Abstract
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. 95 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
(80 km/h) and distance (23 m), the subjects were surprised by the "sudden" release of the
trailer which strongly braked. The three groups are:
- 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; - Drivers of group 2 drive a "recent" vehicle (2004 generation) equipped with BAS
under the same conditions as group 1; - 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 3 rd situation is compared to the cases where drivers have only braked
in the 1 st and the 2 nd 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.
Keywords - Driver behavior, brake assist system (BAS or EBA), accident situation, test track.