KIRO Television filmed people getting stoned—and then stoned-er—and put them behind the wheel to see how they did:
Washington State's new legal limit for driving stoned, according to the legalization law passed in November, is 5 nanograms of active THC per milliliter of whole blood. So KIRO let a regular user, a moderate user, and an infrequent user all smoke pot to exceed that limit and drive on a closed track as officers watched.
While they initially drove fine above that 5 nanogram level—with some minor problems, including clipping a camera and going too slow—their driving got worse the more they smoked. They hit a cone and nearly hit a photographer. So this anecdotal experiment more or less confirms what science has shown before: Pot can compromise motor function. And while some people will look at this and scream that the 5 nanogram level is too low (because these three people didn't roll the sedan), it's worth pointing out three things: (1) THC and alcohol levels need to set the bar for infrequent users who are more likely to have trouble at lower dosages; (2) past scientific research shows crash risk increases above 5 nanograms; and (3) it's impairment officers are primarily after: cops make that clear in the video and there's been no spike in pot DUIs since the law took effect. It's also good to remember that after about two hours, all of these people's THC levels had plummeted from about nine times the legal limit to only about twice the legal limit, suggesting that stoners who wait four to six hours to drive will not only be better, more sober drivers, they'll likely be comfortably within the limits prescribed by law.
But the best part about all this? That there are two cops there monitoring the whole thing—just watching people smoke weed like it ain't no thing.