Drug Policy

Pot Smokers Drive Fine Far Above Legal THC Limit



A recent report by KIRO-TV, the CBS station in Seattle, provides further evidence that Washington's new standard for driving while under the influence of marijuana is a poor measure  of impairment. Initiative 502, which legalized marijuana for recreational use, established a per se standard of five nanograms of THC per milliliter of blood. Critics argued that cannabis consumers may exceed that level even when they are not impaired, and KIRO did a simple driving experiment (video below) that shows they were right. The station enlisted three volunteers: Addy Norton, "a 27-year-old medical marijuana patient and heavy daily marijuana user who smoked pot before arriving at the test site"; Dylan Evans, a 34-year-old weekend pot smoker; and Jeff Underberg, 56-year-old who smokes pot occasionally. All three of them satisfactorily completed a driving course at THC levels far above the legal limit.

Norton arrived with a THC level of 16 nanograms, more than three times the DUID cutoff, but nevertheless drove fine, according to the driving instructor who accompanied her with his foot hovering over a second brake and his hand ready to take the wheel. After Norton smoked three-tenths of a gram, she tested at 36.7 nanograms, more than seven times the legal limit, but still drove OK. Even after she consumed nine-tenths of a gram, a "drug recognition expert" from the Thurston County Sheriff's Office said her driving was merely "borderline." Only after consuming a total of 1.4 grams of pot and achieving a THC level of 58.8 nanograms, almost 12 times the legal limit, was Norton clearly too stoned to drive.

Evans arrived with zero THC in his blood but hit 26 nanograms, more than five times the DUID cutoff, after smoking three-tenths of a gram. He nevertheless was "doing fine behind the wheel." Underberg, who also started at zero, hit 21.7 nanograms, more than four times the legal limit, after smoking his three-tenths of a gram. "While his driving was slow," KIRO reported, "it was still acceptable." According to the driving instructor, "He did real well." Unlike Norton, Evans and Underberg were both clearly impaired after smoking twice more, consuming a total of nine-tenths of a gram. KIRO evidently did not draw blood from Evans or Underberg at that point. But two and a half hours later, Evans tested at 11.1 nanograms, more than twice the legal limit. Underberg was at 12.9 nanograms one hour and 45 minutes after his last puff. Those results suggest that occasional users may exceed the legal limit hours after they smoke, even when they are no longer intoxicated.

Keen not to be seen as encouraging people to drive while stoned, KIRO's correspondent closed his report with some responsible-sounding caveats. "It's true all three volunteers were able to safely drive a car for a while while four times or more over the legal marijuana DUI limit," he said, "but they eventually made driving errors that on a public road could have resulted in getting pulled over by police or much worse." Yes, but they made those errors at THC levels much higher than the legal standard for impairment. It's clear people can be too stoned to drive safely; the question, assuming it is appropriate to have a per se standard at all, is what the cutoff should be. Turning to that issue, KIRO's reporter said:

Some critics argue the legal limit for driving under the influence of marijuana was set too low. So does the fact that our volunteers were able to smoke pot and drive safely at four times the legal limit prove their case? Not necessarily. That's because the intoxicating effects of marijuana vary from plant to plant and from person to person. And you have to remember: Our volunteers were on a closed course, working with a safety net. They weren't out here, driving alone with the rest of us.

I see a couple of red herrings here. The plant-to-plant variation is irrelevant if the measure of impairment is THC in the blood, and the fact that the volunteers were driving "on a closed course, working with a safety net" does not change the fact that they drove competently even when they were far above five nanograms. By contrast, the fact that "the intoxicating effects of marijuana vary…from person to person," which helps explain how Norton was still OK to drive at 36.7 nanograms, is relevant, but it cuts both ways. Perhaps some people are impaired at five nanograms, but it seems clear that many are not. Setting a low cutoff may seem like erring on the side of caution, but that is true only if you discount the injustice of arresting and punishing people for driving under the influence when they do not actually pose a hazard to others. The variation in responses to marijuana, which is partly a function of tolerance and experience (presumably the main factors in Norton's case) but also due to pre-existing differences, argues against having any sort of per se standard.

Washington used to require evidence of impairment, including but not limited to blood test results, which is still the approach taken in Colorado, the other state that legalized marijuana last year. The Colorado legislature has considered a five-nanogram standard in the past and may yet adopt a modified version of it, establishing a rebuttable presumption of impairment at that level. But that makes no sense until we have a clearer idea of how many people really are too stoned to drive at five nanograms. Larger-scale, more systematic research along the lines of what KIRO did should come before any changes to the law.

You can watch video of the driving tests here and below.

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  1. They tested it with the 14yo who got kicked out of school because her hair is red? I guess because she didn’t have school she was available.

    1. Nicely tied together, entropy!

  2. Look, man, if there’s one thing I know, it’s how to drive while I’m stoned. It’s like you know your perspective’s fucked so you just let your hands work the controls as if you were straight.

    1. +1 Heavy Metal

  3. I suppose if you were really, really baked, it might impair your driving, but just being kinda high is not going to do much to your driving ability. And frankly, for good drivers, the same goes for alcohol.

    1. The only impairment I ever noticed from driving while baked was that I would sometimes forget where I was going. But it was usually your mom’s, anyway, so it was better if I forgot.

      1. “Wait a minute. Why am I at the grocery store with bags of trash in the back of the car?”

      2. I remember all the times she was wondering why you didn’t show, and now I know why. You broke her heart, Warty.

        The best driving experience I had was driving on acid and seeing all the shadows in the trees move around me as I drove (it was at night). Creepy and awesome at the same time.

        1. The friend who babysat me the first time I took mushrooms made sure to drive us around. It was AMAZING. We went all around the red-light district in Montreal and through all the tunnels they have running the highways under the city.

          And then I made snow angels. Ahh…

          1. When my friends and I would take mushrooms in college, while waiting for them to kick in, we would play pool and when the pool balls started having trails we knew we were good to go.

            1. In high school, I did some with a bunch of friends. The house we were hanging out at had an organ somehow connected to a dimmer switch. That was a fun effect.

            2. We had this bathroom where there were mirrors set up sort of one behind the other so you could see the back of your head if you angled them right.

              We knew we were good to go when one of the nicoles looked like she was maybe starting to be self-aware.

              1. I had a drive like that in Colorado shrooming hard. We were on the highway at night and the brake lights in front of us as well as the headlights from the oncoming lane were like giant serpent tails slithering in the distance.

                Drugs are fun!

                1. Crack in a Minnesota blizzard disagrees.

          2. Being in a car while tripping is awesome. Unless the car starts making weird noises like it is going to break or something. Driving while tripping I do not like.

            1. The NYC subway is less fun.

              1. Warriors, come out and play!

                Yeah, that sounds fucking horrible.

                1. It was during the day and it was mostly the crush of people. We didn’t peak until we got to the Natural History Museum so it wasn’t all that bad.

        2. Once a guy that looks just like me, was driving around the country tripping balls in a freind’s mom’s ford festiva with 4 other dude that were also tripping balls.

          It started to snow, and snow, and finally full on blizzard conditions were apparent. This guy and his friends drove around at 15 mph as the only car on the road through the wintry weather. They drove on in silence marveling at the crystalline beauty. After a short time or a long time, the quiet was disturbed by the meekest of voices chiming from the backseat. It slowly chirped, “donuts”. Silence then took over the car for a short time or a long time, until another voice repeated, “donuts”. The driver, a boy who looked just as I did as a boy, caught wind of the idea, and just as he did a third voice made it’s quiet vote, “donuts”.

          “Brilliant, brilliant fucking donuts!” my doppelganger exclaimed, and threw the car into fourth gear. To the shopping mall our young heroes went, and when the little car hit the parking lot a mysterious force pulled and tugged the emergency break. The little car spun and spun, a multitude of lights flying past the expanded heads of the youths. Again and again they whirled around, and in the snow of that parking lot was the most beautiful white donuts you ever saw.

          1. Oh, and another time this guy was driving in the mountains afflicted thusly^, of course, and saw a giant albino 12 point buck on the side of the road.

            It stood magnificent and proud on the side of the road, unperturbed by our shocked howls. Damn thing was such a sight that one of the boys pointed and yelled, “It’s a goddamn albino turkey clutch!” And so it was know for all times.

            I actually saw the same deer later on teevee when some guy got some video of it and called the news.

      3. you’re warty, ihaveherpes. let’s party.

    2. I don’t know about where you live, but around here ‘good driver’ is an endangered species.

      1. I think that applies just about everywhere these days.

    3. Agreed. Alcohol’s a problem because it impairs your hand-eye coordination and reaction time and greatly reduces your inhibitions. If you’re good enough then points 1 and 2 don’t really matter. If you’re smart you can train yourself around point 3.

      1. If you’re smart you’re probably not repeatedly putting yourself and others in peril by “training” yourself around point 3.

        1. You’ve missed the point: drunk driving isn’t as (individually) dangerous as you’ve been led to believe, and the very act of getting behind the wheel while loaded no more makes you an existential threat to society than being a black high school dropout does.

          Also, “training” is not “get in the car and practice,” it’s being aware of your own limits and intoxication level and changing your behavior accordingly. For some people and times that means being able to drive but taking it slower, for others it means avoiding the car entirely.

          The draconian enforcement measures for DUI are also unnecessary, but that argument is actually separate. Even if DUI is a systemic problem, the way we deal with it is over the top.

          1. There’s no causal relationship between being black or a high school dropout and crime; there is a proven causal relationship between getting loaded and a deterioration of driving ability. Not every instance of p-in-v sex results in pregnancy, but it’d be wrong to say that there isn’t a causal link.

            Do different people have differing tolerances and thus different limits? Sure. Is the way we handle DUI over the top? It’s certainly possible. Nevertheless, it’s been my observation that most people don’t have a clue what their limit is and don’t consult others to ensure that their self-evaluation has a basis in reality — and hubris is a very poor reason to put other people at risk.

            1. there is a proven causal relationship between getting loaded and a deterioration of driving ability.

              Sure, and I’ve never disputed that (hence I started “Alcohol’s a problem…”). I just don’t think it’s a problem where the state needs to bring such a heavy hand (though it is their roads and their right). Drunk driving’s not the safest activity in the world, but neither is sober driving and a certain amount of alcohol doesn’t really turn the highways into death race.

              it’s been my observation that most people don’t have a clue what their limit is and don’t consult others to ensure that their self-evaluation has a basis in reality — and hubris is a very poor reason to put other people at risk.

              And it’s been my experience that people as a whole are quite a bit better at this than they are given credit for (though this could be because of the draconian enforcement mechanism). There’s always going to be that asshole (harsh DUI laws or not), but your normal everyday person is capable of handling himself in this regard.

  4. I suspect science will confirm what potheads have known, a posteriori, for some time now.

      1. Took exactly as long as I suspected.

        Also, you are the Reason….blah blah bl

      2. Thanks, Warty – and I am supposed to concentrate on work for 2 more hours how?

  5. Sure, if you bring in Dr. Johnny Fever to test.

    1. But you have to use Les Nessman as your control.

    2. Get your AARP card yet?

  6. a “drug recognition expert” from the Thurston County Sheriff’s Office said her driving ….

    I’d prefer an expert on traffic or driving.

    Maybe they could have the K9 trainer weigh in? A Forensic Accountant, just for teh lulz?

    1. “Yep, that’s weed allright.”

      WTF does a drug recognition expert do, anyway? Swab for coke residue on money?

      1. Draws a paycheck, contributes union dues. And for your next question, fuck you, that’s why.

  7. Ideally, the limit would have been established pending statistically significant results from studies.

    Politically, I can understand why a drug legalization bill would crack down hard on real or perceived drawbacks to the drug in question.

  8. My uneducated guess is that medium pot use affects driving ability, but not in the same predictable way alcohol does.

    The problem with pot is excessive focus, not lack of focus. In regular driving, a stoned person might actually be better in some ways, but unexpected events (a swerving vehicle, for example) outside the person’s immediate focus might not be noticed as quickly as with a sober person.

    As others have said, I’m doubtful there’s a given blood/THC level that could tell you how a person react, since people react to pot so differently and have different levels of focus and attentiveness to begin with.

  9. Only after consuming a total of 1.4 grams of pot and achieving a THC level of 58.8 nanograms, almost 12 times the legal limit, was Norton clearly too stoned to drive.

    What’s the nanogram to bong hit conversion ratio?

    1. Depends on how much blood you have

      1. “If we drained out half our blood we could get so high, dude.”

  10. Or, of course, they could also stop looking at chemical residues and start evaluating actual impairment. There are gizmos now that can do that more or less objectively (that is, without any recourse to testilying by the police).

  11. Ugh, I hate this crap. No one should be convicted of DUI unless it can be demonstrated that they were actually impaired. Especially with something like pot which affects people so differently. I know people who should never drive while stoned. I also know people who can smoke pretty much an unlimited amount and be perfectly fine.

    1. No one should be convicted of DUI unless it can be demonstrated that they were actually impaired.

      Oh, come on! How can you measure that?

      Next you’re going to say that teachers should be evaluated based on performance, or some other nonsense that you can’t measure!

    2. yeah, I can drive drunk pretty damn good and usually get slotted as the “designated driver”. Of course if I drink waay to much, then my impairment factor will override my ability.

      However, there have been some times where I’ve been stoned that driving was a chore. I was more nervous about being busted then compared to a few drinks.

  12. Stop smoking weed. Only hippies and third worlders would think it is cool. Libertarians supposedly want a free society, so you should start advocating a responsible one. Taking soma when you feel blue doesn’t make you less of a slave, whether or not it is legal.

    1. Who ain’t a slave? If we want to join hands and squeeze that spermaceti, well…

    2. soma

      Look, someone who thinks Aldous Huxley was against drugs. HA!

      1. Buzzwords without biography is the mark of the quarter-educated.

        1. Maybe he’s referring to the legendary far eastern stuff.

          Doubtful but possible.

          1. Soma in the classical sense wasn’t an opiate of the masses, like Huxley used it. In the Vedas, Soma bought about a sharpening of the senses and an ecstatic joy akin to how the gods felt all the time.

            Even if he meant in it the Vedic since, he’s still wrong.

      2. To be fair, the way the subject is treated in Brave New World would certainly lead one to believe that to be the case.

        For that matter, BNW would lead someone to believe that Huxley was anti-tyranny, rather than merely being an “it’ll be better with the right people in charge” type.

    3. Hey dumbfuck, soma is a muscle relaxer. This is reality, not Brave New World.

    4. Fuck off slaver.

  13. They should just make it illegal to crash up and call it a day.

  14. “the driving instructor who accompanied her with his foot hovering over a second brake and his hand ready to take the wheel.”

    Were I high, that would really freak me out.

  15. Once weed is legal most places, what’s the next big push? From a benign drug viewpoint mushrooms are an obvious choice

    1. LSD, shrooms, MDMA. All are equally beneficial and harmless.

      1. Mushrooms can give you a nasty tummyache, Warty. Be fair.

    2. Peyote might be another one, as it already has an established, concentrated base of users.

      1. Talk about a tummyache.

    3. You need a sizable constituency/market base.

      I’d say Ecstasy, maybe?

      1. That would be pretty high on the list, I think. It is definitely in the at least as safe as alcohol category.

        1. Also, it has massive potential as a psycho-pharmaceutical.

    4. This is the guy to ask.

      Too bad about the surname, though.

  16. I never, ever drive if under the influence of anything that could be considered an impairment. Our company has a zero-tolerance policy on DUI’s.

    Tat said, back in the day I used to drive beyond the legal threshold all the time. I’m not proud of that fact, but it happened. Anyway, I can honestly say that I’ve been in more near-misses of serious accidents due to texting, spending time on my laptop and reading my e-mail than I ever was in while driving “impaired”.

    1. The moral of the story is that we should ban laptops, cellphones, and email.

      1. You sound like you’re ready for the political stage!

        No, the moral of the story is that when people have accidents, there should be penalties for the person at fault. If no accident happens, there’s no crime.

        1. I was kidding, but I do think that DUI laws are justifiable within reason. My story is similar to yours (used to drive above the legal threshold all the time; don’t anymore). The legal threshold is probably too low, but there’s a point at which you’re talking about shooting a loaded gun into a crowd at random levels of negligence. Depending on the traffic where you’re driving and/or other circumstances, I have no problem with a DUI charge for such cases.

          1. I’d generally agree with that. And get rid of the legal threshold altogether. If someone is that wasted, it shouldn’t be too hard to prove actual impairment in court.

            1. We have the tech to have people suspected of DUI put on simulators that determine their ability to drive. If someone can pass then they’re not charged. And you make the test reasonable.

              Also, abolish FST’s. They’re way too fucking subjective, and they should never be allowed in a courtroom.

    2. That’s the thing that bugs me most about DUI laws. They treat intoxication as if it is a uniquely dangerous thing while driving. When things like texting, fiddling with the radio, lighting a cigarette, just being tired or having misbehaving children in the car with you can make a driver just as much of a hazard on the road as someone driving shitfaced.

    1. Worse is the comments on Tesla’s blog.

      I can almost guaran-fucking-tee those people are employees.

    2. What the fuck is a “Tesla”?

      1. A unit for measuring magnetic flux density.

        1. And here I thought it was a really big doorstop.

    3. Seems like there are several.

    4. You mean the guy making every other comment? They had one in the NYT followup article posted earlier. His name was John and he was adamant that anyone who didn’t love Tesla cars was a despicable liar.

      1. Yup. He’s definitely on the payroll. And their might be more than one.

        1. *there* goddammit

  17. The plant-to-plant variation is irrelevant if the measure of impairment is THC in the blood

    That might matter if THC were the only contributor to the high. There are various kinds of high, ranging from cerebral to buried in the couch, and THC levels are but a contributing factor to that.

  18. try driving with herpes. shit is hectic.

  19. try driving with herpes. shit is hectic.

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