WA police need to conduct at least twice as many random breath tests to reduce alcohol-related crashes significantly on State roads, a study comparing RBT rates in Queensland and WA says.
The study, which examined the relationship between RBT rates and alcohol-related accident rates in the two States, showed WA had a ratio of one random breath test to every three licensed drivers four years ago - one of the worst ratios in the country, though it showed the ratio had improved to one RBT to every two licensed drivers by 2012 - the last year data was analysed.
Alcohol-related accidents in WA would be cut by 15 a month if random tests doubled, the research found.
Study co-author Lorraine Mazerolle, of the University of Queensland, said the optimal ratio was one RBT to every licensed driver, such as in Queensland, because it was proved to deter drink-drivers. "The level of saturation seen in WA is not sufficient to have a deterrent effect," Professor Mazerolle said.
"When people think they are likely to get caught by an RBT test, they are less likely to drink and drive because they are afraid of being caught.
"The results are pretty clear in that WA needs to move towards that 1:1 ratio."
Police Minister Liza Harvey said the number of alcohol- related crashes in WA had reduced dramatically over the past two to three years.
Mrs Harvey said funding had been provided through the Road Trauma Trust Fund from May 2012 for extra policing hours to meet a target of 1 million breath tests a year.
"Last financial year, we exceeded that by 516,448, giving a total of 1,516,448 breath tests," she said.
"Of the 1.5 million tested, 14,238 had exceeded the limit - that's down from 19,288 in 2007-08 when 892,751 were tested."
Study co-author Jason Ferris said they found WA's random breath testing strategy was capturing more drink-drivers but not deterring drink-driving in the community.
Mr Ferris said WA's "more targeted" approach, which focused on events and certain times of the day, was not as effective as a deterrent because drivers thought there was less chance of them being caught.
WA police carried out 7275 RBTs on New Year's Eve and 12 people were charged with drink-driving.