Samenvatting
In New South Wales, Australia, the wearing of seat belts was compelled by a regulation under the Motor Traffic Act. The number of occupants of motor vehicles killed in traffic crashes during 1972, the first year of the regulation, was 701, as compared to 860 (18.5% more) in 1971. It was not proved that the new law was responsible for this drop. However, there was no such drop in a number of associated variables. Further, no other measure was introduced at the end of 1971 which might conceivably have had a marked effect on the number of occupants killed. It is reasonable to assume, therefore, that the relationship was a causal one.