Australia is rethinking cannabis and the rules of the road as recent studies have cast doubt on earlier research that drivers with THC in their systems were impaired in their driving skills.
Science writer Frank Schuler says “Just because someone has metabolized THC in their system does not automatically mean that they are intoxicated, and public policies need to reflect that scientific fact.”
Last year Australia, Victoria state relaxed its laws automatically banning the driving privileges of medical cannabis patients if they were found to have THC in their system while operating a motor vehicle on public roadways.
The policy change was a result of the findings of a study which found that medical cannabis use does not negatively impact driving performance in experienced users.
The debate then notched up a level in December last year after Channel 7 TV aired a programme that showed a remarkable improvement in one medical cannabis patient’s reaction time in a simulated driving exercise.
The ‘crash test dummy’ in this case was the director of Australian medical cannabis company, Medcan. Gareth Ball.
The one-off trial, conducted in Queensland in December 2025, compared Ball’s performance before and after taking a 10/25 THC/CBD pastille prescribed for anxiety, which he has been suffering since his teens. It found he recorded a 20% improvement on reaction times during the driving experiment after using his prescribed dosage.
The experiment appeared to confirm the Journal of Safety Research finding that patients who consume botanical cannabis over extended periods do not exhibit significant changes in their simulated driving performance,
This was based on evidence-based studies by the journal, which found there was no automatic connection between cannabis consumption and increased risky road behaviour.
Australian researchers assessed patients’ simulated driving performance at baseline and 45 minutes after they vaporized prescribed doses of cannabis flowers. (Under Australian law, physicians may authorize cannabis products to patients unresponsive to conventional prescription treatments.)
“After vaporizing one dose of their prescribed cannabis flower, participants exhibited no significant changes in performance on any of the video-based tasks (hazard perception skill, gap acceptance, following distance or speed) compared to baseline,” investigators reported.
The study’s authors concluded, “The findings … suggest that 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.”
The study’s findings are consistent with those of several others determining that daily cannabis consumers, and patients especially, exhibit tolerance to many of cannabis’ psychomotor-influencing effects.
According to the findings of a literature review published in the journal of the German Medical Association, “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.”
Full text of the study, “The acute effects of vaporized cannabis on drivers’ hazard perception and risk-taking behaviors in medicinal patients: A within-subjects experiment,” appears in the Journal of Safety Research. Additional information is available in the NORML Fact Sheet, ‘Marijuana and Psychomotor Performance.’
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