Introduction

Traffic accident fatalities in Japan have continuously decreased since the year 2000 to some 6000 people in 2006. However, traffic accident casualties have exceeded one million annually since 1999, meaning that one in every hundred Japanese is involved in a traffic accident each year.   A crossing collision means an accident in which two vehicles (including bicycles and other non-powered vehicles) approaching from non-opposing directions collide at an intersection. Traffic accidents of this type represent the second-largest proportion (after rear-end collisions) of all accidents involving casualties. When limited to accidents resulting in death and/or serious injury, crossing collisions account for a larger proportion than any other type of traffic accident.   Causes of crossing collisions, as shown in ITARDA Information No. 56¹), are mostly human errors in perception (e.g., failure to notice an approaching vehicle), and misjudgment/miscalculation (e.g., false belief in one's right of way, thus expecting the other vehicle to stop). In addition to accidents caused by human error, some accidents are also triggered by road environment: e.g., delayed sighting of an approaching vehicle due to a blocked view.   This issue of ITARDA Information analyzes crossing collision accidents from the viewpoint of road environment, and tries to find ways to prevent such accidents based on the analysis and case studies.

Conclusion   In this issue of ITARDA Information, crossing collision accidents were analyzed in view of road environment, and placed into perspective.   Analysis of traffic accident statistical data indicated that crossing collisions took place most often at "medium-sized or smaller intersections without signals in urban areas". It also become evident that poor visibility due to obstructing buildings, walls, etc., is a frequent cause of such accidents.   Crossing collisions may be categorized by case analysis data into the following three patterns.   Pattern I: Accidents caused by, in addition to human error, road environment factors (poor visibility, lack of safety facilities, etc.)   Pattern II: Accidents caused by perception errors (entirely overlooking an approaching vehicle), with road environment factors playing a minimal role   Pattern III: Accidents caused by judgment/forecasting errors (aware of an approaching vehicle but misjudging its behavior), with road environment factors playing a minimal role   The analysis revealed that frequent causes of accidents in road environment were, among others, poor visibility due to hedges, fences, walls, etc. of private land and public parks, and difficulty judging the right of way, resulting from a lack of road markings, traffic signs, etc.   Countermeasures for road environment-triggered accidents³) would include installation of traffic mirrors and corner cutoffs, as well as adequate traffic control by clarifying the absence of right of way, either by road markings or traffic signs.   In actually implementing such measures, however, it is necessary to study how and why accidents occur at each particular intersection. In addition to improving the road environment, educating cyclists, riders, and drivers would also lead to the reduction of crossing collisions.   This report is based on ITARDA's past research4). For details, refer to the original reports listed below. 1) ITARDA Information No. 56, "Analysis of Human Factors in Crossing Collisions"; Institute for Traffic Accident Research and Data Analysis (ITARDA); May 2005 2) "Study on Human Factors in Accidents Using Variation-Tree Analysis"; Toshiro Ishida; Society of Automotive Engineers of Japan (JSAE) papers, vol.30, No.2, P.125-130; April 1999 3) "Traffic Accident Countermeasures, Evaluation Manual, and Traffic Accident Countermeasure Case Studies"; ITARDA; May 2005 4) Traffic Accident Case Studies and Analysis Report, Fiscal 2005; ITARDA; P.125-174; March 2006 Institute for Traffic Accident Research and Data Analysis (ITARDA)