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After Colorado and Washington state voted to legalize recreational marijuana in 2013, the legislation's opponents and health officials conjured up the specter of stoned drivers turning America's highways into death traps. They warned that increased pot use related to decriminalization would lead to an increase in traffic fatalities due to "drugged driving." 

According to a massive new study from the government's safety body, they were wrong.

A new study from the National Highway Traffic Safety Administration concluded that driving after smoking marijuana does not make you more likely to get into a car crash, especially when compared to driving after alcohol consumption.

"The survey found that marijuana users are more likely to be involved in accidents, but that the increased risk may be due in part because marijuana users are more likely to be in groups at higher risk of crashes," the agency said in a statement. "In particular, marijuana users are more likely to be young men – a group already at high risk."

The study: In the largest study of its kind, NHTSA researchers studied 9,000 drivers over the past year to examine marijuana's impact on driving in the wake of legalization efforts across the country. 

While the researchers found that 25% of marijuana users were more likely to crash than non-users (marijuana does impair your attention, after all), the researchers concluded that demographic differences like gender and age were far more compelling factors in explaining marijuana-related crashes: Younger drivers had a higher crash rate than older ones, and men crashed more than women.

"This study of crash risk found a statistically significant increase in unadjusted crash risk for drivers who tested positive for use of illegal drugs (1.21 times), and THC specifically (1.25 times)," explain researchers Richard P. Compton and Amy Berning. "However, analyses incorporating adjustments for age, gender, ethnicity and alcohol concentration level did not show a significant increase in levels of crash risk associated with the presence of drugs. This finding indicates that these other variables (age, gender ethnicity and alcohol use) were highly correlated with drug use and account for much of the increased risk associated with the use of illegal drugs and with THC."

A convoluted argument for prohibition: Of course, this isn't to say that marijuana is completely harmless, despite the fact that many teenagers who drive under the influence of marijuana say the drug "either improves their performance behind the wheel or is no hindrance." According to the National Institute on Drug Abuse, marijuana is the illicit drug most frequently found in the blood of drivers who have been involved in accidents; the NHTSA report found that marijuana shows up in about 7.6% of drivers involved in crashes.

"Drivers should never get behind the wheel impaired, and we know that marijuana impairs judgment, reaction times and awareness," said Jeff Michael, NHTSA's associate administrator for research and program development, in a statement. "These findings highlight the importance of research to better understand how marijuana use affects drivers so states and communities can craft the best safety policies."

But the specter of stoned drivers conjured up by anti-legalization advocates significantly overstates the potential dangers of marijuana-induced driving. "In fact, highway fatalities have gone down since Colorado legalized marijuana," ThinkProgress reports. A 2013 study of the 19 states that legalized medical marijuana show that overall traffic fatalities in those states have dropped rather than skyrocketing.

The anti-legalization scaremongering over stoned drivers is especially frustrating when the low rate of post-legalization traffic fatalities is compared to those from legal substances like alcohol. According to the NHTSA, drivers with a 0.08 percent breath alcohol level (the legal cutoff for drunken driving in most states) crashed four times more than sober drivers, while those with a 0.15 percent level were 12 times more likely to crash. Considering that more than 3.3 million people around the world suffered alcohol-related deaths in 2012 (while marijuana-related deaths amounted to, well, zero fatalities), the NHTSA reports suggests that paranoia over stoned drivers may be overblown.

Why it matters: When taken together, the NHTSA data effectively debunks one of the biggest myths about marijuana legalization: that an influx of legal weed will lead to legions of high motorists careening across the freeway in search of Funyuns and Mountain Dew. But while this research may be reassuring to budding potheads across the country, we certainly need more research: After all, recreational marijuana has only been legal in Colorado for just under a year. 

"Researchers have developed a deep body of knowledge about the link between drinking, driving and risk. We know [drunken] driving kills," said NHTSA Administrator Mark Rosekind in a statement. "We have much to learn about how illegal drugs and prescription medicines affect highway safety. And developing that knowledge is urgent, because more and more drivers have these drugs in their systems."