Drugs, alcohol, crashes

There has been so much hype over concerns regarding “all the drugged drivers on the road” once marijuana is legalized, and it has been just plain dishonest. Sure, driving impaired is a bad idea regardless of the impairment. But there are many kinds of impairment and many degrees of impairment, and it’s important to know where on the risk scale this lies in order to craft useful public policy.

Driving angry is a terrible impairment, yet we are unlikely to develop a national policy of enforcing a zero-tolerance no-drive rule after getting in an argument.

We know that heavy alcohol use results in some of the highest risks of driving impairment, so it is fitting that we focus efforts on reducing drunk driving and enforcing drunk driving laws. It would be irresponsible to pull resources away from that clear danger toward a much lower risk factor.

And yet, that’s exactly what we’re doing by pushing for zero-tolerance per se laws for cannabis.

This latest study from the Journal of Studies on Alcohol and Drugs once again points out quite clearly this fact.

Drugs and Alcohol: Their Relative Crash Risk – Journal of Studies on Alcohol and Drugs.

Report by Eduardo Romano, Pedro Torres-Saavedra, Robert B. Voas, John H. Lacey

Results: For both sober and drinking drivers, being positive for a drug was found to increase the risk of being fatally injured. When the drug-positive variable was separated into marijuana and other drugs, only the latter was found to contribute significantly to crash risk. In all cases, the contribution of drugs other than alcohol to crash risk was significantly lower than that produced by alcohol.

Conclusions: Although overall, drugs contribute to crash risk regardless of the presence of alcohol, such a contribution is much lower than that by alcohol. The lower contribution of drugs other than alcohol to crash risk relative to that of alcohol suggests caution in focusing too much on drugged driving, potentially diverting scarce resources from curbing drunk driving. [emphasis added]


In reading the full article (yes, I shelled out the $30 for it – let me know if you have any questions about the article itself so you don’t have to), it was interesting to read the article’s authors’ astonishment at discovering that cannabis had so little effect on its own to crash risk. They pointed out the possibility (of which we’ve known for a long time) of drivers who have used cannabis being more aware and thus cautious.

They also pointed out that the government data from which they drew counted any amount of the drug showing up in tests and therefore likely included many drivers who had not recently consumed cannabis. But that’s perhaps an appropriate population to have in your sample when pointing out the stupidity of a public policy that promotes zero-tolerance per se laws.

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