HEADREST POSITION DURING NORMAL DRIVING - IMPLICATION TO NECK INJURY RISK IN REAR CRASHES

The gap and relative height of headrest behind drivers were determined for 1915 vehicles approaching an intersection on a two lane road. Veh icle type and headrest adjustment were also evaluated using film of no rmal driving taken by the Insurance Institute for Highway Safety. Only 10% of drivers had headrests in the most favorable position to preven t neck extension during a rearend crash. 73% of cars had adjustable he adrests, but only a quarter were placed in the up position. 83% of the adjustable headrests could have been raised to better protect the dri ver. Hyge sled tests were run to determine biomechanical responses for the various conditions observed in normal driving. This included thre e headrest heights and three gaps behind the head. Neck extension from the Hybrid III dummy was normalized to the response for a high, close headrest, and injury risk was assumed to be proportional to neck exte nsion. The current driving situation has a relative injury risk of 3.4 in rearend crashes, compared to 1.0 for the favorable condition. If a ll adjustable headrests were placed in the up position, the relative r isk would be lowered to 2.4, a 28.3% reduction in whiplash injury risk . Public education and vehicle design should address the importance of proper headrest placement for driving safety. Copyright (C) 1996 Else vier Science Ltd.