Modeling Driver's Tradeoff between Time Benefit and Traffic Conflict Risk in Gap Acceptance at Signalized Intersections in China

Abstract

The safety and capacity of road intersections with the permissive left-turn phase are influenced significantly by gap acceptance of left-turners. This study aims at modeling driver's tradeoff between time benefit and traffic conflict risk in gap acceptance at signalized intersections in China. A modeling approach for gap acceptance behavior was proposed based on the Risk Homeostasis Theory and Utility Theory. A video survey was conducted at a typical two-phase controlled intersection in Shanghai and eventually 122 left-turners and 538 related gaps in the opposite through traffic were obtained. Various binary logistic models were then developed to explore the influencing factors of gap acceptance. Results showed that the potential time to wait for an acceptable gap in the opposite through traffic, namely time-to-wait, affected gap acceptance behavior more significantly than the time that the left-turner already waited, namely already-waited-time. In addition, the weight ratio of time benefit -- indicated by the time-to-wait -- and traffic conflict risk -- indicated by the post-encroachment time at the conflict point when a left-turner crossing the opposite through traffic -- was found to be 1:67 when a left-turner is making a decision to cross or not. The impact of such tradeoff on the capacity of left-turning traffic was also extensively discussed in this study.