This content is not included in your SAE MOBILUS subscription, or you are not logged in.
Effectiveness of Emergency Brake Assist in Rear-End Accident Scenarios
Published October 22, 2006 by Society of Automotive Engineers of Japan in Japan
Active safety systems, such as Antilock Braking System (ABS), Electronic Stability Control (ESC or ESP) and Brake Assist System (BAS or EBA), are supposed to bring safety to car occupants and also other road users. Most of the recent publications are focused on ESC effectiveness, but very few are interested in the BAS gains. Whereas most of these studies use real-world accident data and either simulation methods or epidemiological designs, the current paper proposes an experimental approach to estimate the expected effectiveness of enhanced braking systems. Crash severity (i.e., collision speed) reduction can be used to estimate the potential gain in casualties (like car occupants and vulnerable road users) thanks to BAS.
The Laboratory of Accidentology, Biomechanics and studies of human behavior, PSA Peugeot Citroën - Renault (LAB), has conducted an experiment on test tracks where driver behavior, cars dynamics and braking system parameters were recorded in three rear-end accident scenarios. Ninety-five common drivers, women and men of various ages, participated in the study. They were dispatched in 3 homogenous groups. After 45 minutes of familiarization with the car in "ecological" conditions, each driver was asked to follow a vehicle pulling a trailer for several laps. In the last lap and under approximately the same conditions of speed (equivalent to 80 km/h) and distance (equivalent to 23 m), the subjects were surprised by the 'sudden' release of the trailer which strongly braked. The three groups are: 1. Drivers of group 1 drive an 'old' vehicle (1995 generation) non-equipped with BAS. Both sides of the drivers' track were free allowing them to avoid the target by steering and/or braking actions. 2. Drivers of group 2 drive a 'recent' vehicle (2004 generation) equipped with BAS under the same conditions as group 1. 3. Drivers of group 3 drive the same vehicle as G2, but some traffic cones were added on both sides of the drivers' way in order to limit their actions to only braking.
The results of the study provide an insight into drivers' use of cars braking aptitude and their potential behavior adaptation with new generation cars. The comparison between situations 1 and 2 gives information about the improvements of braking systems between the two car generations, and particularly the benefits in reducing stopping distance thanks to BAS. The braking maneuver in the 3rd situation is compared to the cases where drivers have only braked in the 1st and the 2nd situations (excluding steering maneuvers). This choice of maneuver is more frequent in urban areas accident situation. The results show a median reduction in the stopping distance between 2 and 9 m when comparing 'recent' to 'old' vehicle.