A roadside survey of the blood alcohol concentration levels of night-time drivers in the Perth metropolitan area

Research and analysis
The aim of this research was to investigate changes in driver blood alcohol concentration (BAC) levels within the Perth metropolitan area over time through a replication of, and comparison with, two previous road side surveys conducted during 1999 and in 2000.
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Data was collected at roadside police Random Breath Testing (RBT) sites during April to May 2012. A total of 8,435 tests were conducted over a six week period on Thursday, Friday and Saturday nights. Around 7% of drivers tested returned a positive BAC, and 1.4% of these had BACs over the legal limit. This represents a significant reduction in the number of drivers detected with an illegal BAC compared to both of the two previous survey findings of 2.1% of drivers in 2000 and 1.9% in 1999.

Amongst the drivers with illegal BACs there was a smaller proportion of drivers detected (0.7%) in the current survey within the ≥0.05-0.079 g/100ml range compared to the two previous surveys (1.0% & 1.1%).

Road safety benefit:
The research was beneficial to the extent that it provided Government with recommendations that include:

  • Regular roadside breath testing enforcement schedules should be extended into the early hours of the morning to reflect the evolving changes in socialisation and alcohol consumption patterns.
  • Removing back calculations for blood alcohol concentrations.
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