PI: Bharat Pathivada, Ph.D.
Co-PI: Yao-Jan Wu, Ph.D., P.E
Sponsor: City of Phoenix
May 2026 - Oct. 2027
The City of Phoenix is actively implementing signal modernizations and modifications to enhance operational efficiency, visibility, and long-term reliability across its traffic signal network. Signal modernizations involve full upgrades to aging infrastructure, such as replacing controllers, signal heads, and accessible pedestrian signals (APS), among others, to enhance visibility, operational consistency, and system performance. These activities typically address equipment nearing the end of its service life. In contrast, signal modifications consist of targeted improvements designed to address specific operational or safety needs. Examples include adding turn arrows and installing additional signal heads. These signal modifications can influence driver behavior and intersection safety. To evaluate the safety effectiveness of these improvements, this project will develop Crash Modification Factors (CMFs) using a before-after Empirical Bayes (EB) methodology. The analysis will incorporate comparable control sites, traffic volumes, geometric characteristics, and crash data to provide a comprehensive assessment of safety impacts. The resulting CMFs will offer the City of Phoenix a robust, evidence-based understanding of how these signal improvements influence crash frequency and severity across diverse intersection settings. The results from this study will support data-driven decision-making and help prioritize future signal upgrades to maximize safety benefits per dollar spent.