# ‘Little evidence’: The flaw in the state’s cannabis driving laws > **Author:** Benjamin Caplan, MD (ABFM Board Certified, MA Lic. #240562, NPI: 1962722637) > **Publisher:** CED Clinic (https://cedclinic.com) > **Canonical URL:** https://cedclinic.com/little-evidence-the-flaw-in-the-states-cannabis-driving-laws/ > **Published:** 2026-06-26T17:29:50-04:00 | **Last Modified / Clinically Audited:** 2026-09-28T10:50:27-04:00 > **Clinical Summary:** Cannabis impairment driving laws often lack transparent scientific basis. Clinical perspective on THC presence vs. actual impairment for patient counseling. --- ✦ New CED Clinical Relevance #55 Clinical Context Background information relevant to the evolving [cannabis medicine](https://cedclinic.com/essential-oils-industrial-hemp-antimicrobial-benefits/) landscape. PolicyResearchSafetyTHCNeurologyMental HealthIndustry Why This Matters Clinicians need to understand that current [cannabis driving laws](https://cedclinic.com/cannabis-impairment-testing-challenges-driving-safety/) in NSW are based on limited scientific evidence, which means they cannot reliably counsel patients on impairment thresholds or safe consumption timing before driving. This gap between policy and evidence creates clinical uncertainty when patients ask about safe driving after [cannabis use](https://cedclinic.com/cannabis-cardiovascular-health-insights-2024/), potentially leaving clinicians without evidence-based guidance to provide. Advocating for transparent, evidence-based driving regulations is important for clinicians who want to give patients accurate information about cannabis-related impairment risks. Clinical Summary # Cannabis Driving Impairment Laws Lack Robust Evidence Base New South Wales has implemented a strict zero-tolerance THC presence limit for driving despite acknowledged gaps in the scientific evidence linking detectable THC levels to actual impairment. The state’s Roads Minister has confirmed that the THC threshold will remain unchanged even as the underlying research justifying this policy remains undisclosed to the public. This disconnect between policy and evidence is clinically significant because it affects how physicians counsel patients regarding [cannabis use](https://cedclinic.com/cannabis-cardiovascular-health-insights-2024/) and driving safety, particularly as [medical cannabis](https://cedclinic.com/therapeutic-benefits-of-thc/) becomes more widely prescribed. The lack of transparent, peer-reviewed evidence on THC concentration thresholds means clinicians cannot confidently distinguish between impaired and non-impaired driving states in their patients, creating liability concerns and potentially limiting appropriate use of cannabis in legitimate medical contexts. Clinicians should be aware that current driving laws may penalize patients using prescribed cannabis without clear evidence that detectable THC levels correlate with impaired driving ability. Physicians working in jurisdictions with similar policies should advocate for evidence-based driving regulations and maintain awareness that legal restrictions may not reflect actual impairment risk when counseling patients about [cannabis use](https://cedclinic.com/cannabis-cardiovascular-health-insights-2024/) and safe driving practices. Dr. Caplan’s Take “The challenge we face with cannabis and impaired driving is that our legal thresholds are based on blood THC levels, but the science showing a reliable correlation between those levels and actual impairment in humans remains genuinely sparse—and that’s a problem worth acknowledging openly with patients and policymakers alike.” Clinical Perspective 🚗 Cannabis-impaired driving remains a significant [public health](https://cedclinic.com/cannabis-mold-contamination-risks-recall-safety/) concern, yet current regulatory approaches in jurisdictions like New South Wales rest on THC presence limits that lack robust supporting evidence, creating a disconnect between policy and scientific reality. The challenge clinicians face is that blood or saliva THC levels correlate poorly with actual impairment—unlike alcohol’s linear dose-response relationship—because THC accumulates in fatty tissues and may persist for days after intoxication resolves, while impairment peaks much earlier. This means patients may test positive under legal thresholds while actually unimpaired, or conversely, be unimpaired yet face legal consequences. When counseling patients on cannabis use, healthcare providers should recognize that current driving laws may not reliably distinguish impaired from non-impaired drivers, and that individual factors like tolerance, route of administration, and time since use substantially affect actual driving ability. Clinicians should advise patients that any acute 💬 Join the Conversation Have a question about how this applies to your situation? [Ask Dr. Caplan →](https://benjamincaplan.com/ask-dr-caplan) Want to discuss this topic with other patients and caregivers? 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