UK cops are persisting in introducing a series of roadside tests for stoned drivers, despite a study released by the UK Transport Research Laboratory in August 2000, which found that pot-smoking has a minimal if not beneficial effect on driving performance.
The government-funded study was launched under pressure from anti-drug and driving groups, and was an embarassment to the British Ministers who had expected it to support their anti-stoned-driving campaigns.
The British study confirmed the results of a wide variety of research into stoned driving from around the world:
A 1983 study by the US National Highway Transportation Safety Administration (NHTSA) used stoned drivers on simulators, and concluded that the only statistically significant effect associated with marijuana use was slower driving.