Auto Accidents Increased In States Where Marijuana Was Legalized: Study

Critics say if technology had been created to test whether drivers were under the influence of marijuana before it was legalized, some auto accidents and fatalities could have been prevented.

States which have legalized the recreational use of marijuana are seeing a greater number of auto accident injuries, according to the findings of a recent study.

Researchers from the Insurance Institute for Highway Safety (IIHS) published findings last month in the Journal of Studies on Alcohol and Drugs, indicating new marijuana policies may come with an unforeseen and under appreciated risk of injury.

Alcohol and drug impairment account for nearly a quarter of the annual traffic fatalities each year. In the United States, the National Highway Traffic Safety Administration (NHTSA) recorded that an estimated 42,915 people died in all traffic crashes in 2021, while over 11,000 of those fatal crashes involved a driver with an illegal Blood Alcohol Concentration (BAC) of .08 or greater.

While research and prevention efforts have been focused for years on reducing the risks from drunk driving, researchers sought to determine what impact legalization of marijuana was having on auto accident rates and potential road safety issues.

The study involved a review of injury and fatality data from auto accidents in 2009 through 2019 in five states that legalized both the sale and the use of marijuana for individuals over the age of 21, which included Colorado, Washington, Oregon, California and Nevada. Researchers then compared the data to the same crash data collected from Arizona, Idaho, Montana, New Mexico, Utah and Wyoming, where marijuana sales and use are still prohibited.

After adjusting for crash rates per mile of travel, along with several other factors, researchers found states that legalized recreational use of marijuana were associated with a 6.5% increase in car crash injury rates and a 4.1% increase in fatal crash rates.

The study found that after marijuana legalization, on average car crash injuries increased by 7% in states where marijuana is recreationally legal, but then dipped slightly after retail sales began. Colorado experienced the largest effects, with an 18% increase in auto accidents after both legalization and retail sales were permitted.

Even though it is illegal to drive under the influence of marijuana, one of the challenges highway officials face is that there is no nationally accepted way of testing drivers for drug impairment at the time of the traffic stop, as officers can do for alcohol by measuring a driver’s blood-alcohol-concentration (BAC) with a breathalyzer. Many experts have claimed this technology was needed prior to mass decriminalization and recreational use.

Drug Impaired Driving Risks

The recreational use of cannabis has been legalized in at least 18 states and the District of Columbia, with at least another 13 having decriminalized marijuana use. While many states have changed their positions on marijuana regulation, prior studies have shown an upward trend in the number of drunk and/or drugged driving automobile fatalities and injuries, with a national average of approximately 10,500 fatalities annually.

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A recent study conducted by the U.S. Centers for Disease Control and Prevention found that 5% of the population in the U.S. admits to driving while under the influence of marijuana. That equates to roughly 12 million Americans over the age of 16 being high while driving.

In January 2020, research from McLean Hospital in Belmont, Massachusetts was published in the journal Drug and Alcohol Dependence, finding marijuana impaired drivers struck pedestrians, went over the speed limit more often, made fewer stops at red lights, and crossed the center line more often during the simulation compared to people who didn’t use marijuana at all.

The driving simulation found marijuana users demonstrated impaired driving compared to non-users, even though they were sober. They consistently performed worse on the driving simulations than non-users.


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