Project: #579 The Effects of Curb Extensions and Stormwater Infrastructure on Traffic Safety in Philadelphia Progress Report - Reporting Period Ending: Aug. 18, 2026 Principal Investigator: Erick Guerra Status: Overdue Project Start Date: July 1, 2025 End Date: June 30, 2026 Research Type: None Grant Type: Research Applied Grant Program: US DOT BIL, Safety21, 2023 - 2028 (4811) Grant Cycle: Safety21 : 25-26 Progress Report (Last Updated: Aug. 18, 2026, 9:20 a.m.) % Project Completed to Date: None % Grant Award Expended: None % Match Expended & Document: None USDOT Requirements Accomplishments The project completed its primary research objectives, including data collection and processing, statistical analysis, preparation of the final report, and peer-reviewed publication. The study evaluated curb extensions installed through Philadelphia’s green stormwater infrastructure program using 94 treated and 269 control intersections and Bayesian negative binomial models. The analysis found that a single curb extension was associated with an estimated 11% reduction in reported crashes and 7% reduction in injurious crashes, although the credible intervals included no effect. The project also completed an economic assessment of the estimated safety benefits. Depending on assumptions about crash severity, estimated benefits ranged from approximately $86,000 to $175,000 per curb extension. The final report and peer-reviewed publication are complete, with inclusion in the FHWA Crash Modification Factors Clearinghouse remaining as an ongoing technology-transfer activity. Impacts The project strengthens the evidence base available to transportation agencies considering curb extensions as a safety intervention. This is particularly valuable because curb extensions are widely implemented despite relatively limited rigorous empirical research on their effects on crashes and injuries. Publication of the research in Transportation Research Record and planned inclusion in the FHWA Crash Modification Factors Clearinghouse provide avenues for the findings to reach transportation researchers and practitioners beyond Philadelphia. The project also had a direct workforce-development impact. A former University of Pennsylvania master’s student who now works for the City of Philadelphia participated in the project and gained applied experience conducting transportation safety research and working with crash and roadway data. This strengthened the connection between academic research and transportation practice while adding research and analytical experience to the local transportation workforce. Other Nothing to report Outcomes New Partners Nothing to report Issues Nothing to report