The utilisation of passive safety systems to protect occupants has attained a very high level over the past thirty years. Although further improvements are still possible, these increasingly minor improvements are only to be had with a high degree of effort. As a result, the key question must always be their efficacy in an accident situation. If reliable information is available on the imminent collision, measures taken in the pre-collision phase can as a rule frequently exert a significantly greater influence on the accident situation. Preventive measures are the key to success here.
This paper aims to show how a preventive safety approach can contribute to lessening the serious consequences of an accident by creating an optimum interplay of active and passive safety measures. To further enhance vehicle safety, driver assistant systems are already available that warn the driver of an imminent rear-end collision, support him in his reactions or if he fails to react sufficiently, to even initiate an automatic braking, should the collision prove unavoidable.
Automatic pre-crash braking can, in an ideal situation, fully prevent such collisions or can greatly reduce the collision speed and thus the impact energy (and in turn the severity of the accident).
If a vehicle is being braked in the lead-up to the collision, the occupants are already being pre-stressed by the deceleration. The information available about the imminent accident can be used to activate the belt tensioners and likewise other passive safety systems in the vehicle before the advent of the impact. The vehicle deceleration before the crash also causes the front of the vehicle to dip. Conventional crash tests do not take this specific impact situation into consideration. This is why, for example, the influences of the pre-collision movements of the occupants are not recorded in the test results. Furthermore, a reproducible representation of the benefit of the vehicle safety systems which prepare the occupants for the imminent impact is not possible.
In order to demonstrate the functions of automated pre-crash braking and to investigate the differences during the impact as a consequence of the altered occupant positions as well as the initiation of force and deformations of the vehicle front, DEKRA teamed up with BMW to carry out a joint crash test with the latest BMW 5 series vehicle.
It involved the vehicle braking automatically from a starting test speed of 64 km/h (corresponding to the impact speed set by Euro NCAP) to 40 km/h. The test was still run by the intelligent drive system of the crash test facility. The test supplemented the work of the vFSS working group (vFSS stands advanced Forward-looking Safety Systems]).
The paper will describe and discuss the relevant test results. In addition, the possible benefits of such systems will also be considered. The test required several modifications to be made to the test facility as well as the vehicle. The paper will also deal with that.