While there is strong evidence that seat belt wearing reduces the incidence of severe injuries to vehicle occupants involved in crashes, there is also evidence that the use of lap/ sash seat belts increases minor and moderate neck injuries in crashes. In recent years, head restraints have been installed in the front seats of cars with the aim of reducing minor neck injuries ("whiplash"), principally in rear impacts where their frequency of occurrence is highest. This study examined the interaction between static lap/ sash belt use and the availability of head restraints installed under Australian design rule 22 (ADR 22), in terms of their effect on neck injury. ADR 22 allowed either fixed or fully height- adjustable head restraints, and many of the adjustable type are not set in the correct position in practice. There was no statistically significant evidence for such an interaction. However there was some evidence that the effect of seat belt use on neck injury severity is smaller when ADR 22 head restraints are available, compared with the belt effect on occupants of pre-ADR 22 cars. ADR 22 head restraints appeared to decrease the risk of whiplash injury, but increase the risk of moderate- to- critical neck injury, especially among static lap/ sash belt users and possibly among non-users as well. It was concluded that ADR 22 head restraints as used in practice are not suitable as a countermeasure to the negative effects of lap / sash seat belt use on neck injury.
Abstract