CNN high driving test shows five nanogram THC limit much too low


Addy, one of the participants in the study.

CNN compiled a report on stoned driving this week focusing Washington state’s passage of Initiative 502 that set the THC blood limit for a driver at five nanograms per milliliter of blood.
While the report no doubt scared a few people into thinking high drivers are a menace, it also shows that impairment doesn’t necessarily happen at five nanograms and that stoned drivers may be safer than people think.

You can view the video over at, but here’s our take: Unlike other news reports that have put people behind simulators, this one actually put three Washington cannabis users behind the wheel on a closed course. A driving instructor and so-called Drug Recognition Experts with the local police force judged them.
The participants – 27-year-old Addy, 34-year-old Dylan and 56-year-old Jeff – varied not only in age but in their usage. Addy, a medical marijuana patient, uses cannabis daily and even showed up to the test with a baseline of 15.9 nanograms of active THC, more than three times the limit in Washington. Dylan says he smokes on weekends, and Jeff says he only smokes occasionally. Both showed up with zero active THC in their system.
While driving the course before the experiment, Addy clips a cone with a portable camera on it – a move that even CNN admits could be more likely due to learning the course. Her driving instructor says he didn’t notice anything wrong with her driving otherwise once they got going.
The real start of the experiment was having each of the participants smoke three-tenths of a gram of herb. After that, blood tests showed that all three were well over the limit. Dylan and Jeff came in at 26 nanograms and 22 nanograms respectively. Abbey was the highest in more ways than one, coming in at 36.7 nanograms of THC per milliliter of blood.
Even then, aside from a few minor gaffes, the driving instructor says he wouldn’t have any concern with them driving. The worst offender – if you can even call it that – was 56-year-old Jeff. The report says he was driving too slow and that his turtle pace could likely garner the attention of a police cruiser if he were out on actual streets. Still, the driving instructor said he did well.
It’s only after having them smoke up to a gram that the Drug Recognition Experts start to notice erratic driving. They point out things like backing over cones and driving too slow as classic signs and say they would likely pull the drivers over.
But here’s the catch: all three drivers were fully aware of how stoned they were, and all three said they wouldn’t ever have been behind the wheel in any other situation. Addy, for example, was clearly baked enough to think that turning the test into a real-life version of Mario Cart would be a good idea. I don’t want to over-generalize here, but you wouldn’t see that sort of self-awareness out of three drinkers in a similar test. They’d insist they were fine to drive until shown the footage sober the next day.
The test also shows another glaring fact that cannabis users have known but politicians seem to ignore: five nanograms is really, really low and the science just isn’t there to prove impairment. That is especially true for medical marijuana patients like Addy, who (again) drove just fine through most of the test until she was literally challenged to smoke herself to the point of being too stoned to drive.
Which we fully acknowledge can happen and in no way endorse driving under the influence of anything (including cell phones).
While it seems too late for any major changes in Washington right now, states like Colorado are still considering a five-nanogram limit and there’s little doubt this issue will come up in any state that legalizes small amounts of herb for personal possession. Discussion on Colorado’s proposed THC DUI bill has been postponed, hopefully giving legislators time to look into experiments and studies like this one.