Is Marijuana Causing More Car Crashes in Washington?

The presence of THC does not necessarily indicate impairment.


Data released by the Washington Traffic Safety Commission (WTSC) this week indicate that the number of drivers involved in fatal crashes with active THC in their blood jumped from 38 in 2013 to 75 last year. As The Seattle Times notes, the reasons for that increase are not entirely clear:

One obvious reason is that state-regulated pot stores opened in 2014, providing access to legal weed. But the first few stores didn't open until July, and their supply was scarce. Seattle, allotted 21 stores by state officials, saw only one shop selling pot until late September.

What's more, there were more marijuana-involved fatal crashes in the first half of 2014, before stores opened, than in the second half of the year.

Contrary to comments by Staci Hoff, the WTSC's director of data and research, the presence of active THC does not necessarily indicate that a driver was impaired by marijuana at the time of the crash, let alone that marijuana caused the accident. Noting that 85 percent of "cannabis-positive" drivers involved in fatal accidents had active THC (as opposed to an inactive THC metabolite) in their blood last year, Hoff concludes that "most of them were high." That is not a safe conclusion to draw, because (as the National Highway Traffic Safety Administration points out) there is no reliable way to relate THC blood levels to impairment.

About half of the 75 drivers who tested positive for active THC had blood levels higher than five nanograms per milliliter, which is Washington's definition of driving under the influence. But that standard is highly controversial because regular users, who develop tolerance and accumulate THC in their fatty tissue, may exceed five nanograms all the time, even when they are not impaired. So while some of the fatally injured drivers may indeed have been "high" at five nanograms, it is not reasonable to assume that all of them were, let alone that the drivers below that arbitrary threshold were.

The picture is further complicated by the presence of other drugs. The Times notes that "half the drivers with active THC in their blood also were under the influence of alcohol, and the majority of those were legally intoxicated." Alcohol has a much more dramatic impact on driving ability than marijuana does, and the two together have a greater effect than either alone. The Times adds that the WTSC's analysis "doesn't account for prescription drugs in the marijuana-positive drivers."

Although marijuana's contribution to traffic accidents is hard to pin down, it is possible than an increase in cannabis consumption following legalization would lead to more stoned drivers on the road, resulting in more crashes. Alternatively, if more pot smoking is accompanied by less drinking, the net result could be fewer crashes, since alcohol impairs drivers a lot more than marijuana does. It is not clear yet whether either of those scenarios is materializing in Washington.

WTSC data show the total number of traffic fatalities rose by 6 percent last year (from 436 to 462) after falling the previous six years (including 2013, the first full year in which recreational use was legal, although state-licensed pot stores were not open yet). The number of fatalities from accidents in which the driver tested positive for marijuana (which does not necessarily mean he was impaired by marijuana) rose by 55 percent (from 64 to 99). Meanwhile, the number of fatalities from accidents in which the driver was deemed to be impaired by alcohol fell by 13 percent (from 127 to 111). That number had declined or remained steady in the previous six years, except for a 14 percent increase in 2009.

The 6 percent increase in total fatalities is consistent with the idea that legalization raises the number of dangerously impaired drivers. But that increase occurred entirely in the first half of 2014, before the pot shops started to open, which is a bit of a puzzle. By comparison, Colorado, where state-licensed marijuana merchants were open for business throughout 2014, saw only a 1.5 percent increase in total traffic fatalities that year. To get a better idea of what is happening, we will need more years of data, plus comparisons to trends in other states that have not legalized marijuana.

NEXT: Pot Pubs in Boston?

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  1. Is Marijuana Causing More Car Crashes in Washington?

    I would rather think it is two other factors…. Epi and STEVE SMITH.

    1. For truth. He drives like a goddamn maniac, by the way, screaming curses in his barely understandable New Joisey accent.

  2. I may be wrong, but I would think they would be testing more people for marijuana than before it was legal, resulting in more positives.

    1. Obviously

    2. Some evidence supporting that assertion is that the median blood serum level of active THC fell 25% between 2013 and 2014, while the number of drivers tested increased by just over 29%.

  3. Pretty sure this is because of the growth in the DC area, leading to more retards who can’t drive, and lots of people smoke pot, so….

    So I’m going with root cause = more dumbasses in DC now.

    1. *rereads*

      Um, yeah, Washington “state” – right.

      OK, same logic, but….

      I have no idea what’s goin’ on….anyone wanna get high?

      1. No, you’re a towel.

        1. …but Nicole is the worst character EVER.

      2. I was wondering just the other day why the heck they approved Washington as the name of a State. Do you know how difficult it is to differentiate the two in a search of Google News? Apparently neither did Congress.

  4. It would also help if they could reliably assign fault for these fatal accidents. Sitting at a stop light with a mild buzz on and getting rear-ended by an 83 year old who just had a stroke shouldn’t factor in to the statistics, but I’d wager that it does.

    With numbers this small, just a little bit of random noise can look like a trend. Also, you have to watch out for bias in the reporting. Counting all fatal crashes removes one researcher degree of freedom, which is a good thing. But ignoring fault and other intoxicants augers in the opposite direction.

    The primary number for this research should be “number of fatal crashes caused by intoxicated drivers”, broken out by intoxicant. Not fatalities, because that would weight a crash that caused 3 fatalities more heavily than a crash that caused one fatality. With numbers this low, a single crash of a minivan could skew the results.

    1. Sitting at a stop light with a mild buzz on and getting rear-ended by an 83 year old who just had a stroke shouldn’t factor in to the statistics, but I’d wager that it does.

      Ah, you are wise in the ways of stat jiggery-pokery! See also: “gun deaths”.

    2. If a party in an accident is in any way intoxicated, then the accident is assumed to be their fault. Doesn’t matter if they were hit by someone who was driving a hundred miles an hour through a red light on the wrong side of the road. It’s the intoxicated person’s fault, and the official report will only mention intoxication as the cause. Everything else will be conveniently omitted.

      1. I guess you think Tracy Morgan didn’t cause the fatal accident with the 24 hr Walmart driver?

        1. I never thought about it, nor will I, since I don’t give a shit.

    3. Look, do you want ammunition in the war to stop recreational drug use or not?

      1. ^this^

        The “if you legalize pot people will drive stoned argument” is so tired. Cause legalizing pot means you condone impaired driving. But hey look at Washington state, they legalized pot and conveniently, it caused more accidents.

    4. In 2007 in Pennsylvania a man was sitting at a red light, smoking a bowl when he was rear ended by a drunk. There wasn’t any doubt that he had been smoking a bowl because just by happenstance the police discovered the accident shortly after it occurred. They actually found the smoking bowl and a bag of pot in the driver’s footwell. Pennsylvania being a zero intelligence State convicted the poor man of vehicularly homiciding the drunk.

      As an added bit of irony I learned of the case because it was featured on the ONDCP’s front page with the headline, “So you think that driving high on pot is safe? Think again!” It told me that not only was John Walters an ignorant peckerhead (still is) but also that it must be very difficult to find incidents of deaths caused by a cannabis addled driver to use in the official hysterical rhetoric.

  5. This was the shit that caused my brain cells to flee out my earhole the other night. The local news was on over at my niece’s when I stopped by and I got hypnotized by the stupid. They were reporting a new anti-cellphone-and-driving ad campaign by the DOT because traffic fatalities were up by 13% due to distracted driving. As proof of this assertion they had their reporter with a camera out by the highway filming people driving by using their cellphones and the reporter actually said “Yep, sure does look like more people are engaging in this risky ‘distracted driving’ behaviour.” Then they cut to the DOT spokesman who confirmed that, yes, indeed, the DOT was seeing an increase in traffic fatalities. Not one single solitary mention of any shred of evidence whatsoever that the increased fatalities were due to increased cellphone use or even a question from the anchor back in the studio addresssed to the field reporter as to how the fuck a single data point can possibly be described as ‘more’.

    1. I worry a lot more about a driver texting or talking on a cell phone than smoking a joint.
      Nothing like talking to a driver using her cell phone who zones out while trying to recall what they have planned next Friday, then suddenly you hear a Thump-thump, and they’re asking you if they hit something.
      Myth busters did a recent episode that shows how much even distraction even hands-free phones cause.

      1. Better ban conversations with passengers.

      2. Paraphrasing Mark Maron: texting and driving is worse than drinking and driving, because at least when you’re drinking and driving, someone is actually driving.

  6. I betchat if you added up all the marijuana-involved, speed related, distracted driving and alcohol related crashes, they add up to more than 100%. Somehow, despite ever lower fatality rates, every one of those categories is increasing dramatically ! and we’re all gonna die !

  7. Remember when Colorado legalized pot and on the very first day a 3 year old toddler found a marijuana cookie on the ground at her aparment complex and ate it. The toddler left unsupervised outside in January.

    Sometimes the anti-pot propaganda is so transparent.

  8. In Washington state it is not illegal to drink and then drive,what is illegal is to be impaired. As the article points out impairment cannot be established on the basis of THC levels. Let Impairment establish impairment, through observation,and field sobriety test. I have seen more dangerous impaired driving by morons on their cell phones.

  9. Are there acronyms for mothers against high driving or texting and driving?

    1. MAHD?

  10. How unlucky a driver do you have to be to find that lone tree in the median of that blvd.?

  11. I drive high just to resist the urge of slamming into the asshole in the lotus in front of me driving like an ass on his way to some faggy meeting.
    Forgive the slur, I mean to trigger no one.

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