Head and Neck Loading Conditions over a Decade of IIHS Rear Impact Seat Testing 2019-01-1227
Rear end impacts are the most common crash scenario in the United States. Although automated vehicle (AV) technologies, such as frontal crash warning and automatic emergency braking, are mitigating and preventing rear end impacts, the technology is only gradually being introduced and has limited effectiveness. Accordingly, there is a need to evaluate the current state of passive safety technologies, including the performance of seatbacks and head restraints. The objective of this study was to examine trends in head and neck loading during rear impact testing in new vehicle models over the prior decade. Data from 601 simulated rear impact sled tests (model years 2004 to 2018) conducted as a part of the Insurance Institute for Highway Safety Vehicle Seat/Head Restraint Evaluation Protocol were obtained. This dynamic evaluation involves a simulated rear-end crash using a BioRID dummy positioned in the seat attached to a crash simulation sled and accelerated to represent a rear crash with a delta V of approximately 15.6kph (15.6±0.26kph). Head injury criterion and neck injury criteria were calculated for all tests to evaluate head and neck loading, respectively. Trends in the test dummy responses were compared across model years and vehicle classes. A one-third reduction in average HIC-15 values was observed for model year seats after 2008 when compared with prior years. When comparing the same periods, average Nij values were found to decrease by 46% and 33% in tension-extension and tension-flexion, respectively. No differences were observed when comparing cars and LTVs. It is noteworthy that all data points were well below published injury assessment reference values for all model years. The results illustrate the current performance of seat and head restraint design in low to moderate severity rear-end impacts. Given the persistence of rear-end impacts and potential changes to the in-vehicle layout with improving AV technology, the data should be considered by designers, researchers, and evaluators looking to project future crash and injury rates in rear end impacts.
John M. Scanlon, Jessica L. Isaacs, Christina Garman