THE EFFECT OF CAR SEATS ON NECK INJURIES IN LOW-SPEED REAR IMPACTS

Paper in proceeding, 1997

Neck injuries often occur at low impact velocities, typically less than 20kph. Such accidents usually result in minor 'whiplash' injuries, but about 10% of them lead to permanent disability with degree of disability over 10%. Factors that could influence the risk of sustaining neck injuries in rear impacts include: (1) the distance between the head and the head restraint; (2) the seat's stiffness structure; and (3) the car's rear structure. This article outlines some tests to show whether the seats or the structure affect neck injuries more. Two cars, with empty weights 705kg and 725kg, were impacted from the rear at 20kph by a mobile barrier in two full-scale rear-impact tests. The drivers' seats were retained, but the front passenger seats and their attachments were swapped over. Various motion sensors and high-speed cameras recorded the motions of the dummies in the passenger seats. The motion of dummies in mini-sled rear-impact tests was also recorded. It was found that seat design, not car structure, was the reason for differential dummy loading. Dummy acceleration does not really start until car acceleration has almost finished. The article finally evaluates some new principles for designing a car seat, which aim to minimise the motion between the lower and upper ends of the cervical spine in a rear collision.