Development of Surrogate Safety Measure Based on the Concept of Vehicle Influence Area

Surrogate safety measure (SSM) plays a key role in early safety evaluation. Previous research has indicated potential associations between SSM and road crashes. Several attempts have been made to develop SSM. Most studies in the field of SSM have only focused on rear-end conflicts in witch the two vehicles move in a just one lane. The principal objective of this paper was to develop a new area-based SSM (ASSM) which can take into account the two-dimensional movement of vehicles. ASSM provides a novel approach to quantifying safety. The two-dimensional hypothetical areas around the vehicle that are required for the safe movement are introduced as the influence area. The mathematical equation of the influence area is derived as a function of vehicle speed, and then ASSM could be calculated by examining the extent of overlap and intersection of the influence areas of different vehicles at any given time. In this study, techniques for ASSM were developed and applied to real-world traffic data (NGSIM). The findings indicated that there was a positive relationship between ASSM and the time of the driver's decision to change his driving position to avoid a collision. The findings can contribute to a better understanding of human driving behavior in critical situation.