WA Police are being equipped with new roadside drug-testing machines that can check for a range of drugs in as little as five minutes.
Police said 20 of the new state-of-the-art devices would be used in the city and in regional areas to test motorists suspected of being affected by drugs.
Police Minister Liza Harvey said the rollout of the machines should have a significant impact.
Mrs Harvey says recent testing of the machines has found a disturbing number of motorists who are drug impaired.
"While it's disturbing, the good news is that police are out there, they're doing this testing," she said.
"They are pulling the drivers over and we are getting those drivers off the road.
"In certain circumstances my expectation is that some of these drivers are likely to be spending some time behind bars."
Police said the machines would be used in the same manner as roadside breath tests for alcohol.
In a statement, WA Police said those found with illicit drugs in their system could be charged with driving with a prescribed illicit drug in oral fluid.
The penalty for a first offence is a $500 maximum fine and three demerit points.
A driver who commits a subsequent offence attracts a $500 to $1,000 fine and could have their licence suspended for a minimum of six months.