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AAA Study: Blood THC Levels After Smoking Pot Are Useless In Defining 'Too High To Drive' (arstechnica.com) 455

An anonymous reader quotes a report from Ars Technica: Blood tests that try to quantify marijuana use are in fact useless at assessing how impaired a driver is, according to a study by the AAA Foundation for Traffic Safety. The study found that people with low blood amounts of THC -- or delta-9-tetrahydrocannabinol, the main psychoactive component of pot -- may still act as if they're really stoned. On the other hand, some people may have THC measurements off the charts yet still act normally. The finding is critical because several states have already set legal limits for the amount of THC a person can have in their blood while driving. AAA concluded that such limits are "arbitrary and unsupported by science, which could result in unsafe motorists going free and others being wrongfully convicted for impaired driving." The conclusion echoes that of other researchers that also noted no correlation between blood THC levels and impairment. Still, there is a need to deter people from smoking pot while driving, AAA argues, as it can impair driving. It recommends that until scientifically valid measures of impairments are put into place, law enforcement should use a combination of behavior and psychological tests to assess whether drivers who use marijuana are safe to drive.
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AAA Study: Blood THC Levels After Smoking Pot Are Useless In Defining 'Too High To Drive'

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  • by Izuzan ( 2620111 ) on Wednesday May 11, 2016 @10:36PM (#52095595)

    The officer plays an Amy Schumer skit. If the person laughs they are to high to drive.....

    • Re: (Score:3, Insightful)

      Many people react differently to alcohol as well. But you have to draw the line somewhere. If we get the drunks and stoners off the road, is it really a big tragedy if a few semi-sober people are removed as well?

      • I personally think people that will drink and drive will do so regardless of the law.
        I think the same will be found with stoners, the ones that will do it are doing it already...
        And, just like booze, the next crop of substance abusers will behave in a similar manner.
        Uber is helping with the more affluent substance abusers, but they always had lawyers in any case.
        Self driving vehicles will help both by adding more mass transit and taking idiots out of the equation... especially if AI gets good enough to de
      • Re:How about... (Score:5, Insightful)

        by AK Marc ( 707885 ) on Wednesday May 11, 2016 @11:11PM (#52095781)

        But you have to draw the line somewhere.

        Yeah, you measure reflexes and decision making skills, and take them off the road if they are unsafe.

        But doing so would make AARP and voters mad, and we all know stoners don't bother to vote, so you make up arbitrary (and wrong) limits for chemicals, not related to the safety of the driver. Great system.

        • by TheGratefulNet ( 143330 ) on Wednesday May 11, 2016 @11:47PM (#52095921)

          But doing so would make AARP and voters mad

          for those cases, there's static routing.

          (wait, wut?)

        • Yeah, you measure reflexes and decision making skills, and take them off the road if they are unsafe.

          There's some obvious sense in this, but I have two concerns with it. One is that I think it may be subjective, in which case police may (consciously or subconsciously) hold different groups to different standards. The other is (assuming this is used as a basis for a conviction) people could be penalised for having a bad day for some reason, without realising it is impairing their driving. For example, peo

          • Re:How about... (Score:5, Insightful)

            by shaitand ( 626655 ) on Thursday May 12, 2016 @08:54AM (#52097435) Journal
            How about the old fashioned way, we punish people for reckless driving and accidents. The officer can ticket for reckless driving at his discretion already. If your driving isn't showing impairment you aren't too intoxicated to drive. If your driving is showing impairment it really doesn't matter why, you need to be taken off the road.
      • Re:How about... (Score:5, Insightful)

        by dala1 ( 1842368 ) on Wednesday May 11, 2016 @11:22PM (#52095827)

        Seriously? You're cool with people being arbitrarily punished for a crime they didn't commit?

        • by KGIII ( 973947 )

          Yes, yes they are. The concept of better 9 criminals be set free than 1 innocent person not going to jail is seen as quaint.

          Yes, they'll deprive all for the sake of the few. (See firearms as an example.)

          There's a certain level of risk assumed with operating a motor vehicle on a public road. I'm not suggesting that we allow unfettered access and lawlessness but I am suggesting that we honestly look at the probabilities and then make a realistic choice regarding where the lines should be drawn.

          However, the id

          • How many times have you seen others suggesting some sort of "final solution" for the religious?

            Never, but I've heard plenty religious talk about the end of the world and smiting by destructo-Jesus

        • by Ichijo ( 607641 )

          And that goes double for airline pilots!

        • by Tukz ( 664339 )

          But they DID commit a crime.
          Driving under influence is a crime.

          You may not agree on what constitutes "under influence", but the law have to draw a line somewhere.

          Personally, I've seen drunk people drive just fine, and at the same time, sober people drive like shit.

          • by DarkOx ( 621550 )

            constitutes "under influence"

            Well for starters their should have to be some evidence that there is influence. We don't put people away for driving under the influence of Cola because there isn't any evidence it impairs driving.

            Obviously being stoned does impair driving, but if blood levels don't correspond to what is going on in the brain, than justice really demands one of two options.

            A zero tolerance, IE if you show any THC in the blood you could potentially be very impaired so you can't drive for days after smoking. Not unreason

  • The same things could be said about Blood Alcohol levels. Someone unaccustomed to drinking can become severely impaired even with low amounts of alcohol while long time alcoholic reaction times might still be reasonably ok even when way over the limit.
    • by PPH ( 736903 ) on Wednesday May 11, 2016 @10:53PM (#52095697)

      long time alcoholic reaction times might still be reasonably ok even when way over the limit

      Not really. What happens is that long time alcoholics become practiced at compensating for lousy reaction times.

      • by fustakrakich ( 1673220 ) on Wednesday May 11, 2016 @11:03PM (#52095743) Journal

        Yeah well, I wish they would practice on their side of the road.

        • by PPH ( 736903 )

          on their side of the road.

          Hey! I am always make sure that my tires are making that "Brrrt, brrrt, brrrt." signal.

        • Yeah well, I wish they would practice on their side of the road.

          That no good if you're too drunk. I mean - there's no telling how many lines you're actually seeing. So, don't try to stay between the lines - just pick one and stick to it.

          • by KGIII ( 973947 )

            Do NOT do this.

            When you drive drunk, and are so drunk that you truly have a hard time seeing, then just close one eye. It actually works. I had a drunken buddy share that kernel of wisdom with me. I have no idea how I never got an OUI or caused an accident - no infractions since a speeding ticket in something like 1975 and zero at-fault accidents ever - and I drive a whole lot more than most.

            So, yeah... Do NOT do that. I learned my lesson without any actual repercussions but I drove drunk more often than I

      • by dbIII ( 701233 ) on Thursday May 12, 2016 @03:09AM (#52096505)
        Just as realistic as teenagers going on about how they are wonderful at multitasking.
        Alcoholics are a mess at everything - very sad to watch it happen.
    • by rahvin112 ( 446269 ) on Wednesday May 11, 2016 @11:22PM (#52095821)

      Yea, but blood alcohol limits had a LOT of science behind them before they became law. There is very good evidence showing reaction times are impaired a minimum of 50% at what are now legal blood limits even in the most tolerant drunk.

      The first person with the money to fight one of these blood THC levels is going to win because the limit is entirely arbitrary and there is in fact no evidence whatsoever that THC impairs reaction time. They'd have as much luck trying to convict someone for having whipped cream in the blood. You can thank that DEA level 1 classification for that as no one has been able to do any real research on cannabis. In time we will find out but the only reason the courts allowed blood alcohol to be used against you was because there was a TON of research and good hard science documenting the connection between blood alcohol and reaction time.

      The legislature can't make something legal to consume being in your blood illegal to drive unless they can demonstrate that it impairs your ability to drive. People have forgotten all the effort it took to get the courts to let blood alcohol content be actionable. Blood alcohol took almost a decade of court wrangling before it was eventually allowed as evidence of impairment. Hell maybe the supreme court will allow it because the most of the court loves jacked booted thugery but IMO the government should have to prove beyond a reasonable doubt that the substance impairs your driving ability to make it illegal to be on it while driving.

      • The legislature can't make something legal to consume being in your blood illegal to drive unless they can demonstrate that it impairs your ability to drive.

        I don't see why not. They can make up any rules they want for the privilege of driving...
        Have to pass tests with arbitrary questions about laws, not driving skill (what does that color curb mean?)
        Have to be a certain age (why not a year lower, or higher)
        Have to have your papers in order
        etc.

        If it is not based on sex, race, creed, etc... it
      • Exactly. Where is the data on THC levels and accident statistics? If THC is a contributing factor in a statistically significant number of accidents, prove it.
      • Yea, but blood alcohol limits had a LOT of science behind them before they became law.

        And also a bunch of dead and severely injured people and drunk drivers in accidents serving as evidence. even with that, alcohol limits changed over the years. It makes it tougher for defining pot limits because there are a lot less of those incidents.

    • No it can't. The evidence is quite clear and blood alcohol level correlates very well with both impairment and the inability to recognise your impairment.

    • by fermion ( 181285 )
      the problem is that we are punishing people for having an arbitrary limit rather than activity that has caused harm. Now, on average, drinking, putting on makeup, texting, and lack of sleep all have the ability to cause significant harm. We are in the current situation because, historically, drinking could be used as an affirmative defense for murder. Killing a family of 5 while under the influence could be used to turn a prosecution for mass murder to a simple accident. As in the case of the affluenza
  • Pupil dilation? (Score:3, Interesting)

    by LostMyBeaver ( 1226054 ) on Wednesday May 11, 2016 @10:44PM (#52095643)
    I used to very successfully know when my friends were stoned by their pupils.

    Ann ipad with a front facing camera capturing and analyzing eye movement and pupil dilation during a series of flashes and moving objects should be perfectly suitable for calculating fitness to drive.

    It would work for testing whether people who may be in shock should drive too. I am pretty sure it would block most politicians from driving though. Has anyone noticed how many politicians are a bit slow to focus their eyes... as if things like sound are confusing?
    • I used to very successfully know when my friends were stoned by their pupils.

      Of course, there are plenty of medical conditions (e.g. Horner's syndrome) which would cause false positives on that kind of test. Hell, it would probably have caught David Bowie.

    • Re:Pupil dilation? (Score:4, Insightful)

      by geekforhire ( 300937 ) on Wednesday May 11, 2016 @11:22PM (#52095823)

      That might work if other factors were not in play. Some prescription meds will screw with your pupil dilation while not impairing you at all outside of perhaps causing your low light vision to suffer a bit. Or be better. And while a similar test might be OK in most cases we need something that shows how high you were when something happened and it needs to be free of false positives. I have no idea how to do it but it is important to avoid ruining peoples lives for doing something that is legal days or weeks prior to an accident that has nothing to do with what happened. At this time it seems that we have many people that want a test simply because they want to say they have it and false positives are not a big worry since they dont really care about the real reason for 'why' they just want to push an agenda or inflate arrest numbers, but I suppose those are kind of the same.

      I dont smoke weed on the regular but I do a few times a month. And when I do its legal. And I never drive when high. The current tests would say that a legit accident (as in: shit happens, not negligence) that I was in was the result of being high despite it being false. I could of been high 24 hours prior, a week, or a month, but if some folks get their way that is the same thing as being stoned as fuck at that very moment. Insane. Do we put people away for DUI when they got ripped a few days prior but were 100% sober when they were involved in an accident?

    • Has anyone noticed how many politicians are a bit slow to focus their eyes... as if things like sound are confusing?

      I tend to attribute that to their age. I did a quick Google search and I see that the average age of a sitting US senator is 62 years old. People complain about how Congress is full of old rich white guys but then keep voting them into office.

      Another thing I noticed is that US senators tend to largely leave office feet first. As in they tend to be in office so long that they die there and must be carried out.

      Bernie Sanders is 74 years old. Hilary Clinton is 68 years old, but looks older. Donald Trump i

      • I would attribute it to them rifling through their prepared sound byte laden scripted responses to see which one will sound like they are trying to answer the question rather than just stumping, evading, or lying.

        Also, as they are quite wealthy, their give-a-fuck-ometer is pegged at 0 for empathetic interest in the actual issues that affect us plebs. They need to have things scripted, vetted, and memorized so they don't sound like themselves when they answer questions in public.

        Also, in the name of fairnes

    • Makes the little veins in the eyes go red, but visine takes care of that.

      LSD and shrooms, those dilate the pupils. And massively fscked with my driving to the point I didn't even try.

  • by PPH ( 736903 )

    Am I driving OK? [youtube.com]

  • by geekd ( 14774 ) on Wednesday May 11, 2016 @10:51PM (#52095687) Homepage

    The hippie going 45 in a 65 zone is high.

    The dude sitting there waiting for the stop sign to turn green is high.

    • The dude sitting there waiting for the stop sign to turn green is high.

      Hey, that's not fair. I might be texting. Or texting AND high.

    • The dude sitting there waiting for the stop sign to turn green is high.

      The dude sitting there waiting... anywhere... is dicking with his phone.
      I see this ALL THE TIME.

  • by EzInKy ( 115248 ) on Wednesday May 11, 2016 @10:52PM (#52095695)

    I'm all for the legalization of pot nation wide, but I'm also against impaired drivers being allowed to menace the roads. Smoke to your hearts content, but don't smoke and drive.

    • If I'm not impaired, there is no justification for arresting me. Your argument would make sense if there were no safe level of consumption. Not being able to determine a safe level of consumption via a blood test is not equivalent to not being able to determine impairment. There are lots of drugs which can impair driving for which there is no blood test. Frankly there aren't a lot of good legal or moral arguments for zero tolerance here. It would be a special exception to the rules about impaired driving, a

  • and then I got high (Score:5, Interesting)

    by PopeRatzo ( 965947 ) on Wednesday May 11, 2016 @11:30PM (#52095861) Journal

    Back in the day, I'd cruise down Halsted with a joint in my hand, a beer between by thighs and black beauties in my blood stream with my Ramones cassette blasting. And I never had a problem with impaired driving.

    Of course, there was the time I broke an axle and sheared off the entire exhaust system on my '68 Caprice while doing donuts in the snow in the mall parking lot at 3am, but it was only because I was distracted by the fact that none of the snowflakes hitting my windshield were exactly the same.

    Goddamn nanny state wants to take away my right to drive fucked up. Not that I get fucked up any more. I'm too old for that now. But every so often, just for kicks, I crank up Rocket to Russia on my mp3 player and do donuts in my mobility scooter down the paper goods aisle at the Wal-Mart.

    https://youtu.be/CVQfVtzFd4U [youtu.be]

  • The study found that people with low blood amounts of THC -- or delta-9-tetrahydrocannabinol, the main psychoactive component of pot -- may still act as if they're really stoned. On the other hand, some people may have THC measurements off the charts yet still act normally.

    This just in! The reaction of a person to a drug can vary from person to person. Also... not everyone starts with the same level of driving ability before they ingest the substance. So it's not really possible to do a fair "one size fits all" law. This goes for alcohol, too.

    • by KGIII ( 973947 )

      >> not everyone starts with the same level of driving ability

      Funny you should mention that. Up above, I mentioned that I used to drive while very intoxicated. I never had an accident, got violated, and got my first (and only) moving violation in 1975. Yet, I drove professionally for a while (it was my MOS) and am an automotive aficionado who has taken many, many lessons and driven on-track and rallied - all strictly amateur. I've even done those things while moderately (for a drunk) intoxicated.

      There

  • That's interesting, and close enough! I'm currently studying some IPv6 features!
  • I think the politics of legalization almost requires a believable and workable DUI measurement system.

    One of the many false narratives against legalizing marijuana for recreational purposes is the "ZOMG, STONED DRIVERS11!!" scare tactic. The idea that if you legalize it for recreational purposes, the roads will suddenly be flooded with stoned drivers, threatening the safety, moral purity and precious bodily fluids of God-fearing Christians and their children driving down the road.

    It's a scare tactic becaus

  • From the Ars article:

    "55.5 percent of drug-free people passed the walk-and-turn test perfectly"

    Only 55% of the sober people passed the test? That's the scary part.

  • by hey! ( 33014 ) on Thursday May 12, 2016 @09:43AM (#52097689) Homepage Journal

    ... have trouble selecting and interpreting medical tests.

    And it turns out cops with no medical training whatsoever are even worse. Who'd have thunk it?

  • by nbauman ( 624611 ) on Thursday May 12, 2016 @02:00PM (#52099697) Homepage Journal

    If you read the Journal of Studies on Alcohol and Drugs, you'd know that marijuana didn't even increase the risks of crashes and fatalities.

    http://www.ncbi.nlm.nih.gov/pm... [nih.gov]
    J Stud Alcohol Drugs. 2014 Jan; 75(1): 56â"64.
    PMCID: PMC3893634
    Drugs and Alcohol: Their Relative Crash Risk
    Eduardo Romano, Ph.D.,a,* Pedro Torres-Saavedra, Ph.D.,b Robert B. Voas, Ph.D.,a and John H. Lacey, M.P.H.a

    Abstract

    Objective: The purpose of this study was to determine (a) whether among sober (blood alcohol concentration [BAC] = .00%) drivers, being drug positive increases the drivers' risk of being killed in a fatal crash; (b) whether among drinking (BAC > .00%) drivers, being drug positive increases the drivers' risk of being killed in a fatal crash; and (c) whether alcohol and other drugs interact in increasing crash risk.

    Method: We compared BACs for the 2006, 2007, and 2008 crash cases drawn from the U.S. Fatality Analysis Reporting System (FARS) with control drug and blood alcohol data from participants in the 2007 U.S. National Roadside Survey. Only FARS drivers from states with drug information on 80% or more of the drivers who also participated in the 2007 National Roadside Survey were selected.

    Results: For both sober and drinking drivers, being positive for a drug was found to increase the risk of being fatally injured. When the drug-positive variable was separated into marijuana and other drugs, only the latter was found to contribute significantly to crash risk. In all cases, the contribution of drugs other than alcohol to crash risk was significantly lower than that produced by alcohol.

    Conclusions: Although overall, drugs contribute to crash risk regardless of the presence of alcohol, such a contribution is much lower than that by alcohol. The lower contribution of drugs other than alcohol to crash risk relative to that of alcohol suggests caution in focusing too much on drugged driving, potentially diverting scarce resources from curbing drunk driving.

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