Many anti-marijuana advocates argue that legalizing cannabis would result in more traffic accidents and therefore more deaths. But then pro-legalization advocates retort that alcohol is also legal and causes many more traffic accidents than marijuana, and that's 100 percent legal. But just how much more dangerous is alcohol use before driving than marijuana?

A recent study from France analyzed drivers and accidents to determine the effects of marijuana and alcohol on causing traffic incidents. According to the study, someone driving under the influence of marijuana was 1.65 times more like to cause a fatal traffic accident than someone driving sober. But someone driving under the influence of alcohol was 17.8 times more likely to cause a fatal accident than someone driving sober. The study also estimated that the number of people to die in traffic accidents would decrease 27.7 percent if no one ever drank alcohol before driving, while that percentage would only be 4.2 percent if no one ever consumed marijuana before driving.

Obviously, this study shows that using marijuana before driving is dangerous and increases the risk of a deadly car crash. But it also shows that the effects of marijuana are not nearly as bad as the effects of alcohol, and that drinking and driving is still far more dangerous than using cannabis.

Now, someone might argue that the alcohol statistics are inflated because more people drive drunk than stoned, and they would actually be wrong. According to the study, 2.1 percent of drivers in France went behind the wheel after drinking, while 3.4 percent of drivers did so after consuming marijuana. So there were actually more people who used marijuana and drove, and yet they still accounted for a small smaller percentage of total traffic fatalities.

Again, the point of the study is not to say that it's ok to drive after using marijuana. But it does illustrate that alcohol use is far more dangerous before driving, and if people want to actually use the "marijuana will cause more traffic fatalities" argument, then they really need to advocate for prohibition of alcohol as well.

(h/t PLOS)