People driving under the influence of drugs are being targeted in a major operation across the north-east of England.
Suspect motorists will face roadside tests
Cleveland, Durham and Northumbria police have joined forces in the campaign.
Road safety organisation and regional drug action teams are also involved.
As part of the operation, traffic officers in Durham are undergoing specialist training to help them identify drivers using drugs.
Suspects will undergo initial roadside tests with a further examination at a police station, if needed.
An advertising campaign across the region will feature posters on more than 200 buses.
Paul Goundry, head of traffic at Durham Police, said: "The tests we are using are absolutely superb at detecting the impaired driver.
"If alcohol has been discounted at a road side test we can now use these additional tests, which are simple to perform when sober but much more difficult to do when impaired."
Vanessa Bainbridge from the Northumberland Drug Action Team said: "We need people to take this issue seriously.
"Drugs affect the way you think and behave and can have a significant effect on your sense of judgement and reaction times."
The Durham force has called for regular drug testing of motorists.
Senior officers have urged the government to develop a new detector to test for drugs like cannabis, ecstasy and cocaine.
The call followed figures from the force, which showed drugs were found in more than half of drivers killed on County Durham's roads in 2002.