Evaluation of Seat Performance Criteria for Rear-End Impact Testing
Conference contribution, 2011
The BioRID II has been recommended to be used in future legislative dynamic rear-end impact seat performance tests. Recommended injury criteria and assessment reference values to be used with the dummy is however still pending. This is mainly due to the incomplete understanding of the injury site and mechanisms responsible for the symptoms presented after such impacts. This lack of biomechanical data limits the possibility to evaluate any proposed injury criteria and associated reference values.
The aim with this study is to address these limitations by comparing crash test dummy parameter values from performed sled tests with real-life accident data. The results are expected to indicate the injury predictability of the complete sled test method, which includes performance criteria, the use of generic sled acceleration pulse, the use of the BioRID II and its current positioning procedure, etc.
Real-life injury risk was calculated for groups with similar seat designs from data provided by Folksam. By introducing grouped data, i.e. by dividing applicable data into groups with similar characteristics, the reliability of the insurance data increased while the dummy measurements remained constant. Two different injury risks were used in this study; those that had documented symptoms for more than 1 month and those that were classified as a permanent impairment as the consequence of a rear-end impact. The injury risks for the groups were compared to single crash test dummy parameter values from sled tests performed with a BioRID II in 16 kph medium Euro-NCAP pulse. In the comparison, 12 seat groups were compared with 6665 insurance cases (range from 94 to 1575 cases/group). Regression coefficients (R2) were calculated.
The analysis of groups with similar seat design provided the most reliable results. The analysis showed that NIC, upper neck shear force, vertical head acceleration and lower neck bending moment were the parameters that best predicted the risk of developing permanent impairment given that the occupant had initial symptoms following a rear-end impact. Similarly, NIC, vertical head acceleration and lower neck moment were parameters that best predicted the risk of short term (> 1 month) symptoms. These results are supported by recent studies.