No 2 2004


Traffic Management for a Sustainable Environment
Road traffic is the most important source of many air pollutants in Sweden . Environmental Quality Standards which prescribe acceptable air quality have been, or will be, introduced within the current decade. Due to the environmental influence of road traffic there is a significant possibility to use traffic management measures in order to reduce the negative environmental effects of traffic. Efficient design of such measures demands models and methods for estimation of the resulting air quality.

This report presents the state of the art in environmentally based traffic management. The work includes a description of the environmental consequences of road traffic and coming air quality standards. Furthermore, models for estimation of the environmental impact of traffic are presented along with examples of possible traffic management measures for a sustainable environment.

Today's air quality estimation systems are used mostly in pollution level control applications. Air quality based traffic management may need a more detailed description of traffic related pollutants. Moreover, it is not clear what opportunities there are for achieving a lower negative environmental impact through traffic management in Sweden . Finally, the question of how to choose between a possible improvement of the environment and other costs needs further investigation.

Title: Traffic management for a sustainable environment
Author: Andreas Tapani
Series: VTI meddelande 954
Language: Swedish with English summary
The report is also available as a pdf file on under Reports.


Mobile Phone Use while Driving

The purpose of these studies was to give a picture of drivers' use of mobile phones while driving and more specifically their attitudes to the use of mobile phones while driving and the types of routines and behaviour practised when using mobile phones. In addition, the purpose was to get some idea of the number of traffic accidents, along with injuries and deaths, which were caused by drivers using their mobile phones.

The number of mobile phone users has increased heavily and has accelerated in the last ten years. This increase is reflected in drivers' use of mobile phones while driving. Results from the Swedish Traffic Safety Survey show that 73 per cent of all drivers had access to a mobile phone in 2001. These drivers accounted for 85 per cent of all yearly mileage. Of the mobile phones, 75 per cent were hand-held without any extra add-on equipment. Hand-held mobile phones were most common among younger and older drivers. 30 per cent of all drivers with mobile phones used them daily while driving.

The average number of drivers' incoming or outgoing calls while driving was, according to results from the questionnaire survey, 1.1 per day. A significant number of drivers reported that they often or almost always stopped their car when they were going to use their mobile phone. As a rule, the driver generally took some kind of safety precaution in conjunction with a mobile phone call. Women stated that they used safety measures more often than men and older drivers more often than younger drivers.

The use of mobile phones affected driving in different ways. Drivers missed exits, failed to observe traffic signals, and forgot to adjust their speed to the speed limit. Incidents or near collisions with other vehicles or objects, or driving off the road, were not unusual when mobile phones were used while driving.

The respondents considered hands-free equipment to be significantly less risky to use than hand-held mobile phones. A third of the respondents favoured a law against use of mobile phones while driving, regardless of the type of mobile phone equipment. Half of all respondents thought that use of hand-held mobile phones should be forbidden during driving. The common answer was that the potential accident risk rate associated with use of hand-held mobile phones was much higher than that for hands-free equipment.

The dominant reason for the driver to have a mobile phone in the car was the security of always being able to contact or be contacted by someone else. According to our estimates, 100,000 drivers each year use the mobile phones to contact the police or call an ambulance after an accident. According to our theoretical estimates, approximately 10–20 people die in traffic accidents each year as a consequence of drivers' use of mobile phones while driving.

Title: Mobile phone use while driving. Conclusions from four investigations
Authors: Hans Thulin and Susanne Gustafsson
Series: VTI rapport 490A
Language: English
The report is also available as a pdf file on under Reports.


Historical Landscape Visualisation Method

The visual qualities of the landscape are often used as a preservation argument in community planning and their consideration is prescribed in several Acts. The visual qualities of the landscape are mainly considered from an aesthetic standpoint, however. The present study emphasises the importance of taking into account the historical dimension also.

The aim of this study has been to develop a method that can describe the historical visual dimension in the cultural environment of today. The method is called the Historical Landscape Visualisation Method.

The method is partly based on other methods that describe the landscape. Such methods often include the comparison of information from historical maps or photographs with the current situation. These methods have some limitations, however. The maps for instance give a bird's eye view of the landscape, and the photographs are often of limited age.

What is new in the Historical Landscape Visualisation Method is that it uses not only photographs but also paintings produced before the advent of photography, and tests the credibility of the paintings. In order to investigate the value of paintings as historical sources, the information they give has been compared with historical maps which are reasonably contemporaneous with the painting. If the landscape painting is considered to be of good historical value, an analysis is carried out based upon a comparison between the painting and the current landscape viewed from the exact location as of the painter.

Title: Historical Landscape Visualisation Method. Development of a tool to describe the historical visual dimension in today's cultural environment

Author: Hans Antonson
Series: VTI meddelande 925
Language: Swedish with English summary
The report is also available as a pdf file on under Reports.

Elastohydrodynamic Aspects of the Tyre-Pavement Contact while Aquaplanning

The objective of the work presented in this report has been to develop a numerical method for the investigation of water-lubricated soft elastohydrodynamic (EHD) situations as it relates to the problem of car tyre aquaplaning.

Aquaplaning occurs when a vehicle rides on the water and completely loses contact with the road, putting drivers in immediate danger of sliding off the road. The factors that most contribute to aquaplaning are vehicle speed, vehicle weight, water depth, tyre size, tread depth, tread pattern, and water composition.

The tyre used in the calculation is a P.I.A.R.C. test tyre. An outline of the smooth P.I.A.R.C. tyre was taken from a construction drawing. Due to the nonavailability of precise information on this tyre the theoretical model is that of a generic radial ply tyre with the correct dimensions.

Two different elastic material models of the car tyre were considered, with an increasing degree of complexity. Numerical results were produced for 20, 40, 60, 120, and 200 km/h. No fluid films separating the surfaces were detected in the range of the above velocities. In the range of velocities from 20 to 200 km/h the contact shapes and pressures were almost exactly identical with dry static contact. As a matter of fact, the velocity has to be around 1.6 103 m/s for the first full film regime to be achieved. This conclusion is valid for both elastic models. Prediction of the EHD fluid layer thickness by the classical theory of lubrication also shows that the effects of viscous flow are very small, even though the film thickness for the isoviscous and incompressible case is somewhat overestimated.

The physics of water films is completely different from the physics of films formed by lubricating oils. Due to its dense molecular structure, water undergoes no or very little compression even under extreme pressures. Pure water is a very bad lubricant and is indeed very rarely used in highly loaded concentrated situations. This is believed to be the major reason why no separating fluid films were detected in the pure viscous water aquaplaning. Another mechanism that can contribute to loss of grip already on a slightly wet road can be described as boundary lubrication. Boundary lubrication is a field of knowledge that combines tribology, chemistry and material science.

Titel: Elastohydrodynamic aspects of the tyre-pavement contact while aquaplaning
Authors: Peter Andrén and Alexei Jolkin
Series: VTI rapport 483A
Language: English
The report is also available as a pdf file on under Reports.


Traffic Safety Measures and Observance of the Law

The effect on traffic safety of full obser-vance of the laws concerning existing speed limits, the use of seat belt and driver sobriety has been estimated.

The observance of the law regarding the three measures varies. The observance of the speed limits is low and the observance of sobriety is high. Reduced observance of the speed limits results in little change for the worse in the traffic safety situation, but driving while intoxicated causes a dramatic increase in risk.

The law observance of the speed limits is the largest problem which results in 150–200 fatalities annually. The other two observance problems concern 50–100 fatalities annually. The report does not show how the observance of the laws can be increased. There exist, however, interlock systems for the measures as a complement to increased surveillance by the police and/or increased sanctions.

The risk of being killed is more than doubled through the lack of observance.

A very high observance of the three laws reduces the number of fatalities in traffic by at least 50 per cent. What is interesting is that the observance of the law is not randomly distributed over the three measures. Both drivers who observe all three laws and drivers who do not observe any of the laws are over-represented in traffic.

It is also important that decreased speeds strengthen the other two traffic safety measures. The estimation of the effect of alcohol on safety is very uncertain as the alcohol limit is different in different countries.

Title: Traffic safety measures and observance of the law. Speed adaptation, usage of seat belt and sober drivers
Author: Göran Nilsson
Series: VTI meddelande 951
Language: Swedish with English summary
The report is also available as a pdf file on under Reports.


Serious Breakdowns in the Track Infrastructure – Calculation of Effects on Rail Traffic

The track infrastructure installations of the railway transport system are at times subjected to stresses which give rise to such serious faults or damages that traffic must be stopped, or cause such serious disturbances that trains must be cancelled. Examples are falls of overhead contact lines, fire in interlocking systems or flooding of the track bed. It is obviously impossible to create a system where such situations never occur, but an attempt can be made to allocate operational and maintenance work in such a way that the probability of such occurrences is reduced to a minimum on those track installations where the impact in the form of comprehensive traffic disturbances is greatest.

Extensive damage to the interlocking system of the rail transport system causes comprehensive disturbances. One example of such damage which gave rise to serious consequences is when the interlocking system at Järna station burned down in 2000. A microsimulation tool for rail traffic, RailSys, which had been developed in Germany , was used to simulate the consequences of the fire. Simulations were also made for rail traffic flows both higher and lower than those that applied after the fire.

Lowering of the highest permitted speed through a track infrastructure installation is one example of the reduction in potential capacity. The delays which then occur can in some situations be recouped through somewhat higher speeds on other parts of the system. Sometimes this is not possible, but the delays which nevertheless occur may be so small that all planned train movements can be carried out. In a lot of circumstances, however, delays are so extensive that rolling stock assignment is affected and trains must be cancelled. Alternatively, the potential capacity may become so low that all planned train movements cannot be carried out.

When faults or damages occur to the signalling system, the highest permitted speed is sometimes reduced to 40 km/h. This may also occur when the bearing strength of the permanent way is reduced or when the track is in a bad condition.

Title: Serious breakdowns in the track infrastructure – Calculation of effects on rail traffic
Author: Mats Wiklund
Series: VTI meddelande 959
Language: Swedish with English summary
The report is also available as a pdf file on under Reports.


Towards Marginal Cost Pricing of Maritime Transport

Pricing based on marginal costs for maritime transports has been intensively discussed and investigated lately, but have not to any larger extent brought the problems of implementation in themselves closer to a solution. One reason for this is the lack of data necessary for marginal cost estimations. The report deals with marginal cost pricing in theory and empirical research and reviews how availability of data and institutional conditions affect the possibilities for implementation of marginal cost based pricing.

Besides the open sea, ports, fairways, pilot services and ice-breaking are the main maritime infrastructure components. Marginal costs of maritime transport can be divided into the following groups: emissions to water and air, accidents, and costs related to infrastructure usage. The first marginal cost type is the occurrence of negative external effects to third-men outside the transport system. The marginal costs from infrastructure use are related to the parts that invest, maintain, and provide the services in themselves as well as to the users. The latter part is affected by restrictions in capacity, which can affect the user costs of the services. This report considers all these marginal cost components, except emission to air.

Title: Towards marginal cost pricing of maritime transport
Author: Carl Magnus Berglund and Robert Ericsson
Series: VTI meddelande 956
Language: Swedish with English summary
The report is also available as a pdf file on under Reports.

Evaluation of the Moose Dummy Mooses II with a View to Consumer Guidance

Four out of five who die after colliding with game in Sweden have hit a moose. The moose appears suddenly and unexpectedly, the driver has little chance to swerve or even break. The long legs of the moose catch the bumper and knock the heavy animal over the bonnet and into the windscreen. What happens next depends mainly on the make of the car and the impact speed. The driver chooses the speed but there is no consumer guidance that gives advice on the “moose safety” of a car model.

The typical moose accident where someone dies or is seriously injured occurs at a public road with the speed limit 90 km/h. The driver is more often than in other accidents sober but has little or no time to react. Primarily the head, neck, chest and arms get injured, both by the moose and intruding parts from the roof and windscreen. A cloud of shattered glass both from the windscreen and side-windows hits the car occupants. Since the moose often penetrates well into the coupe and in addition crushes the roof and windshield towards the occupants, seat belt and airbag make only a marginal improvement, if any. The important factors for the outcome of the accident are the strength and design of the front of the vehicle above the bonnet.

To be able to evaluate the “moose safety” of different car models, VTI has developed a full scale moose dummy. The dummy is made of rubber and has, in contradiction to its precursors, legs that give the dummy a realistic movement during the crash. A number of crash tests have been made to evaluate the qualities of the dummy. It is concluded in the report that the dummy not only behaves as expected but also is very sturdy and withstands repeated impacts at high speed. The results are reproducible under equivalent conditions, which is a very important aspect in all types of crash testing.

The purpose of these test series has been to test the moose dummy rather than the vehicles. In despite of this a method is developed to measure and calculate the “survival space” based on the static deformation after the collision. Through that it is concluded that there are major differences between different makes of a car. The choice of car seems to be just as important as reducing speed on roads where moose can be expected. At a speed just above 70 km/h some car models still have plenty of space for the occupants whereas others are considerably compressed.

Title. Evaluation of the Moose Dummy Mooses II with a View to Consumer Guidance
Author: Ylva Matstoms
Series: VTI meddelande 955
Language: Swedish with English summary
The report is also available as a pdf file on under Reports.


Child Safety in Cars – Socio-Economic Differences

The aim of the study was to identify relationships between no use/misuse of safety belt or child restraints and socio-economic aspects. The conclusions from the study will provide a basis for the future development of information and campaigns to increase the correct use of restraints.

In general, the results showed that the level of misuse among young children was lower than among older children. Approximately 90 per cent of the children in the youngest age group always used the safety belt, while only 74 per cent of children aged 4–9 years did so. The most common circumstance, when the safety belts were not used by older children, was when the travel distance was short. Overall, the parents who regularly or occasionally neglected to use the safety belts themselves were more likely to allow their children to travel without safety belts. Furthermore, parents who were more liberal concerning traffic violations were also more likely to allow their children to travel without using a safety belt.

When all age groups were examined, the results did not indicate relationships between the children's usage of safety belts and any of the following variables: number of inhabitants, highest level of education in the household, household annual gross income, household number of children younger than 10, choice of child's placement in the car, number of seats in the family car, age of the family car, driver's sex, marital status, information received by the parents, parental knowledge about rules and recommendations, and acceptance regarding traffic violations.

Title: Child safety in cars – Socioeconomic differences. Literature review and questionnaire survey
Authors: Anna Anund, Åsa Forsman , Gunilla Sörensen and Susanne Gustafsson
Series: VTI rapport 496
Language: Swedish with English summary
The report is also available as a pdf file on under Reports.