A study reported by the National Organization for the Reform of Marijuana Laws found that regular cannabis consumers showed no significant impairment in simulated driving performance the morning after use, even when THC remained detectable in their blood or oral fluid. Researchers observed no link between cannabinoid levels and driving ability about 12–15 hours after consumption. The findings suggest that residual THC alone does not reliably indicate impairment, raising questions about laws that rely on THC blood thresholds to determine cannabis-related driving offenses.
