AIS 1 neck injuries has become the most common disabling injury in vehicle crashes. Research has shown that there are variations in rear impacts causing short- and long-term disability to the neck. Therefore impacts where the duration of symptoms differ need to be separated in analyses. Crash severity is usually measured as change of velocity. The conelation between injury risk and impact severity parameters based on acceleration levels is to a high extent unknown. Since 1995, approx. 15,000 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 34 real life rear impacts were analysed where the change of velocity and the crash pulse were measured. The injury status of the 49 front occupants was classified as no symptoms, or symptoms less or more than 1 month after the impact. Also injury risk functions were calculated for different duration of symptoms correlated to the crash severity parameters. Most of the occupants that sustained symptoms more than 1 month, the change of velocity was higher than 15 km/h and the mean acceleration more than 5g. The average impact speed and mean acceleration for this group were 23 km/h and 5.4g. Furthermore, the crash pulses form a corridor with acceleration between 5 and 10g and duration between 80 and 150ms. Those occupants that sustained symptoms less than 1 month, the average change of velocity were 10 km/h and the mean acceleration was 3.5g. When designing test methods for evaluating vehicle safety concerning AIS 1 neck injuries, the acceleration pulse will differ considerably depending on focusing short- or long term consequences.
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