By / October 30, 2023

Does Cannabis Legalization Lead to Fewer Accidents?

States that legalized cannabis in 2016 recorded a significant decrease in road accidents in the years immediately following this change, according to a new study conducted by Quartz Advisor. However, over time, the conclusions were less clear, especially during the years that the report describes as “anomalies” in the scale of the United States.

Ultimately, according to the report, road safety “should not be a significant issue for cannabis legalization initiatives,” especially compared to alcohol.

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Cannabis vs Alcohol in Road Safety

“So far, studies have not shown that the legalization of cannabis led to a significant increase in road accidents where it was legalized,” says the report. “This cannot be said about alcohol, an intoxicant that remains legal, widely available, and deeply rooted in our culture.”

In states that legalized cannabis, “the number of road accidents dropped or remained at the same level three years after legalization, compared to a slight increase in states where it was still illegal.”

Legalization and Road Safety: An Analysis

The unrevised study analyzed traffic accident data from four states that legalized cannabis in 2016: California, Maine, Massachusetts, and Nevada. Then, Quartz Advisor compared mortality rates in these states with the national average and rates in five states where cannabis remained illegal during this period: Idaho, Indiana, Kansas, Nebraska, and Wyoming.

In the three years following the change, none of the four states that legalized cannabis recorded an increase in the number of fatal victims in road accidents. Most of them actually recorded declines.

Understanding the Accidents Data Trends

“Three out of four states recorded a significant decrease in the number of fatal victims in road accidents during this period,” says the report, “while the rate in Maine remained unchanged. Massachusetts recorded the largest decline, with rates dropping by 28.6 percent three years after legalization.”

In total, in the four states that legalized cannabis, there was an 11.6 percent decrease in mortality rates in road accidents from 2016 to 2019. This is a bigger drop than the national average, which fell by 10.6 percent over the same period.

Anomalies in the Data on Accidents

However, what seems like a clear picture becomes less clear when researchers extended the analysis to data from 2020 and 2021, the latest years for which data from the National Safety Council (NSC) were available. During this period, the fatal victim rate in road accidents actually increased in states that legalized cannabis, although less than in the entire USA. Meanwhile, states where cannabis was illegal recorded a drop in mortality rates in road accidents.

Research and Findings

“Why is it worth ignoring data from two entire years? The report explains:

“In many respects, 2020 and 2021 were anomalies, which remains true in road accident trends as well. After decades of decline in accident rates in the USA, the number of fatal victims in road accidents increased in 2020 and remained at a high level through 2021.”

Examining Cannabis’s Impact on Driving Behavior

The new Quartz Advisor report states that “while there is no evidence suggesting that legalization or decriminalization of cannabis makes the roads more dangerous, it does not mean that driving under the influence of cannabis is safe.” It refers to a meta-analysis from 2010 published in The American Journal of Addictions, which found that cannabis “causes impairment in every area of functioning that can be considered related to safe vehicle operation.”

It is strange, however, that it does not always seem to lead to correspondingly more dangerous driver behavior.

The 2022 Casualty Actuarial study found that while cannabis use affects driving, “behavior is not always riskier; for example, lower speed and longer distances between vehicles were observed among drivers under the influence of cannabis.”

Challenges in Measuring Impairment

Overriding common concerns about driving under the influence of cannabis is the fact that there is no reliable test for the presence of cannabis. Standard drug tests make it difficult or impossible to determine whether someone is under the influence of cannabis or took it several days or even weeks earlier.

Experts and activists emphasize that the evidence is not clear about the relationship between THC concentration in the blood and impairment.

A study published in 2019 concluded that people driving with the permitted amount of THC – which usually ranges from two to five nanograms of THC per milliliter of blood – were not statistically more likely to have an accident compared to people who did not use cannabis.

(Featured image by Michael Jin via Unsplash)

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