title: Identifying crash patterns on roundabouts.
abstract: OBJECTIVE
  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.
authors.affiliation: a Transportation Research Institute (IMOB) , Hasselt University , Diepenbeek , Belgium.
authors.forename: Evelien
authors.initials: E
authors.lastname: Polders
authors.forename: Stijn
authors.initials: S
authors.lastname: Daniels
authors.forename: Winfried
authors.initials: W
authors.lastname: Casters
authors.forename: Tom
authors.initials: T
authors.lastname: Brijs
mesh_terms: D000063:Accidents, Traffic / Q000706:statistics & numerical data*; D001530:Belgium / Q000453:epidemiology; D001642:Bicycling / Q000293:injuries / Q000706:statistics & numerical data; D004779:Environment Design; D006801:Humans; D009049:Motorcycles / Q000706:statistics & numerical data; D016495:Police; D011996:Records; D012307:Risk Factors; D012449:Safety; D015599:Trauma Severity Indices; D014947:Wounds and Injuries / Q000453:epidemiology
keywords: collision diagram; crash; design; roundabout