Driving After Using Cannabis

The AAA’s report surveyed 2,000 cannabis users using a multiple-choice questionnaire. The participants belong to eight states where cannabis is eight fully legal, partially legal, or fully illegal.

Additionally, 800 more respondents from the same eight states were surveyed to gauge their reaction to cannabis and driving messages. Classified by risk level based on their driving habits after use, they evaluated eight visual messages for appeal, attention-grabbing quality, relevance, believability, image reinforcement, and offensiveness.

Results show that 84.8% of consumers responded that they drive the same day that they consume cannabis, compared to never driving after use. This happened less in fully legal states than in other state categories.

When comparing respondents’ interactions with law enforcement, only 29.2% of participants believed a police officer could detect the influence of cannabis, while 46.7% didn’t think they could detect it, and 24.1% were unsure. This pattern was pretty consistent across all states.

The survey was also able to categorize users by driving risk based on cannabis consumption timing: Ultra-high risk (53%) consumed within an hour before driving, high risk (20%) consumed 2–3 hours prior, and medium risk (12%) consumed 4+ hours before but still on the same day without sleep. Low-risk (15%) waited at least 8 hours and slept before driving.

Among the 800 respondents, the message “If you feel different, you drive different—Drive High. Get a DUI” was the most effective, with 62% saying they’d wait longer before driving and 58% considering alternative transportation. However, only 20-29% were likely to reduce cannabis use. Trust in information sources varied, with high-risk users favoring cannabis brands and medium-risk users trusting medical and safety organizations.

Overall, most cannabis users surveyed drive within one hour of use and have a low level of knowledge about cannabis laws and regulations.

Link Between Cannabis Use And Accidents Remains Unclear

The findings are in line with another AAA survey published in 2019, where it was shown that an estimated 14.8 million motorists said that they drive within an hour of using cannabis.

Another survey on 990 drivers in legal cannabis states conducted by the insurance comparison platform The Zebra found that 51% decide whether to drive based on how they feel, with 47% reporting impaired abilities, while 74% chose alternatives to driving, only 35% were familiar with their state’s cannabis driving laws.

However, assessing the impact of cannabis on motor vehicle fatalities is challenging.

In 2021, a study published in the American Journal of Public Health showed that between 2000 and 2018, while fatalities involving alcohol remained stable, those involving the use of cannabis increased from 9% in 2000 to 21.5% in 2018.

However, when assessing motor vehicle collisions (MVC) that occurred in the presence of cannabis impairment, data published in the journal Accident Analysis and Prevention in 2024 that took into examination more than 1,300 patients recruited from emergency departments in three legal cannabis states showed that cannabis alone was not associated with higher odds of collision, while acute alcohol use alone, and combination of alcohol and cannabis were both independently associated with higher odds of collisions.

Therefore, it’s challenging to assess a correlation between cannabis use and accidents amid the presence of mixed findings.

Law Enforcement Lacks Tools To Detect Cannabis-Impaired Driving

This is because law enforcement lacks reliable tools to detect cannabis-impaired driving in the same way as drunk driving.

Only a few states test for cannabis impairment in drivers when involved in serious accidents, and blood tests aren’t able to assess whether cannabis was used hours or days before, making cannabis impairment challenging to determine.

Unlike alcohol, the effects of cannabis vary based on the method of consumption. For example, smoking cannabis produces a quick but short-lived effect, while edibles take longer to kick in and last longer.

As a result, despite several states having laws prohibiting any detectable THC in drivers, there is no clear consensus on safe cannabis levels for driving.