Swedish Roads Research Articles

Energy security in a decarbonised transport sector: A scenario based analysis of Sweden's transport strategies

Previous research has shown that it is possible to decarbonise Sweden's road transport sector. This study develops a scenario based method and analyses the influence of external factors on energy security, focusing on passenger and freight transport. It does so by analysing the vulnerabilities and capabilities of five different climate mitigation strategies, investigating previous security scenarios and identifying uncertain drivers. These are used to develop four consistent exogenous scenarios using cross impact balance analysis. The vulnerabilities and capabilities of the five different strategies are then compared with the challenges faced in the scenarios and the robustness and adaptive capacity of the resulting systems is analysed.The results shows that strategies which reduce the use of energy (increase efficiency or conservation) are robust, but that demand restrictions are perceived as undesirable by some interest groups. Biofuels perform poorly if too many other countries increase their use of biofuel, whereas electrification performs best when many other countries implement this technology. The strategies are not mutually exclusive and simultaneous implementation of some provides synergies for national energy security. Some directions for further research are suggested, such as framing energy security as subjective, i.e. a result of material and contextual factors that co-evolve.

A Model for Capacity Reduction at Roadwork Zone

This paper presents an investigation of capacity reduction in connection with roadwork. The paper presents a state-of-the-art description on roadwork effects on capacity. The state-of-the art has been used to develop a model for estimation of capacity reduction at roadwork zone on Swedish roads. The model has partly been validated with empirical data from a full scale test at the freeway network in Gothenburg. The studies presented in the literature shows that capacity differs not only between different roadwork designs but also between roadwork with similar design. Thus, one can conclude that there is a high variation between the roadwork zone due to effects of surrounding elements, such as the type of work and external effects such as rain (which affects the capacity even under normal conditions). The differences that exist in the estimation of capacity for motorway sections next to a roadwork zone can be said to consist of four situation-specific variables. These four variables are: the percentage of heavy vehicles, type of road, the width of the remaining lanes and diversion of traffic to the opposite carriageway. An increasing proportion of heavy vehicles have a negative impact on roadwork zone capacity. An increasing complexity of work, from light barrier works to extensive bridge repair, has a negative impact on performance. An increased lane width has a positive effect on capacity. The diversion of traffic to the opposite carriageway is often the cause of the bottleneck and therefore has a significance effect on capacity. The conclusion from the literature review is that the most important parameters that should be incorporated in a Swedish capacity manual for the operation and maintenance of roadwork are: the proportion of heavy traffic, lane width, type of roadwork, number of closed lanes, closed road shoulder, proportion of commuter traffic and length of roadwork zone. In general, there have been (too) few empirical studies focusing on the differences in capacity caused by these situation-specific variables. The paper presents a comparison between the Dutch model for computation of capacity reduction and a composite model of reduction factors from Germany, USA and Denmark. The comparison show that the two models essentially gives the same results. Based on these results a new model was developed. In the developed model, the capacity for the remaining lane is calculated. The paper presents results from a field study in Gothenburg where throughput was measured in three cases during a morning hour and one afternoon hour. The capacity was calculated from the normal site conditions according to historical traffic flow and speed data. The result shows that the empirically estimated confidence interval of capacity reduction is consistent with the reduction calculated with the new model for the different cases. The conclusion is that the model can be used to calculate capacity reductions for different roadwork zone configurations but that validation for more configurations is desirable.

How do drivers overtake cyclists?

In Europe, the number of road crashes is steadily decreasing every year. However, the incidence of bicycle crashes is not declining as fast as that of car crashes. In Sweden, cyclists are the most frequently injured road users. Collisions between bicycles and motorized vehicles are of particular concern because the high speed and large mass of motorized vehicles create a high risk of serious injury to cyclists. In Sweden's urban areas, bicycle lanes keep bicycles separated from motorized vehicles, but on rural roads bicycle lanes are often absent, requiring drivers to interact with cyclists—usually by overtaking them. During this maneuver, drivers regulate speed and lateral position, negotiating with potential oncoming traffic to stay within their comfort zones while approaching and passing cyclists.In this study an instrumented bicycle recorded 145 overtaking maneuvers performed by car and truck drivers on public rural roads in Sweden. The bicycle was equipped with a LIDAR and two cameras to assess how drivers approached and circumvented the bicycle. The collected data allowed us to identify four overtaking phases and quantify the corresponding driver comfort zones. The presence of an oncoming vehicle was the factor that most influenced the maneuver, whereas neither vehicle speed, lane width, shoulder width nor posted speed limit significantly affected the driver comfort zone or the overtaking dynamics.

STRADA: Road traffic accident and injury data in Sweden

If every driver in Sweden were to obey the speed limits there would be more than 100 lives spared each year. Every reduction of 1 km/h on average speed in the country saves approximately 20 lives per year (SRA 2015). One of many important measures in the later road safety work in Sweden is a project attempting to reduce speed, namely the implementation of speed cameras. Without a comprehensive increase in traffic surveillance it is difficult to achieve traffic safety (VTI 2005). The Swedish Road Administration together with the National Police Board put up the first speed cameras, or road safety cameras, in the late 1990’s and at the end of 2014 there were 1200 cameras monitoring 3000 kilometer of road stretches in Sweden. Before deciding where to install the road safety cameras the Swedish road traffic crash- and injury surveillance system, STRADA, was used to spot where accidents happened most frequently. STRADA is also a tool in the follow up work when evaluating the effects of the road safety cameras. The road safety camera project has been and still is a successful road safety work. When looking at data from STRADA from three examples (road 222, 225 and 268) of the approximately 120 roads with speed cameras one can see, when comparing a four year period before and after speed cameras, fatal accidents was reduced from a total of 8 to 3, and accidents with serious injuries as an outcome was reduced from 65 to 28. The road safety cameras have reduced the average speed on roads with cameras with 5% and are now appreciated to save up 20 lives and up to 50 persons from being seriously injured per year in Sweden. Speed monitoring with road safety cameras has shown to be a successful way of reducing speed and save lives on Swedish roads. Every year the cameras prevent 20 people from being killed in traffic and 50 persons are prevented from being seriously injured. In order to evaluate road safety work such as speed cameras there has to be measurements made before and after the intervention. Using data from STRADA has both been contributing to the foundation of the road safety camera project and also one of the important tools for follow up.

On-Scene Injury Severity Prediction (OSISP) Algorithm for Truck Occupants

Objective: The aim of this study is to develop an on-scene injury severity prediction (OSISP) algorithm for truck occupants using only accident characteristics that are feasible to assess at the scene of the accident. The purpose of developing this algorithm is to use it as a basis for a field triage tool used in traffic accidents involving trucks. In addition, the model can be valuable for recognizing important factors for improving triage protocols used in Sweden and possibly in other countries with similar traffic environments and prehospital procedures.Methods: The scope is adult truck occupants involved in traffic accidents on Swedish public roads registered in the Swedish Traffic Accident Data Acquisition (STRADA) database for calendar years 2003 to 2013. STRADA contains information reported by the police and medical data on injured road users treated at emergency hospitals. Using data from STRADA, 2 OSISP multivariate logistic regression models for deriving the probability of severe injury (defined here as having an Injury Severity Score [ISS] > 15) were implemented for light and heavy trucks; that is, trucks with weight up to 3,500 kg and ⩾ 16,500 kg, respectively. A 10-fold cross-validation procedure was used to estimate the performance of the OSISP algorithm in terms of the area under the receiver operating characteristic curve (AUC).Results: The rate of belt use was low, especially for heavy truck occupants. The OSISP models developed for light and heavy trucks achieved cross-validation AUC of 0.81 and 0.74, respectively. The AUC values obtained when the models were evaluated on all data without cross-validation were 0.87 for both light and heavy trucks. The difference in the AUC values with and without use of cross-validation indicates overfitting of the model, which may be a consequence of relatively small data sets. Belt use stands out as the most valuable predictor in both types of trucks; accident type and age are important predictors for light trucks.Conclusions: The OSISP models achieve good discriminating capability for light truck occupants and a reasonable performance for heavy truck occupants. The prediction accuracy may be increased by acquiring more data. Belt use was the strongest predictor of severe injury for both light and heavy truck occupants. There is a need for behavior-based safety programs and/or other means to encourage truck occupants to always wear a seat belt.

High prevalence of previous arrests for illicit drug use and/or impaired driving among drivers killed in motor vehicle crashes in Sweden with amphetamine in blood at autopsy

BackgroundAmphetamine, and to a lesser extent the secondary amine methamphetamine, are major recreational drugs of abuse in Sweden. These central stimulant amines are identified in blood from roughly 50% of people arrested for driving under the influence of drugs (DUID). However, much less information is available about the presence of amphetamine in blood of drivers killed in road-traffic crashes. MethodsThis retrospective 10-year study (2001–2010) used a forensic toxicology database (TOXBASE) to retrieve information about road-traffic crashes when the driver had amphetamine and/or methamphetamine in autopsy blood. Forensic toxicology results were available from over 95% of all drivers killed on Swedish roads during this 10-year period. ResultsAmphetamine was present in the blood of 106 drivers (3.9%) either alone or together with other psychoactive substances (e.g. alcohol, cannabis, diazepam, alprazolam, etc.). The vast majority of fatalities were male (95%) with a mean age (±standard deviation) of 37±11.4 years (range 16–67 years). The mean (median) and highest concentrations of amphetamine in femoral blood were 1.36mg/L (1.0mg/L) and 6.74mg/L, respectively. Many of the victims (75%) had been arrested previously for use of illicit drugs or DUID. The median number of previous arrests was 4 (range 0–83) and amphetamine or methamphetamine were among the drugs identified in blood samples from 89% of cases (0–100%). ConclusionThe high prevalence of repeat DUID offending and/or use of illicit drugs among the drivers killed in road-traffic crashes suggests that an early intervention and treatment for stimulant abuse might have been more beneficial than conventional punishments for such drug-related crimes.

Life cycle cost considerations in project appraisals of collision-free roads

In the last decade, many single carriageway roads in Sweden have been converted to collision-free roads as a cost-effective alternative to conventional motorways. Investigations have concluded that the road type has been successful in reducing the number of fatal accidents, despite increased operation and maintenance costs. In recent years, the focus has shifted to converting narrower roads which are anticipated to further increase operation and maintenance cost but also complicate traffic management during road works. There are concerns that when life cycle cost is considered in the investment assessment the socioeconomic profitability could be reduced. This article examines this issue by first assessing changes in costs for operation and maintenance using a life cycle cost analysis approach applied on a case study. The results from the analysis were thereafter integrated into a cost–benefit analysis to assess changes in costs in relation to benefits in improved traffic safety and travel time. The analysis indicated profitability even with substantial increase in operation, maintenance and road user work zone costs. Results are discussed from project implementation and road management perspectives.

Possibilities to reduce pavement rehabilitation cost of a collision-free road investment using an LCCA design procedure

In the past decades, many single carriageway roads in Sweden have been converted to collision-free roads as a cost-effective alternative to conventional motorways. Investigations have concluded that the road type has been successful in reducing the number of fatal accidents, despite increased operation and maintenance costs. In recent years, the focus has shifted to converting narrower roads, which are anticipated to further increase pavement rehabilitation cost but also complicate traffic management during road works. This paper first examines the consequences in terms of road agency and road user costs; second, the possibilities to influence future costs by design alternatives. A life cycle cost analysis was employed to study future costs. The analysis indicated significant increase in life cycle cost compared to a single carriageway road. The analysis of design alternatives also indicated that future agency and road user cost can be substantially improved by finding an optimal alternative.

Calculating rutting of some thin flexible pavements from repeated load triaxial test data

This paper describes parts of a Nordic pavement performance prediction model study (at the project level of the NordFoU project) where a material performance model, developed at VTT research centre in Finland, has been selected as a mean of calculating the permanently accumulated (plastic) deformation (i.e. rutting) of unbound granular materials (UGMs) in flexible pavements subjected to trafficking. The paper aims to assess the suitability of this VTT model application to Swedish roads comprising thin asphalt layers over a thick UGM base. To achieve this, the VTT model has been used to calculate the deformations of two tested road sections in Sweden. These calculations have been compared with another permanent deformation model for UGM (the Gidel model) and with rutting measurements from trafficked pavements. It is shown from this study that the applied rutting prediction method with VTT model is capable of predicting the development of rutting depth despite some overestimations.

Farm tractors on Swedish public roads – age-related perspectives on police reported incidents and injuries

Agriculture consistently ranks as one of the highest risk industries in North America and Europe. In addition to vehicle injuries and other injuries that occur on farms, farm vehicle drivers are also involved in collisions involving tractors and other slow-moving vehicles (SMVs) on public roads. These collisions often lead to injuries among farmers, family members, farm workers, and other road users. To conduct a demographic analysis of road traffic incidents involving tractors in Sweden during the time period 1992-2009, with special consideration of how incidents vary with driver age. Statistics from 2,305 police reports describing tractor-related road traffic incidents in Sweden in 1992-2009 were analysed with respect to driver age, type of incident, severity of injury, type of road user and other circumstances at the accident site. Tractors of all kinds were involved in 128 road traffic incidents annually, with 7 people killed, 44 seriously injured and 143 suffering minor injuries each year. The annual number of fatalities represented 1.2% of all Swedish road fatalities. Most road traffic incidents with farm tractors involved people aged 25-55 years (mean 45 years). However, most farm tractor drivers killed or injured belonged to younger or older age groups. Drivers aged 12-16 years were over-represented in tractor incidents with no other vehicle involved. Older tractor drivers (> 55 years) were more often involved in incidents with passenger vehicles on entering traffic flows. The youngest tractor drivers aged 12-16 years were more often involved in road traffic incidents during school holidays, and both youngest and oldest drivers (>65 years) during harvest time. Sweden has an ageing fleet of tractors, so increased attention to vehicle maintenance is needed to improve road safety. The over-representation of young children in tractor incidents suggests that it is questionable whether they should be allowed to operate farm vehicles. Farm vehicle drivers suffering the inevitable effects of ageing need increase their awareness of added risks. As road traffic incidents with tractors often involve private vehicles, creating awareness among the public of slow-moving farm vehicles is essential for improving overall road safety.

Prevalence of alcohol and other drugs and the concentrations in blood of drivers killed in road traffic crashes in Sweden

Drunk or drug-impaired drivers represent a major public health and societal problem worldwide. Because over 95% of drivers killed on the roads in Sweden are autopsied, reliable information is available about the use of alcohol and/or other drug before the crash. This retrospective 4-year study (2008-2011) used a forensic toxicology database (TOXBASE) to evaluate the concentrations of alcohol and other drugs in blood samples from drivers killed in road-traffic crashes. The mean age of all victims (N = 895) was 48 ± 20 years, and the majority were male (86%). In 504 drivers (56%), the results of toxicological analysis were negative and these victims were older; mean age (± SD) 47 ± 20 years, than alcohol positive cases (35 ± 14 years) and illicit drug users (34 ± 15 years). In 21% of fatalities, blood-alcohol concentration (BAC) was above the statutory limit for driving (0.2 g/L), although the median BAC was appreciably higher (1.72 g/L). Illicit drugs (mainly amphetamine and cannabis) were identified in ~7% of victims, either alone (2.5%), together with alcohol (1.8%) or a prescription drug (2%). The psychoactive prescription drugs identified were mainly benzodiazepines, z-hypnotics and tramadol, which were found in the blood of 7.6% of crash victims. The high median BAC in fatally-injured drivers speaks strongly towards alcohol-induced impairment as being responsible for the crash. Compared with alcohol, the prevalence of illicit and psychoactive prescription drugs was fairly low despite a dramatic increase in the number of drug-impaired drivers arrested by the police after a zero-tolerance law was introduced in 1999.

Car Crash Fatalities Associated With Fire in Sweden

Objective: To study the epidemiology and causes of death in fatal car crashes on Swedish roads in which the victim's vehicle caught fire. Methods: The data set is from the Swedish Transport Administrations in-depth studies of fatal crashes 1998–2008. Autopsies from all cases provided data on injuries, toxicological analyses, and cause of death. Results: In total, 181 people died in 133 burning cars, accounting for 5 percent of all deaths in passenger cars, sport utility vehicles, vans, and minibuses during 1998 to 2008. The cause of death for a third of the victims was fire related, as burns and/or smoke inhalation injuries, with no fatal trauma injuries. Twenty-five of these 55 deaths were persons 19 years or younger and included 15 of 18 rear seat deaths. Over half of the 181 deaths were in vehicles that had collided with another vehicle and, of these cases, half were killed in collisions with heavy vehicles. The percentage of drivers with illegal blood alcohol concentrations (27%) and suicides (5.5%) were not higher than in other fatal crashes on Swedish roads. The ignition point of the fire was indicated in only half of the cases and, of those, half started in the engine compartment and one fourth started around the fuel tank or lines. Conclusions: Car fires are a deadly postcrash problem. Reducing this risk would be primarily a responsibility for the automotive industry. A multifactor approach could be considered as follows: risk-reducing design, insulation, reduced flammability in motor compartment fluids and plastics, and automatic fire extinguishing equipment. Inspiration could be found in how, for example, the auto racing and aviation industries handle this problem.

Opportunities for environmentally improved asphalt recycling: the example of Sweden

Asphalt waste from State roads in Sweden is usually recycled in order to preserve natural resources and reduce the burden on landfill. However, there appears to be a knowledge gap regarding the met ...

Tractor accidents in Swedish traffic

The objective of this study is to reach a better understanding of accidents on Swedish roads involving tractors and to suggest ways of preventing them. In an earlier study we analyzed police-reported fatal accidents and accidents that led to physical injuries from 1992 to 2005. During each year of this period, tractors were involved in 128 traffic accidents on average, an average of 7 people were killed, 44 sustained serious injuries, and 143 sustained slight injuries. The number of fatalities in these tractor accidents was about 1.3% of all deaths in traffic accidents in Sweden. Cars were most often involved in the tractor accidents (58%) and 15% were single vehicle accidents. The mean age of the tractor driver involved was 39.8 years and young drivers (15-24 years) were overrepresented (30%). We are now increasing the data collected with the years 2006-2010 in order to study the changes in the number of accidents. Special attention will be given to the younger drivers and to single vehicle accidents. Based on the results we aim to develop suggestions for reducing road accidents, e.g. including measures for making farm vehicles more visible and improvement of the training provided at driving schools.

The effects of studded tires on fatal crashes with passenger cars and the benefits of electronic stability control (ESC) in Swedish winter driving

This study set out to examine the effects of studded tires on fatal crashes on roads covered with ice or snow in Sweden and also to investigate the extra benefits of electronic stability control (ESC) during the winter months. Two different studies are presented in this paper. Both studies used an induced exposure approach. In the main study, 369 in-depth studies of fatal crashes with passenger cars were analyzed to determine whether loss-of-control (LOC) had been a major component or not. Only crashes involving cars without ESC and equipped with approved studded or non-studded winter tires were analyzed. The additional study used police-reported crashes that occurred during the winter seasons 2003–2010, involving passenger cars with and without ESC. While police records in Sweden do not include any tire information, it was assumed that most cars involved in crashes during the winter period would be equipped with studded tires.Findings in the main study showed that in 64% of the fatal crashes on roads covered with ice or snow LOC had been a major component. Furthermore, in 82% of LOC crashes, the passenger car over-steered prior to collision. Studded tires were found to have a statistically significant effect of 42% in terms of fatal crash reduction on roads covered with ice or snow, compared to non-studded winter tires. The effect on dry or wet roads in the winter was negative, although statistically non-significant. In the additional study, it was found that ESC further reduced crashes with injuries by 29%. The benefits on severe and fatal crashes were slightly greater (32%), although the lower 95% confidence limit was lower.Although studded tires were shown to reduce the risk of fatal crash involvement, compared to non-studded winter tires, the proportion of LOC and over-steering among cars with studded tires was large (59% and 49%, respectively). It was therefore concluded that studded tires do not prevent all LOC crashes, while ESC has benefits in those crashes since this technology mostly addresses over-steering. This is also supported by the fact that the share of LOC fatal crashes is considerably lower for ESC-equipped cars.This study recommends that non-ESC cars should be fitted with studded tires if they are to be driven on roads covered by ice or snow. If the proportion of studded tires is to be decreased on Swedish roads to reduce the about of hazardous particulates especially in built up areas, from a road safety point of view it is recommended that this should be done in phase with the implementation of ESC on all passenger cars.

Vision Zero – a road safety policy innovation

The aim of this paper is to examine Sweden's Vision Zero road safety policy. In particular, the paper focuses on how safety issues were framed, which decisions were made, and what are the distinctive features of Vision Zero. The analysis reveals that the decision by the Swedish Parliament to adopt Vision Zero as Sweden's road safety policy was a radical innovation. The policy is different in kind from traditional traffic safety policy with regard to problem formulation, its view on responsibility, its requirements for the safety of road users, and the ultimate objective of road safety work. The paper briefly examines the implications of these findings for national and global road safety efforts that aspire to achieving innovative road safety policies in line with the Decade of Action for Road Safety 2011–2020, declared by the United Nations General Assembly in March 2010.

Vehicle Motion Estimation Using an Infrared Camera

AbstractThis paper is concerned with vehicle motion estimation. The problem is formulated as a sensor fusion problem, where the vehicle motion is estimated based on the information from a far infrared camera, inertial sensors and the vehicle speed. This information is already present in premium cars. This work is concerned with the off-line situation and the approach taken is to formulate the problem as a nonlinear least squares problem. In order to illustrate the performance of the proposed method experiments on rural roads in Sweden during night time driving have been performed. The results clearly indicates the efficacy of the approach.

Joint ego-motion and road geometry estimation

We provide a sensor fusion framework for solving the problem of joint ego-motion and road geometry estimation. More specifically we employ a sensor fusion framework to make systematic use of the measurements from a forward looking radar and camera, steering wheel angle sensor, wheel speed sensors and inertial sensors to compute good estimates of the road geometry and the motion of the ego vehicle on this road. In order to solve this problem we derive dynamical models for the ego vehicle, the road and the leading vehicles. The main difference to existing approaches is that we make use of a new dynamic model for the road. An extended Kalman filter is used to fuse data and to filter measurements from the camera in order to improve the road geometry estimate. The proposed solution has been tested and compared to existing algorithms for this problem, using measurements from authentic traffic environments on public roads in Sweden. The results clearly indicate that the proposed method provides better estimates.

From consultation to deliberation? Tracing deliberative norms in EIA frameworks in Swedish roads planning

This paper presents the results of an analysis of deliberative norms in the framework for Environmental Impact Assessment (EIA) in roads planning in Sweden. The more specific question is how this framework has responded to the shift towards more deliberative approaches to planning and decision making, advocated in planning theory and policy literature over the last decade. The analysis, which compares the current framework and guidance with an earlier iteration, identifies a shift towards deliberation; deliberative norms are present, and even dominate recent guidance. However, an instrumental norm permeates both the former and the current guidance, suggesting that even as a language of consultation is replaced by one of deliberation, the intention remains to secure and legitimise a smooth development pathway. Evidence from interviews with professionals working in the Swedish EIA system highlights the difficulties of navigating these uncertainties in practice. By opening up critical analysis of deliberative norms as they shape the conditions for practice, this study contributes to the continuous development of planning practice, by supporting a more normatively reflexive approach to framework-design.

RuttOpt — a decision support system for routing of logging trucks

We describe the decision support system RuttOpt, which is developed for scheduling logging trucks in the forest industry. The system is made up of a number of modules. One module is the Swedish road database NVDB, which consists of detailed information of all of the roads in Sweden. This also includes a tool to compute distances between locations. A second module is an optimization routine that finds a schedule, i.e., set of routes for all trucks. This is based on a two-phase algorithm where linear programming and a standard tabu search method are used. A third module is a database storing all relevant information. At the center of the system is a user interface where information and results can be viewed on maps, Gantt schedules, and result reports. The RuttOpt system has been used in a number of case studies and we describe four of these. The case studies have been made in both forest companies and hauling companies. The cases range from 10 to 110 trucks and with a planning horizon ranging between 1 and 5 days. The results show that the system can be used to solve large case studies and that the potential savings are in the range 5%–30%.