As introduction, the report describes Australian design rules 22 and 22a requiring head restraints to be fitted to driver and front left seats of all new cars in australia from 1972 models onwards. The effective heights of these restraints are discussed, as well as the nature of whiplash injuries which they are designed to prevent. Other studies of head restraint effectiveness are reviewed. Data on 1974-75 claims to the motor accidents board in victoria for injury compensation are then analysed to evaluate the effectiveness of ADR 22. Potential benefit groups (front outboard seat occupants in rear end impacts) and disbenefit groups (rear seat occupants in front end impacts) are considered, as well as other occupants and crash circumstances as a control for crash severity differences. The report concludes that there is weak evidence that ADR 22 is effective in reducing whiplash injuries sustained in rear end impacts. The benefit is almost entirely confined to female occupants of front left seats. There is no evidence of disbenefits in terms of head or facial injuries to rear seat occupants. However there is evidence of disbenefits in terms of whiplash and major intracranial injuries to drivers involved in front end impacts in ADR 22 cars compared with pre-ADR 22 cars.
Abstract