In January 2019 researchers from Germany published their study to contribute to the ongoing discussion about threshold limits of tetrahydrocannabinol in the blood with respect to driving. In their study 15 individuals who regularly consume cannabis undertook a driving simulator test. The individuals were tested on different routes before, immediately after and then at 3 and 6 hours after the consumption of a maximum of three cannabis joints, each containing 300 μg tetrahydrocannabinol/kg body weight. In addition, the individuals underwent a medical examination including blood tests. Driving faults and specific features observed during medical examinations were allocated penalty points. Results showed that blood tetrahydrocannabinol concentrations > 15 ng/ml significantly increased the number of penalty points incurred by the individuals. In addition there were significantly more driving faults committed directly after consumption, no significant increase at 3 hours after consumption but an increase of insignificant driving faults at 6 hours after consumption. Further studies focusing on the time dependent impact of cannabis consumption on road traffic are required.
Tank A et al. On the impact of cannabis consumption on traffic safety: a driving simulator study with habitual cannabis consumers. Int J Legal Med. 2019 Jan 30. [Epub ahead of print]