Drivers' behavioral responses to combined speed and red light cameras.

BACKGROUND: Numerous signalized intersections worldwide have been equipped with enforcement cameras in order to tackle red light running and often also to enforce speed limits. However, various impact evaluation studies of red light cameras (RLCs) showed an increase of rear-end collisions (up to 44%). OBJECTIVE: The principal objective of this study is to provide a better insight in possible explaining factors for the increase in rear-end collisions that is caused by placing combined speed and red light cameras (SRLCs). METHOD: Real-world observations and driving simulator-based observations are combined. Video recordings at two signalized intersections where SRLCs were about to be installed are used to analyze rear-end conflicts, interactions and driver behavior in two conditions (i.e., with and without SRLC). Furthermore, one of these intersections was rebuilt in a driving simulator equipped with an eye tracking system. At this location, two test conditions (i.e., SRLC and SRLC with a warning sign) and one control condition (i.e., no SRLC) are examined. The data of 63 participants were used to estimate the risk of rear-end collisions by means of a Monte Carlo Simulation. RESULTS: The results of the on-site observation study reveal decreases in the number of red and yellow light violations, a shift (i.e., closer to the stop line) in the dilemma zone and a time headway reduction after the installation of the SRLC. Based on the driving simulator data, the odds of rear-end collisions (compared to the control condition) for the conditions with SRLC and SRLC+warning sign is 6.42 and 4.01, respectively. CONCLUSION: The real-world and driving simulator observations indicate that the risk of rear-end collisions increases when SRLCs are installed. However, this risk might decrease when a warning sign is placed upstream.

Identifying crash patterns on roundabouts.

OBJECTIVES: Roundabouts are a type of circular intersection control generally associated with a favorable influence on traffic safety. International studies of intersections converted to roundabouts indicate a strong reduction in injury crashes, particularly for crashes with fatal or serious injuries. Nevertheless, some crashes still occur at roundabouts. The present study aims to improve the understanding of roundabout safety by identifying crash types, locations, and factors that are associated with roundabout crashes. METHODS: An analysis of 399 crashes on 28 roundabouts in Flanders, Belgium, was carried out based on detailed crash descriptions; that is, crash data and collision diagrams. The crashes are sampled from police-reported crashes at roundabouts in the region of Flanders, Belgium. Collision diagrams of the registered crashes were used to distinguish 8 different crash types. The roundabout itself is divided into 11 detailed and different typical segments, according to previously established knowledge on the occurrence of crashes at roundabouts. The 8 roundabout crash types are examined by injury severity, crash location within the roundabout, type of roundabout, type of cycle facility, and type of involved road user. RESULTS: Four dominant crash types are identified: rear-end crashes, collisions with vulnerable road users, entering-circulating crashes, and single-vehicle collisions with the central island. Crashes with vulnerable road users and collisions with the central island are characterized by significantly higher proportions of injury crashes. About 80% of the crashes occurred on the entry lanes and the circulatory road (segments 1-4). Road users who are the most at risk to be involved in serious injury crashes at roundabouts are cyclists and moped riders. CONCLUSIONS: The main goal of this study was to identify and analyze dominant crash types at roundabouts by taking into account detailed information on the crash location. Some connections between certain roundabout crash types, their crash location, and roundabout design characteristics have been found.