Neck injuries in frontal impacts: influence of crash pulse characteristics on injury risk

AIS1 neck injuries are the most frequent disabling injuries among car occupants in road traffic accidents. Although neck injury is mostly regarded as resulting from rear end collisions, almost one third of all neck injuries occur in frontal impacts. The injury mechanisms in both rear-end and frontal impacts are still not known, although different hypotheses exist. Since 1992, approx. 100,000 vehicles on the Swedish market have been equipped with crash recorders to measuring frontal impacts. This paper analyses the influence of different characteristics derived from the acceleration time history on the risk of short- and long-term disability to the neck in frontal impacts. The study includes injury outcomes from 187 restrained front seat occupants in 143 frontal collisions with an overlap exceeding 25%, where the crash pulses have been recorded using crash pulse recorders. The results show that the shape of the crash pulse influences the risk of long-term disability to the neck. The vehicle accelerations in the mid and last third of the crash pulse seem to be important. It is also shown how change of velocity and mean and peak accelerations influence the neck-injury risk. It is suggested that the risk of sustaining an AIS1 neck injury in frontal impacts could be reduced by using more effective pretensioners and more advanced belt-load limiters. These results may also have implications for neck injury mechanisms in rear-end impacts.