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Stoned Driving Limits: You Asked To “Treat It Like Alcohol”


police with bag of marijuanaWith Washington State’s I-502 legalization came a 5ng/ml limit of active THC in blood.  This is now per se evidence to convict on a DUI charge.

In Colorado, the governor is poised to sign a bill creating a 5ng/ml limit that has failed to pass in six previous attempts.  This would set a permissible inference of guilt on a DUI charge.

To my fellow supporters of marijuana legalization, I’m reminded of the saying, “Be careful what you wish for because you might get it.”

Before I explain that, let’s make sure everyone reading is familiar with the concepts:

  • These limits in Colorado and Washington refer to active THC in the blood, not the inactive metabolites you get busted for on a workplace pee test, sometimes days or weeks after cannabis use.
  • per se limit means you’re automatically guilty and have no defense.  You could be driving absolutely perfectly and still be guilty of a DUI if your blood is >5ng/ml.
  • permissible inference means that you’re presumed to be guilty, but you can defend yourself if you can prove you weren’t driving impaired, even if your blood is >5ng/ml.

Now, back to our wishes.  For years now, we have been lobbying for marijuana legalization with frames like “treat marijuana like alcohol” and “tax and regulate marijuana like alcohol” and “marijuana is safer than alcohol”.  It’s not a bad strategy, obviously, because it’s brought us two legalized marijuana states.  However, setting marijuana in a frame alongside alcohol has molded the public’s understanding of the drugs to think of them similarly.

Is this supposed to be some kind of a bribe?

Is this supposed to be some kind of a bribe?

So now they want to know: where’s the marijuana breathalyzer?  What’s the magic number that tells us someone’s too stoned to drive, like the magic .08 BAC number that enables us to nab drunk drivers?

It’s at this point when one of us pipes up with “impairment!”  The marijuana limits don’t test for impairment.  Many people, like medical marijuana patients, can be above 5ng/ml and be completely unimpaired.  We need to test for impairment.

Yes.  And this is a case where being right isn’t going to win the argument.

Part of the problem is that we’re seen as being hypocritical.  If we really believe that blood chemistry doesn’t determine impairment, why aren’t we rallying to repeal alcohol per se limits?  Yes, there is quite a difference between alcohol and marijuana in the blood and there is a much more reliable dose-dependent relationship between alcohol and impairment than THC and impairment.  However, I know plenty of people who drink regularly who can drive in a satisfactory manner at >0.08 BAC.  So, we end up saying people who use pot all the time can develop a tolerance and drive fine over the limit… but alcoholics can’t?

The majority of the problem, however, is a critical misunderstanding of what DUI is to the public.  The “DUI” doesn’t stand for “driving under impairment“; it stands for “driving under the influence“.

C+?  I'd be a better driver than you on heroin! (Danica Patrick wallpaper by CarAddicts.com)

C+? I’d be a better driver than you on heroin! (Danica Patrick wallpaper by CarAddicts.com)

In our society, we’re not punishing people based on their impairment.  We’re punishing them based on their irresponsibility.  Imagine this: we take Danica Patrick, me, and a random elderly grandmother and test our driving ability while sober.  On a letter-grading system, let’s say Danica gets an A+, I get a B, and Granny, whose reflexes are slow and can barely see over the steering wheel, gets a C-.  In other words, Danica is a pro driver, I’m a decent driver, and Granny barely passes.

Then, we get Danica drunk (yay!) and I smoke a joint.  Danica’s at .08 BAC, my THC is at 35ng/ml, and Granny’s still sober.  Danica drives again and tests out at a C.  I test out and get a C+.  Granny’s still at a C-.  But despite the fact that both of us drive better than Granny even when buzzed, Danica and I are going to get DUIs, legally because we are “under the influence”, but culturally because we irresponsibly chose to drive after reducing our ability to drive as safely as possible.  That’s what the public supports in punishing >.08 BAC drivers and that’s why they want a magic number for THC.  Granny, despite her inability to merge on the freeway, her forever left-turn blinker, and tendency to drive 20MPH too slow, is still driving at the best of her ability and not irresponsibly reducing that ability.

Now’s the time when another one of us pipes up with studies and anecdotes.  William Breathes tested at 15ng after a night’s sleep.  KIRO filmed “all-day Addy” driving just fine at seven times the limit.  Pot smokers tend to adjust their driving, drive slower, more distance between cars, etc.  And all the public can hear when you say that is, “we should be able to smoke pot and then get behind the wheel.”

As each state ponders marijuana legalization, you can bet the “stoned driver” issue will be at the forefront.  If we are going to successfully deal with this issue and avoid Washington and Colorado’s 5ng/ml becoming the standard, we need to adjust our tactics.  Every indication shows the trend will be toward more scientific testing of drivers, with saliva swabs and drug breathalyzers already developed and being tested in Europe.  Here are some angles I suggest:

  1. Accept that there will be a limit and work to make it reasonable.  The people don’t fear a little intoxication on the road.  The .08 BAC leaves plenty of room for someone to have a margarita with dinner or a beer at the game and still be OK to drive home.  Emphasize that the 5ng/ml limit is just way too low – like setting BAC down to .02 (which is actually the limit in some European countries).  People want to catch the irresponsible user who just consumed and is way too messed up to drive.  Show them that THC in blood spikes over 100ng shortly after consuming.  Find the level at which nobody could possibly be unless they were recently consuming (35ng? 5ong?) and set it there.  This would address the public’s concern over driving immediately after smoking and being too impaired while sparing those who drive hours after smoking who aren’t impaired.
  2. Make the limit a permissible inference that gives the marijuana user a chance to prove his or her driving wasn’t impaired.  Combined with a reasonable limit, this should give all but the actually-too-stoned-to-drive drivers a fair day in court.
  3. Give a little to get a little.  Since what people fear is people blazing up and then driving, use the existing “treat marijuana like alcohol” frame to offer the public the marijuana equivalent of the “open container”.  Any usable marijuana in an unlocked container or used paraphernalia / smoldering joints within the driving compartment is treated like an open container of alcohol.  I believe offering this kind of compromise could go a long way toward getting reasonable, permissible inference limits.

I know these suggestions will be controversial.  Some will suggest that we’ve had DUI laws against toking and driving forever and they require that police prove impairment.  Yes, indeed, but we’re talking about public and lawmaker perceptions, not courtroom reality.  In their minds, the way we keep stoners off the road is when we pull them over and smell weed, we can arrest them for having weed.  Now that we propose taking that option away from police, the public feels like there will be no way to keep stoners off the road.  As illogical as it is, to the public’s mind, legalization introduces a brand new drug to society and we’re seen as opposing for marijuana the same policies that keep drunk drivers in check.

If you can get marijuana legalization in your state without any sort of THC in blood limit, more power to you.  I believe the political realities won’t make that possible.  Colorado did it, only to see its legislature hammer away at a 5ng limit until it seems now likely to become law.  If the choice is legalization that will pass with limits or continuing to arrest and imprison marijuana smokers, the smart thing to do would be to lobby for fairer limits.


About Author

Executive Director: Russ Belville has been active in Oregon marijuana reform since 2005, when he was elected second-in-command of the state affiliate, Oregon NORML. After four years with Oregon NORML, Russ was hired by National NORML in 2009, working as Outreach Coordinator and hosting the NORML Daily Audio Stash podcast until 2012. Since then, Russ launched the 420RADIO marijuana legalization network and is the host of The Russ Belville Show, a live daily marijuana news talk radio program. Russ is also a prolific writer, with over 300 articles posted online and in print in HIGH TIMES, Huffington Post, Alternet, The Weed Blog, Marijuana Politics, and more.


  1. Krymsun Gorean on

    Why does most everyone automatically jump to the impulsive knee-jerk, FALSE assumption that cannabis impairs drivers much the same as does alcohol? Why let uninformed opinions be the basis of new laws? It took me very little time to do a search, and find actual scientific studies which indicate just how incorrect such an assumption is.

    See: http://norml.org/library/item/marijuana-and-driving-a-review-of-the-scientific-evidence

    Per Se Drugged Driving Laws and Traffic Fatalities concluded that, as currently implemented, making it illegal to operate a motor vehicle with drugs (or drug metabolites) in the system, has no discernible impact on traffic fatalities.
    See: http://ftp.iza.org/dp7048.pdf

    Driving High on Marijuana Is Safer Than Driving Drunk [ or driving sober ]
    See: http://blogs.lawyers.com/2012/04/cruising-the-high-way-safer-than-drunk-driving/

    For some Top Ten Reasons Marijuana Users Are Safe Drivers
    See: http://www.theweeklyconstitutional.com/news/headlines/1035-why-you-should-always-spark-up-before-hitting-the-road

    Marijuana By Itself Not a Significant Factor in Fatal and Injury Crashes in 2012, DPS Data Shows

  2. So, if we are to agree on a blood test, will that require cops to carry blood draw equipment in their cars? Or will anyone suspected of having THC in their blood be detained and hauled to a police station or ER where a phlebotomist performs the draw?

  3. Pat Cowdin on

    What if Granny decides to increase her pain meds and drive to the Safeway totally blitzed on synthetic opiates? She’s sure as heck impaired, but probably legal unless she drives her Buick into the produce department. Shouldn’t all these substance-specific rules be tossed in favor of accurate field-administered impairment tests?

  4. ok but it seems the limit theyve come up with would be equivalant to ,02 bal, would lawmakers/drunks stand for that?

  5. Standard drug tests only test for the inactive component. It stays in your system for a while but isn’t actually affecting you. That includes all of their methods – Urine, saliva, hair, blood. The reason your friend doesn’t know is because he’s probably never heard of it or understands that he only tests for the inactive component.

    As far as I’m aware, the active component only shows up in blood tests, and for a relatively short period of time compared to the inactive. According to the little bit of research that they did it generally drops below 5ng/ml in 2-3 hours. But they didn’t do enough research to actually justify impairment standards, and in some heavier users (which medical falls under) it stays above that level for longer.

    There’s a reason why Washington only targets active THC and Colorado is trying for the same. The information is our there and has been put out there many times – it’s your responsibility to read it, educate yourself, and spread the knowledge.

  6. I’m pretty sure nobody has suggested there be no such thing as a DUI limit.

    I think everyone agrees and has made quite vocal that the 5ng/ml limit is an arbitrary number — that there *could be* an appropriate limit based on BMI and measurable levels of, yes, the ACTIVE metabolites… Although you have made the distinction linguistically, those of us without advanced biochemistry degrees don’t understand what’s so special about an active metabolite.

    I admit that I have operated strictly upon what I’ve learned anecdotally from a friend of mine who performs drug tests. Shockingly, he’s never attempted to make any sort of distinction between active metabolites and inactive ones, (I’m still uncertain that makes any sense at all). What he’s told me? The measurement is the same — the results of the measurement are what must be appropriately interpreted. In simple English — in his lab, if your blood comes back with less than 50 ng/ml — indicating you haven’t consumed cannabis in at least a few weeks — your test result is NEGATIVE. That’s ten times less than 5 ng/ml.

    As I think I’ve successfully implied — I’m not a biochemist. The closest I’ve ever come was writing software for a corporate blood bank that needed to computerize their phlebotomy labs and quality assurance department.

    One would think that the controversy could be cleared up succinctly if, in fact, there is such a thing as distinguishing between active vs inactive metabolites when measuring quantities of something in the blood. We can throw around hypotheticals about Danika and grandma to put minds at ease, but I’d rather know that laws ARE just and fair, not just that they’re comparably unfair.
    This article was a well-written and informative justification for GIVING UP the struggle for just laws. Never thought I’d read an article by a supposed advocate — advocating that we give up.

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