Cyclist safety assessment using autonomous vehicles

Proactive and holistic safety management approaches should consider multi-modal crash risk. Cyclist crash risk should be prioritized given the high-severity of vehicle-cyclist crashes. Cyclist crash risk is difficult to quantify given the sparse nature of cyclist collisions and collisions in general. There is thus a need to develop a more proactive approach for multi-modal road-safety management by leveraging new technologies. This study proposes a conflict-based methodology to estimate cyclist crash risk using autonomous vehicle data, extrapolating from observed conflicts to real-time dynamic crash risk. Using 87 hours of data from an autonomous vehicle dataset from downtown Boston (nuPlan), traffic conflicts were identified. A Bayesian Hierarchical Extreme Value model was created representing driver and cyclist crash risk over short time intervals. This allows for identifying the real-time crash risk of various intersections and mid-blocks, enabling route-level safety metrics. The spatiotemporal characteristics of crash risk were examined in this study. Routes with cyclist facilities were found to be safer for cyclists, on average, than those with shared facilities. However, substantial fluctuations in crash risk were observed at different time intervals, with the shared facilities sometimes being safer than those with painted or buffered bicycle lanes. This highlights the need for real-time safety monitoring. At the user-level, a safest route application was also proposed, allowing for an impedance function to be developed based on realtime crash risk and the comparison of any number of nodes and links along a particular route.