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  • 1.
    Ahlström, Christer
    et al.
    Swedish National Road and Transport Research Institute, Traffic and road users, Human-vehicle-transport system interaction.
    Bolling, Anne
    Swedish National Road and Transport Research Institute, Traffic and road users, Vehicle technology and simulation.
    Sörensen, Gunilla
    Swedish National Road and Transport Research Institute, Traffic and road users, Traffic safety, society and road-user.
    Eriksson, Olle
    Swedish National Road and Transport Research Institute, Infrastructure, Infrastructure maintenance.
    Andersson, Anders
    Swedish National Road and Transport Research Institute, Traffic and road users, Vehicle technology and simulation.
    Validating speed and road surface realism in VTI driving simulator III2012Report (Other academic)
    Abstract [en]

    New simulator models concerning vibration, noise and graphics have been designed and implemented in the VTI Simulator III. The objective of this study is to validate this simulator in terms of road surface realism. Twenty-four drivers participated in the study and drove the same route both in the simulator and on real roads. Three road sections ranging from very smooth to rather uneven were incorporated in the design. The comparison included the objective driving parameter speed as well as subjective parameters from questionnaires and rating scales (evenness, quietness and comfort level). A road section with five speed limit changes was of particular interest in the analyses. No statistically significant difference could be found between the simulator and the car, neither in the parameter speed (in sections with no speed limit changes) nor in the ratings evenness and quietness. Despite similar speed profiles surrounding the speed limit signs, there was a statistically significant difference between the speed in the car and in the simulator, with more rapid accelerations and decelerations in the simulator. The comfort rating was shown to be higher in the car compared to the simulator, but in both cases the general trend showed higher comfort on smoother roads. These results indicate absolute validity for the ratings evenness and quietness, and for the measure speed, and relative validity for comfort and speed surrounding speed limit signs.

  • 2.
    Andrén, Peter
    et al.
    Datamani.
    Eriksson, Olle
    Swedish National Road and Transport Research Institute, Infrastructure, Infrastructure maintenance.
    Lundberg, Thomas
    Swedish National Road and Transport Research Institute, Infrastructure, Infrastructure maintenance.
    Prognosmodeller för tillståndsmått i Trafikverkets Pavement Management System: IRI och spårdjup2014Report (Other academic)
    Abstract [en]

    In Sweden, the road surface condition is assessed regularly with laser-based profilographs. This has been done since 1987. All roads are, for financial reasons, not assessed every year, but one way to describe the condition of the entire road network is to work with models. The purpose of these assessments is to provide the Swedish Transport Administration’s Pavement Management System (PMS) with data. The main uses of the PMS are: • To provide a description of the overall road condition and its changes to determine if the selected operation and maintenance strategies are successful, and if an acceptable road standard can be offered. • Support the maintenance planning (prioritization and selection of sections for maintenance). • Support for the choice of maintenance method. • Monitoring of performance of construction or maintenance, for example, functional related contracts. • To support research. The Swedish Transport Administration needs a complete description of the road condition in order to demonstrate to the government and parliament how the mission to maintain the roads is achieved. One way to describe the condition of the entire road network is to work with models that forecast the condition the years when measurements are missing. In the choice between using a global or local model to describe the state of development for IRI (International Roughness Index) and rut depth on individual 100-meter segments, the present report shows that a local model is preferred. The coefficient of determination is not high enough in a global model. Also, the researchers cannot see any consequent pattern in the regression coefficients for the explanatory variables we have tried.

  • 3.
    Arvidsson, Anna K
    et al.
    Swedish National Road and Transport Research Institute, Infrastructure, Infrastructure maintenance.
    Eriksson, Olle
    Swedish National Road and Transport Research Institute, Infrastructure, Infrastructure maintenance.
    Wärme, Mats
    B&M System AB.
    Bäckström, Andreas
    Svevia.
    Dynamic Forecast Controlled Road Maintenance2018Conference paper (Refereed)
  • 4.
    Arvidsson, Anna K
    et al.
    Swedish National Road and Transport Research Institute, Infrastructure, Infrastructure maintenance.
    Lundberg, Thomas
    Swedish National Road and Transport Research Institute, Infrastructure, Infrastructure maintenance.
    Kalman, Björn
    Swedish National Road and Transport Research Institute, Infrastructure, Pavement Technology.
    Ekström, Camilla
    Swedish National Road and Transport Research Institute, Traffic and road users, Traffic Safety and Traffic System.
    Cruz del Aguila, Fernando
    Swedish National Road and Transport Research Institute, Infrastructure, Infrastructure maintenance.
    Eriksson, Olle
    Swedish National Road and Transport Research Institute, Infrastructure, Infrastructure maintenance.
    Friktions- och texturutveckling på nya beläggningar2019Report (Other academic)
    Abstract [en]

    A new pavement should be and be perceived as safe by road users, regardless of the road condition. It is therefore important that the road has a satisfactory level of friction already when the road is opened. There is limited documented knowledge of how the road change in the beginning after a paving performance.

    The purpose of this project is to determine how friction changes during the first period after road pavement is laid and traffic is permitted. The ambition is to determine if new road sections have reduced friction and provide recommendations for when a friction measurement is to be performed, and how warning signs should be displayed in connection with the pavement work. The study plan has been to follow different objects with frequent friction and texture measurements from just before the stretch is opened for traffic until the levels have stabilised.

    Initially, friction is high, and then decreases with the amount of traffic. After 1-3 weeks the lowest value was reached and then the friction increased or stabilized. Common to all investigated stretches, there are major changes in texture levels from the first vehicle and then a decreasing textural level until a stable level is reached after 1-3 weeks.

  • 5.
    Arvidsson, Anna K
    et al.
    Swedish National Road and Transport Research Institute, Infrastructure, Infrastructure maintenance.
    Wärme, Mats
    B&M system AB.
    Eriksson, Olle
    Swedish National Road and Transport Research Institute, Infrastructure, Infrastructure maintenance.
    Bäckström, Andreas
    Svevia.
    Dynamisk prognosstyrd vintervägdrift: Summering av Fas 12017Report (Other academic)
    Abstract [en]

    The task of the winter maintenance operations is to ensure that the roads are accessible and safe to use. In practice, by means of ploughing, sand and salt spreading, keeping the roads free of snow and ice in accordance with the current requirements. Experience in operational winter management is a shortcoming, which is partly due to the more flexible labour market with short contract periods, but also due to the major retirements that have been in recent years. In order for the winter maintenance contractor to maintain and at the same time increase the productivity, it is essential to develop decision support systems.

    There are today several road weather forecast services that can provide qualified support to decisionmakers in winter road maintenance. As a basis, current weather information from the Swedish RWIS-outstations (Road Weather Information System), which is deployed along the state roads, is used. Some services also use data from sensors in cars. The services provide dynamic road conditions forecasts and in some cases even proposals for actions needed for different road sections. They deliver detailed decision-making prognosis that enable high quality decisions for the correct action in the right time at the right place. Perhaps the main advantage of the forecasts is that they clearly show that only parts of the road network need to be addressed and that the surface temperature forecast, in addition to the forecast of the road surface condition, is important input for determining the needed amount of salt.

    Today’s route optimisation program performs optimisations for the shortest time based on the road owner's road classification, that is based on annual average daily traffic. However, road climate may vary considerably within an operating area, and the need to adjust for these variations in order to achieve an increased resource efficiency, can currently only be corrected manually for resource planning, and usually before the winter season starts.

    The purpose of the project is to provide a more dynamic information to create a more productive winter road maintenance with dynamic road conditions information. Integrating data from a road weather forecast service into existing systems, such as a route guidance driver system, would allow the workforce to work significantly more detailed and dynamically, allowing for significant efficiency gains. In the project, an evaluation of a weather service has also been made with regards to which forecast window is suitable to use in the optimization. The project in this first phase can be described as a first attempt to make the systems working together, validate that it is feasible and that results will be reliable routes for the decisionmakers in winter road maintenance.

    The project has shown that a dynamic forecasting route optimisation for preventative salting can improve the environment by reducing emissions from lorries due to shorter driving distances and reduction of salt usage. The work environment for the maintenance vehicle drivers is enhanced by a higher degree of automation, which means it is less to keep track of, resulting in reduced stress at high performance requirements. Better quality in the winter road maintenance also benefits accessibility for the road users.

  • 6.
    Arvidsson, Håkan
    et al.
    Swedish National Road and Transport Research Institute, Infrastructure, Pavement Technology.
    Eriksson, Olle
    Swedish National Road and Transport Research Institute, Infrastructure, Infrastructure maintenance.
    Jämförande provning – ballast 2017: micro-Deval och Los Angeles2018Report (Other academic)
    Abstract [en]

    This report shows results, some statistical analysis and precision data for interlaboratory comparison (round robin) in Sweden performed on three materials of aggregate during 2017. The properties that was determined was resistance to wear by wet micro-Deval test (EN 1097-1) and resistance to fragmentation, Los Angeles test (EN1097-2). The number of participating laboratories were for micro- Deval 37 pcs. and for Los Angeles 34 pcs.

    There were three materials used for this comparison, the materials were called F, S and V. They were delivered to the participating laboratories in the grading 8/11 mm and 11/16 mm for each material. The laboratories should then generate the proper analyze fraction of 10/14 mm.

    The average results for micro-Deval were at the range of 6–8 for all of the materials. The standard deviations were also similar (0,43–0,50).

    For Los Angeles there were the average for one of the materials at 12 and for the other two materials the averages were around 26–27. The standard deviations are proportional to the averages.

  • 7.
    Arvidsson, Håkan
    et al.
    Swedish National Road and Transport Research Institute, Infrastructure, Pavement Technology.
    Eriksson, Olle
    Swedish National Road and Transport Research Institute, Infrastructure, Infrastructure maintenance.
    Jämförande provning – grovsiktning: ballast 20182019Report (Other academic)
    Abstract [en]

    This report shows results, some statistical analysis and precision data for interlaboratory comparison (round robin) in Sweden performed on a proportioned base layer material of crushed rock for grain size distribution according to TDOK 2014:0145 (coarse material sieving) and EN 933-1:2012 (sieving on 0/16 mm).

    There were 48 laboratories participating.

    In the sieving on coarse material, ≥ 16 mm, the deviations are small (standard deviations approx. 0,7%) and the difference between maximum and minimum value for each sieve is only 3–4%.

    The results for material finer than 16 mm (relatively to whole of the sample) are deviations wider. Especially for sieves 1/11,2 mm with difference between maximum and minimum values are up to 7% and the standard deviation for those sieves are around 1,4%. For sieves finer than 1 mm (0,5 mm and less) the differences are less than 3% and the standard deviation is less than 0,8%.

    The spreading’s for the fine material sieving is wider than for the coarse sieving part. It could depend on less accurate gradings on the fractions finer than 16 mm that were used in the proportioning. For the coarse sieving the whole sample (18 kg) were the test portion, for the fine sieving the material 0/16 mm had to be divided to get the test portion (approx. 2,6 kg). The dividing can also be one of the reasons to less accurate results for the 0/16 mm-part.

  • 8.
    Blissing, Björn
    et al.
    Swedish National Road and Transport Research Institute, Traffic and road users, Körsimulering och visualisering, SIM.
    Bruzelius, Fredrik
    Swedish National Road and Transport Research Institute, Traffic and road users, Körsimulering och visualisering, SIM.
    Eriksson, Olle
    Swedish National Road and Transport Research Institute, Infrastructure, Infrastructure maintenance.
    Driver behavior in mixed and virtual reality: a comparative study2016In: Proceedings of the DSC 2016 Europe / [ed] Andras Kemeny, Frédéric Mérienne, Florent Columbet, Stéphane Espié, Paris, France: Driving Simulation Association , 2016, p. 179-186Conference paper (Refereed)
    Abstract [en]

    This paper presents a comparative study of driving behavior when using different virtual reality modes. Test subjects were exposed to mixed, virtual, and real reality using a head mounted display capable of video see-through, while performing a simple driving task. The driving behavior was quantified in steering and acceleration/deceleration activities, divided into local and global components. There was a distinct effect of wearing a head mounted display, which affected all measured variables. Results show that average speed was the most significant difference between mixed and virtual reality, while the steering behavior was consistent between modes. All subjects but one were able to successfully complete the driving task, suggesting that virtual driving could be a potential complement to driving simulators.

  • 9.
    Blissing, Björn
    et al.
    Swedish National Road and Transport Research Institute, Traffic and road users, Driving Simulation and Visualization.
    Bruzelius, Fredrik
    Swedish National Road and Transport Research Institute, Traffic and road users, Driving Simulation and Visualization.
    Eriksson, Olle
    Swedish National Road and Transport Research Institute, Infrastructure, Infrastructure maintenance.
    Driver behavior in mixed and virtual reality: A comparative study2017In: Transportation Research Part F: Traffic Psychology and Behaviour, ISSN 1369-8478, E-ISSN 1873-5517Article in journal (Refereed)
    Abstract [en]

    This paper presents a comparative study of driving behavior when using different virtual reality modes. Test subjects were exposed to mixed, virtual, and real reality using a head mounted display capable of video see-through, while performing a simple driving task. The driving behavior was quantified in steering and acceleration/deceleration activities, divided into local and global components. There was a distinct effect of wearing a head mounted display, which affected all measured variables. Results show that average speed was the most significant difference between mixed and virtual reality, while the steering behavior was consistent between modes. All subjects but one were able to successfully complete the driving task, suggesting that virtual driving could be a potential complement to driving simulators.

  • 10.
    Blissing, Björn
    et al.
    Swedish National Road and Transport Research Institute, Traffic and road users, Körsimulering och visualisering, SIM.
    Bruzelius, Fredrik
    Swedish National Road and Transport Research Institute, Traffic and road users, Körsimulering och visualisering, SIM.
    Eriksson, Olle
    Swedish National Road and Transport Research Institute, Infrastructure, Infrastructure maintenance.
    Effects of Visual Latency on Vehicle Driving Behavior2016In: ACM Transactions on Applied Perception, ISSN 1544-3558, E-ISSN 1544-3965, Vol. 14, no 1, p. 5:1-5:12Article in journal (Refereed)
    Abstract [en]

    Using mixed reality in vehicles provides a potential alternative to using driving simulators when studying driver-vehicle inter- action. However, virtual reality systems introduce latency in the visual system that may alter driving behavior, which, in turn, results in questionable validity. Previous studies have mainly focused on visual latency as a separate phenomenon. In this work, latency is studied from a task-dependent viewpoint to investigate how participants’ driving behavior changed with increased latency. In this study, the investigation was performed through experiments in which regular drivers were subjected to different levels of visual latency while performing a simple slalom driving task. The drivers’ performances were recorded and evaluated in both lateral and longitudinal directions along with self-assessment questionnaires regarding task performance and difficulty. All participants managed to complete the driving tasks successfully, even under high latency conditions, but were clearly affected by the increased visual latency. The results suggest that drivers compensate for longer latencies by steering more and increasing the safety margins but without reducing their speed.

  • 11.
    Carlson, Annelie
    et al.
    Swedish National Road and Transport Research Institute, Society, environment and transport, Environment.
    Karlsson, Robert
    Trafikverket.
    Eriksson, Olle
    Swedish National Road and Transport Research Institute, Infrastructure, Infrastructure maintenance.
    Energy use due to traffic and pavement maintenance: the cost effectiveness of reducing rolling resistance2016Report (Other academic)
    Abstract [en]

    There is a potential to reduce energy use of traffic by performing maintenance measures that lower the rolling resistance. However, the overall aim should be to decrease the total energy use in a life cycle perspective, including energy for both traffic and maintenance. When choosing maintenance alternative, it is also of importance to consider the costs involved. Pavement management is focused on keeping wide spread road networks in acceptable condition given certain budget constraints. Therefore, the economic constraints need to be addressed and in the case of choosing a maintenance alternative that reduces total energy, it also has to be cost-efficient in order for it to be performed. The main scope of the research presented in this report is to investigate how road management should act to reduce total energy use of roads, including traffic and maintenance induced energy use, while also taking cost efficiency and the aspect of uncertainty into consideration. The purpose is to enable a better consideration of the total energy used and maintenance cost when managing the road network. The objective is to derive a meaningful instrument for decision making situations such as when selecting and designing maintenance treatments, in which total energy use and maintenance cost is considered. A general method is developed and presented. A criterion, CR, has been identified for how to choose a pavement maintenance strategy in regards to cost and energy efficiency. A cost benefit analysis approach using Benefit to Cost Ratio, BCR, has been adopted. The study indicates that it is difficult to establish a simple rule of thumb. However, the CR-value may be a useful criterion in some circumstances and it is important to have guidelines as decision support where assessments are made of the road surface characteristics, total energy use and maintenance cost and where the different aspects are valued. This is especially important on an object level.

  • 12.
    Eriksson, Olle
    Swedish National Road and Transport Research Institute, Infrastructure, Infrastructure maintenance.
    Känslighetsanalys av en modell för asfaltsdeformation2015Report (Other academic)
    Abstract [en]

    Increased commercial traffic volume, higher axle load limit, more frequent use of wide tyres, and a tendency towards higher tyre pressure have resulted in increased rates of rutting on asphalt pavements. Strain in asphalt pavements, caused by heavy traffic, is described by different models and serves as a basis for rut prediction. Prediction is however problematic because of varying and uncertain conditions. Studying the change in model output for a given change in input helps when trying to understand the importance of a correct input. In this report, it is shown how strain depends on compressibility, axle load, contact pressure, and, in some cases, variation in lateral position. Different variables affect the results in different ways. Results are therefore dependent on the choice of variables and the accounting area. The results, formulated from different perspectives, describe the significance of a variables influence on strain measurement without comparison in any definitive manner.

  • 13.
    Eriksson, Olle
    Swedish National Road and Transport Research Institute, Infrastructure, Infrastructure maintenance.
    Olycksrisk vid lokala ojämnheter och andra ytdefekter2014Report (Other academic)
    Abstract [en]

    This study has examined, in particular, the effect road surface “local unevenness” has on traffic accident risk. Effects from other road surface defects were also considered but to a lesser extent. Test results are non-significant when considering if local unevenness has any main effect. Local unevenness has also not been chosen as part of any significant term of higher order. The analysis provides no support that local unevenness influences the risk of accidents. With regards to other variables related to the road or road surface, there is a negative correlation between rut depth and accident risk, and a positive correlation between longitudinal gradient and accident risk. Accident risk varies in correlation with IRI (International roughness index) and the permitted speed limit in a way that implies that risk decreases with higher speed and low IRI, and higher IRI and low speed. The risk increases when both IRI and speed increase. Precipitation information is an example of a variable that has been included in the analysis but is not related to the road or road surface. Data indicates that accident risk is lower in places where heavy rainfall often occurs.

  • 14.
    Eriksson, Olle
    Swedish National Road and Transport Research Institute, Infrastructure, Infrastructure maintenance.
    The new proposed ISO macrotexture standard vs. the old2016Conference paper (Other academic)
  • 15.
    Eriksson, Olle
    et al.
    Swedish National Road and Transport Research Institute, Infrastructure, Infrastructure maintenance.
    Andrén, Peter
    Swedish National Road and Transport Research Institute, Infrastructure, Infrastructure maintenance.
    Prognosmetoder för spårdjup och IRI: vägytedata 1997–20162019Report (Other academic)
    Abstract [en]

    This report presents a proposal for a prediction method for future values of rut depth and IRI on the paved state road network and various measures of forecast exactness. The method can also be used to fill in missing values backward in time.

    An earlier VTI report within the same area concluded that a prediction method should use only data about the development locally and based its prediction on data from the current pavement cycle only. A major difference here is that the method has been expanded to include data from previous pavement cycles in the prediction method, with presentation of the advantages and disadvantages that this entails. Other parts, e.g. how data is prepared, has not been changed in any great extent.

    The results are mainly that forecasts do not generally become clearly better, nor clearly worse, by including data from previous pavement cycles. There is nevertheless an advantage in including these data because that makes prediction based on local conditions possible for more sections.

  • 16.
    Eriksson, Olle
    et al.
    Swedish National Road and Transport Research Institute, Infrastructure, Infrastructure maintenance.
    Lundberg, Thomas
    Swedish National Road and Transport Research Institute, Infrastructure, Infrastructure maintenance.
    MPD and IRI in the position of large goods vehicles: network measurements2016Report (Other academic)
    Abstract [en]

    Monitoring of the state road network in Sweden includes the longitudinal measurements of International Roughness Index (IRI) and Mean Profile Depth (MPD). This data can be used to predict values associated with rolling resistance, comfort and vehicle wear. The paths of the measurements correspond to the surface contact points of the wheels of a light passenger vehicle. In Sweden, lateral position comparisons made between medium and large goods vehicles show that right wheel track positions are not similar. This applies to larger and wider roads (typical motorways and other wide main roads). Knowledge of the surface conditions (IRI and MPD) at the surface contact points associated with a large goods vehicle would prove to be useful when predicting e.g. rolling resistance for large goods vehicles on entire or local road networks. If these conditions are not measured, it is important to know how they differ from the values in the measured path. Using this knowledge VTI’s measurement vehicle was equipped with two extra texture lasers which were mounted to the right of the ordinary texture laser in the right wheel track. Data was collected on a road network with mixed categories of road standard, from secondary roads to motorways. During the study, differences in IRI and MPD values were analysed. Values corresponded to the position of light passenger vehicles right wheel paths and two other paths 25 centimetre and 45 centimetre further out to the right (position of medium and large goods vehicles). The possibility of predicting local differences (shorter sections) and average differences was analysed.

  • 17.
    Eriksson, Olle
    et al.
    Swedish National Road and Transport Research Institute, Infrastructure, Infrastructure maintenance.
    Lundberg, Thomas
    Swedish National Road and Transport Research Institute, Infrastructure, Infrastructure maintenance.
    MPD/IRI Transverse Position2015Conference paper (Other academic)
    Abstract [en]

    Road monitoring of the state road network in Sweden includes for the longitudinal measurement of international roughness index (IRI) and mean profile depth (MPD). In Sweden the paths of the longitudinal measurements correspond to the surface contact points between the wheels of a light passenger vehicle. This data can be used to estimate values for friction, rolling resistance, comfort and vehicle wear. Knowledge of the surface condition (IRI and MPD) at the surface contact points associated with a large goods vehicle would prove to be useful when estimating similar values for large goods vehicle on an entire or local road network. If these conditions are not measured, it is important to know how they differ from the measured path.

    In Sweden, lateral position comparisons made between light and heavy vehicles show that left wheel track positions are similar. This applies to larger and wider roads (typical motorways and other wide main roads). Using this knowledge VTI’s measurement vehicle was equipped with two extra texture lasers which were mounted to the right of the ordinary texture laser in the right wheel track. Data was collected on a road network with mixed categories of road standard, from secondary roads to motorways.

    In this talk, we will present a study of the differences of IRI and MPD corresponding to the position of light vehicles right wheel path with two other paths, 25 and 45 cm further out to the right (position of large goods vehicles). We also will discuss the possibility to predict the differences between the tracks. A statistical analysis procedure for calculating the mean difference and an error margin is suggested. The results showed that although it is very difficult to explain or predict local differences, average differences can be estimated.

  • 18.
    Eriksson, Olle
    et al.
    Swedish National Road and Transport Research Institute, Infrastructure, Infrastructure maintenance.
    Lundberg, Thomas
    Swedish National Road and Transport Research Institute, Infrastructure, Infrastructure maintenance.
    Prediction models for international roughness index and rut depth2019In: Pavement and Asset Management - Proceedings of the World Conference on Pavement and Asset Management, WCPAM 2017, CRC Press/Balkema , 2019, p. 225-230Conference paper (Refereed)
    Abstract [en]

    In Sweden, road surface conditions have been assessed with laser-based profilographs since 1987. The Swedish Transport Administration needs a complete description and prediction but not all roads are assessed every year. Therefore, models are needed to forecast and complete the data. We propose a linear regression model of International Roughness Index (IRI) and rut depth against pavement age on individual 100-meter segments, with a random component pooled for all segments within the same pavement category and county. This method depends heavily on the rate at individual segments. A model that uses explanatory variables like Annual Average Daily Traffic (AADT), road with etc. has not showed better results. Also, the analysis does not show that the rate of change is higher the first year. We describe available data and corrections for outliers, unregistered maintenance activities and sudden changes. We also show the widths of confidence and prediction intervals for new observations.

  • 19.
    Eriksson, Olle
    et al.
    Swedish National Road and Transport Research Institute, Infrastructure, Infrastructure maintenance.
    Sörensen, Gunilla
    Swedish National Road and Transport Research Institute, Traffic and road users, Traffic Safety and Traffic System.
    Motorcykelflöden sommarhalvåren 2006 – 2017: teknisk rapport, version 1.02018Report (Other academic)
    Abstract [sv]

    Trafikverket ser ett ökat behov av uppgifter om trafikflöden och fordonshastigheter för motorcyklar, speciellt med avseende på tillförlitliga data inom trafiksäkerhetsområdet. Vid olycksanalys är det till exempel svårt att finna exponeringsdata för motorcykliste. För mc-flöden finns en särskild metod framtagen, se PM ”Beräkningar av mc-flöden på Trafikverkets ÅDT-avsnitt” (Eriksson, 2013).

    Skattningar av trafikflöden tas fram på basis av ett 12-årigt mätprogram för årsmedel-dygnstrafik (ÅDT). Sedan år 2006 skattas även mc-flöde under sommarhalvåret med hjälp av data från mätprogrammet. Skattningar av mc-flöden på de statliga vägarna år 2006–2012 utfördes enligt metoden beskriven i Eriksson (2013). Motsvarande skattningar gjordes även för år 2013–2014 med denna metod, enligt uppgift från Trafikverket. Metoden användes också för skattningar år 2015, men då genomfördes dessutom ytterligare rimlighetskontroller och korrigeringar av data, vilket är beskrivet i teknisk rapport ”Trafikflöden för motorcyklar 2015” (Sörensen och Eriksson, 2016). Metoden vidareutvecklades för skattningarna år 2016, se Sörensen, Henriksson och Yahya (2017).

    Resultaten av mc-flödesskattningarna har rapporterats till Trafikverket i tabellform uppdelade per mätår och vägkategori. Trafikverket har publicerat resultaten i kartor på sin websida.

  • 20.
    Forsman, Åsa
    et al.
    Swedish National Road and Transport Research Institute, Traffic and road users, Traffic safety, society and road-user.
    Eriksson, Olle
    Swedish National Road and Transport Research Institute, Infrastructure, Infrastructure maintenance.
    Eriksson, Jenny
    Swedish National Road and Transport Research Institute, Traffic and road users, Traffic safety, society and road-user.
    Prognosintervall för antal allvarligt skadade i vägtrafikolyckor2016Report (Other academic)
    Abstract [en]

    The number of seriously injured road users is used both as an indicator of traffic safety trends in Sweden and in more specific studies of, for example, different road user groups. A seriously injured person is defined as a person who suffers injuries that lead to permanent medical impairment of at least 1 percent. The term very seriously injured is used as a complement and is defined correspondingly but refers to injuries that lead to permanent medical impairment of at least 10 percent. In practice, the level of impairment is not known at the time of the accident, and therefore the number of seriously and very seriously injured persons are forecasted. The basis for the forecasts are Strada, the national database for road traffic accidents in Sweden, and a method developed by Folksam (a Swedish insurance company) that estimates the risk that a person’s injuries will lead to permanent medical impairment in the future. The aim of this study is to present the size of the uncertainty of the forecasts for different subpopulations such as geographical areas, roads user groups, age and gender. The uncertainty of the forecasts is illustrated as forecasting intervals. It became clear during the study that derivation of the intervals was relatively easy for the case with one injury per person but considerably more difficult when the persons had a combination of several injuries. Therefore, the width of the intervals was determined using simulation instead of theoretical calculations.

  • 21.
    Grigoratos, Theodoros
    et al.
    European Commission Joint Research Centre.
    Gustafsson, Mats
    Swedish National Road and Transport Research Institute, Society, environment and transport, Environment.
    Eriksson, Olle
    Swedish National Road and Transport Research Institute, Infrastructure, Infrastructure maintenance.
    Martini, Giorgio
    European Commission Joint Research Centre.
    Experimental investigation of tread wear and particle emission from tyres with different treadwear marking2018In: Atmospheric Environment, ISSN 1352-2310, E-ISSN 1873-2844, Vol. 182, p. 200-212Article in journal (Refereed)
    Abstract [en]

    The Treadwear Rating (TWR) provided on the sidewall of the tyre is a marking intended to inform the customer about the expected durability of the tyre. The current study explores whether there is a correlation between the TWR and tyres' tread mass loss. Furthermore, it explores the possible correlation between the TWR and tyre wear dust emitted in the form of PM10 and PM2.5. For that reason, two tyres of the same brand (B) but with different TWR and three tyres of different brands (C and D with the same TWR as one of the B tyres and A with a lower TWR) were tested at a constant speed of 70 km/h by means of the Swedish National Road and Transport Research Institute (VTI) road simulator. Tyres of the same TWR but of different brands showed different behaviour in terms of material loss, PM, and PN emissions under the selected testing conditions. This means that it is not feasible to categorize tyres of different brands in terms of their emissions based on their TWR. The test performed on the two tyres of the same brand but with different TWR showed instead a substantial (not statistically significant) difference in both total wear and PM10 emissions. The tyre with the higher TWR (B2) showed less wear and PM10 emissions compared to the B1 tyre having a lower TWR. Since only two tyres of the same brand and with different TWR were tested, this result cannot be generalized and more tests are necessary to confirm the relation within the same brand. In general, the tyre tread mass loss showed no obvious statistical relation to PM10, PM2.5 or PN concentration. In all cases approximately 50% (by mass) of emitted PM10 fall within the size range of fine particles, while PN size distribution is dominated by nanoparticles most often peaking at 20-30 nm.

  • 22.
    Gustafsson, Mats
    et al.
    Swedish National Road and Transport Research Institute, Society, environment and transport, Environment.
    Eriksson, Olle
    Swedish National Road and Transport Research Institute, Infrastructure, Infrastructure maintenance.
    Emission of inhalable particles from studded tyre wear of road pavements: a comparative study2015Report (Other academic)
    Abstract [en]

    New restrictions on the number of studs on studded tyres were introduced in Sweden and Finland in 2013. Regulations now allows 50 studs per meter rolling circumference. Alternatively, the tyres can be tested in a special wear test, the so-called over-run test, to be approved. This has resulted in studded tyres that follows the rule of the number of studs per rolling circumference meters, but also studded tyres that pass the over-run test, even though they have considerably more spikes are present on the market. The over-run test shall ensure that the tested tyre will not cause more road wear than a tyre with a maximum of 50 studs per meter rolling circumference. Since studded tyres are a major source of inhalable particles (PM10) in road and street environments, it is of interest to investigate the difference between the various studded tyre types also from particle emission point of view. In the present study, the particle generation from seven studded tyres was tested in the VTI road simulator. The tyres have been tested at 50 km/h in a statistically optimal sequence during the four test days where various order of tyres used each day of testing. Concentrations (mass and number) and size distributions were measured during the experiments, as well as environmental parameters (temperature and humidity). In the statistical analysis of particle data was partly analysed as constants and partly as depending on ambient and tyre-specific parameters. The results show that the tyre with the most studs (190) generates significantly higher PM10 levels than other tyres while one of the tyres following the stud number regulations and have 96 studs results in significantly lower formation of inhalable particles than all other tyres tested. Increased number of studs increases PM10, PM2.5 and number concentration significantly, while increasing stud force significantly increases the concentration of PM10 and PM2.5. Temperatures in the tyre, pavement and air as well as relative humidity also have an effect on the particle levels. A calculation example was performed where the relationship between the tested highest and lowest emitting tyres was applied in a process based emissions model in which studded tyre wear is included (NORTRIP model). This demonstrated that the effect of variations in the studded tyre wear on both PM10-levels and the number of limit value exceedances for the current data set used was significant.

  • 23.
    Gustafsson, Susanne
    et al.
    Swedish National Road and Transport Research Institute, Traffic and road users, Traffic safety, society and road-user.
    Sörensen, Gunilla
    Swedish National Road and Transport Research Institute, Traffic and road users, Traffic safety, society and road-user.
    Eriksson, Olle
    Swedish National Road and Transport Research Institute, Infrastructure, Infrastructure maintenance.
    Genell, Anders
    Swedish National Road and Transport Research Institute, Society, environment and transport, Environment.
    Jägerbrand, Annika
    Swedish National Road and Transport Research Institute, Society, environment and transport, Environment.
    Ljudvarningar vid vägarbetsplatser för att uppnå sänkta hastigheter: Kartläggning och praktisk utvärdering2014Report (Other academic)
    Abstract [en]

    A project has been carried out to find methods that effectively decrease drivers’ speeds at road work sites through real-time audio warnings. The project consisted of two parts. First, a survey of existing studies took place. The results show that the characteristics of a successful audio alert are female voice, direct and informative messages, an interaction between semantics and acoustics, successively increased intensity, and the dimming of secondary audio distractions. Based on the results of the survey, a practical evaluation of the potential use of audio warnings at road work sites was carried out in a VTI driver simulator. Twenty-two car drivers drove 25 kilometer on a motorway where two road works were placed on the hard shoulder. Half of the subjects were given an audio warning before the first road work and the other half prior to the second roadwork. The audio warning consisted of a sound similar to that of a GPS warning signal, followed by a female voice saying "Warning! Road work within 500 meters. Adjust the speed!". The message was sent via the car's internal speaker system. The speed reducing effect is significant and the average decrease is estimated to be 9–17 km/h greater with audio warning than without. Furthermore, there was still a small effect (0.5–3.3 km h) left of the audio alert after the road works. More results of the simulation tests are presented along with the drivers’ subjective opinions of such systems.

  • 24.
    Göransson, Nils-Gunnar
    et al.
    Swedish National Road and Transport Research Institute, Infrastructure, Infrastructure maintenance.
    Viman, Leif
    Swedish National Road and Transport Research Institute, Infrastructure, Pavement Technology.
    Eriksson, Olle
    Swedish National Road and Transport Research Institute, Infrastructure, Infrastructure maintenance.
    Avnötningsbeständighet för högkvalitativa slitlagerbeläggningar: slitagemätningar i VTI:s provvägsmaskin (PVM) och jämförelser med laboratorietester enligt Prall2018Report (Other academic)
    Abstract [en]

    Samples from high-quality wearing course asphalt mixes were collected during production in the seasons 2009-2013. The samples included modified asphalts as well as reference mixes. Three different surface wear tests, with respect to abrasion from studded tyres, were carried out using VTIs circular road simulator (PVM). In order to verify the correlation between the three different test modes, tests according to EN 12697-16, Prall method, have been carried out.

    Each of the tests included 14 mix types, including a reference mix, distributed over 28 test plates. The test plates were constructed in a laboratory environment. Extra plates were also constructed for laboratory testing. In total, 42 plates were required per test. Standard plates for PVM testing were used and had a thickness of about 40 millimetres.

    Each test used tyres that had been “run-in” for about 500 kilometres. Sixteen tyres (including 4 reserve) were required for the test runs. Tyres were purchased at the same time from the same manufacturer and divided up randomly.

    Testing was carried out until a constant linear rate of surface wear was achieved. The minimum and maximum number of machine revolutions were set at 200 000 and 300 000 respectively. Surface wear measurements were made by a laser profilometer and were taken at regular intervals on all 28 sample plates.

  • 25. Hammarström, Ulf
    et al.
    Björketun, Urban
    Eriksson, Olle
    Swedish National Road and Transport Research Institute, Infrastructure, Infrastructure maintenance.
    Yahya, Mohammad-Reza
    Swedish National Road and Transport Research Institute, Infrastructure, Measurement technology and engineering workshop.
    Hastighet – vägyta: problemet, kunskapsläget, fördjupad analys och förslag till fortsatt forskning2016Report (Other academic)
    Abstract [en]

    The correlation between speed and road surface condition is of interest for the planning of pavement maintenance on the road network. The costs and the target variables that are affected by this correlation are, in addition to travel time, fuel consumption (vehicle costs), energy and environment.According to previous studies of the road surface influence on the vehicle speed increased rut depth (RUT) and increasing longitudinal road unevenness (IRI) causes decreased vehicle speed. In the description of the road surface macro texture (MPD) is normally also included. There has, however, been a lack of knowledge about the importance of MPD on vehicle speed. The main purpose of the present study was to supplement existing knowledge about the vehicle speed with the importance of MPD.Mean values of ADC, RF, RUT, IRI and MPD, has been calculated for pre-sections of different lengths between 100 metre and 1 000 metre. These averages can sometimes change significantly with changes in section length while the speed data is the same. The sometimes systematic variation is in part a consequence of the positions of the measurement sites (TMS) not being randomly selected.

  • 26.
    Hedström, Ragnar
    et al.
    Swedish National Road and Transport Research Institute, Infrastructure, Infrastructure maintenance.
    Eriksson, Olle
    Swedish National Road and Transport Research Institute, Infrastructure, Infrastructure maintenance.
    Godstågs avvikande hastighet: analys av förekomst, orsaker och konsekvenser2018Report (Other academic)
    Abstract [en]

    It happens that freight trains deviate from the times of the timetable on their transport route between arrival and end station and there are several reasons that this happens. Examples of the consequences of disruptions occurring include low punctuality, general capacity problems, reprioritization of the freight train and delayed delivery to the end customer.

    The aim of this project was to develop a method for analysing the existence of freight trains that deviate from the set timetable, as well as the reason for it. The results presented in the report are based solely on data from the Swedish Transport Administration’s database Lupp.

    From a limited material (four freight trains over two years), it was difficult to find clear cause-and-effect relationships between different factors. However, some conclusions from the project may be interesting to highlight. In 2015, the punctuality of the four freight trains upon departure from the Hallsberg marshalling yard was about 60 percent and about 50 percent upon arrival at the Malmö goods station. Scheduled stops at some stations between Hallsberg and Malmö are not always used. Disruptions linked to the causes “infrastructure" and “railway companies” together account for between 60 percent and 70 percent of the total number of disruptions.

  • 27.
    Hedström, Ragnar
    et al.
    Swedish National Road and Transport Research Institute, Infrastructure, Infrastructure maintenance.
    Johansson, Thomas
    TJ kommunikation.
    Eriksson, Olle
    Swedish National Road and Transport Research Institute, Infrastructure, Infrastructure maintenance.
    McGarvey, Terry
    Swedish National Road and Transport Research Institute, Infrastructure, Infrastructure maintenance.
    Rekommendationer för funktionell utformning av spårvägssystem2018Report (Other academic)
    Abstract [en]

    Trams are not a common feature in Sweden, which leads to some uncertainty about how they work in an urban environment alongside other transport segments. Trams can take many forms, from the classic trams that use the same lanes as cars, to express trams with their own fenced-off embankments, with higher speeds and possibly some form of signal safety system. The purpose of the project is to formulate recommendations for the design and function of new tram systems or changes to existing systems. The goal is to create clearer, more uniform conditions, allowing for good planning and construction outcomes from the beginning and avoiding subsequent costly changes.

    The results presented in this report are based on both national and international experiences of different tram systems. Different cities have different conditions, for example in terms of traffic, population and land, which means that the tram systems need to be planned and built in different ways. Technical solutions such as track designs, curve radiuses, signal systems etc. therefore differ from one tram system to the next. However, the design of the system must guarantee rigorous safety and good efficiency for passengers, staff, and persons and vehicles near or crossing the tracks. The tram system, like all traffic environments, must be clear, simple, predictable and easy to understand.

  • 28.
    Hjort, Mattias
    et al.
    Swedish National Road and Transport Research Institute, Traffic and road users, Vehicle technology and simulation.
    Eriksson, Olle
    Swedish National Road and Transport Research Institute, Infrastructure, Infrastructure maintenance.
    Test av is- och snögrepp för slitna vinterdäck: jämförelse av olika kategorier av vinterdäck2015Report (Other academic)
    Abstract [en]

    This study has measured ice and snow grip for used and new winter tyres, with the purpose to investigate how the road grip on ice and snow for different types of winter tyres degrade by age and degree of wear. In total, 77 tyres have been tested, of which 27 were completely new while 50 were used. The tyres have been tested on smooth ice and packed snow. The results show that with respect to ice grip, the studded tyres have a larger performance decrease when worn, than the unstudded winter tyres. However, the ice grip of worn studded tyres were still clearly superior to that of worn unstudded tyres. The used unstudded tyres of European type have in general a very poor ice grip, on level with two summer tyres that were also tested. On snow, the unstudded winter tyres of Nordic type in general have a slightly better grip than the studded tyres, while the unstudded tyres of European type performs worse. The snow grip for the used tyres is significantly worse than used tyres of the other two types. The study also shows that the premium tyres in general have better ice and snow performance compared to the budget tyres, for both new and used tyres.

  • 29.
    Hjort, Mattias
    et al.
    Swedish National Road and Transport Research Institute, Traffic and road users, Driving Simulation and Visualization.
    Eriksson, Olle
    Swedish National Road and Transport Research Institute, Infrastructure, Infrastructure maintenance.
    Väggrepp på våt asfalt för slitna och nya vinterdäck: jämförelse av olika kategorier av vinterdäck2016Report (Other academic)
    Abstract [sv]

    Denna studie har mätt väggrepp på våt, saltad asfaltväg vid temperaturer kring noll grader för slitna och nya vinterdäck i syfte att undersöka hur väggreppet för de tre olika förekommande typerna av vinterdäck i Sverige försämras med ålder och slitage. Även sommardäck har ingått i studien. Totalt har 84 däck testats, varav 31 helt nya däck och 53 begagnade. Resultaten visar att dubbdäck och nordiska odubbade vinterdäck presterar likvärdigt på detta underlag. Skillnaden mellan nya och slitna däck av dessa två typer är för de flesta undersökta prestandamått i praktiken obefintlig. De nya europeiska däcken presterar cirka 10–13 procent bättre än nya dubbdäck och nordiska odubbade vinterdäck på den våta asfalten vid det aktuella väderförhållandet. För de slitna däcken är prestandaövertaget för de europeiska däcken mindre, cirka 5–7 procent bättre än de andra två typerna av vinterdäck. Sommardäcken presterar i princip likvärdigt eller bättre än de europeiska vinterdäcken, både som nya och slitna.

  • 30.
    Hjort, Mattias
    et al.
    Swedish National Road and Transport Research Institute, Traffic and road users, Driver and vehicle.
    Eriksson, Olle
    Swedish National Road and Transport Research Institute, Infrastructure, Infrastructure maintenance.
    Bruzelius, Fredrik
    Swedish National Road and Transport Research Institute, Traffic and road users, Driving Simulation and Visualization.
    Comprehensive study of the performance of winter tires on ice, snow, and asphalt roads: The influence of tire type and wear2017In: Tire Science and Technology, ISSN 0090-8657, Vol. 45, no 3, p. 175-199Article in journal (Refereed)
    Abstract [en]

    This work presents a comprehensive study of the performance of winter tires on snow, ice, and asphalt. A set of 77 different winter tires were carefully selected for the study. Of these, 27 were new and 50 were worn from real traffic use. All three tire types for winter conditions (Nordic, European, and studded) were represented. All tires have been tested using a mobile tire-testing device for snow and asphalt and using a stationary tire-testing facility for ice. Both devices recorded the tire forces and motions, enabling a close to complete stationary characterization of the tires. In addition, 42 of the tires were tested on a passenger car, where brake performance was evaluated for the three different road conditions. This enables a comparative study of performance between tire types and wear for various winter road conditions. The results suggest that the recorded data represent real vehicle performance. Some conclusions from the measurements are that the effect of wear is consistent between the tire groups and that the performance degradation is most noticeable on studded tires on ice and on European tires on snow.

  • 31.
    Hjort, Mattias
    et al.
    Swedish National Road and Transport Research Institute, Traffic and road users, Vehicle technology and simulation.
    Kharrazi, Sogol
    Swedish National Road and Transport Research Institute, Traffic and road users, Vehicle technology and simulation.
    Eriksson, Olle
    Swedish National Road and Transport Research Institute, Infrastructure, Infrastructure maintenance.
    Hjälmdahl, Magnus
    Swedish National Road and Transport Research Institute, Traffic and road users, Human-vehicle-transport system interaction.
    Limit handling in a driving simulator2015Report (Other academic)
    Abstract [en]

    The purpose of this work has been to investigate how the driving simulator performs at the handling limit of a vehicle and improve its function so that the simulator feels and behaves more like a real vehicle when driving on the limit. Tests were performed with a Volvo S40, the same vehicle model for which the driving simulator vehicle dynamics model is based upon. Based on these test results the vehicle model that is currently used in VTI’s driving simulator III was modified in order to better simulate vehicle characteristics when driving on the handling limit. A method for validation of handling characteristics was developed. The method is based on the double lane change manoeuvre, and comprise a subjective and an objective part. The method was regarded to work well, and the validation tests showed that the modified vehicle model closer captures the understeer and time lag properties of a real Volvo S40 compared to the original model. Still, additional improvements need to be made before the model can be regarded as fully useful for on-the-limit driving situations.

  • 32.
    Hjort, Mattias
    et al.
    Swedish National Road and Transport Research Institute, Traffic and road users, Vehicle technology and simulation.
    Kharrazi, Sogol
    Swedish National Road and Transport Research Institute, Traffic and road users, Vehicle technology and simulation.
    Eriksson, Olle
    Swedish National Road and Transport Research Institute, Infrastructure, Infrastructure maintenance.
    Hjälmdahl, Magnus
    Swedish National Road and Transport Research Institute, Traffic and road users, Human-vehicle-transport system interaction.
    Andersson Hultgren, Jonas
    Swedish National Road and Transport Research Institute, Traffic and road users, Vehicle technology and simulation.
    Validating on-the-limit properties of a driving simulator2014In: New development in driving simulation design and experiments: Driving simulation conference Europe 2014 proceedings, 2014Conference paper (Refereed)
    Abstract [en]

    The paper describes a validation model for both subjective and objective comparison of on-the-limit properties of a driving simulator. VTI moving base driving simulator, SIM III, has been used with three different versions of VTI’s vehicle model, for validation toward field tests involving double lane change manoeuvres. Methods for handling evaluation suggested in the literature were adapted to our circumstances. The results are encouraging, although we found some limitations with respect to the objective evaluations that need to be addressed in future studies.

  • 33.
    Ihs, Anita
    et al.
    Swedish National Road and Transport Research Institute, Infrastructure, Infrastructure maintenance.
    Gustafsson, Mika
    Swedish National Road and Transport Research Institute, Infrastructure, Infrastructure maintenance.
    Eriksson, Olle
    Swedish National Road and Transport Research Institute, Infrastructure, Infrastructure maintenance.
    Wiklund, Mats
    Swedish National Road and Transport Research Institute, Infrastructure, Infrastructure maintenance.
    Sjögren, Leif
    Swedish National Road and Transport Research Institute, Infrastructure, Infrastructure maintenance.
    Road user effect models: the influence of rut depth on traffic safety2011Report (Other academic)
    Abstract [en]

    There are currently no satisfactory effect models for calculating the consequences and costs for road users of different maintenance strategies. The main problems identified by the Transport/Road Administrations in Finland, Sweden, Norway and Estonia, are the relationship between road surface condition and accidents, the effect of the most important state parameter rut depth on road user costs, as well as the role of road-user costs/effects of a road network that is mostly in good condition. These are problems that must be resolved in order to better justify budget allocation for road maintenance. VTI has therefore on commission by the Finnish Transport Administration and with funding from the other Transport/Road Administrations conducted a study to determine the influence of rut depth effects on the accident risk of road users. Separate analyses were made of data from Sweden, Finland and Norway, respectively. It was assumed that the accident risk also depends on other road condition variables, such as longitudinal unevenness, texture, cross slope, geographic location (country), vehicle flow, climate, weather, etc. A model approach was chosen that could address the impact of all these other road condition variables, and the possible interactions between them, on the accident risk. It was assumed that the relationship between accident risk and rut depth is not necessarily a linear function, why rut depth was divided into several categories. It was also agreed that separate equations should be derived for different speed and AADT (Annual average daily traffic) classes. Rut depth categories, as well as speed and AADT classes were chosen to match each country's strategies for maintenance. The overall conclusion of the analysis is that the data does not support any general rules for a maintenance scheme. There are no results to show that deeper ruts generally tend to increase the accident risk. Nor are there results that show that ruts have the same influence on the accident risk for different AADT classes at a given speed or vice versa. There seems to be at increased risk for ruts ? about 15 mm in the highest speed class, but the results differ between AADT classes and are not similar in adjacent speed classes, making the results difficult to understand and less useful to specify the rules for maintenance. For the Norwegian data this trend can not be seen in the highest speed class (> = 90 km/h), but then this speed class differs from the Swedish and Finnish highest speed classes (> = 110 km/h roads and motorways, respectively).

  • 34.
    Karlsson, Rune
    et al.
    Swedish National Road and Transport Research Institute, Society, environment and transport, Enviroment and traffic analysis.
    Hammarström, Ulf
    Swedish National Road and Transport Research Institute, Society, environment and transport, Enviroment and traffic analysis.
    Sörensen, Harry
    Swedish National Road and Transport Research Institute, Infrastructure, Measurement technology and engineering workshop.
    Eriksson, Olle
    Swedish National Road and Transport Research Institute, Infrastructure, Infrastructure maintenance.
    Road surface influence on rolling resistance: coastdown measurements for a car and an HGV2011Report (Other academic)
    Abstract [en]

    The influence of road surface properties, such as macrotexture and unevenness, on rolling resistance and fuel consumption is an important factor to consider when deter¬mining the coating of a road surface. Results of a VTI study show that the effect of unevenness is in general significantly smaller than that of macrotexture.

    The relative smallness of this influence makes measurements of it a challenging task. In literature a wide range of results can be found and there is still much confusion and uncertainty about how large the influence actually is. In this study, an attempt is made to obtain more reliable estimates of how macrotexture and unevenness affect rolling resistance. The primary method used here is the coastdown method. It has been applied to a private car and to a heavy goods vehicle (HGV). Concerning the effect of unevenness on rolling resistance, only the coastdown method provides any information. Results show that the effect of unevenness is in general significantly smaller than that of macrotexture.

    The coastdown method provides, besides information about rolling resistance, other useful data for the vehicle, such as air resistance coefficients, temperature coefficients and transmission resistance.

  • 35.
    Kircher, Katja
    et al.
    Swedish National Road and Transport Research Institute, Traffic and road users, Trafikanttillstånd, TIL.
    Eriksson, Olle
    Swedish National Road and Transport Research Institute, Infrastructure, Infrastructure maintenance.
    Forsman, Åsa
    Swedish National Road and Transport Research Institute, Traffic and road users, Traffic safety, society and road-user.
    Vadeby, Anna
    Swedish National Road and Transport Research Institute, Traffic and road users, Traffic safety, society and road-user.
    Ahlström, Christer
    Swedish National Road and Transport Research Institute, Traffic and road users, Trafikanttillstånd, TIL.
    Design and analysis of semi-controlled studies2016In: Transportation Research Part F: Traffic Psychology and Behaviour, ISSN 1369-8478, E-ISSN 1873-5517Article in journal (Refereed)
    Abstract [en]

    Semi-controlled studies provide a hybrid approach in between controlled experiments and naturalistic driving studies. As in controlled experiments, the researcher can assign participants to groups, select the route and define the tasks, but the participants are given more freedom when it comes to if, when, where and how to perform the tasks. Increased flexibility makes it possible to investigate how drivers use tactical behaviour to accommodate task execution. The disadvantage is decreased control and more complicated analyses.

    The main objective of this paper is to discuss how to analyse data obtained in semi-controlled studies.The analysis of data from a semi-controlled study include three types of variables:

    • variables that describe the experimental design
    • variables that describe the tactical choices of the participants
    • operational variables such as speed, lateral position or glance behaviour

    To analyse the three types of variables a two-step procedure is suggested. First, the tactical indicators are analysed with regard to the experimental design. Second, the operational indicators are analysed and the tactical indicators are used to divide participants into sub-populations.

    The semi-controlled design does not need any new statistical procedures to be developed. It is more important that the analysis conditions on the initial properties and not on structures that happen to occur during the experiment, like where the participant chose to do a certain task.We recommend to use the semi-controlled study method when investigating questions involving adaptive and compensatory behaviour on the tactical level. It is especially useful if causal relationships are of interest, if the data collection should be accelerated in comparison to naturalistic studies, and if certain geographical locations definitely should be included.

  • 36.
    Lidestam, Björn
    et al.
    Swedish National Road and Transport Research Institute, Traffic and road users, Driver and vehicle.
    Eriksson, Lars
    Karlstads Universitet.
    Eriksson, Olle
    Swedish National Road and Transport Research Institute, Infrastructure, Infrastructure maintenance.
    Speed perception affected by field of view: Energy-based versus rhythm-based processing2019In: Transportation Research Part F: Traffic Psychology and Behaviour, ISSN 1369-8478, E-ISSN 1873-5517, Vol. 65, p. 227-241Article in journal (Refereed)
    Abstract [en]

    Two experiments were carried out to test speed perception dependency on field of view (FoV), virtual road markings (VRMs), and presentation orders. The primary purpose was to examine how the extent of the optic flow (foremost peripherally–vertically) informs the driver about egospeed. A second purpose was to examine different task demands and stimulus characteristics supporting rhythm-based versus energy-based processing. A third purpose was to examine speed changes indicative of changes in motion sensitivity. Participants were tested in a car simulator, with FoV resembling low front-door windows, and with VRMs inside the car. Three main results were found. Larger FoV, both horizontally and peripherally–vertically, significantly reduced participants' speed, as did VRMs. Delineator posts and road center lines were used for participants' rhythm-based processing, when the task was to drive at target speeds. Rich motion-flow cues presented initially resulted in lower egospeed in subsequent conditions with relatively less motion-flow cues. The practical implication is that non-iconic, naturalistic and intuitive interfaces can effectively instill spontaneous speed adaptation in drivers.

  • 37.
    Lundberg, Thomas
    et al.
    Swedish National Road and Transport Research Institute, Infrastructure, Infrastructure maintenance.
    Andrén, Peter
    Swedish National Road and Transport Research Institute, Infrastructure, Infrastructure maintenance.
    Wahlman, Thomas
    Ramböll.
    Eriksson, Olle
    Swedish National Road and Transport Research Institute, Infrastructure, Infrastructure maintenance.
    Sjögren, Leif
    Swedish National Road and Transport Research Institute, Infrastructure, Infrastructure maintenance.
    Ekdahl, Peter
    Ramböll.
    New technology for road surface measurement: transverse profile and rut depth2018Report (Other academic)
    Abstract [en]

    The condition of the national coated road network is measured annually in Sweden and Finland. The measuring technology has been unchanged over a long period of time, which has its benefits. As the measurements are performed using the same technology, trends and measurement series are retained without any disruption. In addition, the technology currently used is reliable and can be procured at a price level that has fallen rather than risen over the years. The principal area of use for condition measurement is to provide maintenance work with an objective basis for the planning of surfacing, but when it is found that current objective condition data can only explain between 40 and 75 percent (depending on class of traffic) of the action actually taken on the road network, consideration must be given to whether new condition data need to be added. The information that is lacking is thought to be information on surface damage and cracks. This requires new measuring technology.

    If new technology will be adopted, for the collection of condition data, the dependability of the basic measured quantities must be ensured before new options and measured quantities are examined. This study is therefore focused only on transverse-profile measurement and measures of unevenness in the transverse direction (rut depth and ridge height).

    The study has examined two of the leading new technologies that operate with scanning lasers, LCMS from Pavemetrics and PPF from Fraunhofer. The outcome of the study shows that the technology is good, and that accuracy and repeatability are comparable to the present-day point-laser systems. It is also deemed possible to retain criteria and requirements for the procurement of measurement services when the new technology is used.

  • 38.
    Lundberg, Thomas
    et al.
    Swedish National Road and Transport Research Institute, Infrastructure, Infrastructure maintenance.
    Andrén, Peter
    Swedish National Road and Transport Research Institute, Infrastructure, Infrastructure maintenance.
    Wahlman, Thomas
    Ramböll.
    Eriksson, Olle
    Swedish National Road and Transport Research Institute, Infrastructure, Infrastructure maintenance.
    Sjögren, Leif
    Swedish National Road and Transport Research Institute, Infrastructure, Infrastructure maintenance.
    Ekdahl, Peter
    Ramböll.
    Ny teknik för vägytemätning: tvärprofil och spårdjup2018Report (Other academic)
    Abstract [en]

    The condition of the national coated road network is measured annually in Sweden and Finland. The measuring technology has been unchanged over a long period of time, which has its benefits. As the measurements are performed using the same technology, trends and measurement series are retained without any disruption. In addition, the technology currently used is reliable and can be procured at a price level that has fallen rather than risen over the years. The principal area of use for condition measurement is to provide maintenance work with an objective basis for the planning of surfacing, but when it is found that current objective condition data can only explain between 40 and 75 percent (depending on class of traffic) of the action actually taken on the road network, consideration must be given to whether new condition data need to be added. The information that is lacking is thought to be information on surface damage and cracks. This requires new measuring technology.

    If new technology will be adopted, for the collection of condition data, the dependability of the basic measured quantities must be ensured before new options and measured quantities are examined. This study is therefore focused only on transverse-profile measurement and measures of unevenness in the transverse direction (rut depth and ridge height).

    The study has examined two of the leading new technologies that operate with scanning lasers, LCMS from Pavemetrics and PPF from Fraunhofer. The outcome of the study shows that the technology is good, and that accuracy and repeatability are comparable to the present-day point-laser systems. It is also deemed possible to retain criteria and requirements for the procurement of measurement services when the new technology is used

  • 39.
    Lundberg, Thomas
    et al.
    Swedish National Road and Transport Research Institute, Infrastructure, Infrastructure maintenance.
    Eriksson, Olle
    Swedish National Road and Transport Research Institute, Infrastructure, Infrastructure maintenance.
    Glantz, Christian
    Ramböll.
    Kontroll och uppföljning av entreprenader - del 2, tillståndsutveckling, mätfel och risker: Vägytemätning med mätbil2019Report (Other academic)
    Abstract [en]

    The Swedish Transport Administration aims to increase the number of design build contracts. To get a functioning control device around the contracts, well defined requirements must be set for the warranty period of the road. In this survey we focus on functional requirements that are set for design build contracts and which can be checked by means of a road surface testing.

    In the report, measurement errors are highlighted in object measurement (control measurement). The measurement error is divided into different components: random, systematic and variation between different suppliers. Risk assessment is also discussed where calculations of the risk of error assessment of a section are presented.

    Finally, it is presented how the results of the condition (evenness) affect the future development of the road and what initial values we can expect from a design build contract and maintenance work. We see that a road of good evenness, longitudinally and transversally, gives a lower development rate during the life of the road.

  • 40.
    Nilsson, Peter
    et al.
    Chalmers Tekniska Högskola.
    Laine, Leo
    Chalmers Tekniska Högskola.
    Sandin, Jesper
    Swedish National Road and Transport Research Institute, Traffic and road users, Driver and vehicle.
    Jacobson, Bengt
    Chalmers Tekniska Högskola.
    Eriksson, Olle
    Swedish National Road and Transport Research Institute, Infrastructure, Infrastructure maintenance.
    On actions of long combination vehicle drivers prior to lane changes in dense highway traffic: A driving simulator study2018In: Transportation Research Part F: Traffic Psychology and Behaviour, ISSN 1369-8478, E-ISSN 1873-5517, Vol. 55, p. 25-37Article in journal (Refereed)
    Abstract [en]

    In this paper we address drivers’ actions prior to mandatory lane changes of long combination vehicles in dense highway traffic. The studied driver actions were: turn indicator activation, speed reduction and lateral intrusion. We categorised and compared the drivers’ actions with respect to the surrounding traffic cooperation and the level of urgency. Urgency here was based on the remaining distance to a targeted exit ramp. The results show that when the subject vehicle is close to the exit ramp, drivers used speed reduction significantly more than when the vehicle is further away. No significant difference was found for the use of lateral intrusion considering the distance to the exit ramp. As regards traffic cooperation, significant differences were found for both speed reduction and lateral intrusion. The drivers’ speed reduction and lateral intrusion were significantly greater when the surrounding traffic cooperation was low.

  • 41.
    Thorslund, Birgitta
    et al.
    Swedish National Road and Transport Research Institute, Traffic and road users, Human-vehicle-transport system interaction.
    Ahlström, Christer
    Swedish National Road and Transport Research Institute, Traffic and road users, Human-vehicle-transport system interaction.
    Peters, Björn
    Swedish National Road and Transport Research Institute, Traffic and road users, Human-vehicle-transport system interaction.
    Eriksson, Olle
    Swedish National Road and Transport Research Institute, Infrastructure, Infrastructure maintenance.
    Lidestam, Björn
    Linnaeus Centre Head.
    Lyxell, Björn
    Linnaeus Centre Head.
    Cognitive workload and visual behavior in elderly drivers with hearing loss2014In: European Transport Research Review, ISSN 1867-0717, E-ISSN 1866-8887, Vol. 6, no 4, p. 377-385Article in journal (Refereed)
    Abstract [en]

    The purpose was to examine eye tracking data and compare visual behavior in individuals with normal hearing (NH) and with moderate hearing loss (HL) during two types of driving conditions: normal driving and driving while performing a secondary task.

    Methods

    24 participants with HL and 24 with NH were exposed to normal driving and to driving with a secondary task (observation and recall of 4 visually displayed letters). Eye movement behavior was assessed during normal driving by the following performance indicators: number of glances away from the road; mean duration of glances away from the road; maximum duration of glances away from the road; and percentage of time looking at the road. During driving with the secondary task, eye movement data were assessed in terms of number of glances to the secondary task display, mean duration of glances to the secondary task display, and maximum duration of glances to the secondary task display. The secondary task performance was assessed as well, counting the number of correct letters, the number of skipped letters, and the number of correct letters ignoring order.

    Results

    While driving with the secondary task, drivers with HL looked twice as often in the rear-view mirror than during normal driving and twice as often as drivers with NH regardless of condition. During secondary task, the HL group looked away from the road more frequently but for shorter durations than the NH group. Drivers with HL had fewer correct letters and more skipped letters than drivers with NH.

  • 42.
    Waldemarson, Andreas
    et al.
    Swedish National Road and Transport Research Institute, Infrastructure, Pavement Technology.
    Eriksson, Olle
    Swedish National Road and Transport Research Institute, Infrastructure, Infrastructure maintenance.
    Ahmed, Abubeker W
    Swedish National Road and Transport Research Institute, Infrastructure, Pavement Technology.
    Validering av ålderssamband för asfaltbeläggningar2018Report (Other academic)
    Abstract [en]

    Asphalt pavements age due to climatic impact and oxidation. Aging affects the physical and chemical properties of the adhesive and results in an increase of stiffness and reduced sensitivity to deformation. As a result, asphalt pavement usually become harder, stiffer and brittle thus more sensitive to cracking over time.

    The Swedish Transport Administration specification document contains calculation formulas (aging models) which take the changes in mechanical properties over time into account. These formulas were derived based on asphalt mixtures with conventional binders. To investigate whether these formulas are valid for asphalt mixtures with modified bitumen, a study was conducted using laboratory manufactured samples of mix type ABb 16 with three different binders from Nynas, namely, 70/100, Nypol 67 and Nypol 73.

    The samples were drilled from compacted asphalt slabs and cyclic compression creep and indirect tensile stiffness modules tests were carried out at a predefined time schedule. The drilled samples werestored at room temperature whereas the slabs were stored in a cold storehouse. Before testing, the densities of the constituent material were determined and theoretical air void content in each sample were calculated.

    The main purpose of the study was to validate the existing aging models for cyclic compression creep test and stiffness modulus tests using the collected test data. The collected data from the tests were analyzed using non-linear regression. The results indicated that time coefficient (exponent) for both test methods have lower absolute value in this study than stated in the specifications. The coefficients are different for penetration and polymer modified bitumen.

    There may be several reasons why the models in this study differ from the results of the previous investigations. The earlier relationships were derived based on analysis of samples aged in the field while the models in this study are based on analysis of samples aging in a more controlled laboratory environment. Another possible reason for the higher time coefficients (exponents) from the previousinvestigations could be that manufacturing temperatures for asphalt mixtures were generally significantly higher at that time.

    To establish a broader basis to assesses the impact of aging on asphalt mixture mechanical properties, it is recommended to investigate several types of polymer bitumen. A more frequent field follow-up ofnewly paved pavement sections should be carried out.

  • 43.
    Wiklund, Mats
    et al.
    Transportanalys.
    Carlsson, Arne
    Swedish National Road and Transport Research Institute, Society, environment and transport, Traffic analysis and logistics.
    Eriksson, Olle
    Swedish National Road and Transport Research Institute, Infrastructure, Infrastructure maintenance.
    Olstam, Johan
    Swedish National Road and Transport Research Institute, Society, environment and transport, Traffic analysis and logistics. Linköpings Universitet.
    Tapani, Andreas
    Swedish National Road and Transport Research Institute, Society, environment and transport, Traffic analysis and logistics. Linköpings Universitet.
    Effects of desired speeds for queuing and delay on single-lane road segments2015In: Transportmetrica A: Transport Science, ISSN 2324-9935, Vol. 11, no 8, p. 716-728Article in journal (Refereed)
    Abstract [en]

    To improve road safety on parts of the road network carrying low traffic volumes, road designs are proposed including single-lane road segments and periodic overtaking lanes. These roads have been proven to contribute to substantial benefits in terms of road safety. However, overtaking of slower vehicles is only possible on segments including an overtaking lane and not on the single-lane road segments. Driver and vehicle heterogeneity resulting in differences in desired speeds are consequently decisive for the traffic performance. Sufficient quality of service is relying on an appropriate design and distribution of single-lane segments and overtaking lanes. In this paper, we study the effect of the desired speed distribution on traffic performance on single-lane road segments. Expressions are derived for the travel time, delay and percent time spent following. The derived expressions link the desired speed distribution, the single-lane segment length and the traffic flow to the resulting traffic performance. The results are verified through comparison with measures based on microscopic traffic simulation. The conclusion is that there is a good agreement between derived measures and simulation results. The derived measures should therefore not only be of theoretical interest, but also of practical use to estimate traffic performance on single-lane road segments.

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