How Does Pavement Friction Affect Motorcycle Crashes? A Florida Analysis

Pavement friction performance is crucial to motorcycle safety because of the unique dynamics and vulnerabilities of motorcycles compared with other vehicles. Maintaining adequate pavement friction prevents motorcyclists from losing control and reduces motorcycle crashes. However, the impacts of friction characteristics on motorcycle crashes are not well quantified. Florida Department of Transportation District 7 collected continuous pavement friction measurement data for over 2,000 lane miles on its state roads utilizing the Sideway-Force Coefficient Routine Investigation Machine (SCRIM). Based on the SCRIM data, this study developed safety performance functions (SPFs) and crash modification factors (CMFs) for motorcycles considering facility types and pavement types. The modeling results indicate that increased friction is more likely to reduce motorcycle crash frequencies, while intensified friction variation tends to increase crash frequencies in specific scenarios. Other pavement surface characteristics affecting motorcycle crash frequencies include macrotexture and pavement conditions (roughness, cracks, and ruts). Investigatory levels (ILs) to determine friction and macrotexture demands for motorcycle safety were developed based on the SPFs. The study outcomes, such as SPFs, CMFs, and ILs, can be integrated into motorcycle safety management and select resurfacing, restoration, and rehabilitation projects for motorcycle safety improvement.