The epidemiology of traffic accidents and the effect of the 1969 breathalyser amendment in Canada

An epidemiologic evaluation employing incidence, case-fatality and mortality rates has permitted extrapolation of trends of pre-1969 Breathalyser Amendment rates for the post breathalyser years 1970, 1971 and 1972 in Canada. The difference between actual and predicted rates after the introduction of the 1969 Breathalyser Amendment was explained by initial reductions in the incidence of injury (the greatest reductions in incidence occurred at “heavy drinking” periods—6 p.m. to 12 midnight and 12 midnight to 6 a.m.) and initial reductions in the severity of the resulting injury, producing a magnified downward movement in mortality rate. However, this early “shock” effect lasted less than one and a half years with 1971 and 1972 mortality rates exceeding pre-breathalyser levels. Similarities of the Canadian experience with the introduction of a breathalyser law in the United Kingdom and possible refinements of existing breathalyser legislation are discussed.