In an Australian study evaluating the effect of Cannabidiol and Δ9-Tetrahydrocannabinol on Driving Performance, inhaled CBD-dominant cannabis 14mg (THC/CBD ratio 1:9) did not cause cognitive or psychomotor impairment compared with placebo. Drivers with CBD were just as likely to show improvement relative to placebo. THC in the same dose did cause impaired driving on par with 0.02-0.05% blood alcohol. But, CBD did not reduce THC impairment of driving. In the study all effects were gone after four hours. However, the authors note that Impairment could be extended with use of oral products or higher inhaled doses.

Philip Blair comment: A big problem is THC testing. Positive testing only indicates THC exposure in previous weeks or days but not impairment. Yet many workers lose their jobs or have adverse action based on detection and not impairment. It’s time to change all THC testing standards and consequences based on science. JAMA. 2020;324(21):2177-2186

https://pubmed.ncbi.nlm.nih.gov/33258890/