A compulsory seat belt wearing law in South Australia was preceded by a rise in the belt wearing rate and was accompanied by a further substantial rise. Casualty rates per 1000 involved vehicles, reported on a property-damage criterion, showed lower rates for 1967 and later models, which had belts compulsorily fitted, both before and after the wearing law. A before and after comparison showed reductions in the serious grades of casualties and an increase in the least serious. There was a differential effect on casualty reduction in 1967 and later models, which accounted entirely for the 7.5% overall reduction in the fatality rate. These comparisons are substantially free of effects due to concurrent changes in exposure to risk of accident and the observed reductions can be attributed to the belt wearing law.
Abstract