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Pot smokers get into fewer deadly car crashes than beer drinkers, a recent study (.pdf file) finds, although its authors say the conclusion shouldn't be seen as encouragement to smoke marijuana and drive.

Your car insurance company certainly isn't cutting stoners a break.

The study found that in the 16 states where medical marijuana is legal, there has been a drop of nearly 9% in traffic deaths since the laws took effect and a 5% drop in beer sales. Marijuana and alcohol are substitutes for each other, the researchers found, with fewer people drinking alcohol in states with medicinal marijuana. Pot use, however, increases.

"Use of marijuana, in general, increases in states that have medical marijuana laws," says D. Mark Anderson, an assistant professor of economics at Montana State University and co-author of the study with Daniel Rees, an economics professor at the University of Colorado, Denver.

Drugged or drunk, your car insurance doesn't care

Driving under the influence is often assumed to involve alcohol, but it actually can involve any substance that impairs judgment. And to an insurance company looking at your driving record, it's all the same.

"When it comes to drug use, there's no middle ground, there's no safety zone," says Eustace Greaves, an independent insurance agent in Brooklyn, N.Y.

In New York, for example, a person who drives under the influence loses his or her license for at least a year, must turn in vehicle license plates and carry the infraction on his or her driving record for 10 years, Greaves says. "As soon as you lose your license, that's going to be reported to your insurance company," he says. (CarInsurance.com's "What's Your Limit?" tool, though geared toward those planning to drink, spells out the state by state penalties for a DUI conviction.)

When you are allowed to drive again, your insurance rates will be higher and you won't qualify for the car insurance discounts that longtime drivers usually enjoy, Greaves says.

If you legally carry medicinal marijuana in your car, you may be able to get out of a traffic citation if you're stopped by police -- and thus avoid increased car insurance rates or cancellation. But your car insurance company will drop you if you're convicted of driving under the influence of drugs, whether used legally as a medicine or not, says Raphael Baker, an agent in Atlanta.

Your policy will be rewritten by a nonstandard company at rates that are usually twice as high as standard rates, Baker says.

The science isn't definitive

While the university study showed a direct link between marijuana and reduced alcohol consumption, it wasn't clear about why pot smokers get into fewer deadly car crashes. The researchers cautioned that legalizing medical marijuana may result in fewer traffic deaths because it's typically used in private, while alcohol is often consumed at bars and restaurants. Pot smokers typically stay home and use the drug without driving, while alcohol drinkers typically drink away from home and then drive home.

The two substances affect drivers in different ways, either of which can lead to accidents while driving. The study's authors found previous research suggesting that drunken drivers underestimate how badly their skills are impaired, and thus drive faster and take more risks. Stoned drivers, however, tend to avoid risks.

Traffic fatalities are the leading cause of death among Americans ages 5 to 34, according to the National Highway Transportation Safety Administration. Since marijuana is typically used by younger people, at least recreationally, Anderson said the study could be a step toward decriminalizing marijuana use and lowering traffic fatalities among younger people.

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