One in Five Cannabis Users in Australia Drove Within 3 Hours of Using | Research

The takeaway

Among 385 cannabis users in the Australian Capital Territory, 21.5% reported driving within 3 hours of use, with heavier users and those less concerned about roadside testing most likely to drive shortly after consuming.

Road safety officials, cannabis users who drive, and policymakers designing impaired driving laws.

21.5% of users drove within 3 hours of cannabis use

What the researchers found

67.9% of participants reported waiting 7+ hours before driving, but 21.5% reported waiting 3 hours or less. Those driving soonest had the highest cannabis and THC intakes. Shorter wait times were associated with less concern about roadside drug testing, more frequent use, larger amounts, and exclusive non-medicinal use.

Why it matters

Cannabis decriminalization created a legal home-growing population whose driving behavior can be studied openly for the first time. The finding that heavy users are most likely to drive shortly after use highlights a road safety challenge that legalization alone does not solve.

The numbers in context

N = 385 survey, 52 submitted cannabis samples. 67.9% (224/330) waited 7+ hours. 21.5% (71/330) waited 3 hours or less. Shortest wait-time users had highest cannabis and THC intakes.

How the study worked

Two-part cross-sectional study in the ACT following 2020 cannabis decriminalization. Part 1: 385 cannabis users completed an online survey. Part 2: 52 submitted home-grown cannabis for phytocannabinoid analysis to estimate usual THC intakes.

What this study cannot tell us

Self-reported wait times may be inaccurate. Online recruitment may not reach all cannabis users. Cross-sectional design cannot track behavior changes over time. THC intake estimates relied on small subsample of 52 cannabis samples.

How to read the evidence

Cross-sectional survey with direct phytocannabinoid analysis of user samples. Moderate evidence limited by self-report and convenience sampling.

When this study was published

Published in 2025.

The bigger picture

As jurisdictions decriminalize and legalize, understanding driving behavior becomes critical for road safety policy. The ACT provides a natural experiment where cannabis users can be studied without the confound of criminal stigma affecting honest reporting.

Questions still open

Would standardized wait-time guidelines reduce cannabis-impaired driving? Are current roadside testing thresholds appropriate for regular users with higher tolerance?

Common questions

How long should you wait after using cannabis before driving?

This study found that most users (68%) waited 7+ hours, but a concerning minority drove within 3 hours. Research generally suggests THC impairment peaks within 1-3 hours and diminishes over 4-6 hours, but individual variation is significant.

Does frequent use make it safer to drive sooner?

Frequent users in this study drove sooner after use and consumed more, putting themselves at higher risk despite potential tolerance. Tolerance does not eliminate impairment, especially at the higher doses these users consumed.

Read the original research

The driving-related attitudes, beliefs and behaviours of cannabis users in the Australian Capital Territory following decriminalisation.

Drug and alcohol review, 44(2), 588-601

View on PubMed ↗Publisher’s paper ↗

Citation

McCartney, Danielle; Zhou, Cilla; Lavender, Isobel; Gordon, Rebecca; Kevin, Richard C; Bedoya-Pérez, Miguel; McGregor, Iain S. (2025). The driving-related attitudes, beliefs and behaviours of cannabis users in the Australian Capital Territory following decriminalisation.. Drug and alcohol review, 44(2), 588-601. https://doi.org/10.1111/dar.13983