Human Performance Evaluation of Light Vehicle Brake Assist Systems

The Brake Assist System (BAS) is a safety feature that supplements drivers' inadequate braking force during panic braking maneuvers upon the detection of a rapid brake pedal application. This report presents an evaluation of drivers' panic braking performance using BAS. Two vehicles with electronic BASs were selected: a 2006 Mercedes-Benz R350 and a 2007 Volvo S80. Sixty-four participants, balanced for age and gender, drove one of the instrumented vehicles at 45 mph and stopped at an unexpected barricade. Following debriefing, drivers performed another braking maneuver at the barricade, were shown how to perform a hard stop, and performed hard-braking maneuvers in which BAS was either enabled or disabled. Twenty-eight percent of drivers activated BAS subsequent to the demonstration. In the most conservative analysis, where the effect of BAS activation was isolated from driver panic-braking variability, it was found that BAS-active stopping distances were on average 1.43 ft (s.e. = 1.19 ft) shorter than BAS-disabled stopping distances. Yet, two drivers, who differed in age, sex, and vehicle driven, exhibited reductions in stopping distance exceeding 10 ft. Overall, the as-tested BAS has potential safety benefit that could be accrued from reduced stopping distance, but were not realized in this evaluation. Moreover, BAS implementations that do not completely rely on the driver may offer greater safety benefits.