Marijuana DUI’s: Are You Driving While Impaired?


Too drunk to drive? What about too high to drive? Before you smoke and drive, make sure you know how states are testing for impaired driving.

Despite the increasing number of states that have legalized some uses of marijuana, there still is a lot of discussion – and disagreement – about how to determine whether a person who has smoked a bowl or consumed an edible is “impaired.” Of the four states where recreational use is legal – Alaska, Washington, Oregon and Colorado –only Washington and Colorado have actually quantified a biological marker for impairment — or a marijuana DUI.

Washington and Colorado

Washington and Colorado both administer blood tests to determine whether blood-THC levels are at or above 5.00ng/mL.

The Revised Code of Washington § 46.61.502(1) says that a person is guilty of DUI if, “within two hours after driving, a THC concentration of 5.00 or higher as shown by analysis of the person’s blood…” Colorado has a less specific standard; though it uses the same 5.00 nanogram per milliliter (ng/mL) standard as Washington, it doesn’t have any time-frame for the concentration. Colorado’s so-called “per se” rule has led to “complications for law enforcement and citizens,” a phenomenon some call “sober DUIs,” because the ratio of intoxication to blood THC level depends largely on the individual and their smoking habits.

The 5.00 ng/mL standard sounds useful if only because it provides a degree of certainty, but this standard means different things to different people. Lots of smokers may be feel like they are high at that point, but lots of other people may feel perfectly sober. The 5 ng/mL limit reportedly was taken from a study of nearly 3,400 fatally injured drivers in Australia, which found that the “risk of a crash begins to rise between 3.5 and 5 ng/mL of THC in a driver’s blood.” That data was pulled from  a single study, and there’s been little corresponding evidence to support it since.


Alaska requires that law enforcement officials call a Drug Recognition Expert if no other reason for impairment can be deduced.

Chief Mark Mew of the Anchorage Police Department has explained that when an officer observes signs of impairment in a driver, who then fails a standardized field sobriety test but blows less than .08 BAC in a breath test, the officer tries to determine what other factors (like illness, other medications, exhaust fumes) might be at play. If the officer at the scene is unable to determine the source of the seeming impairment, the next step is to call a Drug Recognition Expert (DRE) if one is available. The Anchorage PD also will try to get a search warrant for a blood test.


The newest state to join the legalization club, Oregon is still establishing their marijuana DUI las.

As of August 2015, Oregon had yet to establish any biological standards measuring THC or any other grass-related biologic component but relies on its officers’ subjective observations. So far, there’s no established limit for the amount of THC that you can have in your blood before you will be presumed to be impaired while driving. And like Alaska, Oregon is busy training its own cadre of Drug Recognition Experts; 180 agents were in the program at the beginning of the year but that number has increased to over 200.

Testing Yourself

People who have been smoking should use their best judgement, but if you’d like some help, there’s an app for that. Canary, which was designed in part by NORML, administers 4 tests that may reflect whether you can safely drive. You take the tests when sober to establish a “baseline” and then use it after smoking or drinking or otherwise consuming to see how well you perform. If the app gives you anything other than a green light, don’t get behind the wheel!

Just like any other intoxicating substance, marijuana should be enjoyed responsibly; if you have any concerns about whether or not you’re too high to drive, your best option is to wait it out and sober up.


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If you enjoyed this, you may also like:

Scared of Heights: What to Do if You Get Too High

 Fired for Using Legal Marijuana? One Woman’s Story

Colorado, the Poster Child of Legal Marijuana


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