Developing Safety Performance Functions for Fatal and Severe Motorcycle Crashes at Intersections

Abstract

Although intersections are major contributors to traffic fatalities and severe injuries, research on motorcycle safety performance functions (SPFs) at intersections, particularly in the U.S., has been limited. This study takes the initiative and develops SPFs for fatal and severe injury (FSI) motorcycle crashes at intersections in Kentucky. Data from the Kentucky Transportation Cabinet (KYTC) on FSI motorcycle crashes (2015–2022) and extensive intersection-specific information (e.g., traffic control type and presence of exclusive turn lanes) at 1,372 intersections were analyzed. The zero-inflated heterogeneous Conway–Maxwell-Poisson (ZI-HTCMP) model provided the best fit for the data. The SPF model results showed that the presence of two through lanes or fewer on the major road (as opposed to three or more) was associated with reduced FSI motorcycle crashes. Furthermore, compared with unsignalized intersections (i.e., with stop signs, no control, and yield signs), the presence of traffic signals reduced FSI motorcycle crashes. Additionally, compared with three-legged intersections, four-legged intersections were associated with reduced FSI crashes, mainly owing to drivers being more cautious at those four-legged intersections with more conflicting movements. Also, right shoulder widths of less than 3 ft on major approaches were associated with increased motorcycle FSI motorcycle crash counts owing to insufficient recovery room to compensate for roadway departure crashes at intersections. To improve motorcycle safety at intersections, several countermeasures were provided, e.g., provision of right shoulder width of at least 3 ft on major approaches, provision of physical medians on minor approaches, and provision of daytime running lights (DRLs) to enhance motorcycle conspicuity.