Integrated Pedestrian Safety Assessment Procedure

Structural improvements at the vehicle front are state of the art in the field of pedestrian safety today and offer a basic passive protection. Meanwhile advanced safety systems have entered the market. Deployable systems, like the active bonnet or the windscreen airbag, further enhance the passive protection of passenger vehicles while systems of active safety such as autonomous emergency braking (AEB) are able to mitigate or even avoid an accident due to a reduction in collision speed. However, an integrated assessment of active and passive pedestrian safety is a current challenge. A procedure to assess and compare the safety potential as well as the effectiveness of active and passive safety measures on one scale was presented at the last ESV conference (paper 11-0057) and has been further enhanced since then. In addition, an existing external test protocol for advanced forward-looking pedestrian safety systems has been implemented into the assessment procedure, which enables a vehicle-model-specific evaluation of active safety systems for children and adults. An important characteristic of the assessment procedure is its modular design, combining structural characteristics of a vehicle front with accident kinematics and accident research data. The procedure uses the results of the Euro NCAP pedestrian protection tests of the car to be assessed and adapts the HIC values to the real accident kinematics derived from numerical simulations. Kinematics parameters are the head impact velocity, impact angle and impact probability. The assessment procedure finally provides index values for children and adults, which indicate the risk for an AIS3+ head injury due to the primary impact depending on the collision speed. A first update to the procedure, which is already prepared for the Euro NCAP-GRID, has been made with respect to the pedestrian size distributions used to determine the impact probabilities for the particular wrap-around-distance zones of the vehicle front. Both distributions, i.e. for children and adults, are now based on current GIDAS data and establish a direct link to the actual accident situation. Further changes have been carried out regarding the weighting and adaptation of the Euro NCAP values, resulting in a new correlation between head impact velocity and HIC. At last the index calculation itself has been revised by the use of a more convenient injury risk curve. For active pedestrian safety systems the reduction in collision speed achieved within the particular test scenarios specified in the external test protocol forms the main assessment criterion. A methodology has been developed, which implements those test results according to their relevance into the assessment procedure and enables the calculation of a corresponding index value. A case example describing an AEB system equipped with a warning function has been defined in order to demonstrate the methodology. Index values are calculated for six real passenger car fronts, all representing different vehicle classes. Beside the basic vehicle, an active bonnet, a windscreen airbag and the generic AEB system are each assessed. The corresponding index values reveal, which pedestrian safety systems are most effective for the different vehicle classes as well as pedestrian groups.