Influence of head restraint position on long-term AIS 1 neck injury risk

Abstract

Although head restraints became mandatory in several countries during the 1960s and 1970s, the number of neck injuries is still rising, which indicates that current head restraints are not giving sufficient protection. Despite numerous epidemiological and parameter studies, there are no methods to estimate in advance the potential neck injury risk reduction as a result of a better positioned head restraint. The purpose of this study is to assess the influence of the head restraints on the long-term AIS I neck injury risk for real-life crash conditions. Madymo simulations of rear-end crashes were performed. The BioRID II seated in three car models was exposed to 20 recorded crash pulses with the potential to cause neck injuries. For each crash pulse, 132 head restraint positions were analysed in terms of NICmax value and long-term AIS I neck injury risk. It was found that the optimal head restraint position for almost all crashes was that with zero backset and the top of the head restraint at the same level as the top of the head. In general, the NICmax and the injury risk were primarily influenced by the backset and only to a small extent by the head-to-head-restraint height; the neck injury risk was reduced by 0.1 for every 2.5 cm decrease of the backset. The results of this study show that it is possible during the development phase to estimate the potential protection for redesigned or active head restraints.