Marijuana and Driving

Marijuana produces a moderate degree of driving impairment which is related to the consumed tetrahydrocannabinol, THC, dose. The impairment manifests itself mainly in the ability to maintain a steady lateral position on the road. Driver's under the influence of marijuana retain insight in their performance and will compensate, where they can for example, by slowing down or increasing effort. As a consequence, THC's adverse effects on driving performance appear relatively small.