Drink-driving Law: Enforcement and the Legal Blood Alcohol Limit in New South Wales

Abstract

This paper reports the results of a preliminary analysis of daily fatal crashes in New South Wales, Australia, between July 1975 and December 1986. The analysis unexpectedly uncovered a small but statistically significant decline in crashes coinciding with the introduction of a law lowering the legal blood alcohol concentration (BAC) from .08 to .05 g%. The original aim of the analysis was to develop for a larger study appropriate log-linear techniques to assess the impact of a range of government initiatives, including laws aimed at the drinking driver: increased penalties, the .05 law, and random breath testing (RBT). The analysis showed that RBT immediately reduced fatal crashes by 19.5% overall and by 30% during holiday periods, and that the .05 law, introduced two years before RBT, apparently reduced fatal crashes by 13% on Saturdays. There was no significant effect of the .05 law on any other day of the week, and there was no clear evidence that any other initiative had a statistically significant effect on accidents. Although the apparent impact of the .05 law was small, it is surprising that any effect was discernible, since the law was not extensively advertised and police enforcement was no more intense than is usual over Christmas. However, any effects of the .05 law may not have been sustained if RBT had not been introduced two years later.