOK 92 in Oslo and NOK 158 in Akershus.

Figure 1: Evaluation of frequency, walking time to bus stop, journey time on board public transport and waiting time between buses. NOK per hour. (1 EURO = 8,2 NOK)

Changing buses

It is neither possible nor rational to develop a public transport system where all passengers can travel from door-to-door without changing buses. This would mean a public transport service with low frequency and parallel routes on a number of stretches. It is therefore necessary to develop junctions where passengers can change buses during their journey in order to give the best possible, most frequent and cost-effective service.

Around 1/3 of passengers have to change buses in the course of their actual journey, 29 per cent in Oslo and 36 per cent in Akershus. The vast majority only have to change once during their journey.

For passengers who regard changes during their journey as a disadvantage, the disadvantage can be divided into two: • resistance to changing, which can be due to the disadvantage of having to get up and move, uncertainty as to whether one will get a seat on the new form of trans-port and uncertainty regarding whether both vehicles are in operation• extra waiting time which occurs when having to change. The waiting time asso-ciated with changes cannot be chosen, in contrast to the waiting time for the first form of transport.

Resistance to changing buses is relatively high.




Resistance to changing buses is rela-tively high (figure 3). The disadvantage of changing without waiting time (direct change) is valued at NOK 2.40 per jour-ney in Oslo while in Akershus the resist-ance is valued at NOK 4.60. The evalua-tion of changing without waiting time is thus almost twice as high in Akershus as in Oslo.

In the analysis, the disadvantage of a change with 5 minutes waiting time between buses is valued at NOK 7.70 per journey for Oslo and NOK 10.90 per jour-ney in Akershus. If the waiting time is 10 minutes, the figures are NOK 12.20 and NOK 18.90 respectively (figure 3).

The longer the journey time, the greater the disadvantage which passengers expe-rience when changing buses.

This means that a strategy for devel-oping junctions in Oslo and Akershus must seek to reduce waiting times when changing as far as possible, with higher frequency, links between waiting buses and accessibility measures which ensure a high degree of punctuality.

The rail factor

An interesting problem is whether there is a ”rail factor”, i.e. whether public trans-port users choose transport by rail rather than by bus when they travel.

The form of public transport chosen by the individual passenger depends on com-fort, information and personal general preference for the form of transport.

We find that public transport users have a general preference for rail transport rather than buses (table 2). Willingness to pay for rail rather than bus is NOK 2.80 in Oslo and NOK 5.50 in Akershus.

Evaluation Confidence interval Fare increase Effect1

Oslo 2,80 1,8-3,8 12% 5%Akershus 5,50 2,6-8,4 12% 5%

Figure 2: Evaluation of delays – Evaluation of a reduction in frequency of 10 % and evalua-tion of a one minute reduction in delay once a delay has occurred. NOK per 10 % and NOK per minute. (1 EURO = 8,2 NOK).

Figure 3: Evaluation of the disadvantage of changing buses during the journey, depending on waiting time at the junction. NOK per journey (1 EURO = 8,2 NOK).

Table 2: Passengers’ willingness to pay for public transport by rail rather than by bus, with simi-lar increases in fares and demand effect. Non-weighed average for conjoint nos. 1,2 and 3. NOK per journey, 95 per cent confidence interval and percentage. Source: Stated preference analysis for Oslo and Akershus 2002.

Demand effect1 with elasticity of –0.4

Title: Public transport in the Osloregion – Travellers´ valuation of timeAuthor: Åse NossumSeries: TØI report 633/2003Language: Norwegian with English summary. The summary is available at: http://www.toi.no/program/program.asp?id=134273


Annotated reports from the Danish Road Directorate (DRD)

Modeling of pavement response is central in mechanistic pavement analysis and design. Hence, the validity of response models is an important prerequisite for reliable evaluation of structural pavement condition. As measurements of pavement response at several pavement tests have shown a lack of fit between observed and calculated response using state-of-the-practice response models there is a need to focus on the validity of these models.

An instrumented field test pavement was established on top of a sandy mate-rial sufficiently thick to be considered a halfspace to allow verification of pave-ment response for both the simple case, a halfspace, and for the more complex case, a multilayered flexible pavement. Falling Weight Deflectometer (FWD) loads were applied at each layer of the pavement to provide input to built-in instruments, which registered stress and strain in three orthogonal directions in the sandy sub-

grade. At each pavement layer additional FWD and surface wave measurements were carried out at several locations to determine elastic layer moduli.

The experimental results showed good agreement between elastic layer moduli from the FWD backcalculation and moduli from the in situ response observa-tions. Results from the surface wave tests did not compare well with results from the other tests.

Based on the FWD backcalculated layer moduli, pavement response was predicted using a wide range of response methods from a simple Boussinesq model to finite element methods. Comparison between the predicted and observed pavement response showed very good agreement for strain response while the agreement was more questionable for stress. The latter may have been caused by flawed stress response registrations, however.

It is concluded that the reliable pre-

diction of pavement response requires verification of the response models, which includes the development and use of suitable constitutive material models. The study showed that although it was difficult to establish a completely homogeneous test field, several response models reliably predicted strain response in a halfspace, while a three-dimensional finite element program considering the dynamic load situation performed best in the prediction of response in a multilayer pavement system.

Verification of Flexible Pavement Response from a Field Test

Title: Verification of flexible pavement response from a field test Author: Gregers HildebrandSeries; Danish Road Institute, Report 121. The report is only available elec-tronically on http://www.vd.dk/wimpdoc.asp?page=document&objno=70114Language: Danish with English summary

The Danish Road Directorate has com-pared the results of bearing capacity measurements on granular base materi-als by means of three different types of tests: static plate bearing test, FWD and a mini-FWD. The tests show very good correlation between the results from the static plate bearing test and FWD. Three different mini-FWDs showed promising results, but this type of equipment has greatest potential for measurements on natural soil and subbase layers as well as in places where it is impossible to use a FWD.

The primary purpose of the research was to examine to which extent equip-ment for static plate bearing tests can be replaced by the FWD. Based on calculation of the surface modulus E0 in the centre of the loading, it appears that there is a very good and direct correlation between the results from the two types of equipment. A final evaluation must how-ever, be based on tests on other subgrade

types and at the same time the examina-tion should be based on a determination of E-values for the basecourse, subbase layer and subgrade.

A field test showed that the FWD results in surface moduli are almost iden-tical to those obtained from the static plate bearing equipment, whereas the three mini FWDs give surface moduli which to some or limited extent resemble the results from the plate bearing equipment. The tests show that the mini-FWD from Keros Technology and to a limited extent the Loadman-equipment agree to some extent with results from the plate bear-ing equipment and the FWD. The surface moduli from the Zorn mini-FWD are con-siderably lower than those determined by other equipment.

Based on the tests carried out, it can be concluded that the Danish Road Directo-rate should concentrate on the use of the FWD as a replacement for plate bearing equipment on completed surfaces of gran-

ular base material. On the other hand, a considerable use of the mini-FWD is foreseen for measurement on natural soil, subbase layers and in places, where it is not possible to use the FWD. It is recom-mended that the Danish Road Directorate examines how the mini FWD could play an active role in connection with super-vision during construction of new roads – possibly as a supplement to existing methods.

Static Plate Bearing Tests, Falling Weight Deflectometer (FWD) and Mini-FWD

Title: Static plate bearing tests, Falling Weight Deflectometer (FWD) and mini-FWDAuthors: Gregers Hildebrand and Susanne BaltzerSeries: External Report 16. The report is only available electronically on http://www.vd.dk/wimpdoc.asp?page=document&objno=71673Language: Danish with English summary


Annotated reports from the Danish Road Directorate (DRD)

The aim of the literature review is to survey Swedish and foreign design solu-tions to meet mainly speed and accessi-bility requirements for roundabouts and to see if foreign experiences are relevant for Swedish conditions. Great importance has also been given to studying to what extent there are “functional categories” of roundabouts.

The survey shows that roundabouts with lower speeds and single lanes improve traffic safety. Furthermore that there are good opportunities to control speed through design, e.g. using narrow, radial entries and exits with small entry radius, entry and exit deflection to the left, design for an entry path curvature with small radius and traffic island.

The survey also shows that give way regulations between vulnerable road users and motor vehicles in Sweden can be made clearer.

The idea of dividing roundabouts and the entire traffic system into distinct “functional categories” is to improve traf-fic safety by decreasing the risk that the road user misunderstands the situation. To create good categories of roundabouts, an

investigation ought to be made of what is needed and of the way the road user can be informed of the functional category classification of the roundabout that he is about to enter. In the same way as in Sweden, several countries have a not very pronounced category classification of roundabouts.

Annotated reports from the Swedish National Road and Transport Research Institute, VTI

Roundabouts – Design and Function

Title: Roundabouts – design and function. Swedish and foreign recom-mendations and design rules with analyses and commentsAuthors: Lisa Herland and Gabriel HelmersSeries: VTI meddelande 895Language: Swedish with English summaryThe report is also available as a pdf file on www.vti.se under Reports

Title: Clogging of porous bituminous surfacings – an investigation in Copen-hagen Authors: Hans Bendtsen, Carsten B. Nielsen, Jørn Raaberg and Robin A. MacdonaldSeries: Report 120, Danish Road Institute. The report is only available electronically on http://www.vd.dk/wimpdoc.asp?page=document&objno=63822Language: Danish with English summary

Four road sections were constructed in Oester Soegade in Copenhagen, Den-mark, to investigate porous bituminous surfacings. Three were surfaced with a two-layer porous asphalt surfacing and a fourth reference section was surfaced with a conventional dense Asphalt Concrete. The objective of the study was to inves-tigate the durability of two-layer porous bituminous surfacings under Danish weather conditions and to measure noise level attenuation during their lifetimes. Permeabilities (Becker’s Tube method) and void distributions for the three porous asphalt test sections were compared with noise levels (SPB Method) for the four test sections investigated; Plane and Thin

sections were also prepared from asphalt surfacing cores.

These investigations, together with results from routine permeability meas-urements, gave an indication of the mechanisms and rates of clogging of the voids in the surfacings. The thin sections also provided useful information about the condition of the surfacings, e.g., on binder stripping. Permeability and noise level measurement comparisons showed some degree of mutual relationships. However, no significant difference could be detected between permeability meas-urements made before and after flushing. Thin sections from cores extracted after more than one year of trafficking, showed

that clogging occurred in the top 10 to 25 mm of the surfacings.

Clogging of Porous Bituminous Surfacings

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Annotated reports from the Swedish National Road and Transport Research Institute, VTI

There are several indications that the ear-lier favourable traffic safety development in Sweden has slowed down in recent years. VTI has therefore been commis-sioned by the Swedish National Road Administration and the Swedish Police Board to describe and analyse the changes in the traffic system which may have either a positive or negative significance for traffic safety development.

Since the overarching goal of traffic safety work is a gradual year by year reduction in the number of those killed in traffic, the question arises why this goal could not be reached during the period 1994–2000. Large investments and

changes have been made which resulted in both decreases and increases in the risk of being killed in traffic during the period. The report makes an examination of the different problem areas which were con-sidered in relation to the different meas-ures or changes during the period, and the way these ought to have affected the risk of being killed in traffic.

An overall summary is that the increased speeds were compensated for by the increased number of cars equipped with airbags. Road improvements for greater safety, motorways, roundabouts, road barriers etc., together with higher petrol prices and the winter tyre law com-

In the late 1990s, attention was paid to the need to conduct research on decision-making processes as regards investments in roads and traffic lanes. This study delivers its contribution by describing and analysing the decision-making proc-ess that resulted in wire railings being set up in central reserves and a 2+1 lane road being built on a stretch of the European Highway No. 4.

By means of documents, press cuttings and interviews, light is being thrown on the development from the establishment of the Vision Zero to the consequences of the project in the form of a new type of wire railings. Factors such as problem for-mulation, search for options and assess-ment of consequences are described. Ways of organising the process, external interested parties’ influence and the par-ticipants’ roles, activities and attitude development are highlighted.

This process submits to testing an entirely new design of roads and puts it into practice. Attention focuses on the process of acquiring experiences. It applies to both the feasibility study, including the problem of convincing sceptics and gaining their acceptance, and the experience of achieving a substantial innovation in the road safety area. The study emphasises both the specific aspect of this case and its general applicability to

road planning and thus infrastructure. The need for further development of know-how for a theoretical and empiri-cal knowledge bank of decision-making processes is additionally highlighted.

Title: Lifeline on the E4. Decision-making and traffic safetyAuthors: Sven-Olov Larsson, Östersund University College, Sonja Forward and Sanja Obrenovic, VTISeries: VTI rapport 484Language: Swedish with English summaryThe report is also available as a pdf file on www.vti.se under Reports

Decision-Making and Traffic Safety

Traffic Safety Development in Sweden until 2001

Title: Traffic safety development in Sweden until 2001Authors: Göran Nilsson, Gunnar Andersson, Ulf Brüde, Jörgen Larsson and Hans Thulin Series: VTI rapport 484Language: Swedish with English summaryThe report is also available in Swedish as a pdf file on www.vti.se under Reports.

pensated for the reduction in safety owing to greater vehicular traffic, especially the increased lorry traffic, and the higher average age of drivers increases the risk of being killed due to an injury in a traffic accident.

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Annotated reports from the Institute of Transport Economics (TØI)

Travellers’ Valuation of Traffic Information The survey was carried out in order to gain knowledge about travellers’ prefer-ences with respect to traffic information and their willingness to pay for it. This kind of knowledge is useful in the plan-ning of future traffic information systems. It could also contribute to a better under-standing of how user benefits of traffic information should be included in cost benefit analyses of traffic information measures. The study was limited to people who commute by car to work in Oslo. The questionnaire was carried out using inter-

during the trip to work and, though some were not interested to pay for it, most respondents wanted more detailed traffic information in the future.

net. We used stated preference techniques and produced “custom-built” questions for each respondent, in the sense that figures presented in some questions could depend on answers from previous ques-tions. The willingness to pay for reduced travel time, delay and travel time vari-ability was found to be somewhat lower than experienced in other simular studies. How we chose to recruite travellers in this study may explain some of the dis-crepancy. Most of the respondents choose to receive information both before and

Title: Travellers’ valuation of traffic information based on work journeysAuthors: Marit Killi, Hanne SamstadSeries: TØI report 620/2002.Language: Norwegian with English summarySummary: http://www.toi.no/attach/a84037r275127/sum_620_02.pdf

Injury Severity DensityVision Zero has been adopted as the basis for road safety policy in Norway. As a consequence of this, more emphasis is now put on preventing fatal and serious injuries. In order to identify road sections that have a high expected number of fatal and serious injury accidents, the Institute of Transport Economics has developed a new indicator called “injury severity density”. Injury severity density is based on weighting the number of injured road

given road- and traffic characteristics.users by the societal cost of the injuries. The empirical Bayes method has been applied to estimate injury severity den-sity. Briefly speaking, this means that the recorded value of injury severity density for a given road section is adjusted by means of a normal value of injury sever-ity density, estimated by means of a mul-tivariate accident model. The result is an estimate of the expected value of injury severity density for road sections with

Title: Injury severity density. A new approach to identifying hazardous road sectionsAuthors: Arild Ragnøy, Peter Christensen, Rune ElvikSeries: TØI report 618/2002.Language: Norwegian with English summarySummary: http://www.toi.no/attach/a90252r461956/618_2002_sum.pdf

Transport Performance in Norway 1946-2001In this report, transport performance figures for the year 2001 are presented together with other relevant Norwegian transport statistics. Domestic passenger transport performance increased by 1.2 per cent in 2001. Private car transport rose by 2.3 per cent, while public trans-port mainly remained at the 2000-level or decreased. Air traffic decreased by nearly seven per cent. Road traffic between

shelf increased by five per cent in the same year.

Norway and abroad rose by 9 per cent in 2001, while international air and ferry transport remained at the same level as in 2000. Domestic transport of goods increased by 4.5 per cent in 2001, mainly due to a considerable growth in sea and rail transport. The quantity of freight to and from the mainland showed a marked decrease in 2001. Oil and gas export directly from the Norwegian continental

Title: Transport performance in Norway 1946-2001Author: Arne RidengSeries: TØI report 621/2002.Language: Norwegian with English summarySummary: http://www.toi.no/attach/a120635r488582/sum_621_02.pdf

Accident Data Recorders (ADR)Accident Data Recorders (ADR) that monitor and record important details of traffic accidents is available and used since the beginning of 1990. In this report, we have described two different systems accessible on the market. The first has its own sensors and is designed for installing in all kind of vehicles. The second is a system delivered as original equipment by a vehicle manufacturer. Conventional

have discussed is how ADR affect the driving behaviour and thereby have a favourable influence on traffic risk.

practices for reconstruction and analys-ing causality may be both time and cost demanding. Utilizing ADR give access to objective information which never have existed before. In this report, based on experience from Europe and USA, we have focused on how the application of ADR can increase the precision when investigating a traffic accident. Another effect by installing ADR in vehicles we

Title: Accident Data Recorders (ADR). Literature Review of effects and experiences with use of ADRAuthor: Per G. KarlsenSeries: TØI report 617/2002.Language: Norwegian with English summary


Annotated reports from VTT, Building and Transport

Operation LifesaverOperation Lifesaver (OL) is North Ameri-ca’s premier public education program dedicated to railway safety. In the USA and also in Europe over 90 per cent of rail-related fatalities involve level cross-ing collisions or trespasser accidents. OL started in 1972 in Idaho as a one-time six-week campaign. During the first year of the campaign Idaho’s level crossing fatalities dropped by 43 per cent. In 1986 OL was incorporated as a national non-profit education organisation (Operation Lifesaver Incorporation, OLI). Today in the USA there are 49 state programs. They have more than 2,500 trained, cer-tified public speakers and hundreds of partners in the public and private sectors. International OL Programs have been established in Canada, Mexico, and South and Central America. During 2002 the program was introduced in Australia, the UK and Estonia. Some OL based trials on

aimed at different student age groups are available for teachers. They are available from the OL web site (http://www.oli.org) or on CD-ROM.

The second task of OLI is media education aiming to promote OLI film and photography guidelines and to raise awareness of ‘bad ads’ (advertisements in the media with no regard to rail safety). OLI has advertisements on television, radio and in print.

The next challenge of Operation Life-saver in the USA is to involve the light rail industry.

trespassing safety are planned for 2003 in Finland.

OL is based on the “three Es” of Edu-cation, Engineering and Enforcement. In Education OL strives to increase public awareness about the dangers around the rails. In Enforcement OL promotes active enforcement of traffic laws relating to crossing signs and signals and private property laws related to trespassing. In Engineering OL encourages continued research and innovation to improve the safety of railway crossings.

The first task of OLI is public educa-tion. In the USA some 40,000 presenta-tions are given annually, reaching an audience of about 2.5 million people. Target audiences include professional truck drivers, students, school bus drivers and law enforcement officials. The educa-tion materials include videos, CD-ROMs and brochures. Pre-prepared lesson plans

Title: Campaigning on level crossing safety – Operation LifesaverAuthor: Kirsi PajunenSeries: VTT Building and Transport, Contractor Report Language: Finnish with English abstract

Transport Telematics-ArchitectureThe national architecture system is a reference architecture through which the Finnish Ministry of Transport and Com-munications supports the national devel-opment of transport telematics, estimates the usefulness of individual projects and monitors how the architecture is fol-lowed.

The objective of the architecture is to provide the opportunity to improve an organisation’s competitiveness on the market in the form of more efficient oper-ations, a more versatile service supply or better compatibility. An organisation can compare its present operations with a national vision of the target conditions as a starting point for development of its operations, actor-specific architecture or individual systems. The time horizon is at least 10 years and the central parts of the architecture are ’eternal ’.

The viewpoint of the architecture is the freight and related information flowing through the logistics chain from sender to receiver. The architecture focuses on the processes that are directly related to the transport of goods and on the information flows of these processes. The architecture

covers the different modes of transport including road, rail, water and air.

The study identifies the deficiencies and needs of the present situation in the light of a future vision. Three areas for development have been defined: infor-mation infrastructure, identification and processes. The descriptions of area 8 of the European ITS Framework Architec-ture (KAREN) highlight the same prob-lem area for road transport. In this work KAREN architecture descriptions have been used as a checklist for both functions and data flows.

Title: Transport telematics-architecture. Final reportAuthors: Jani Granqvist, Harri Hiljanen, Antti Permala, Pasi Mäkinen, Valtteri Rantala and Aki Siponen Series: Ministry of Transport and Communications, FITS publications 25/2003 http://www.vtt.fi/rte/projects/fits/julkaisut/hanke1/fits25_2003.pdfLanguage: English

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Nordic Road and Transport Research 2-2003

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