An integrated system of forward collision warning and adaptive cruise control functions was projected to prevent about 10 percent of all rear-end crashes, and 10 to 20 percent of severe near-crashes.

April 2006
United States

Summary Information

This benefits summary is drawn from the results of an independent evaluation of the Automotive Collision Avoidance System (ACAS). The forward collision warning (FCW) system detects, assesses, and alerts the driver of a potential hazard in the forward region of the vehicle. The adaptive cruise control (ACC) system provides automatic brake and throttle actuation in order to maintain speed and longitudinal headway control. Through the integration of these two functions, ACAS is intended to improve automotive safety by assisting drivers to avoid rear-end crashes. To accomplish this goal, the ACAS must also prove useful and acceptable to drivers.


An independent evaluation of the ACAS was conducted based on data collected from a field operational test (FOT) and from an independent system characterization test. The goals of the independent evaluation were to: characterize ACAS performance and capability, achieve a detailed understanding of ACAS safety benefits, and determine driver acceptance of ACAS. Data were collected from the ACAS FOT that employed 10 vehicles using a total of 66 drivers that included three age groups (younger, middle-age, and older) with equal numbers of male and female drivers.

Based on data collected from the FOT involving 10 vehicles and 66 drivers, an integrated system of FCW and ACC functions was projected to prevent about 10 percent of all rear-end crashes, and 10 to 20 percent of severe near-crashes (minimum time-to-collision of less than 3 seconds with a peak deceleration level by the host vehicle of over 0.3g). No unintended negative consequences were observed by examining travel speed, time headway, distraction, and eyes-off-the-road. Long-term positive or negative safety effects were not evaluated due to the nature of the FOT.

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Evaluation of an Automotive Rear-End Collision Avoidance System

Author: Najm, Wassim G., et al.


Published By: Prepared by Volpe for the U.S. Department of Transportation

Source Date: April 2006

EDL Number: 14303



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Goal Areas


Typical Deployment Locations



intelligent cruise control, ICC, ACC, Intelligent Speed Adaptation, ISA

Benefit ID: 2008-00576