Advancing Safety Performance Monitoring at Signalized Intersections Through Use of Connected Vehicle Technology

Crash-based safety evaluation is often hampered by randomness, lack of timeliness, and rarity of crash occurrences. This situation is particularly true for technology-driven safety improvement projects that are frequently updated or replaced by newer ones before adequate crash data for a reliable and defensible before-and-after evaluation can be gathered. Surrogate safety data are commonly used as alternatives to crash data; however, the current practice is resource intensive and prone to human errors. The advent of connected vehicle technology allows vehicles to communicate with each other and with the infrastructure wirelessly. Through this platform, vehicle movements and signal status at facilities can be automatically and continually monitored in real time. This study explored the viability of long-term monitoring of connected vehicle data for evaluation of safety performance. A safety monitoring application that used connected vehicle data to detect potential safety indicators at signalized intersections was proposed. As limited saturation of onboard equipment (OBE) was expected in near-term evolution, development focused on a roadside equipment application to process data elements from OBE by way of vehicle-to-infrastructure communications through standard message sets. A microscopic simulation was designed to evaluate effectiveness of the proposed safety indicators in detection of degrading safety performance. A signalized intersection test bed was created in VISSIM, while the wireless communications capability and the application were implemented in a car-to-devices application programming interface. Evaluation results indicated that the application could effectively detect changes in safety performance at full market penetration. Future research needs to quantify the combination of penetration rates and monitoring periods that can yield effective detection of changes in safety performance at intersections with varying operating characteristics.