The Most Dangerous Cannabis Pothole

Ever since its introduction to mainstream America in the early 1900s, marijuana has found staunch opponents that decried the negative effects of the drug. Perhaps the most famous example is the 1936 anti-marijuana exploitation film, Reefer Madness.

I’ve you’ve never had a chance to see the film for yourself, the gist of the story – as told by high school Principal Dr. Carroll to parents at a PTA meeting – is that marijuana turns people into raving, maniacally laughing, lustful, and murderous lunatics.

Among the many sins committed by the characters in the story – in fact, the first offense that begins the eventual downfall of most of the main characters – is young Jimmy smoking a joint, getting behind the wheel (of a very stylish convertible), and consequently running over and killing a pedestrian.

While today many of the claims in the film about marijuana and the actors’ portrayal of “reefer heads” are seen as exaggerated, the issue of driving while inebriated remains one of the biggest concerns when debating marijuana legalization.

In our last article in this series we concluded that THC, the psychoactive component in marijuana, does impair driving. As we discussed, this creates numerous enforcement issues since there is currently nothing as simple as a breathalyzer to determine impairment level; furthermore, impairment varies by individual. The important question this raises: how is legalization of medical marijuana and recreational marijuana impacting traffic safety? Are traffic accidents and deaths on the rise in states with legalization? The issue is significant since traffic accidents are a leading cause of death in the United States.


I’d love to say that there’s a very clear-cut difference in driving safety before and after various state weed legalization dates. Ah, but that would be too easy. The answer about the impact of marijuana on traffic accidents and fatalities is sometimes conflicting, often biased to one point of view and nowhere near definitive. Here are a few snippets:

A 2018 report from Insurance Institute for Highway Safety’s Highway Loss Data Institute said that crashes are up as much as 6 percent in Colorado, Washington, Oregon, and Nevada compared with four neighboring states that haven’t legalized recreational use of marijuana.

A study by the Rocky Mountain High Intensity Drug Trafficking Area (RMHIDTA) looked at the data from Colorado and came to the following conclusions about impaired driving and fatalities:

  • Marijuana-related traffic deaths when a driver was positive for marijuana more than doubled from 55 deaths in 2013 to 125 deaths in 2016.
  • Marijuana-related traffic deaths increased 66 percent in the four-year average (2013-2016) since Colorado legalized recreational marijuana compared to the four-year average (2009-2012) prior to legalization.
  • During the same time period, all traffic deaths increased 16 percent.
  • In 2009, Colorado marijuana-related traffic deaths involving drivers testing positive for marijuana represented 9 percent of all traffic deaths. By 2016, that number had more than doubled to 21 percent.

However, authors of the report “Does Marijuana Legalization Increase Traffic Accidents?” for the Reason Foundation assert that RMHIDTA’s report looks at “total ‘marijuana related’ deaths without accounting for other factors, which highly distorts the true impact of legalization. Moreover, these studies equated marijuana presence with not only impairment but causality, regardless of whether alcohol was present.”

A study published in 2017 in the American Journal of Public Health found that the annual changes in vehicle crash fatality rates in Colorado and Washington did not differ from control states where marijuana remains illegal. The methodology used by the authors of this study accounted for a range of factors, including age, gender, and economic activity, that might have led to differences in the rate of crashes between the states.

In the 2017 National Highway Traffic Safety Administration (NHTSA) report to Congress “Marijuana-Impaired Driving,” they note the following information regarding the crash risk of drivers impaired by alcohol and marijuana:

  • The highest risk of crash involvement was for drivers with high alcohol concentrations (above .12 BAC)-they had a crash risk 20-200 times that of sober drivers.
  • Drivers with BACs between .08 and .12 were estimated to be 5-30 times more likely to crash than sober drivers.
  • Drivers positive for THC were estimated to be at elevated risk (1-3 times that of drivers not positive for THC), similar to drivers with BAC levels between .01 to < 0.05.

The same report discussed NHTSA’s crash-risk study that found the unadjusted odds ratio for crash risk and THC was 1.25-meaning THC elevates the risk of crashing by about 1.25 times or 25 percent, but those ratios do not account for factors that may contribute to increased crash risk. When the odds ratios were adjusted for demographic and other variables and for the presence of alcohol, risk associated with THC disappeared. The study showed there was no difference in crash risk for marijuana-positive drivers who were also positive for alcohol than for marijuana-positive drivers with no alcohol, beyond the risk attributable to alcohol.

Interestingly enough, there’s a study that suggests the legalization of medical marijuana may have had a positive impact on traffic fatalities involving alcohol. The study in the Journal of Law and Economics looked at traffic fatalities from 1990 to 2010. During this time, 14 states and Washington D.C. legalized medical marijuana. The authors found that traffic fatalities fell between 8 and 11 percent in the first year after the laws were passed and continued to fall over three additional years. The study notes that the reduced fatalities are almost entirely attributable to a reduction in the number of accidents involving individuals with high blood alcohol content; the authors suggest that medical marijuana is likely serving as an alcohol substitute.

THC impaired driving is certainly a safety concern. But outside the somewhat controversial RMHIDTA report (described above), almost all reports point to a mild to modest impact of pot legalization on driving safety.

A request for readers: If I’ve missed an important report or study on driving safety, please let me know in the comments section!

Bottom Line Morality: Impaired driving of any kind is dangerous and irresponsible. The impact of weed legalization seems, so far, to have a muted effect on overall safety statistics.

Bottom Line Investing: This one falls into the positive column – societal costs (in terms of safety) are not likely to impact pot stock investments unless new data or evidence comes to light.

So, while there may be a moderate increased crash risk in having marijuana more readily available, it seems that the concern raised by Reefer Madness – that the roads would become a dangerous speedway for wanton and reckless driving – is just another of the film’s overly-exaggerated claims.

Great Trading and God bless you,

D.R. Barton, Jr.

7 Responses to “The Most Dangerous Cannabis Pothole”

  1. “So, while there may be a moderate increased crash risk in having marijuana more readily available,….” This is a direct quote from the article.
    ANY increase in crash risk that can be avoided, whether moderate or not, should be avoided, and if driving after using pot increases the crash risk, then this should be illegal. I completely fail to understand why any individual would want to become high in the first place. As far as I know, every person has only one brain. Why would you ever deliberately want to mess with it? We read and assume that the human being is the most intelligent life form presently known. But in some ways, such as the above, the human appears to be the stupidest also.

  2. It would also have been interesting to see a comparison to alcohol related fatalities in Colorado during that same time period. It would be interesting to know if people under the influence of marijuana are less likely to drive than those who are under the influence of alcohol? From my experience in social circles, I believe so. Thanks!

  3. The one thing most people don’t realize, the THC contents now days is off the charts. The weed can be from 15%= 29% THC, extremely potent, and affects people all differently, and can be dangerous as hell driving and getting high. I have smoked for 50 years, and I have to be careful, even though I’ve smoked and know what I can handle. I don’t smoke and drive, because the one time I did, I almost got run over by a semi,coming out of a rest stop. Because I got high when I shouldn’t of, and almost cost me my life, if it wasn’t for an alert great truck driver, I would be pushing up daises. I thanked the LORD and the Truck driver and have never smoked and drove again.It only takes a second to lose your life, don’t smoke and drive it’s plain stupid, I speak from experience. Good luck.

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