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Study Shows Decrease in Heavy Truck Crash Rates Since Cannabis Legalization

As cannabis legalization continues to sweep states across the country, we’re collectively able to examine trends regarding the potential positive and negative effects of a more widespread, adult-use cannabis market. While the common perception is that cannabis legalization will lead to more accidents on the roads and greater danger, a new study focusing specifically on cannabis legalization and trucking suggests otherwise.

The study, humorously titled “Marijuana Legalization and Truck Safety: Does the Pineapple Express Damage More Pineapples?” has researchers from the University of Tennessee, University of Arkansas, and Iowa State University honing in on America’s $800 billion truck driving industry. 

Using a state-level panel of heavy truck crash statistics from 2005 to 2019, and a difference-indifference estimation strategy, the researchers tested whether legalization of cannabis has affected the crash rate of heavy trucks. These results showed that there is no increase in average crashes in any of the state studied by legalization.

Research has shown that legalizing recreational marijuana actually decreased the number of truck crashes by 11%. Six of eight states were affected by a decline in the number of truck-related accidents, while two experienced an increase. Washington and Vermont saw significant decreases of -21.5% and 20.1% respectively. Massachusetts and Colorado followed at -18.3% & -18% respectively. Oregon and California were at -3.7% & -3.2%. At 4.18%, Maine and Nevada reported the largest increases. Nevada was at 25.6%.

It’s important to note that this is a preprint, meaning that the study has yet to undergo peer review.

Researchers didn’t offer a solid explanation around the reduction in crashes following cannabis legalization, though they offered a couple of theories:

Some people who would normally drink alcohol might have tried cannabis. Though it’s still against the law to drive under the influence of cannabis, research suggests that driving high is far less likely to cause a fatal accident than driving under the influence of alcohol. The safest way to drive is fully sobriety.

They also cite that cannabis is generally consumed at home, rather than at a bar or a restaurant, so even if a trucker partakes, they probably aren’t able to easily access or consume cannabis on the job.

They also wanted to study the rise in Nevada crashes by comparing Nevada to Vermont. Vermont had the highest decrease per state. They found that Vermont has far less tourism than Nevada, meaning that there are more people traveling who are unfamiliar with the state’s roadways in Nevada. Travelers in Nevada are also more likely to use cannabis outside of the home—like those visiting Las Vegas, for example—indicating a higher likelihood of those folks getting behind the wheel after using cannabis.

Nevada is more populous than Vermont, so Vermont has a longer road stretch that can lead to more crashes.

Some findings refer to other research on legal cannabis driving. One 2021 study from Boston University found that fatal car crashes involving alcohol haven’t decreased over the past two decades, though cannabis-involved fatal accidents doubled, according to the study. Other studies have found that the risk of car crashes involving cannabis could increase, but not necessarily lead to more fatalities.

In light of the legalization of marijuana, trucking has seen many changes. The Federal Motor Carrier Safety Administration opened its alcohol and drug clearinghouse in January 2020. The clearinghouse lists commercial drivers who failed to pass a drug and alcohol test. However, drivers can clear their name by going through a return-to duty process.

The clearinghouse is aimed to ensure truck drivers violating drug and alcohol rules aren’t able to quickly secure another trucking job without amending their past behavior and ultimately aims to increase truck safety on the road.

While it’s not fully clear yet how much these aims have increased safety for truckers on the road and other drivers, it has removed a number of drivers. Around 124,000 truck driver sacked for failing drug screenings between January 2020 and April 2022. 31,000 drivers have successfully completed the return-to duty procedure.

Though, the majority of the violations don’t involve drugs like opioids, amphetamines, methamphetamine or cocaine but, you guessed it, cannabis. Since January 2020, more than 74,000 commercial truck drivers who had tested positive for marijuana have been banned from driving.