论文部分内容阅读
Capacity of signalized intersections with the permissive left-turn phase is influenced significantly by the gap acceptance of left-turners.Risk perception of left-turners when deciding to accept a gap or not is of great importance for understanding such type of driver behavior and developing intersection improvement countermeasures.The objective of this study is thus to model the tradeoff relationship between the perceived risk and the time-saving benefit in the gap acceptance for left-turners at signalized intersections in China.In the proposed model,the perceived risk is measured by the Post Encroachment Time (PET) of the left-turn vehicle and the gap-ending through vehicle at the conflict,and the time-saving benefit is indicated by the potential time to wait for the next acceptable gap.A gap acceptance model that incorporates both of the variables was then developed and validated using the data collected at two intersections in Shanghai.The acceptable risk level of left-turners can then be defined as the ratio of the estimated model coefficients of those two variables.Results indicate that the time-to-wait significantly affects the gap acceptance and the critical gap decreases as the acceptable risk level rises.In addition,it was found that the acceptable risk level appeared to be approximately 60 at the observed intersections.Based on the results,impacts of the acceptable risk level on the capacity of permissive left-turn traffic were then investigated through a numerical study.The findings reveal that the capacity of permissive left-turn traffic could be stochastic in nature rather than constant,due to the random traffic flow characteristics as well as the different risk perceptions of drivers.