Cyclist-Involved Crashes and Level of Traffic Stress: Evidence from Arizona

Abstract

Confronted by growing environmental and health concerns, many transportation agencies are instituting new policies and programmatic interventions aimed at further motivating cycling as a mobility option. Yet, in most American metropolitan regions, cycling rates remain relatively low in comparison to other modes despite a suspected desire among many urban residents, workers, and visitors to expand their transportation portfolio. A primary reason for this stagnation in cycling relates to continued and mounting concerns about the personal safety and comfort of current and prospective cyclists using high-stress facilities to reach their destinations. To help understand the extent of this identified impediment to increased cycling adoption, this study examines the association between the level of traffic stress and traffic safety for cyclists measured by crash frequency at segment level and the severity of injury to cyclists at the incident level. By estimating a pair of negative binomial and binary logit models, respectively, this study adopts a two-pronged analytic framework to assess the significance of four different levels of traffic stress and their components (posted speed limit, number of travel lanes, annual average daily traffic) in predicting crash frequency and injury severity. Findings from this study of a 7-year crash data set collected across all metropolitan planning organization jurisdictional boundaries in Arizona show that an increase in the level of traffic stress of a segment is associated with an increase in the frequency of crashes involving cyclists and that cyclists are more likely to experience a more severe injury if involved in a crash with a motorist on a higher-stress facility.