Influence of Crash Pulse Characteristics on Whiplash Associated Disorders in Rear Impacts—Crash Recording in Real Life Crashes

There are variations in rear impacts causing Whiplash Associated Disorders (WADs) which lead to short-and long-term consequences. Most rear impacts lead to no injury or to symptoms that are temporary. Impacts where the duration of symptoms differs need to be separated in analyses in order to isolate representative rear impact conditions in which more long-lasting WADs occur. The correlation between injury risk and impact severity parameters based on acceleration levels is largely unknown.Since 1995, approx. 40,000 vehicles on the Swedish market have been equipped with crash pulse recorders measuring the acceleration time history in rear impacts. In the present study, the results from crash recording of 66 real-life rear impacts were analyzed, where the change of velocity and the crash pulse were measured. The injury status of 94 front-seat occupants was classified as: no injury, symptoms for less than 1 month, symptoms for more than 1 month, or symptoms for more than 6 months after the impact. The injury risk was calculated for different duration of symptoms and grades of WAD, 0–3, correlated to the crash severity parameters.For most of the occupants that sustained symptoms for more than 1 month, mean acceleration was more than 4.5 g, and change of velocity higher than 15 km/h. The average mean acceleration and change of velocity for this group were 5.3 g and 20 km/h, respectively. For those occupants that sustained symptoms for less than 1 month, the average change of velocity was 10 km/h and the mean acceleration 3.9 g. Mean acceleration was found to be the best candidate to predict duration of symptoms compared to change of velocity and peak acceleration. There was no significant correlation between different grades of WAD and crash severity. When designing test methods for evaluating vehicle safety concerning WAD, the acceleration pulse differs considerably, depending on whether the focus is on short-or long-term consequences.