Application of surrogate safety measures for assessment of pedestrian versus left-turning vehicle conflict at signalized crosswalks

Pedestrian safety improvement at signalized intersections remains a critical issue. The major threat comes from frequent interaction with turning vehicles, especially left-turners (left-hand traffic system). This study gains insights into how surrogate safety measure (SSM) can be utilized for pedestrian versus left-turning vehicle conflict assessment, and although a small step, how to relate SSM to limited crash records for crash risk estimation. Based on the video data collected at several crosswalks in Nagoya City, Japan, SSMs, i.e., Post Encroachment Time (PET) and vehicle passing speed at conflict point were extracted for analysis. PETs were estimated for both near-side and far-side approaching pedestrians by identifying the potential conflict points and considering the physical size of left-turning vehicles. The effectiveness of SSMs to reflect the impact of site-specific geometric characteristics and operational conditions upon conflict risk has been demonstrated. Furthermore, crash risk estimation models were developed by using Poisson regression methods based on mean PET, the number of short PETs per hour and average vehicle passing speed at conflict point at each crosswalk. It demonstrates that high turning speed, in conjunction with higher frequency of short PETs result in higher crash rates.