Partial cannabis legalization and the increase of the THC threshold in road traffic: a statistical analysis of traffic cases before and after legal changes

Our data indicate a modest upward shift in THC concentrations, continuing beyond April 2024, alongside a demographic shift toward older drivers. The nearly identical THC medians between drivers with and without conspicuous driving performance challenge the validity of the new threshold. Notably, almost half of the unimpaired drivers exceeded 3.5 ng/mL, whereas half of the impaired drivers remained below it. 7.4% of the frequent users benefited from the raised threshold, while at the same time 58.3% of occasional users-whose driving ability at THC concentrations between 1 and <3.5 ng/mL may be compromised-fell out of legal sanction. While substantial doubt remains if the initial goal was achieved, the question of an appropriate THC threshold remains unresolved and calls for alternative legal approaches.