The government is planning to include criminal limits for drug driving into legislation before Parliament, to give police more options to deal with those driving under the influence.
There will also be thresholds set at which people would only get an infringement and a fine, rather than a criminal conviction.
The Land Transport (Drug Driving) Amendment Bill - currently before select committee - gives police the power to conduct random roadside testing.
An expert panel has advised the government about 25 impairing drugs and thresholds for driving set in other countries.
The drugs include prescription medicines, cannabis, cocaine and MDMA.
The thresholds would be similar to those used for drink driving - setting a certain limit for concentration of a drug in the blood.
Transport Minister Michael Wood says the government wants to include these measures in the legislation but is asking for feedback from the public first over the next few weeks.
"Last year, 71 people died when drivers crashed on our roads with drugs in their system, while in 2019 it was 108 people," Wood says.
"We're talking about families, friends and communities who have lost a loved one, or someone close to them."
Police Minister Poto Williams says driving while impaired by drugs or alcohol is one of the main contributors to death and injury on New Zealand roads.
Based on ESR data, in 2018 half of all drivers killed in crashes had drugs in their system, Williams says.
"Cannabis was the drug most commonly detected for deceased drivers involved in fatal crashes and tested for drugs, accounting for 27 percent of all deceased drivers.
"Methamphetamine was the next common detected drug, accounting for 11 percent of deceased drivers."
While drug drivers "already face serious criminal penalties if they are caught", Williams says, "the current law makes it hard for police to carry out more tests that could deter drug driving."
"The current approach to drug driving enforcement is not as effective as it could be at deterring this high-risk behaviour."
Ministers will write to the Transport and Infrastructure Committee requesting they consider the changes contained in an amendment to the Land Transport (Drug Driving) Amendment Bill.
Roadside saliva testing
However, Wood says the only penalty that could be applied after a roadside saliva test would be an infringement notice.
The only way a criminal conviction could follow is if someone then opted to take an evidential blood test, he says.
That was one of the protections written into the legislation to "ensure that we are putting in place a strong defense disincentive for drunk driving, but also dealing with the civil liberties issues that are at play here".
If an officer suspected someone was severely impaired, they could have them do a compulsory impairment test at the roadside, "a range of tests, walking in a straight line, touch your nose with your left hand, that sort of thing," he says, and if they fail - a blood test can then be requested.
"But the officer can't mix those things up, so once the officer has elected to go down the path of a random, oral fluid test, that is that is the only test that can apply at that time," Wood says.
"If the person returns two positive tests they can then request an evidential blood test after that, but if they do so, they run the risk there may be a criminal penalty that applies, if they are above the criminal threshold limit."