DUI risks: marijuana and alcohol combined

Ever since Washington and Oregon legalized recreational marijuana use (in 2012 and 2015, respectively), traffic-safety experts have tried to gauge how it affects drivers compared to alcohol. Is driving high safer than driving drunk? What happens when you combine weed with booze? And can they cancel each other out? 

Studies published last year seem to have the answer: Neither is good, and when used together, they’re worse. The combination further diminishes drivers’ ability to stay in their lane compared to either substance when used alone. Unfortunately, “polydrug” DUI is now the most common (more on that below) type of infraction--even more than driving drunk (alcohol alone).

How do alcohol and marijuana differ in how they affect drivers? 

Alcohol, researchers say, tends to make drivers speed up, overestimate their abilities, and have trouble maintaining control; marijuana can cause weaving in the lane, despite a tendency to drive slower. Like drinkers, marijuana users suffer dampened reaction times and falter when confronted with driving challenges, such as avoiding a collision when another driver makes an error. 

Researchers struggle when trying to put percentages on the degree of impairment cannabis causes and the extent to which it contributes to accidents. There’s no test for marijuana that’s comparable to a breathalyzer for alcohol, and impairment varies depending on a user’s tolerance to it. Post-crash testing for the presence of THC (marijuana’s high-inducing ingredient) can be tricky, too, since it’s still detectable in a user’s system after the high wears off.  

In contrast, we know that a blood alcohol level of 0.08% increases the risk of a crash by approximately four times compared to a sober driver, according to the National Highway Traffic Safety Administration (more in Forbes Advisor). Bump the blood alcohol level to 0.15%, and the risk climbs to 12 times. Diminished capabilities can be seen in people with levels as low as 0.02%.  

Because testing for alcohol impairment is clear-cut and has a decades-long track record, the National Institute on Drug Abuse notes that law enforcement often won’t test for drugs if drivers have reached an illegal blood alcohol level because there’s already enough evidence for DUI charges.  

That may result in an official undercount of this disturbing trend shared by the Insurance Institute for Highway Safety (IIHS): Among people who use alcohol and marijuana together, one-third admitted to driving within two hours of doing so. Following the publication of a similar study from Columbia University, a University of Michigan researcher told CNN, “most DUI now is not related to alcohol use alone.”  

Has legalizing recreational marijuana impacted the amount of car accidents in the PNW?

IIHS says that police-reported crash rates jumped 5% in Washington, Oregon, and Colorado compared with neighboring control states after legalization. It also points to an alcohol-marijuana connection, and says, “Legalization may be encouraging more people to drink and use marijuana together.” 

The Washington Traffic Safety Commission took a deep dive into fatal crashes on the state’s highways five years after legalization. The results showed plenty of drivers who mixed cannabis and alcohol, which researchers put under the umbrella of “polydrug use.” The short version: During the study’s five-year span, the number of polydrug drivers involved in fatal crashes increased an average of 15% each year. By 2016, the number of polydrug drivers involved in fatal crashes were more than double the number of alcohol-only drivers and five times higher than the number of positive THC-only drivers. 

What are the consequences of driving under the influence? 

In addition to its tragic human toll, driving under the influence can have serious legal* penalties that vary by state and the specifics of the case.  

In Washington, according to the online legal resource NOLO, a first offense may result in up to 364 days in jail, a fine of up to $5,000, compulsory participation in a sobriety program, and a license suspension. In Oregon, it could bring up to a year in jail, a fine of up to $6,250, a license suspension, installation of an ignition interlock device, and required participation in a substance abuse treatment program. Subsequent offenses in both states can result in harsher penalties. 

Your ability to buy affordable insurance would take a hit, too. 

Nationally, a DUI in 2023 adds an average of 70% to a driver’s insurance bill, according to Forbes Advisor, which used state-by-state data compiled by Quadrant Information Services. Analysts pegged average increases in Washington and Oregon at 55% and 68%, respectively.  

“That number is going to vary case-by-case depending on the exact citation, overall driving history, and the other characteristics of the policy, so even within the same insurance company, the impact of a DUI on individual drivers may differ,” said PEMCO’s Vice President of Product and Underwriting, Dawn Lee. “It also impacts things like eligibility for accident forgiveness.  

“DUI is an extremely serious infraction from any insurance company’s point of view,” she added. “Because of its potentially catastrophic results, impaired driving catapults you into a high-risk category.”  

Both Washington and Oregon require insurers to file what’s called an SR-22 form with the state proving that high-risk drivers (like those with a DUI) are maintaining at least the minimum required insurance limits. If they don’t, their licenses may be suspended. 

Reduce the risk of DUI 

Try these anti-impairment strategies, no matter where you or your loved ones drive: 

• You’re going out. If your celebration includes intoxicants, make alternative transportation arrangements such as staying the night at the host’s home or in a hotel, taking a taxi or rideshare service, or designating a sober driver.  

• You’re hosting. Mix drinks modestly and stop serving alcohol at least 90 minutes before the party ends. Serve plenty of protein-rich food (slows digestion) and avoid salty snacks since they make people thirsty and likely to drink more. If a guest still overdoes it, offer a ride home or call a rideshare service. Alcohol counselors tell us that the best way to convince someone not to drive is to express concern they may get ticketed or lose their license. That’s a stronger motivator than your worries about their safety. 

• You’re a parent. Tell teens they always can call you for a no-questions-asked safe ride home.  

• You’re running errands. Buckle up every time. Even if you’re in the backseat or using a rideshare, shoulder belts dramatically reduce your chance of injury in an accident. And, if you see a driver who appears to be impaired, report it. In Washington, call 9-1-1; in Oregon, call *677 from a mobile phone or 9-1-1 from any phone. 

Learn more about staying safe on the road 

Sharing timely, carefully sourced information from trusted safety organizations is an important part of PEMCO’s worry less, live more commitment to PNW drivers. To learn more about staying safe on the road, check out our auto safety collection, and please let us know in “Comments” about future topics that interest you. 

* NOTE: While we’re experts in loss prevention and auto/home safety, we don’t consider ourselves experts in traffic laws or their enforcement. Information shared here is for educational purposes only and is not legal advice. If you have legal concerns, we urge you to contact a law enforcement source or attorney in your community. 

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