The relationship of seat backrest angle and neck injury in low-velocity rear impacts

Abstract

Car-rear-impact-induced cervical spine injuries present a serious burden on society and, in response, seats offering enhanced protection have been introduced. Seats are evaluated for neck protection performance but only at one specific backrest angle, whereas in the real world this varies greatly owing to the variation in occupant physique. Changing the backrest angle modifies the seat geometry and thereby the nature of its interaction with the occupant. Low-velocity rear-impact tests on a BioRID II anthropomorphic test dummy (ATD) have shown that changes in backrest angle have a significant proportionate effect on dummy kinematics. A close correlation was found between changes in backrest angle and the responses of neck injury predictors such as lower neck loading and lower neck shear but not for the neck injury criterion NICmax. Torso ramping was evident, however, with negligible effect in low-velocity impacts. The backrest angle ranged from 20° to 30° whereas the BioRID II spine was adapted to a range from 20° to 26.5°. Nevertheless, in general, instrumentation outputs correlated well, indicating that this ATD could be used for evaluating seats over a 20–30° range rather than solely at 25° as required by current approval test specifications.