EXAMINATION OF INTERSECTION, LEFT TURN ACROSS PATH CRASHES AND POTENTIAL IVHS COUNTERMEASURES. FINAL REPORT

This report provides a preliminary analysis of intersection-related, left turn across path (LTAP) crashes and applicable countermeasure concepts for the Intelligent Vehicle Highway System (IVHS) program. An LTAP crash occurs when the subject vehicle (SV) approaches an intersection, attempts to turn left, and either strikes or is struck by the principal other vehicle (POV) traveling in the opposing traffic lanes. A detailed analysis of 154 such crashes showed that 49% are caused by drivers who were unaware of the oncoming vehicle, and that 30% were caused by drivers who saw but misjudged the velocity/gap of the oncoming vehicle. Moreover, two LTAP crash subtypes are identified: the SV slows, but does not stop, begins the left turn, and strikes or is struck by the oncoming POV in 71.6% of these crashes; and the SV stops, then proceeds with the left turn, and strikes or is struck by the POV in the remaining 28.4% of these crashes. The crash avoidance system (CAS) concepts discussed in this report include driver warnings, partially automatic vehicle control systems, and fully automatic vehicle control systems. This report concludes with a number of research needs to better understand LTAP crashes and guide CAS development.