Police hope a new device could help to catch more motorists who take drugs before getting behind the wheel of a car.
Officers will be conducting a simple saliva test, which can test for cannabis use at the roadside, to screen drivers across Northamptonshire.
The test will be carried out when officers suspect somebody has taken drugs having arrested them for a road traffic offence.
It will give an indication about whether further tests are needed.
Inspector Jen Helm, said: “The force supports any new tactics or equipment that can help us to make the roads safer for the people of Northamptonshire.
“Road collisions are not just statistics; there are real victims at the centre of every one. If this device helps reduce the number of traffic collisions on our roads it can only be good thing for the county.”