The crackdown on drug drivers is due to start today.

Starting in Wellington first, saliva testing will be used to test the drivers for 4 drugs; cannabis, meth, MDMA and cocaine.

Police Minister Mark Mitchell told Heather du Plessis-Allan that the drug tests being used are new to police, and a trial period is necessary before a national rollout. 

"We will scale it up, but the police have to make sure. It's a new form of testing, so it's important to trial it."

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