Assessing Safety Improvements to Pedestrian Crossings Using Automated Conflict Analysis

Surrogate safety measures, such as the traffic conflict technique, have been promoted as an alternative or complementary approach to evaluate road safety from a broader perspective than collision statistics alone. The before-and-after evaluation of safety treatments is one application that can significantly benefit from the use of surrogate safety measures. This study demonstrated the use of automated traffic conflict analysis to conduct before-and-after safety evaluations. The objective was to conduct a time-series (before-to-after) safety evaluation for an intersection in Surrey, British Columbia, Canada, where several pedestrian-related countermeasures were implemented. Treatments included one or more of the following: use of protected-only turns for left-turning vehicles, installation of pedestrian countdown timers, crosswalk realignment, and use of drop-down sidewalks. Results indicated a significant decrease in both pedestrian conflict frequency and severity at the intersection following the treatments. A greater reduction of conflicts was exhibited on the western portion of the intersection where several countermeasures were implemented, including a protected left-turn phase, dual drop-down ramps, and a shift in the crosswalk further west. This variation in conflict reduction along different segments of the same intersection gives a particularized view of the impact of the adopted countermeasures. The outcome of this research provides evidence that surrogate safety indicators can be used effectively to diagnose safety problems and evaluate countermeasures at intersections.