Incorporating a Safety Index into Pathfinding

Travelers around the world are concerned with choosing not only the quickest route from one point to another but also the safest route. Traffic safety has always been a major public concern, and traffic safety performance should be constantly evaluated so that both reactive and proactive countermeasures can help reduce crashes. This study developed a methodology for incorporating safety aspects into travelers’ pathfinding process. The safe pathfinding process included two main parts: a route-specific safety hazard index and a route-finding algorithm that considered both travel time and safety. The ratio of the deceleration rate to avoid a crash to the maximum available deceleration rate was chosen as the proxy for traffic safety. The safety hazard index was formulated by using the collision mechanism along the roadway segment and at the intersection. Motorist-specific information (e.g., vehicle type, age, pavement condition) was also included in the safety index model so that a traveler’s individual needs could be considered. The pathfinding algorithm, which combined mobility and safety, had three objectives: shorter travel time, lower route safety hazard index, and avoidance of sites with the highest safety hazard index along the route. The methodology was applied in a real-world street network to demonstrate its use and prove the concept of finding a safe path.