On 10 March, New Zealand’s parliament has passed the Land Transport Drug Driving Amendment Act 2024 – which swaps out any pretense of measuring impairment with accurate devices, to just detecting recent use of drugs – and the following day it was signed into law.
This new law, passed by all MPs from National, Labour, NZ First and Act, but opposed by MPs from The Greens and Te Pāti Māori, amends the existing driving legislation to allow:
• The Minister of Police can now approve devices and methods that are inaccurate and that do not measure impairment;
• Oral Fluid Testing Devices to be used to swab driver’s mouths can now indicate ‘recent use’ rather than actually finding impairment;
• Failing two oral swabs will result in a driver being immediately prohibited from driving for 12 hours, and a blood sample is sent to a lab for evidential analysis;
• The second test may not be at the roadside; the new law allows police to detain and take drivers away to another location for that second test and/or a blood test. The second test may be a machine at their station or regional headquarters.
• The blood test may be taken by any officer, and by force if necessary.
• If the evidential blood test result is over 1ng THC this is deemed low risk and the driver will be fined and will incur some demerit points.
• If the result is over 3ng this is deemed to be high risk and the driver will face criminal charges and incur more demerit points. These levels are not related to impairment, but seem to have been picked to match available devices.
• It allows devices, tests and methods to be for ‘families of substances’, not just specified substances. This means there will be increased false positives. For example, “meth” will actually be amphetamine-type substances which includes Ritalin (prescribed for ADHD). The non-psychoactive medicine CBD will trigger a false positive for THC. Taking Lidocaine will cause a false positive for cocaine.
• A driver may now have samples re-tested independently, at their own cost. This is equivalent to drink-driving laws.
• The law must be reviewed in 5 years, but MPs deleted all criteria for that review and instead inserted new text that allows the Minister of Police to appoint their own reviewer and to set the terms for that review.
Attorney General Judith Collins says the new law breaches the Bill of Rights which protects against arbitrary detainment and unreasonable search and seizure. MPs from Labour, NZ First and ACT all said they shared these concerns but voted for it anyway.
There is a medical defence for users of prescribed drugs including medicinal cannabis. Drivers must have a “current and valid” prescription and be following their doctor’s instructions (which may include, for example, not driving for 4 hours after use).
The Police’s tender for the Oral Fluid Testing Devices they intend to use is for:
i. THC (Cannabinoids)
ii. Methamphetamine (as an amphetamine type substance)
iii. MDMA (or ‘ecstasy’, as an amphetamine type substance)
iv. Cocaine and metabolites
The roadside devices will not test for opioids, sleeping pills like benzodiazapines, or fatigue, etc. Aside from the inherently inaccurate devices making up positive results when they should not, there will also be false positives from non-impairing substances (eg CBD = THC, Ritalin = meth/mdma, lidocaine = cocaine).
Meanwhile, SBS reports Victoria’s Parliament drops automatic licence bans for cannabis using drivers
Legalise Cannabis MP David Ettershank introduced the Bill which has been passed by a majority of MPs. Victorian Premier Jacinta Allan said “ Victoria is happy to lead the way on cannabis policy.” Drivers there who test positive on the roadside will no longer be automatically barred from driving.
What does the science say?
Neither the detection of THC nor its metabolites in blood, breath, urine, or saliva is predictive of behavioral impairment, according to a literature review.
According to a new Australian study published last month in the Journal of Safety Research, patients who consume botanical cannabis over extended periods do not exhibit significant changes in their simulated driving performance.
• Researchers assessed patients’ simulated driving performance at baseline and 45 minutes after they vaporized prescribed doses of cannabis flowers
• The video-based tasks included hazard perception skill, gap acceptance, following distance or speed: “participants exhibited no significant changes in performance”
• The findings suggest “a dose of vaporized cannabis (consumed in accordance with prescription) may not affect hazard perception ability or driving-related risk-taking behavior among medicinal cannabis patients.”
NORML says the study’s findings are consistent with those of several others finding that daily cannabis consumers, and patients especially, exhibit tolerance to many of cannabis’ psychomotor-influencing effects.
NORML also pointed to a literature review in the journal of the German Medical Association, which found “Patients who take cannabinoids at a constant dosage over an extensive period of time often develop tolerance to the impairment of psychomotor performance, so that they can drive vehicles safely.”
Picking a number to indicate ‘impairment’ or even ‘recent use’ is not evidence based. Not only do regular users have traces of THC in their system for weeks or even months (and so would fail any tests long after the window of impairment), regular users also have lower impairment from the same dose as they acclimatise to the effects of regular cannabis use.
Furthermore, levels in oral fluids – like other bodily fluids – can vary dramatically between users and also for the same user; levels of THC in saliva for example are affected by what a person eats and drinks or whether they chew gum.
THC in saliva is not a result of ingestion into the bloodstream which then somehow ends up in saliva. It is actually trapped there during inhalation or eating, much like the tar inside a smoking pipe. This means a driver who eats or drinks after ingestion will clean their mouth and have a dramatically lower result than a driver who does not. It also means a driver who ingests cannabis in a way it does not touch their mouth (eg inside capsules) will not test positive.
This all goes to show the detection of either THC or its metabolites is not evidence of impairment or recent exposure. Instead, NORML calls for the expanded use of performance-based tests, like DRUID or Predictive Safety’s AlertMeter.
More reading:
Legislation: Land Transport (Drug Driving) Amendment Act 2024
Parliament: Land Transport (Drug Driving) Amendment Bill (submissions, reports, Hansard, voting record)
RNZ (18/2/25): Law change to allow drug-testing devices to do roadside screenings
RNZ (26/2/25): Drug-driving testing legislation passes in Parliament despite concerns
RNZ Nights (26/2/25): Flaws in the plan for roadside drug testing, says civil liberties group
RNZ Morning Report (27/2/25): Concerns new drug-driving testing could detect medication