A Northland road safety exponent has welcomed an initiative to catch drug-impaired drivers through roadside saliva testing, saying motorists under the influence of drugs need to be stopped in their tracks.

Ministry of Transport figures show drugs were a factor in 23 crashes in Northland between 2011 and 2015, with 10 fatal accidents, five injury and eight non-injury accidents.

Roadsafe Northland Whangarei and Kaipara road safety education programme manager Gillian Archer said the new testing regime would have the same beneficial effect as breath alcohol impairment testing has had.

Associate Transport Minister Craig Foss plans to recommend saliva testing to Cabinet based on a review of the drug-driving enforcement regime.

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Police carry out random alcohol breath tests on any driver but test for illegal drugs only if they suspect a driver is under the influence. The current method involves only a manual impairment test that, if failed, requires a blood test.

Saliva tests take up to five minutes - much longer than a breathalyser. A failed test would still require a follow-up test. Random testing could be introduced as the technology allowed.

"It is well known that cannabis and other drug users currently believe themselves safe from detection and many do not seem to realise that impairment puts them and everyone else at risk," Ms Archer said.

"Drugs contributing to extreme and risky behaviour are a scourge on our community and those who are high and driving need to be stopped in their tracks."

Whangarei criminal lawyer Kelly Ellis said anything getting impaired drivers off the road had to be a good thing.

"Since cannabis stays in the system for a long time, saliva is a better test because it's a better indication of recent use," she said.