Study: Marijuana Worsens Distracted Driving, And That's About It

Edward Niedermeyer
by Edward Niedermeyer

On the heels of a Ben Gurion University study showing that drivers under the influence of marijuana are less dangerous than drunk drivers, comes yet another study indicating that driving stoned might not be quite as bad as some think. Published in the Journal of Psychoactive Drugs, the Hartford Hospital/University of Iowa study titled “Sex differences in the effects of marijuana on simulated driving performance,” concludes that:

Under the influence of marijuana, participants decreased their speed and failed to show expected practice effects during a distracted drive. No differences were found during the baseline driving segment or collision avoidance scenarios. No differences attributable to sex were observed. This study enhances the current literature by identifying distracted driving and the integration of prior experience as particularly problematic under the influence of marijuana.


Of course, the researchers behind this research don’t want you to get the wrong idea about this illegal substance. One of the study’s authors tells InsideLine:

It does not in any way say that it is safe to drive under the influence of any drug. It merely shows us, we need to study this further. We need to know what marijuana does to the brain. We need to understand the ramifications. To create public policy and to keep people safe, you need to know what’s really happening in the brain.

The National Organization to Reform Marijuana Law (NORML) echoes this sentiment, maintaining that

Although cannabis is said by most experts to be safer with motorists than alcohol and many prescription drugs, responsible cannabis consumers never operate motor vehicles in an impaired condition… the development of cannabis-sensitive technology to rapidly identify the presence of THC in drivers, such as a roadside saliva test, would provide utility to law enforcement in their efforts to better identify intoxicated drivers. The development of such technology would also increase public support for the taxation and regulation of cannabis by helping to assuage concerns that liberalizing marijuana policies could potentially lead to an increase in incidences of drugged driving. Such concerns are a significant impediment to the enactment of marijuana law reform, and must be sufficiently addressed before a majority of the public will embrace any public policy that proposes regulating adult cannabis use like alcohol.

Meanwhile, if you absolutely must drive while baked, make sure you read up on the rules of driving at Maximum Stoned Speed, as submitted by TTAC’s grooviest commentators.

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  • Brandloyalty Brandloyalty on Jun 10, 2010

    I ride a bicycle a lot in a large west-coast city. I'd estimate that the ventilation systems of one-in-twenty to one-in-fifty cars in this city emit marijuana fumes. If this many people are stoned while driving, and if it impaired driving, you'd think this would be obvious in accident statistics. Since it's not, it raises the possibility that stoned drivers (adjusted for age etc.) are LESS likely to be in accidents than straight drivers. It certainly bears objective and fair research. Which of course is impossible in the current anti-drug hysteria.

  • Obbop Obbop on Jun 11, 2010

    Quite a few years ago the California Highway Patrol conducted a study regarding pot smoking and accidents while driving. The results of that study made it to a few newspapers (this was before the general public had access to the Web) and was typically greatly condensed as such news stories typically are. One conclusion... the CHP could not prove that even one fatality could be blamed upon pot use ALONE though many other factors, especially alcohol use, could be directly blamed for causing a wreck that involved a fatality.

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