Cannabis is by far the most common illegal drug found in the bloodstream of road accident victims.
The active ingredient, THC, can remain in the body for more than a month. New Scientist magazine reports that the TRL team recruited 15 volunteers to complete tests on a sophisticated driving simulator while under the influence of low or high doses of cannabis. The volunteers either smoked ready-rolled cannabis joints or rolled their own with resin supplied under government licence. The researchers measured the volunteer's accuracy at steering the car, response to hazards and braking times. They also took blood and saliva samples at regular intervals and also tested the subjects' coordination, balance and timing.