What’s the deal with traffic deaths and marijuana legalization?

Traffic deaths rose in three states that legalized recreational marijuana, temporarily, and then fell according to a new study. However, modern science still has much to learn about how much marijuana impairs someone behind the wheel.

According to a study published on Monday in the journal Addiction, in Colorado, Oregon, and Washington State, each had one additional death per million in the year after cannabis legalization, with a flexible 6-month ‘phase in’ period accounting for lags in production. Then, interestingly, their death numbers dropped back to normal. The same was seen in neighboring states. The Verge says that in total, 170 additional people died in the first sixth months after legalization in those areas, all put together. The study measured neighboring states because, presumably, people were driving across state lines to buy some bud.

[Maryland introduces two bills and one constitutional amendment to end the prohibition of marijuana in the old line state]

Study co-author Tyler Lane, a post-doc at Monash University in Australia, posited that the rise in deaths could be because a jump in new, less experienced pot users (or perhaps less experienced drivers going to get pot. The study wasn’t designed to tell why it happened) were getting behind the wheel. However, those users would have quickly gained experience, allowing the statistics to return to normal. Anyways, the effect the study finds is fairly smalls and does goe away fairly quickly. In the numbers of road deaths anywhere, as unfortunate as any death is, literally an additional one in a million is not a lot.

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The Verge reports that this is the latest in a series of studies that have seemingly flip-flopped on the dangers of marijuana driving. In another study, the Insurance Institute for Highway Safety and the Highway Loss Data Institutes jointly said automotive crashes were six percent higher in states that legalized marijuana, compared to four neighboring states where they did not rise. Interestingly their results did not account for patrons crossing state lines.

Another study, forthcoming in the journal Economic Inquiry, imagines hypothetical versions of Colorado and Washington States where marijuana was never legalized. Study author Benjamin Hansen, from the University of Colorado, says “When we do that approach, what we find is that the synthetically created Colorado and synthetically created Washington see very similar trends [as the real states], both for marijuana-related fatalities and drunk-driving and overall fatalities.” This means, according to Hansen’s study, the death rates would have temporarily gone up anyways. Those accidents could have been caused by something else.

So, what’s the deal with marijuana and impaired driving, automotive accidents, and marijuana-related automotive deaths? Whether or not it impairs driving ability, does it increase accidents or automotive deaths in any significant way? Maybe it just increases fender benders? The above studies looked at different things, both accidents and deaths, so it could be possible that more minor accidents increase significantly with marijuana legalization, but automotive deaths increase only slightly, while then returning to normal. However, in the absence of conclusive results that’s merely speculation.

[Denver launches new series of public service announcements to deter teen pot use]

Additionally, each of the studies has delivered different results, meaning there may be variables not yet identified. Ultimately, the real answer is probably that we just don’t know yet and more research is needed. There isn’t even a scientific way to measure marijuana impairment, like a breathalyzer, yet. So, how can we honestly tell what’s happening when someone gets behind the wheel after smoking a little mary jane? So far, the simple answer seems to be that we can’t.

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