| 11. |
|
|
| 12. |
- Borsos, Attila, et al.
(författare)
-
Are collision and crossing course surrogate safety indicators transferable? A probability based approach using extreme value theory
- 2020
-
Ingår i: Accident Analysis and Prevention. - : Elsevier BV. - 0001-4575. ; 143
-
Tidskriftsartikel (refereegranskat)abstract
- In order to overcome the shortcomings of crash data a number of surrogate measures of safety have been developed and proposed by various researchers. One of the most widely used temporal indicators is time-to-collision (TTC) which requires the road users to be on a collision course. Road users that are strictly speaking not on a collision course actually might behave and take evasive actions as if they were, thus indicating that such near-miss situations might also be relevant for safety analysis. Taking that into account, a more flexible indicator T2, which does not require the two vehicles to be on a collision course, describes the expected time for the second road user to arrive at the conflict point. Recently extreme value theory (EVT) offering two approaches, block maxima (BM) and Peak over Threshold (POT), has been applied in combination with surrogate indicators to estimate crash probabilities. Most of this research has focused on testing BM and POT as well as validating various surrogate safety indicators by comparing model estimates to actual crash frequencies. The comparison of collision course indicators with indicators including crossing course interactions and their performance using EVT has not been investigated yet. In this study we are seeking answers to under what conditions these indicators perform better and whether they are transferable. Using data gathered at a signalized intersection focusing on left-turning and straight moving vehicle interactions our analysis concluded that the two indicators are transferable with stricter threshold values for T2 and that POT gives more reasonable results.
|
|
| 13. |
- Bulla-Cruz, Lenin Alexander, et al.
(författare)
-
Event-based road safety assessment : A novel approach towards risk microsimulation in roundabouts
- 2020
-
Ingår i: Measurement: Journal of the International Measurement Confederation. - : Elsevier BV. - 0263-2241. ; 165
-
Tidskriftsartikel (refereegranskat)abstract
- Conventional road accident risk is measured by the undesirable events/exposure ratio. Common exposure indicators are activity-based, so event-based exposure is needed to achieve event-based safety assessment. Furthermore, road safety simulation is a growing research field. The influence of some software parameters is still unknown. Besides, the use of simulation for exposure assessment is incipient. This paper aims to validate a preventive event-based risk indicator: traffic conflicts/encounters, extending to risk microsimulation by a novel procedure to identify encounters in VISSIM. We evaluated the safety of a roundabout by three independent methods: [i] Swedish Traffic Conflict Technique using T-Analyst tool, [ii] VISSIM/SSAM conflict analysis, and, [iii] exposure mapping using encounters. Findings show that, once calibrated the safety distance factor of VISSIM conflict areas at 0.5, we got a similar number of observed and simulated conflicts, similar severities and similar number of encounters, resulting in similar observed and simulated risk outcomes.
|
|
| 14. |
- Chen, Zhankun, et al.
(författare)
-
Stochastic method based on copulas for predicting severe road traffic interactions
- 2024
-
Ingår i: Analytic Methods in Accident Research. - 2213-6657. ; 44
-
Tidskriftsartikel (refereegranskat)abstract
- A major difficulty in assessing road traffic safety is the scarcity of historical accident data. xxThis is a common problem in contexts where a certain level of safety has been reached or where exposure is low, such as mixed traffic conditions with different levels of transport automation. Recent studies have demonstrated how severe interactions between road users and/or road users and infrastructure can be a direct measure of safety. However, limiting the investigation to only the most extreme events may lead to inconclusive results considering the lack of prediction robustness and the possible selection bias. In this context, extreme value theory (EVT) is commonly used to extrapolate crashes from road traffic interactions, even combining several indicators. The present work extends the EVT paradigm by proposing a method based on copula functions and EVT, which enables a more specific and continuous evaluation of interaction severity. Compared with pure EVT, this new approach extends the boundary to interactions of all severities while implicitly assuming that the relationship between safety-relevant events and road casualties is stochastic. This EVT-copula approach was also compared with bivariate peaks over threshold (BPOT). It was found that the two approaches yield similar prediction results for crash probabilities. Furthermore, the proposed approach applies to events not properly defined in BPOT and provides more accurate predictions for severe (and less severe) interactions compared with BPOT, when benchmarked against observations.
|
|
| 15. |
- De Ceunynck, Tim, et al.
(författare)
-
Interact or counteract? Behavioural observation of interactions between vulnerable road users and autonomous shuttles in Oslo, Norway
- 2022
-
Ingår i: Traffic Safety Research. - : Dept. of Technology & Society, Faculty of Engineering, LTH, Lund University. - 2004-3082. ; 2
-
Tidskriftsartikel (refereegranskat)abstract
- The current paper presents the results of behavioural observations in a field experiment with automated shuttles in Oslo, Norway. Video observations were conducted at five fixed locations along a challenging 1.2 km automated shuttle line with varying traffic conditions. Observed interactions between vulnerable road users and automated shuttles were coded using a predefined codebook, which allowed a structured quantitative analysis. The paper identified several potentially risky types of situations in which the automated shuttles did not always behave according to the traffic rules. Generally, the automated shuttles failed to give way to pedestrians at pedestrian crossings in 26%–50% of the interactions. Right-turning shuttles failed to yield to cyclists going straight in 38% of the interactions at observation Site 1 (the only location where the automated shuttle takes a right turn). In majority of same direction interactions between cyclists and automated shuttles, the interactions resulted in the cyclist overtaking the automated shuttle, usually on the left-hand side. Generally, the paper found little evidence of road users trying to bully or otherwise take advantage of the defensive driving style of the automated shuttles and identified only a limited number of interactions in which a vulnerable road user behaved ignorant or aggressive towards the automated shuttles. In addition, the paper found very little indication of temporal effects that suggest changes in the interaction patterns over time.
|
|
| 16. |
- De Ceunynck, Tim, et al.
(författare)
-
Sharing is (s)caring? Interactions between buses and bicyclists on bus lanes shared with bicyclists
- 2017
-
Ingår i: Transportation Research Part F: Traffic Psychology and Behaviour. - : Elsevier BV. - 1369-8478. ; 46, s. 301-315
-
Tidskriftsartikel (refereegranskat)abstract
- This paper presents the results of an observation study of interactions between bicyclists and buses on shared bus lanes. The aim of the paper is to analyse bicyclists' safety on bus lanes shared with bicyclists. Straight sections of two bus lanes shared with bicyclists in Belgium are observed. All interactions between bicyclists and buses over two full weeks are recorded and analysed. Additionally, the lateral position and riding speed of bicyclists that are in interaction with buses are compared with the behaviour of bicyclists that are not in interaction with buses. One of the observed bus lanes is in line with road design guidelines in a number of countries that state that a sufficiently narrow bus lane (<3.5. m) is hypothesised to be safer than a somewhat wider bus lane; the other observed bus lane is deemed too wide according to these guidelines and is hypothesised to lead to close overtaking manoeuvres.The results show that close interactions between bicyclists and buses are relatively frequent on both types of analysed bus lanes. Close overtaking manoeuvres (a bus overtakes a bicyclist with a lateral distance less than 1. m) as well as close bicycle-following situations (a bus drives behind a bicyclist with a time gap less than 2. s) are quite common on both analysed bus lanes. The analyses could not confirm the hypothesis that a sufficiently narrow bus lane is safer than a wider bus lane. On the contrary, close interactions seem even slightly more common on the narrower bus lane. Slightly more close overtaking manoeuvres take place on the narrower bus lane, but the difference is not statistically significant. Additionally, more bicycle-following situations take place on the narrower bus lane because overtaking is more difficult. The results show that buses often maintain a close time gap in these situations. The overtaking speed of the buses is, however, significantly higher on the wider bus lane compared to the narrower one.Moreover, the presence of a bus has an influence on the behaviour of bicyclists. Bicyclists who get overtaken by a bus ride more closely to the edge of the road than bicyclists who are not in interaction with a bus. While the road design guidelines assume that bicyclists take up a width of one meter from the edge on bus lanes shared with bicyclists, the observations show that bicyclists take up much less space while being overtaken. The presence of a bus does not have a significant influence on the standard deviation of the lateral position of the bicyclist. On the narrower bus lane, some findings suggest that bicyclists who are involved in an interaction with a bus ride faster than bicyclists who are not involved in an interaction with a bus.
|
|
| 17. |
- Hammad, Samir, et al.
(författare)
-
Utvärdering av hastighetssäkrade åtgärder på landsbygdsvägar
- 2023
-
Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Detta arbete har utvärderat hastighetssäkrade åtgärders effekt på landsbygdsvägar genom att filma totalt 34 olika sådana åtgärder i södra Sverige och studera hastigheten av frigående bilar och tunga fordon när de passerar de olika åtgärderna.Varje plats har filmats med drönare och alla fordon har automatiskt spårats m.h.a. videoanalys. Därefter har frigående fordon identifierats och deras hastighet analyserats.Analysen har gjorts i två huvudsakliga steg: (1) en visualisering av fordonens rörelser genom alla studerade åtgärder har gjorts och hastighetsprofilerna återfinns i Bilaga A, B och C; och (2) en matematisk modell har skapats som beskriver förhållandet mellan ett fordons minsta radie genom en åtgärd och fordonets hastighet i samma punkt.Resultaten visar att de studerade hastighetssäkrade åtgärderna på landsbygdsvägar fungerar generellt bra och sänker hastigheten. Alla platser fungerar dock inte lika bra och det är fortfarande oklart exakt vad som avgör varför vissa platser med liknande åtgärder fungerar olika bra. Generellt så verkar Avsmalningar vara mest hastighetssänkande, Portar resulterar i 16% högre hastighet och Chikaner visar 30% högre hastigheter än avsmalningar.
|
|
| 18. |
- Høye, Alena, et al.
(författare)
-
SeeMe at the crosswalk : Before-after study of a pedestrian crosswalk warning system
- 2019
-
Ingår i: Transportation Research Part F: Traffic Psychology and Behaviour. - : Elsevier BV. - 1369-8478. ; 60, s. 723-733
-
Tidskriftsartikel (refereegranskat)abstract
- SeeMe is a pedestrian crosswalk warning system with automatic pedestrian detection that is mounted on crosswalk signs. Amber flashing lights are activated when pedestrians are approaching or crossing the crosswalk. The aim is to attract motorists’ attention, to improve yielding behavior and to reduce conflicts. A before-after study with a matched comparison group has been conducted in the Norwegian municipality of Trondheim. Video observations were made at eight crosswalks (four of which were equipped with SeeMe in the after period) of 1825 pedestrian-motorist interactions. On average, yielding rates at SeeMe equipped crosswalks increased by 14% (statistically significant) when changes at the comparison sites are taken into account. However, the results are inconsistent between crosswalks. At two of the crosswalks with SeeMe in the after period, yielding rates increased by 39% (statistically significant), while they decreased by 4% at the other two crosswalks (not statistically significant). There were several differences between crosswalks with increased and unchanged yielding rates: Initial yielding rates (below vs. above 80%), placement of crosswalk signs (immediately at vs. at some distance from the crosswalk) and false alarm rates (30% vs. 57% on average). These factors may have affected the effect of SeeMe on yielding rates, but the number of crosswalks included in the study is too small to generalize the differences between different types of crosswalks. The results do not indicate that SeeMe has negatively affected pedestrian behavior or provoked conflicts. It is concluded that SeeMe may be effective in increasing motorist yielding rates at crosswalks with similar characteristics as in the present study - two-lane roads in residential areas with moderate motor vehicle volumes and speed limits of 50 kph or below - and that high initial yielding rates and high rates of false alarms may limit its effectiveness.
|
|
| 19. |
- Johansson, Maria, et al.
(författare)
-
Metodutveckling för att studera allmänhetens respons på energieffektiv utomhusbelysning
- 2017
-
Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Artificial outdoor lighting for pedestrians should provide for a safe and secure outdoor environment after dark. Pedestrian lighting thereby has implications for active transportation and sustainable mobility. Installations of new energy efficient lighting applications should be evaluated in terms of pedestrian’s perception, evaluation and behaviour in the lit environment. Today there is a lack of methods to assess such pedestrian responses, in particular pedestrian behaviour. In a multidisciplinary context this project aimed to develop two methods to capture pedestrians’ behavioural responses possible to employ in urban outdoor spaces and among different user groups: Random Environmental Walking (REW) and Video Analysis of Pedestrian Movement (VAPM). Development of REW and VAPM was carried out in a series of empirical studies. In the final studies the new methods were combined with established methods in environmental psychology. It is proposed that REW and VAPM could complement lighting standards and energy measures to obtain optimal solutions for outdoor lighting. At present REW and VAPM work well in a research context, but further refinement of the procedures and analyses will be necessary for large scale implementation. VAPM constitutes a special case as the mounting of cameras in public spaces increasingly requires special permit, at least in Sweden. The development of REW aimed to obtain pedestrians’ behavioural preference of outdoor lighting applications. The REW was tested in a within-subject design with 80 participants who evaluated four lighting applications placed close to each other in an urban park: Application 1 was a clear Ceramic Metal Halide (CMH), Lighting Application 2 was a frosted CMH, Lighting Application 3 was Light-Emitting Diode (LED), Lighting Application 4 was a LED. The results of REW showed that the participants walked most frequently to Application 3, indicating that this was the behaviorally preferred lighting application. This result agreed well with participants’ self-report ratings of their visual experience of the lit environment and perceived lighting qualities. In this respect, REW was shown to be a viable technique for use in the field. The VAPM aimed to provide detailed data on pedestrians’ microscopic movement. VAPM was tested in a between-subject design with 62 participants who evaluated two lighting applications along a 130 meter traffic-separated walking and cycle path. Twenty-nine participants walked the path with Application I (Philips SGS203 50 Watt SON-T, mounted at lamp-posts with a distance of 33 meters), thirtythree participants walked the path with Application II (Philips P17 Master City White CDO/ET 50W/828, mounted at lamp-posts with a distance of 16.5 meters). In Application II the illuminance on the path was considerable increased. The results of VAPM revealed that participants walked systematically closer to the centre-line of the path in Application II as compared to Application I. Participants assessed Application II to provide better conditions to see along the path but the surroundings where considered too dark, indicating that the brighter and more focused light created a visual tunnel. The VAPM showed a great potential in capturing pedestrian behaviour under different lighting applications. The research project has been situated at Lund University and carried out in close collaboration with Malmö City and Axis Communications.
|
|
| 20. |
- Johansson, Maria, et al.
(författare)
-
Video analysis of pedestrian movement (VAPM) under different lighting conditions—method exploration
- 2020
-
Ingår i: Energies. - : MDPI AG. - 1996-1073. ; 13:6
-
Tidskriftsartikel (refereegranskat)abstract
- When daylight hours are limited, pedestrians are dependent on appropriate outdoor lighting. Although new city lighting applications must consider both energy usage and pedestrian responses, current methods used to capture pedestrian walking behaviour during dark conditions in real settings are limited. This study reports on the development and evaluation of a video-based method that analyses pedestrians’ microscopic movements (VAPM—video analysis of pedestrian movements), including placement and speed, in an artificially lit outdoor environment. In a field study utilising between-subjects design, 62 pedestrians walked along the same path under two different lighting applications. VAPM accurately discriminated pedestrians’ microscopic movements in the two lighting applications. By incorporating methodological triangulation, VAPM successfully complemented observer-based assessments of pedestrians’ perceptions and evaluations of the two lighting applications. It is suggested that in evaluations of pedestrian responses to city lighting applications, observer-based assessments could be successfully combined with an analysis of actual pedestrian movement while walking in the lit environment. However, prior to employing a large-scale application of VAPM, the methodology needs to be further adapted for use with drones and integration into smart city lighting systems.
|
|
