Cannabis driving tests

Several studies have found that cannabis and alcohol produce additive detrimental effects on driving performance, but other studies have failed to show any potentiation. This is probably due to the variety of simulated driving tests used and possibly the time lag between the administration of alcohol and cannabis behavioural impairment after cannabis has been reported to peak within 30 minutes of smoking. Nevertheless, both drugs have been shown to affect some aspects of driving performance and increase the risk of fatal car accidents. Concurrent use of cannabis and alcohol before driving should therefore be avoided. 

One study in 14 regular cannabis users (long-term daily use) and 14 infrequent cannabis users found that regular use reduced the disruptive effects of alcohol on some psychomotor skills relevant to driving, whereas infrequent use did not have this effect. In this study, neither group had smoked any cannabis in the 12 hours before the alcohol test. Another study found that moderate doses of alcohol and cannabis, consumed either alone or in combination, did not produce significant behavioural or subjective impairment the following day... 

Cannabis administration acutely disrupts performance of complex tasks requiring continuous monitoring and the ability to shift attention rapidly between various stimuli (54,55). These same attentional abilities are required when operating a motor vehicle. Cannabis administration impairs performance on laboratory tests that model various components of driving (56) and increas-... 

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