Scepticism from drug experts on whether we're ready to implement law to allow Police to randomly test drivers for drugs.

Jami-Lee Ross' private members' bill has been drawn from the ballot, which if approved, would allow police to test drivers for cannabis, MDMA and methamphetamine via a saliva swab.

Drug Detection Agency CEO Kirk Hardy says while he likes the idea there's evidence from across the Tasman that the technology isn't quite ready.

"I think one in three of those devices were actually failing to work at all, so you can imagine the cost there, and the accuracy rate was around 67%."

Under the existing system police use impairment tests for detecting drug-driving, such as making a motorist walk in a straight line.

LISTEN ABOVE AS KIRK HARDY SPEAKS WITH MIKE HOSKING