The global climate change is a reality and affecting society and transport systems. Climate change adaptation of transport systems will make the means of transportation more resilient and decrease the risk and magnitude of disruptions. Generally, climate change adaptations in road construction, operation and maintenance will need relatively large changes, but there is a shortage of the specific knowledge required as to what steps need to be taken, when and where, before measures can actually be implemented. Since climate change effects vary among Sweden's climatic zones, the impact of climate change on the road behavior and longevity is extremely difficult to predict. The need for winter maintenance in Sweden will generally decrease due to the warmer climate. Ploughing frequency will probably decrease as well, but preparedness should not be reduced too much since occasions with more extreme instances will increase. In order to succeed in making the road transport system resilient to climate change, we conclude that there is a need to develop more knowledge about the impact on the road infrastructure system as well as the operation and maintenance of the system including how to adapt through different types of variable and flexible climate adaptation measures and the effects of extreme weather events.
The future needs for winter maintenance will probably be influenced by the climate change in different ways in different parts of the world. As Sweden is a country with several climate zones, the influence of climate change on winter maintenance will therefore differ between regions within the country. To understand the influence of climate change on the future needs of salt consumption in winter maintenance, modeled road weather data were calculated in the IRWIN project (a joint research project through ERA-NET ROAD funded by the 6th Framework Program of the European Commission), where climate change scenarios from ECHAM5 (the fifth generation of the European Centre Hamburg Model general circulation model from the Max-Planck Institute for Meteorology) were combined with field data from the road weather information system in Sweden.
These modeled road weather data were used in project KLIVIN (the study presented here) in three Swedish regions (Gothenburg, Stockholm, and Sundsvall) and was combined with the Swedish winter severity index in order to calculate the trends of future salt needs. In this study the needs of salt for each of the three investigated regions were calculated in 30-year periods between 1970 and 2100. The results show that salt use related to snowfall will decrease in all three regions, while the salt use related to temperature will increase in the northernmost region (Sundsvall) and show a small decrease in the two other regions (Gothenburg and Stockholm).
The goal with this investigation is a revision of earlier investigations of studded tyres, i.e. the socio-economic consequences that may be expected from a ban on such tyres.
The calculations were made for winter 1993/1994 and for winter 1999/2000. The conditions in winter 1993/1994 form the basis for the calculations, a quite normal winter. The conditions in 1999/20 00 are the same, except for the assumptions that all those using studded tyres will then be using lightweight studs and that wear resistant pavements will be more common. Everything else, for example winter maintenance will be the same as in 1993/1994.
The following effects are included:
Accidents (direct: at slipperiness. indirect: because of pavement wear)
Road wear (pavement and road markings, cleaning signs)
Car costs (tyres/rims, fuel consumption, washing)
Environment (car washing)
Utvecklingen av de statliga belagda vägarnas tillstånd är inte entydig visar denna rapport. I en del avseenden och med hittills använda mått kan vi se förbättringar, i andra finns inte tillräckligt underlag för att ange om läget generellt försämras. Ändå finns det indikationer på att försämringar sker i andra avseenden än vad vägytemätningarna visar. Det system som Vägverket har byggt upp för styrning av beläggningsunderhåll är i stor utsträckning baserad på de tillstånd vad gäller spårdjup och IRI som vägytemätningarna med RST beskriver. Eftersom vägarnas tillstånd i dessa avseenden blivit bättre visar det att systemet fungerar.
Nya regler för dubbdäck och bättre beläggningar har minskat slitaget på vägytan i mycket stor omfattning. Vägarna bryts ned kontinuerligt till följd av särskilt den tunga trafikens omfattning och materialets åldrande. Sprickbildningar uppträder redan efter mindre än halva tiden på vägar som är dimensionerade för 20 års trafik. Den tunga trafiken (trafikarbetet) har under 1990-talet ökat med i genomsnitt nästan 4 procent årligen. Till följd av det minskade slitaget av vägytan läggs ny beläggning allt mer sällan och de nylagda ytskikten tenderar dessutom att bli tunnare. Därmed får vägarna inte samma bärighetsförstärkning som tidigare och sprickbildningar och slaghål uppträder snabbare. Det svenska vägnätet kräver omfattande underhållsinsatser för att vägstandarden generellt ska bibehållas och förbättras. Bedömningen av de exakta underhållsinsatserna är ett svåravvägt problem som VTI inte tar ställning till i denna rapport. Den annorlunda problembilden jämfört med tidigare motiverar på sikt en förändring och strategisk omläggning av underhållsstrategin. För att resurserna ska användas rätt måste nya mått för framför allt bärighetsförändringar tas fram. En kartläggning av det svenska vägnätet måste också göras och nya beslutsmodeller utvecklas för att de rätta avvägningarna ska kunna göras.
Choice of winter tyres has, from mainly being a matter of safety and economic costs for wearing of road pavements, during later years also become a matter of inhalable particles formed during pavement wear from studded tyres and their negative effects on public health. Further, the tyres' effects on environment and noise have been illustrated in several studies. The issue is also complicated by the fact that tyre choice effects on traffic safety have several components, including such diverging parameters as friction and behaviour. Finally all aspects have to be evaluated from a socioeconomic point of view for society to be able to decide which kind of distribution of tyre types that is the most profitable. This report is a summary of current knowledge in this complex research field.
Earlier studies have shown that buses are overrepresented at accidents during winter road conditions compared to other vehicle types. Hence, the traffic safety of buses during the wintertime has been studied in more detail. The study comprised the following parts: - Gripping power studies on ice in VTI's tyre test facility. - Accident study and a survey of the use of tyre. - Focus group to gain knowledge about dangerous situations. - Driving simulator study to test the importance of the tyres during problematic situations.
Tests in VTI's tyre test facility on smooth ice did not show any significant difference between summer tyres and non-studded winter tyres, while studded tyres exhibit a better ice grip than non-studded tyres. Nor did driving simulator tests when driving on ice covered road under the influence of heavy wind from the side show a difference between summer tyres and non-studded winter tyres. Also in these tests the studded tyres were superior to the non-studded. If studded tyres are used only on one axle, the driving simulator study showed that during side wind the ability to steer is important. The accident study showed that the buses that have summer tyres on the steering axle and winter tyres on the drivé axle has the lowest estimated accident risk, although it is not statistically significant. The buses equipped with studded tyres on both axles could not be statistically analysed since only 2 accidents occurred on bare roadways, and none on icy/snowy roadways, while at the same time the buses in this category drive a lot on icy/snowy roadways. This probably makes these buses the safest on winter roadways. From the focus groups it was clear that the time table has a great influence on the creating of stress and the demands on the drivers to keep the speed even during slippery roadways. Many bus drivers experience large problems with bad snow clearance, or other winter maintenance. At the same time there is a large consciousness among the drivers that it is always their own way of handling the vehicle that is the determining factor for traffic safety. The drivers were expressing a lack of further education and practical exercises with buses on slippery roads.
Buses in Sweden have a low accident risk. However, statistics from 1996 - 2002 indicate that the number of bus accidents in Sweden with personal injuries have been increasing by 4% yearly. Buses also have a higher percentage of accidents that occur on ice/snow covered roads than other vehicles. In Sweden passenger cars must be equipped with winter tyres during the winter period. There is no such regulation for heavy vehicles, and many buses are using summer tyres all around the year. The present project had the purpose of looking at the bus-winter problem in more detail, with the main focus on tyres. Four different studies were carried out: tyre tests, focus group discussions, driving simulator tests and an accident study. Here is given a short summary concerning methods and conclusions of each sub project.
Tyre tests on smooth ice did not show any significant difference between summer tyres and non-studded winter tyres, while studded tyres exhibits a better ice grip than non-studded tyres. Nor did driving simulator tests with driving on ice covered road under the influence of heavy wind from the side show a difference between summer tyres and non-studded winter tyres. Also in these tests studded tyres were superior to non-studded. Accident statistics indicate that buses with summer tyres on the steering axle and winter tyres on the drive axle have the lowest estimated accident risk, which is in accordance with the results in a previous study. The results are however not statistically significant due the low number of accidents. Three focus groups were carried out and the importance of the tyres for traffic safety during winter was discussed. It is however hard from the gathered discussion material to estimate just how important the tyres really are. The results do not warrant a winter tyre regulation for heavy vehicles, and a restriction of the use of studded tyres for buses would probably have negative consequences on traffic safety.
Today the Swedish Road Administration (SRA) regularly follows up the condition of the state roads by means of road surface measurements. It is mainly rut depth (mm) and roughness expressed in the measure International Roughness Index (IRI, mm/m) that is the bases for assessment of the road surface condition. Based on these measurements it can generally be said that the condition of the roads neither have considerably improved nor become considerably worse over the years. The trend however looks a bit different in the different SRA Regions. At the same time it is also yearly investigated how content or discontent the road users are with the maintenance of the state roads. The road users are asked about their opinion on the operation and maintenance of the roads in general as well as more specifically about their opinion concerning rutting and unevenness, i.e. the factors that are followed up by measurements. The general tendency, except for the last year, is the percentage of satisfied road users is decreasing. The percentage of satisfied road users is also low. This applies not least that the professional drivers. The agreement between the objective measurements of the condition of roads (or rather the condition measures that are used) that are done and the opinions given by the road users is not very good. There is reason to go deeper into this question and examine what requirements and expectations the road users have on the roads/road surface condition and also what measures are needed to describe the condition in a satisfactory way.
This is the third study of the effects on traffic accidents of resurfacing measures that Region West of the Swedish National Road Administration has commissioned. All three have been carried out as before-and-after studies with two years before and two years after the measure.
In the study reported here, the third in order, roads resurfaced during 1997 and 1998 were examined.
When the two resurfacing years are examined individually, an accident increase is obtained for all police-reported accidents after resurfacing. If personal injury accidents are analysed separately, accident decreases are obtained for both resurfacing years: the number of accidents decreases also when only accidents with seriously injured and killed are analysed. None of the results are statistically verified.
C-G. Wallman: The Winter Model - A winter maintenance management system/Le Winter Model - Un système de management de l'entretien des routes en hiver S. Möller: Winter Road Condition Model/Modele sur la condition de la route en hiver A. Bergström: Variation in car accident risk during winter/Variation du risque d'accidents de voitures durant l'hiver G. Blomqvist & M. Gustafsson: The environmental sub-model of the Swedish winter model from real world data to a modelled scenario/Le sous-modèle environmental du modele d'hiver (Winter model) Suedois des valeurs du monde reel vers un scenario modelise H. Antonson & G. Blomqvist: Does the official strategy protect or destroy our cultural heritage? - Corrosion of archaeological artefacts exposed to de-icing salt in Sweden/La strategie officielle protégé-t-elle ou detruit-elle notre heritage culturel? - Corrosion des vestiges archeologiques exposes au sel de degivrage des routes en Suede B. Wälivaara, G. Blomqvist, T. Andersson, H. Wilhelmsson: Automated monitoring of groundwater contamination along salted roads/Surveillance automatique de la contamination des eaux souterraines lelong des routes salees M. Gustafsson, G. Blomqvist, A. Gudmundsson, A. Dahl, E. Swietlicki: Studies of wear particles using the VTI Road Simulator/Particle Generator/Etudes des particules d'usure en utilisant le Simulateur de Route/Generateur de Particules du VTI
The aim of the Winter Model is to estimate and put a value on the most important impacts of the strategies and measures in winter road management for road users, road management authorities and society at large. The main report itself is a summary of the reports that describe the submodels in the Winter Model. The hub of the model is the Road Condition Model which, on the basis of weather data, undertaken road management measures and traffic, calculates road conditions hour by hour during the winter season. The Road Condition Model controls calculations in the effect models: Accident Model, Accessibility Model, Vehicle Cost Model, Environment Model and Model for Road Management Costs. The Accident Model calculates accident rates, accident types and consequences, all coupled with different road conditions and their duration. The Accessibility Model calculates the effect of different road conditions on mean speeds and trip times. The Vehicle Cost Model calculates the costs of fuel consumption and corrosion due to road salt. The Environment Model calculates the impacts on roadside vegetation due to road salt. The Model for Road Management Costs calculates both the direct costs of the measures and the costs of damage to, and wear of, road surfacing, road markings etc as a result of road management measures.
The study constitutes the basis for the model to be used as a guideline for determining winter road standards within the framework of the public economy. Driving speeds vary widely on winter roads. However, it is estimated that passenger cars travel at 75-90 % of the speeds they normally travel at on bare roads. In order to maintain a consistent stopping distance, speeds should virtually be halved. The appearance of the road has a greater affect on the reduction in speed than friction/road traction. Precipitation entails a much greater reduction than slippery road surfaces alone. Accident rates on winter roads vary greatly. However, studies based on the observation of road conditions and traffic measurements show an increased risk on icy/snowy roads. The more unusual these conditions, the greater the risk. Aggregated studies do not support the presumption of increased risk in winter. Statistics from the Swedish Motor Vehicle Inspection Co. were analysed as a result of notations of rust defects that caused cars to fail inspection. In Västervik, where roads are salted, cars fail inspection 24times more often than on Gotland, where salt is not used. Experts estimate that the life expectancy of cars would increase by 25 % if roads were not salted. Corrosion costs will continue to be high since new corrosion problems occur in conjunction with the effects on electronic equipment. Many breaches of knowledge are identified.