The AA is calling for urgent funding for police to randomly test drivers at the roadside for drug intoxication, calling it New Zealand's "hidden killer".
Dylan Thomsen of the AA, speaking this morning to TVNZ 1's Breakfast, said driving under the influence of drugs is very common in New Zealand, with cannabis the most prevalent drug.
P or methamphetamine intoxication was also being seen on New Zealand roads, he said.
Roadside saliva testing showed recent use, rather than long term use such as the results produced by a urine test.
The effects of drugs on drivers varied with the drug, Mr Thomsen said, with cannabis making people more inattentive and tired, while P often made drivers more aggressive and reckless.
"You've got a small device that you put into your mouth that you lick a couple of times," he said.
"You give that back to the police officer and it takes a couple of minutes for the results to come through."
The cost would be about $9 million to test about 45,000 motorists per year - New Zealand spends about $40 million per year on its drink driving enforcement.
Mr Thomsen said analysis had shown for every $1 invested, about $8 in benefits from reduced crashes could be expected.