Exploring the impacts of intersection and traffic characteristics on the frequency and severity of bicycle-vehicle conflicts

In urban locations, intersections are areas where a variety of modes converge, thus leading to an increased potential for conflicts. A common crash type involving bicycles at intersections is the “right/left-hook” where a right/left-turning vehicle collides with a through bicyclist. While geometric treatments and signal control strategies have been used to mitigate right-left/hook conflicts, agencies often face questions about optimal treatments and when to use these treatments at intersections. This exploratory study aims to fill that gap by exploring the safety impacts of split leading bike interval (LBI) and mixing zone treatments to reduce conflicts between bicycles and turning vehicles at intersections using surrogate safety measures with video observations. The surrogate safety measure post encroachment time (PET) was used to classify conflicts by severity based on the magnitude of the value. Next, a negative binomial regression model was estimated to observe the relationship between conflicts, bicycle and motor vehicle volumes. The results revealed that through bicycle and turning motor vehicle volumes, as well as intersection treatment, are significant predictors of conflicts between bicycles and motor vehicles at signalized intersections, which could allow for targeted implementation of safety measures at candidate locations identified through volume analysis. Additionally, a random parameters ordered logit model was estimated to examine factors which impact the severity of bicycle-vehicle conflicts if they occur. It was found that both intersection treatment and time of day were both associated with conflict severities. The results of this study provide guidance for potential improvement of bicycle safety at intersections, which could increase the attractiveness of this mode for possible new cyclists.