Evaluation of Safety Benefits from a Heavy-Vehicle Forward Collision Warning System

Abstract

Forward collision warning (FCW) systems are designed to alert drivers to an impending rear-end (RE) crash, to allow drivers to respond to a crash threat sooner, and thus to reduce their impact speed or allow them to avoid a crash altogether. This study estimates the safety benefits that may be attained by deploying an FCW system across the national fleet of heavy vehicles. The approach involved identifying RE conflicts within a heavy-vehicle naturalistic driving data set with the use of algorithms that identified potential RE events and removed nonthreatening events. Since the heavy vehicles in this data set were not equipped with FCW systems, the FCW auditory alarm severity and timing were introduced into the data with existing FCW system algorithms. Driver perception–response times and braking levels to the computed FCW alarms were modeled with actual driver alarm response behavior recorded in a previous heavy-vehicle FCW field operational test. Driver RE collision avoidance behavior, both with and without FCW alarm feedback, was then simulated with a Monte Carlo simulation approach. The simulation assumed that drivers selected the optimal braking response in the event that multiple FCW alarms were triggered. The number of conflicts avoided and the additional response time available before a crash were then used to assess the safety benefits. This study estimated that FCW systems may afford a 21% reduction in heavy-vehicle RE crashes, which translates to 4,800 crashes per year on U.S. highways.