1,721,084 research outputs found
Surrogate measures of safety : Site-based observations
No full textTraditionally, traffic safety is expressed through the number of accidents (crashes) or people injured, since these are the most direct manifestations of an unsafe traffic environment. As we discuss in this chapter, such an approach has its limitations due to the low frequency of accidents and some other issues. Neither is it unusual that accident data is not available, not reliable or lacks important details, particularly in the context of low- and middle-income countries. Surrogate measures of safety (SMoS), based on the observation of traffic conflicts or near-misses, may serve as a viable alternative, or a complement, to accident/injury counts
Healthcare data
No full textIn this chapter, we will discuss the limitations of police accident data and the added value of health data as a complementary source. Several types of health organisations exist that cover a certain severity of traffic casualties. A number of medical indicators will be discussed, as well as methods to estimate the true number of serious injuries and the completeness of the police reporting. For two countries (the Netherlands and Sweden), the processes, research options and lessons learned will be discussed more comprehensively
Application of automated video analysis to road user behaviour
Full text linkThe successful planning, design and management of a traffic system is impossible without knowledge of how the traffic environment affects the behaviour of road users and how the behaviour is related to the main qualities of the traffic system (e.g. safety, efficiency). Automated video analysis is a promising tool for traffic behaviour research in that it enables collection of micro-level behaviour data for large populations of road users and provides a detailed description of their motion. This thesis describes the tests done with an automated video analysis system developed at Lund University. The system was used in two large scale studies with the main task of detecting the presence of road users of a particular type. Accuracy of position and speed estimates were tested in a study specially designed for that purpose. The thesis also elaborates on the problem of relating the behaviour of road users to safety and proposes organising all the elementary events in traffic (defined here as encounters between two road users) into a severity hierarchy. The process of an encounter is described with a set of continuous safety indicators that can handle the various approach angles and transfer between being and not being on a collision course. When an objective measure for an encounter severity is found, the severity hierarchies may be used not only for describing safety but also for studying the balance between safety and other qualities valued by road users
Defining and applying surrogate safety measures and behavioural indicators through site-based observations
No full textThis dissertation looks into surrogate safety measures and behavioural indicators that are collected through site-based observations. Surrogate safety measures are defined as measurements that are used to describe the relationship between two road users in a traffic event for the purpose of quantifying the crash probability and/or the potential crash severity in a meaningful way. The main goal of this dissertation is to contribute to filling methodological knowledge gaps in site-based observations of surrogate safety measures and road users’ behaviour, and to investigate how such observations can be used to study road safety issues for which crash data appear to be less suitable.
The dissertation includes a scoping review that investigates in a comprehensive and quantitative way how surrogate safety measures have been applied so far. The theoretical framework and first implementation of a new indicator, Extended Delta-V, are presented. Three case studies have been conducted that aim to further investigate how site-based observations of road users’ behaviour and interactions could supplement or even replace surrogate safety measures, especially when severe events take place infrequently and/or dispersed. The case studies relate to: 1) the safety of bicyclists on bus lanes shared with bicyclists, 2) drivers’ behavioural adaptions caused by wind turbines alongside the roadway, and 3) differences in drivers’ interactions at right-hand priority intersections and priority-controlled intersections. The case studies provide some safety-relevant insights into topics that have rarely been addressed in scientific literature before. Policy and design implications are discussed
Defining and applying surrogate safety measures and behavioural indicators through site-based observations
No full textThis dissertation looks into surrogate safety measures and behavioural indicators that are collected through site-based observations. Surrogate safety measures are defined as measurements that are used to describe the relationship between two road users in a traffic event for the purpose of quantifying the crash probability and/or the potential crash severity in a meaningful way. The main goal of this dissertation is to contribute to filling methodological knowledge gaps in site-based observations of surrogate safety measures and road users’ behaviour, and to investigate how such observations can be used to study road safety issues for which crash data appear to be less suitable.
The dissertation includes a scoping review that investigates in a comprehensive and quantitative way how surrogate safety measures have been applied so far. The theoretical framework and first implementation of a new indicator, Extended Delta-V, are presented. Three case studies have been conducted that aim to further investigate how site-based observations of road users’ behaviour and interactions could supplement or even replace surrogate safety measures, especially when severe events take place infrequently and/or dispersed. The case studies relate to: 1) the safety of bicyclists on bus lanes shared with bicyclists, 2) drivers’ behavioural adaptions caused by wind turbines alongside the roadway, and 3) differences in drivers’ interactions at right-hand priority intersections and priority-controlled intersections. The case studies provide some safety-relevant insights into topics that have rarely been addressed in scientific literature before. Policy and design implications are discussed
Comparison of severity assessments based on Czech and Swedish traffic conflict techniques
No full textWorst Case Analysis : A Video Analysis Approach to Injury Potential in Traffic
No full textThis paper presents a method for evaluating the potential for injury in any traffic scenario involving road user interactions based on trajectory data from a few hours of data of typical traffic conditions. The basic idea was to evaluate to what extent interactions at a location are limited in speed, direction, and whether the interactions happen at a safe speed. Specifically, the method works by applying an existing injury model to the highest observed values at a specific point in space. The injury model is used to estimate a worst-case scenario at that point in space. By generating a heat map, it is possible to analyse a location and evaluate the injury potential at a location. The method does not provide a complete safety analysis with exposure or risk but instead focuses specifically on the potential consequences. The method is suitable for preliminary safety analyses that focus on determining areas of particular interest for further study
Identification of evasive manoeuvres in traffic interactions and conflicts
No full textThe study presents a simple and easy to implement method for detection of the evasive action start in traffic interactions. The method is based on comparison of the studied trajectory with a reference set of ‘unhindered’ trajectories, interpreting the start of evasive action as the moment when no more similarities can be found. The suggested algorithm performs well for primary interactions when road users arrive in an unhindered state. It fails, however, in case of secondary interactions. Explorative application of the method on a large dataset of normal and conflict traffic situations concludes that traffic conflicts occur more frequently in secondary interactions, presumably due to higher cognitive load on the involved road users. Despite the limitations, the method can be used both for the safety studies based on traffic conflicts and for more general quantification and visualisation of the road user behaviour
SeeMe at the crosswalk : Before-after study of a pedestrian crosswalk warning system
No full textSeeMe 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
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