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Marijuana legalization not linked to traffic accidents, study shows

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Marijuana, and all its related and derivative products, represent thorny legal territory for the trucking industry, but despite decades of claims of "reefer madness," its legalization appears to have no impact on traffic accidents, according to a new report from academics at the University of Arkansas, Iowa State University, and the University of Tennessee. 

The paper, entitled "Marijuana Legalization and Truck Safety: Does the Pineapple Express Damage More Pineapples?," sets out to assess "whether legalization has affected the crash rates of heavy trucks" and promptly concludes that "legalization does not increase average crash rates." 

The paper's authors analyzed heavy-truck crash data for years 2005-2019, so the results haven't been skewed by the pandemic, which saw many fewer drivers on the road but more severe crashes and more speeding among many drivers, particularly those who share the road with professionals. Researchers then basically looked at heavy truck crashes before and after states enacted a form of legalization or otherwise liberalized rules around marijuana consumption. They found some states faired better and some worse after legalization, but the trend overall pointed down. Vermont and Washington, for instance, saw "large crash reductions," while Nevada on the other hand experienced a big increase, according to the study. 

The paper does not suggest that marijuana use represents a safe choice for commercial vehicle operators, and indeed cites other research that shows THC, the principal psychoactive component of the plant, "diminishes drivers’ ability to perform key tasks such as maintaining the correct road position..., quickly reacting to unexpected events ..., and focusing on the task at hand."

The study cites past research finding that people high on marijuana "tend to compensate for their impairment by slowing down and driving more cautiously," but that "experienced marijuana users show virtually no functional impairment while driving under the influence of THC alone."

In the end, the study's authors chalk up the road safety improvements in states with marijuana legalization to its impact on alcohol abuse, which data shows really does seem to drive increased crash numbers. In essence, when marijuana becomes legal, many people, including the most dangerous cohort of drivers (young men), reduce their problem drinking behaviors and increase their marijuana consumption. 

Andrew Balthrop, a research associate at the University of Arkansas and one of the study's authors, said the main implication of the research in his view is for drug testing. 

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