The challenge
New South Wales wanted to deter drink driving and cut alcohol-related crashes.
The case
New South Wales introduced random breath testing (RBT) on 17 December 1982, allowing police to stop and test drivers at random. Researchers Homel, McKay and Henstridge analysed daily crash data from 1976 to 1992, controlling for weather, road use, economic conditions and an earlier change to the legal alcohol limit. Total fatal crashes dropped 48% at first, though that effect lasted only about two months. The lasting effect showed in single-vehicle night-time crashes, which fell 24% and stayed lower for nearly five years. There were an estimated 12% fewer such crashes for every 1,000 drivers tested, and the effect grew as testing increased from 1987.
Why it worked
The results support the theory that RBT works through deterrence: the effect grew with the number of drivers tested, and there was almost no effect on crashes not related to alcohol.
Sources
- Homel, R., McKay, P., & Henstridge, J. (1995). The impact on accidents of random breath testing in New South Wales: 1982–1992. Proceedings of the 13th International Conference on Alcohol, Drugs and Traffic Safety (T'95), Adelaide (TRID abstract).
- Henstridge, J., Homel, R., & Mackay, P. (1997). The long-term effects of random breath testing in four Australian states: a time series analysis (CR 162). Federal Office of Road Safety.
- NSW Traffic Authority (1985). Evaluation of random breath testing (RN10/85) (TRID abstract).
- Homel, R., Span, D., & Stanislaw, H. (1996). Drink drive enforcement: some lessons learned from 12 years of random breath testing in New South Wales. VTI Konferens (TRID abstract).
- Cashmore, J., & Vignes, G. (1984). Evaluation of random breath-testing: police operation of random breath-testing, 17 December 1982 to 31 December 1983. NSW Bureau of Crime Statistics and Research (TRID abstract).
- Australian Seniors News (2022). 40 years of random breath testing.
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