SEAT-BELT LEGISLATION AND RISK HOMEOSTASIS - FURTHER ANALYSIS OF THE BRITISH DATA

It has been suggested that seat-belt legislation may result in drivers ' feeling overprotected and their consequent riskier driving may lead to more injuries to other road users (the risk homeostasis or compensa tion theory). We have examined data in Britain before and after legisl ation made seat-belt use compulsory for front-seat occupants of specif ied vehicles. The relative numbers of injuries to cyclists and pedestr ians in collisions with vehicles requiring and not requiring seat-belt use were compared, using a loglinear analysis taking into account pos sible confounding variables. It was not possible directly to incorpora te vehicle distance travelled for the two categories of vehicle. Howev er, a simple adjustment for differential vehicle use accounted for mos t of an apparent effect. The revised odds ratio (for mandated seat-bel t use vehicles versus nonmandated, post- versus prelegislation) was 1. 04 for cyclists and 1.06 for pedestrians, showing minimal, if any, evi dence for the theory.