Evaluating the impact of speed enforcement in urban areas using probe vehicle data and traffic conflicts

This study is motivated by the recent deployment of speed enforcement programs in Egypt. Despite the wide deployment of the program, its impact on pedestrian conflicts and driver behavior in non-lane-based traffic conditions is understudied. Therefore, this study aims to investigate the impact of speed enforcement implementation on driver’s speed and traffic conflicts (including vehicle-pedestrian conflict) along an urban corridor in Cairo, Egypt. Traffic conflicts were extracted using a computer vision safety analytics tool, focusing on pedestrian-vehicle and rear-end conflicts using post-encroachment time (PET) and time to collision (TTC), respectively. The study utilizes the probe vehicle technique to capture speed profiles for both directions. The speed enforcement implementation reduced the drivers' speeds significantly. Moreover, a statistically significant decrease in pedestrian-vehicle conflict frequency and severity (average PET value increased from 1.64 sec to 1.78 sec) was observed. This substantial reduction in conflict frequency highlights a key safety improvement and underscores the effectiveness of enforcement measures in enhancing pedestrian safety. On the other hand, the results revealed a risk potential, with the majority of vehicle-to-vehicle conflicts occurring within a narrow TTC interval of ]0, 0.2] seconds after the speed enforcement implementation, which is attributed to driver sudden braking behavior just before radar locations.