Evaluation of the Prince William County Collision Countermeasure System

摘要

The Collision Countermeasure System (CCS) is an ITS application intended toreduce side-impact accident potential at rural, limited sight-distance intersections. It consists of activated warning signs and pavement loop detectors designed to enhance driver awareness of cross traffic. This field evaluation, comprising a four-phase observational effort (before, Acclimation, 4-month after, and 1-year after studies) assessed novelty and longer term CCS effects. Results reported herein are based on a 48-day, 109,000-vehicle data sample. In order to address CCS accident reduction potential, the study targeted 2,242 high-speed vehicles arriving at the intersection in close time proximity to cross traffic. This study also assessed the potential 'familiarization' effect, i.e., driver response to the device in its non-activated condition, and conducted a benefit/cost analysis. Vehicle behavioral measure of effectiveness (MOEs) were derived from CCS accident-avoidance objectives, i.e., specifically addressing intersection arrivals in close proximity to cross traffic. Applied MOEs were (1) drivers' CCS speed responses in the presence of cross traffic; (2) intersection approach speed reductions; and (3) projected times-to-collision (PTCs), i.e., the elapsed time to which an approaching vehicle would collide with a vehicle in its path in the absence of a timely avoidance response. Human factors (e.g., driver perception-reaction time) accident avoidance requirements determined the critical values that were used in the analysis.