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Mega Study Says Driving After Smoking Pot is Dangerous

By Erica C. Barnett February 10, 2012

In a finding that could have implications for backers and opponents of Initiative 502, the marijuana-legalization measure that will be on the ballot statewide in November, a British Medical Journal review of nine different studies on the impacts of driving while stoned found that driving after smoking pot nearly doubles the risk of a fatal crash. The studies only included drivers impaired by marijuana only, rather than marijuana and alcohol or other drugs. I-502 was the subject of a joint house-senate work session yesterday.

Compared to sober drivers, drivers who've smoked pot within three hours of getting behind the wheel were 92 percent more likely to cause a fatal crash, the reports, which included 50,000 drivers in different countries, concluded---and, Time reports, "The better the quality of the study, the more likely it was to show an increase in marijuana-related risk." The study concluded that the risk of minor accidents while driving stoned "remains unclear," partly because drivers in non-fatal crashes are likely to refuse drug tests.

Some medical-marijuana advocates oppose I-502 because it includes a DUI provision based on how much THC is in a driver's system, rather than whether the driver is impaired. They argue that most medical pot users are routinely above the threshold in the legislation (five nanograms per milliliter of blood) and can drive at that level without being impaired. That may be true, but cops still have to have probable cause and evidence of impairment to accuse someone of DUI.

Driving drunk, the study found, remains more dangerous than driving under the influence of marijuana.
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