U.S. Government Studies Marijuana & Alcohol
Marijuana alone is not significant, but combining it with alcohol is truly dangerous.
Traffic Tech Technology Transfer Series Number 225 May 2000
MARIJUANA & ALCOHOL TOGETHER REDUCE VISUAL SEARCH FREQUENCY
At intersections, participants looked at side streets from the right an average of 84 percent in all cases in the placebo condition. Visual search frequency of these subjects did not change much with either the low dose alcohol or low dose marijuana. Visual search in the combination of both alcohol and marijuana condition, however, dropped by 3 percent. Low doses of marijuana (100 µg/kg) taken alone, did not impair city driving performance and did not diminish visual search frequency for traffic at intersections in this study. Low doses of alcohol sufficient for producing a BAC of 0.04 g/dl did not impair city driving performance and did not diminish visual search frequency for traffic at intersections in this study. Low doses of marijuana in combination with low doses of alcohol did not affect city driving proficiency, but it did impair peripheral search for traffic in this study. The effects of low doses of marijuana (100 µg/kg) and BAC about 0.04 g/dl on city driving proficiency and visual search were minimal when taken alone, but potentially dangerous for traffic safety when combined. Drivers' perception of their performance did not necessarily match their actual visual search performance.
Traffic Tech Technology Transfer Series Number 201 June 1999
MARIJUANA & ALCOHOL COMBINED INCREASE IMPAIRMENT
The effect of combining moderate doses of alcohol and moderate doses of marijuana resulted in a dramatic performance decrement and levels of impairment, as great as observed when at 0.14 BAC alone.