Surrogate safety evaluation and validation with crash history for interurban midblock sections under heterogeneous traffic conditions in India

Traditionally, road safety analysis has been conducted by analysing collision records, which has a reactive approach as the analyst waits for collisions to occur. The alternate proactive approach in the form of surrogate safety measures is to study traffic conflicts which are bound to occur more frequently and thus has related them to the possible incidences of collisions. In the present study, traffic conflict indicators have been used to assess the level of safety by considering the typical midblock sections of an interurban corridor using vehicle trajectory data extracted through microscopic simulation. The surrogate safety parameters such as Time to Collision (TTC), Deceleration Rate (DR), change in velocity (Delta V) as well as conflicting vehicle Speed (Max S) have been extracted from trajectory data through the application of numerical elaboration to evaluate safety. Further, an attempt has been made to quantify the traffic conflicts occurring at the midblock of referred study. The proposed threshold values of surrogate safety parameters have been validated using the reported three years’ crash data. The approach presented in the paper has helped in the identification of midblock locations prone to road crashes and hence has served as a proactive alternative as opposed to historical crash based analysis.