Quantifying the Safety Benefits of Transit Signal Priority Using Full Bayes Before-After Study

Transit signal priority (TSP) is a strategy that prioritizes the movement of transit vehicles through a signalized intersection to minimize transit delay and improve travel time reliability. Although the operational benefits are usually considered the primary criteria when deploying TSP, little attention is given to the anticipated safety impacts of TSP. Few studies that examined the safety impacts of TSP indicated inconsistent results. The objective of this study was to evaluate the safety performance of TSP. An observational before-after full Bayesian with a comparison-group approach was adopted to develop crash modification factors for total, fatal and injury (FI), and property damage only (PDO) crashes. The analysis was based on 41 transit corridors in Florida. Deployment of TSP resulted in a 12%, 14%, and 18% reduction in total, FI, and PDO crashes, respectively. Overall, the study results indicate that the deployment of TSP improves safety along the corridors. The study findings provide researchers and practitioners with an effective means for quantifying the safety benefits of the TSP and conducting an economic appraisal of TSP.