A roadside survey of the blood alcohol concentration levels of nighttime drivers in the Perth metropolitan area

Belinda Clark, Peter Palamara

Research output: Book/ReportCommissioned ReportResearch


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 (Ryan, 2000) and in 2000 (Kirov, 2001). 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. There was a relatively even proportion of drink drivers detected across the three week nights, Thursday, Friday and Saturday but a greater proportion of drink drivers were detected in the early morning sessions between 1am and 4:45 am. The back-calculation process applied to BAC evidentiary tests in Western Australia resulted in 26 drivers not receiving a drink driving charge and 65 drivers receiving a reduced BAC level charge. It is recommended that RBT schedules be amended to achieve greater coverage during early morning periods to accommodate the evolving changes in socialisation and alcohol consumption patterns and that this survey be conducted on annual basis to monitor drink driving patterns.
Original languageEnglish
Place of PublicationPerth WA Australia
PublisherRoad Safety Council of Western Australia
Commissioning bodyRoad Safety Council of Western Australia
Number of pages47
Publication statusPublished - Jun 2014


  • BAC
  • drink driving
  • RBT random breath testing
  • roadside survey
  • back-calculation

Cite this