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Legalization of marijuana linked to rise in traffic crashes

A new study published in the Journal of Studies on Alcohol and Drugs has found that states that legalized recreational marijuana have witnessed a subsequent increase in traffic crashes and fatalities. The analysis of data on traffic incidents from 2009 to 2019 in five states that allow the recreational use of marijuana for adults aged 21 and older has revealed a 5.8 percent increase in the rate of traffic crash injuries and a 4.1 percent increase in fatal crash rates after the legalization and the beginning of retail sales.

“Legalization removes the stigma of marijuana use, while the onset of retail sales merely increases access,” said study lead author Charles M. Farmer, the vice president for research and statistical services at the Insurance Institute for Highway Safety (IIHS). “But access to marijuana isn’t difficult, even in places without retail sales. Users who previously avoided driving high may feel that it’s okay after legalization.”    However, the “legalization of marijuana doesn’t come without cost,” Farmer warned.

According to the researchers, previous studies involving driving simulators have shown that marijuana use affects reaction time, road tracking, lane keeping, and overall attention. In the current study, the scientists collected data on traffic crashes and fatalities in five states that legalized marijuana (Colorado, Washington, Oregon, California, and Nevada) and compared them to six states where marijuana was still illegal (Arizona, Idaho, Montana, New Mexico, Utah, and Wyoming). 

The analysis revealed that the initial rise in the injury crash rate occurred after legalization but before retail sales began – with an initial increase of 6.5 percent, followed by a slight decrease (by 0.7 percent) after retail sales commenced. However, fatal crash rates increased both after legalization (by 2.3 percent) and authorization of retail sales (by 1.8 percent).

The sharper relationship between marijuana legalization and traffic injuries rather than fatalities may be due to the fact that many drivers under the influence of marijuana slow down and maintain larger distances from other vehicles. In such cases, while drivers may often not be able to avoid a crash, these crashes may be less likely to be lethal, since they are driving at lower speeds.

However, it is not yet clear whether there is a direct causal link between marijuana use and risk of traffic accidents. “Studies looking for a direct causal link between marijuana use and crash risk have been inconclusive,” Dr. Farmer said. “Unlike alcohol, there is no good objective measure of just how impaired a marijuana user has become. Until we can accurately measure marijuana impairment, we won’t be able to link it to crash risk.”

Nonetheless, states considering the legalization of marijuana should consider a few important steps to mitigate its health impact. “First, convince everyone that driving under the influence of marijuana is not okay. Then, enact laws and sanctions penalizing those who ignore the message. Finally, make sure you have the resources (i.e., staffing and training) to enforce these laws and sanctions,” Dr. Farmer concluded.

By Andrei Ionescu, Staff Writer  

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