Police Commissioner Karl O'Callaghan believes a big rise in the number of cars monitored by speed cameras is changing driver behaviour, with new figures showing a significant fall in the percentage of motorists caught speeding.
Figures in the latest WA Police annual report show 22.9 million cars were monitored by speed cameras in the 2011-12 financial year - a rise of more than 66 per cent on the 2010-11 year when 13.7 million cars passed the devices.
While the number of motorists detected speeding increased from almost 3.6 million to about 4.2 million, the percentage of speeding drivers fell. More than 26 per cent of motorists who passed a speed camera in 2010-11 were speeding, compared with 18.5 per cent in 2011-12.
The high percentage from 2010-11 was attributed to the introduction of dual lens Vitronic speed cameras which caught more speeders. Police believe the fall in 2011-12 was because of a change in driver behaviour.
Mr O'Callaghan said the changes might also be in part a result of more detections at intersections monitored by integrated speed and red light cameras.
Figures from the 2011-12 annual report show 2.28 million vehicles were caught speeding at such intersections - a rise from 1.94 million in 2010-11.
"I can tell you where I see it most - the red light speed cameras," Mr O'Callaghan said.
"The community quickly work out where they are, and if you follow them around to these intersections, you can see them baulking and slowing down as they approach these intersections because they know the cameras are there. There is no doubt it is changing driver behaviour because they know how effective these cameras are.
"I think the Vitronic, fixed and red light speed cameras have had an enormous impact, as have the static cameras on the freeway."
In January, The West Australian revealed police were developing roof-mounted speed cameras on patrol cars that could dramatically boost the number of vehicles monitored for speeding.
Police conducted more random breath tests - 767,226 in 2010-11, compared with 883,046 in 2011-12. Of those, 2.2 per cent exceeded the limit in 2010-11, compared with 1.7 per cent in 2011-12, the lowest in at least five years. The number of motorists caught not wearing seatbelts increased from 14,204 in 2010-11 to 15,384 in 2011-12.