From mid-December, police will begin testing drivers for THC (cannabis), meth, MDMA (ecstasy) and cocaine.
Drivers who test positive will be banned from driving for 12 hours and will need to submit a saliva sample for more detailed lab testing. If the lab test finds drugs are present, drivers will face fines and demerits.
The roll-out, which is expected to be nationwide by mid-2026, aims to reduce car accidents caused by drivers under the influence of drugs.
The SMC asked experts to comment.
Dr Rose Crossin, Senior Lecturer, Department of Public Health, University of Otago, Christchurch, comments:
“Driving while impaired, whether that be by tiredness, prescription painkillers, or illegal drugs is a serious issue in New Zealand, and one that merits attention. My concern with the planned roadside drug testing regime is that it is only testing for the presence of a drug, not impairment. This is particularly an issue for cannabis (the mostly commonly used illegal drug in NZ), which stays in the body for longer, and can be detected after any intoxication or impairing effects have passed.
“This perpetuates a significant issue in our understanding of drugs – the equating of use with harm. I query the value of investing in a programme that is only testing for the presence of illegal drugs, rather than focussing the programme on impairment, where the potential for harm truly lies.
“I am also concerned about the possibility of inequitable outcomes from roadside drug testing, particularly if it is not systematic but rather targeted at particular neighbourhoods or cars or drivers, but I acknowledge that this will depend on how it is rolled out.
“Given that this programme is new to NZ, I hope that a robust and independent evaluation is carried out, before expanding nationally.”
Conflict of interest statement: “Nothing.”
Dr Fiona Hutton, Associate Professor, Institute of Criminology, Victoria University of Wellington, comments:
“Driving while impaired with any drug, whether it be prescribed medications, drugs like alcohol or illicit drugs like cannabis, is dangerous and should be avoided. However, this is an ill thought out piece of legislation, focused on a small number of illicit drugs, that will not address the harms from drug impaired driving – mainly because it will be testing for presence rather than impairment.
“If members of the public are going to be fined and banned from driving for 12 hours then Police need to be absolutely sure that they are actually impaired – we cannot and should not punish people who are not impaired. Many drugs, like cannabis for example, stay in the system for up to three weeks so testing positive does not automatically mean the person is impaired. Someone could smoke cannabis on a Saturday and test positive on the way to work on Monday when they are unimpaired and fit to drive.
“The use of statistics such ‘drugs are present in nearly a third of all fatal crashes’ should be avoided as this is highly misleading – just because drugs are present does not mean that the driver was impaired or that drugs were the cause of the fatal crash. This just reinforces inaccurate information. That these basic issues have not been properly addressed in the legislation is concerning.
“There are also questions around objections to the legislation based on the 1990 Bill of Rights Act and the inaccuracy of the proposed testing devices that remain unanswered. Further concerns have been raised about the effect on particular groups e.g., Māori who are already overrepresented in criminal justice statistics, and those who are using drugs like cannabis medicinally.”
Conflict of interest statement: “No conflict of interest.”
Dr Geoff Noller, Research Fellow, Department of Primary Health Care and Rural Health, University of Otago, comments:
“While up to 25 drugs are targeted, initially four “key” drugs will be focused on — THC (cannabis), methamphetamine (meth), MDMA (ecstasy) and cocaine. Testing will be undertaken with an Australian-made device, the Securetec Drugwipe 3s, which tests for impairing drugs in oral fluid.
“Clearly, improving road safety is an important priority, with Government data suggesting around 30% of road deaths potentially involve an impairing drug. The new strategy is, however, not without issues, both technical and social. Testing for THC is a case in point. With cannabis that is vaped or smoked, the device can detect THC in the oral cavity for around 8 to 12 hours at least. With frequent or heavy users this can potentially extend to 30 hours, well beyond the time that a person consuming cannabis might be impaired.
“One of the questions arising from this type of testing, therefore, is whether it detects actual impairment or is more likely to identify that a person has used cannabis at some time but is not impaired.
“In 2021 when the Independent Expert Panel provided advice leading to the Land Transport (Drug Driving) Amendment Act 2025, both illicit and prescription drugs were considered. At that time there was only one legally available medicinal cannabis product, which the panel considered would not be commonly prescribed.
“Fast forward to 2025 and the impact of the earlier Misuse of Drugs (Medicinal Cannabis) Regulations 2019 has seen a significant bloom in legal medicinal cannabis products, with over 50 currently available and at least 20 of these containing THC, the psychoactive ingredient. Consequently, there exists the real possibility that people legally and appropriately using medicinal cannabis, i.e. consuming long enough prior to driving to not be impaired, may test positive. This would impact not only the general public but potentially professional drivers too.
“There are also social issues related to the deployment of this type of testing. In their submission to the Land Transport Amendment Bill, the NZ Law Society noted the risk of inequitable consequences for Māori, as well as young people, lower socio-economic communities and rural communities. Both Māori and youth are more likely to use cannabis and while the Law Society was careful to note that it does not follow that Māori are any more likely than non-Māori to drive while drug-impaired, there is some risk that certain groups, including Māori, could be unfairly targeted.
“The above issues make it clear that while the new initiative may have a positive impact on road safety, there will potentially be problems associated with its implementation and people may find themselves unfairly caught up in legal and real world fallout from roadside drug testing. Given the legislation includes a medical defence where prescribed medications are concerned, at the least, those using legal medicinal cannabis would be well advised to carry some evidence of their prescription.”
Conflict of interest statement: “No conflicts of interest.”
Professor Joseph Boden, Principal Scientist, Christchurch Health and Development Study, Department of Psychological Medicine, University of Otago Christchurch, comments:
An article written by Professor Boden for The Conversation is excerpted here with his permission.
“With nearly a third of all road deaths involving an impairing drug, moves like this are clearly aimed at a serious problem.
“The research on cannabis and driving impairment is mixed. Many studies show an associative rather than causal link: people who use cannabis more often tend to report more crashes, but not whether those crashes happened while they were impaired. Unlike alcohol – where blood-alcohol concentration closely tracks impairment – no such relationship exists for THC. Cannabis is fat-soluble, so traces linger in the body and appear in saliva long after any intoxicating effect has passed, making saliva testing a relatively poor proxy for impairment.
“For the other targeted drugs – the stimulants methamphetamine, cocaine and MDMA – the connection to driving impairment is also unclear. At lower doses, stimulants can even improve certain motor skills. The risks are instead tied to perceptual shifts or lapses in attention, which a saliva test cannot detect. Because cocaine and meth remain illegal globally, it is difficult to conduct the controlled studies needed to link presence and impairment.
“The policy’s focus on just four illicit drugs also raises questions of scope. In practice, these are among the easiest and most visible substances to target: the low-hanging fruit. Yet impairment from prescription medications such as sedatives or painkillers is far more common and remains largely self-policed.
“Another pressing question is what happens when the test detects traces of cannabis long after impairment has passed. THC can remain detectable in regular users for up to 72 hours, even though its intoxicating effects last only a few. That means a medicinal cannabis patient who took a prescribed dose the night before – or a habitual user with high baseline levels – could therefore test positive while driving safely.
“Although the law provides for a medical defence, there is still no clear procedure for proving a prescription at the roadside. Few people carry that documentation, and it’s uncertain whether digital GP records would be accepted. In practice, some law-abiding drivers will inevitably be caught up in the process simply because of residual traces that pose no safety risk. Conversely, an inexperienced cannabis user may feel heavily impaired yet return a low reading.
“This uncertainty reflects a deeper flaw in the system. When the previous government first designed the policy, it intended to test for impairment. Because no devices could meet the evidentiary standard, the law was amended to test only for presence.
“In the end, a test that measures presence rather than impairment risks confusing detection with prevention – and may do little to make New Zealand’s roads any safer.”
Note: Professor Boden has added the following new comment:
“Medicinal cannabis users should be mindful of having evidence of their prescriptions available. Not that it will help at the roadside, but rather after an infringement notice is lodged.”
Conflict of interest statement: “No conflicts of interest.”