| 1. |
- Andersson, Jan, et al.
(författare)
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Traffic safety effects when overtaking 30 meter trucks
- 2012
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Ingår i: Advances in Human Factors and Ergonomics 2012- 14 Volume Set. - : Taylor & Francis. - 146655262X - 9781466552623
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Konferensbidrag (refereegranskat)abstract
- The purpose of this paper is to investigate if the introduction of extra-long and heavy trucks has an effect on traffic safety on Swedish roads, especially in relation to overtaking maneuvers. Traffic safety effects will be measured in terms of road user behavior concerning accelerations and time slots. First, focus group interviews with heavy truck drivers. Truck drivers that do not drive extra-long trucks believe that the introduction of extra-long trucks will create a number of traffic safety problems especially in terms of conflicts with ordinary road users. The drivers of extra-long trucks do not experience the problems that ordinary truck drivers predict. The problems they experience can be taken care of with more planning (thinking ahead). They also believe that the traffic sign on the back of the extra-long vehicle has a positive effect. The truck company, working environment and truck equipment are other important aspects mentioned by the drivers of the extra-long vehicles.The simulator study investigates overtaking situations on a 2+1-lane highway, with extra-long trucks (30.4 m) and ordinary trucks (18.75 m). The results reveal that the distance from the rear/front of the truck to the point where only one lane exists affects car drivers’ decision to overtake, independently of truck length. If the truck is in the relatively same position, the timeslot for a safe overtaking maneuver before next one-lane section was reduced significantly for extra-long trucks compared to ordinary trucks. The conclusion is that there exist small tendencies which point in the direction of enhanced traffic safety problems with the introduction of extra-long trucks. The results should, however, be interpreted with caution as the number of data points was few and collected in specific situations and in specific conditions. It was neither considered how the introduction of longer and heavier trucks, given a constant amount of goods, reduces the number of heavy trucks on the road network.
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| 2. |
- Andersson, Jan, et al.
(författare)
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Trafiksäkerhetspåverkan vid omkörning av 30-metersfordon
- 2011
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Trafikverket överväger att tillåta längre och tyngre fordon på vägarna förutsatt att de inte påverkar trafiksäkerheten negativt. Syftet med studien var att undersöka säkerhetseffekten av fordonslängd, speciellt med avseende på olycksrisken vid omkörningar. Intervjuade förare av en 30-meters timmerbil hade inte upplevt de farhågor som förare av normallånga lastbilar uttryckt i samband med trånga rondeller och korsningar, men de nämner betydelsen av stödjande åkeri, arbetsmiljö och fordonsutrustning. En simulatorstudie studerade bilförares omkörningar av ett 30- och ett 18,75-metersfordon på en 2+1-väg i situationen då två körfält går ihop till ett. Tidluckan till ett återstående körfält var i genomsnitt 0,2 s (sign.) kortare efter omkörningar av 30-metersfordonet i situationer då bakänden var i samma relativa position som för 18,75-metersfordonet vid början av omkörningen. En fältstudie analyserade videoinspelade omkörningar av en 30- och en 24-meters timmerbil på en 2+1-väg och en tvåfältig väg. Ingen signifikant skillnad i tidluckor kunde påvisas mellan omkörningar av de två fordonen för någon av vägtyperna. Det senare resultatet ska dock tolkas med försiktighet på grund av ojämnt distribuerad data som insamlats under specifika förhållanden. Slutsatserna är att det finns en liten tendens till negativ säkerhetseffekt vid omkörningar av längre fordon, och att fler fältstudier är nödvändiga.
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| 3. |
- Bolling, Anne, et al.
(författare)
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SHAKE - an approach for realistic simulation of rough roads in a moving base driving simulator
- 2010
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Ingår i: Trends in driving simulation design and experiments. - Arcueil : Institut national de recherche sur les transports et leur securite, INRETS. - 9782857826859 ; , s. 135-143
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Konferensbidrag (refereegranskat)abstract
- With today’s advanced measurement equipment for measuring roads, it is possible to measure road geometry at high precision within a large span of wavelengths. Detailed information about the roads longitudinal and lateral profile, including macro texture, would in theory be sufficient for a realistic reproduction of road induced vibration and noise in a driving simulator. Especially, it would be possible to create a direct connection between the visual information of the road condition and the ride experience, which would increase the level of realism in the simulation. VTI has during three years performed an internal project called SHAKE with the aim to develop and implement models in VTI driving simulator III that use measured road data for generating realistic vibrations and audible road noise connected to the visual impression presented on the projection screen. This has indeed resulted in an more realistic driving experience, and a validation study with test persons driving both in the simulator and in the field has been undertaken. The OpenDRIVE standard is used as a framework for describing the road properties (e.g. visual, vibrations and noise). For this purpose some augumentations to the OpenDRIVE standard had to be made. This paper describes the technical implementations in the driving simulator, along with results from test drives on the implemented road sections
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| 4. |
- Bruzelius, Fredrik, 1974-, et al.
(författare)
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Validation of a basic combined slip tyre model for use in friction estimation applications
- 2014
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Ingår i: Proceedings of the Institution of mechanical engineers. Part D, journal of automobile engineering. - : SAGE Publications. - 0954-4070 .- 2041-2991. ; 228:13, s. 1622-1629
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Tidskriftsartikel (refereegranskat)abstract
- Tyre modelling is an important part of understanding and estimating the tyre-road friction. In this paper a basic steady-state tyre model for the combined-slip case is derived. The model is intended to be used in friction estimations applications, where the model complexity is of high priority. The model, described using only two parameters, is validated with measured data from various conditions and tyre types using mobile measurement equipment. The performance from the measurements suggests that only two parameters are sufficient for the combined-slip case.
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| 5. |
- Hjort, Mattias, 1972-, et al.
(författare)
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Bus accidents in wintertime
- 2010
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Ingår i: PIARC 2010 XIII International Winter Road Congress, February 8-11, 2010, Quebec, Canada.
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Konferensbidrag (refereegranskat)abstract
- Buses in Sweden have a low accident risk. However, statistics from 1996 - 2002 indicate that the number of bus accidents in Sweden with personal injuries have been increasing by 4% yearly. Buses also have a higher percentage of accidents that occur on ice/snow covered roads than other vehicles. In Sweden passenger cars must be equipped with winter tyres during the winter period. There is no such regulation for heavy vehicles, and many buses are using summer tyres all around the year. The present project had the purpose of looking at the bus-winter problem in more detail, with the main focus on tyres. Four different studies were carried out: tyre tests, focus group discussions, driving simulator tests and an accident study. Here is given a short summary concerning methods and conclusions of each sub project.Tyre tests on smooth ice did not show any significant difference between summer tyres and non-studded winter tyres, while studded tyres exhibits a better ice grip than non-studded tyres. Nor did driving simulator tests with driving on ice covered road under the influence of heavy wind from the side show a difference between summer tyres and non-studded winter tyres. Also in these tests studded tyres were superior to non-studded. Accident statistics indicate that buses with summer tyres on the steering axle and winter tyres on the drive axle have the lowest estimated accident risk, which is in accordance with the results in a previous study. The results are however not statistically significant due the low number of accidents. Three focus groups were carried out and the importance of the tyres for traffic safety during winter was discussed. It is however hard from the gathered discussion material to estimate just how important the tyres really are. The results do not warrant a winter tyre regulation for heavy vehicles, and a restriction of the use of studded tyres for buses would probably have negative consequences on traffic safety.
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| 6. |
- Hjort, Mattias, 1972-, et al.
(författare)
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Handling of buses on slippery roads during the influence of side wind : A study of the effects of different tyres
- 2010
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Ingår i: Accident Analysis and Prevention. - : Elsevier. - 0001-4575 .- 1879-2057. ; 42:3, s. 972-977
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Tidskriftsartikel (refereegranskat)abstract
- Accident statistics assembled by the Swedish National Road and Transport Research Institute (VTI) have shown that buses are overrepresented when it comes to accidents on icy and snowy roads. For a better understanding of the problem, the performance of modern summer and winter tyres on winter road conditions had to be assessed. The objective of this work has been to go beyond standard road grip studies, and instead investigate how the driver's possibility to deal with one challenging situation depends on the tyres and tyre configuration. This paper describes a novel methodology where measurements with different tyres on ice in VTI's tyre test facility, enabled a simulator study for evaluating the impact of different tyre characteristics when driving in conditions with strong side wind on a slippery road.The main results of the study are: to deal with strong side wind, good front wheel grip is most important, and while non-studded winter tyres provided little or no improvement over summer tyres, studded winter tyres significantly reduced the risk to run off the road. Furthermore, it is very difficult for the drivers to judge, beforehand, whether a vehicle with a particular tyre configuration will perform good or bad.
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| 7. |
- Hjort, Mattias, 1972-
(författare)
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Measuring tyre performance in ESC intervention situations
- 2013
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Ingår i: Proceedings of the international conference Science meets Tires.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Fatal accidents during winter time in Sweden are to a large extent due to vehicle spinning. Therefore, it is crucial to analyse and compare vehicle/tyre performance on slippery roads with respect to oversteering. We have performed experimental tests to compare the stability performance of various winter tyres on ice, with and without an electronic stability system (ESC). Two different test methods are presented, one closed loop and one open loop test. Results from both studies are discussed, and it is clear that different tyres may have a large impact on vehicle stability even with ESC activated
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| 8. |
- Hjort, Mattias, 1972-, et al.
(författare)
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The importance of tyre grip for the ESC function on icy roads
- 2011
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Konferensbidrag (refereegranskat)abstract
- In this study we have investigated how tyres with different road grip affect the stability of passenger cars equipped with Electronic Stability Control (ESC) systems during winter road conditions. A field test with a double lane change manoeuvre on ice was performed using 6 test drivers, 4 different passenger cars and 4 different studless winter tyres. The specific tyres were chosen to represent a large difference of road grip on ice and snow. The results show that there was a large performance difference between the best and worst tyres with ESC off, and that activating ESC only resulted in a minor increase of performance.
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| 9. |
- Hjort, Mattias, 1972-
(författare)
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The Snow Grip of Heavy Vehicle Drive Axle Winter Tyres
- 2012
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Ingår i: Proceeding at the International Symposium on Heavy Vehicle Transport Technology.
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Konferensbidrag (refereegranskat)abstract
- Every winter in Sweden, winter roadways pose problems for heavy vehicles. Steep gradients can be difficult to pass when it is slippery, which has implications also for other traffic when congestion occurs. To reduce the problems it has been discussed whether to impose a legal requirement for winter tyres on drive axle for trucks. This papers presents test results of the available snow grip from test track measurements comparing different drive axle tyres. A summer tyre, together with three winter tyres, of which one was retreaded, were selected for tests. The results of the traction tests show that there can be a big difference in grip between winter and summer tyres on packed snow. The difference between the tyres, however, is strongly dependent on the nature of the snow surface, so it is difficult to give general values. Theoretical calculations show that a vehicle’s rolling resistance can have a major impact on a vehicles climbing ability. With a high rolling resistance, which may be the result of loose snow on the road, the difference between good and bad grip on the drive tyres becomes even more significant.
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| 10. |
- Hjort, Mattias, 1972-, et al.
(författare)
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Towards a method for determining maximum oversteer in slippery conditions
- 2013
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Ingår i: Proceedings of 23rd International Symposium on Dynamics of Vehicles on Roads and Tracks (IAVSD'13). Qingdao, China, 19-23 August, 2013..
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Konferensbidrag (refereegranskat)abstract
- Fatal accidents during winter time in Sweden are to a large extent due to vehicle spinning. Therefore, it is crucial to analyse and compare vehicle/tyre performance on slippery roads with respect to oversteering. In this study, a new test method for evaluation of vehicle's stability during oversteering on icy roadways is developed and evaluated using a series of tests with a rear wheel driven car, equipped with ESC, and six different tyres on ice test tracks in northern Sweden. The test method consists of an asymmetric sine-with-dwell manoeuvre and a measure forquantifying the level of oversteering based on the relation between yaw rate and lateral acceleration. The test results show good robustness of the method, and that it can successfully rate the various tyres performance on polished ice. However, to have a fair comparison, the proposed method should be modified to take into account the steering ability of the tyres and the consequent difference in the manoeuvre severity when tested with tyres with different side grip.
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