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Reminder: To Make Tests for Stoned Drivers, Some Guy Is Smoking in a Simulator

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Usually, the person inside the vehicle asks, "What seems to be the issue, Officer?"Image: Coolcaesar

Image: Coolcaesar

As recreational marijuana becomes legal in more and more states, one particular question is assailing traffic cops: exactly how high is too high to drive?

This can be a bit of a complicated issue, according to Igor Grant, Professor and Chair of the Department of Psychiatry and Director for the Center for Medical Cannabis Research at the University of California in San Diego.

As he nicely put it in a November article on The Conversation, “right now we don’t have a fast, reliable test to gauge whether someone is too doped up to drive.”

That question is a little complicated because of the way marijuana affects users and the way the body absorbs THC. When testing for alcohol, the relationship between how impaired the drinker is and the amount of alcohol is in their bloodstream is pretty linear—the more alcohol, the more impaired.

However, smoked marijuana causes a large initial spike in THC in the blood, which declines as the chemical is absorbed—so, someone who has just smoked may not yet feel the effects, but someone who smokes and waits for a few hours may be far more impaired. So, the amount of THC in the bloodstream doesn’t really reflect the user’s impairment.

So, Grant and his team are currently studying using test subjects in driving simulators, in the attempt to answer the question of just how much marijuana is too much to drive. In the mean time, though, the main tool for traffic officers seems to be the good old field sobriety test.

News Source: The Conversation