How Stoned is Too Stoned to Drive? The Feds Want To Know

Aaron Cole
by Aaron Cole

Puff, puff, pass that bill. Federal authorities want to know how stoned is too stoned for drivers, according to a provision in the recently signed Federal Highways Bill.

The new law directs U.S. Department of Transportation Secretary Anthony Foxx to study the effects of marijuana on drivers and present those findings to Congress by the end of 2016.

As more states legalize marijuana — Oregon and Alaska joined Washington and Colorado with legal pot, and 12 states have decriminalized possession — Congress asked the department to determine how to train police to spot stoned drivers and how to test them.

According to a Gallup Poll this year, 47 percent of American surveyed said they thought marijuana would make the roads less safe in states with legalized cannabis.

Authorities in Colorado initially struggled with how to test drivers and measure levels of THC in their systems. Colorado’s threshold of 5 nanograms of THC to qualify as “too stoned to drive” was met with opposition in 2012. Medical marijuana proponents said the per se limit was too low, but the limit was passed into law anyway.

Interestingly, Westword’s pot critic in Denver, William Breathes, had a resting THC level three-times the legal limit the newspaper discovered in 2013.

This year, the University of Iowa discovered that the marijuana equivalent for 0.08 blood-alcohol content (the legal limit for drunk driving in many states) is roughly 13 nanograms of THC. But marijuana and alcohol are very different drugs. Marijuana lasts far longer in users’ blood streams and is difficult to metabolize.

“Everyone wants a Breathalyzer which works for alcohol because alcohol is metabolized in the lungs,” Andrew Spurgin, a postdoctoral research fellow with the UI College of Pharmacy said in a statement announcing the results. “But for cannabis this isn’t as simple due to THC’s metabolic and chemical properties.”

Nonetheless, the feds want to know how stoned is too stoned, and how many stoned drivers are drunk too. (Anecdotally: Many Denver police officers say that they issue more DUI and driving while stoned tickets at the same time than they issue drugged driving tickets alone.)

It looks like the feds just got a lot of money to find out.


Aaron Cole
Aaron Cole

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  • Corey Lewis Corey Lewis on Dec 15, 2015

    "12 states have decriminalized possession" What does this mean, you just get a fine but not a ride in a police car?

  • Lou_BC Lou_BC on Dec 15, 2015

    Decriminalization just means it is not a criminal code violation. One way to look at is a speeding ticket versus speeding causing death. There will be infractions but they won't mean criminal court or a criminal record. Too many violations would mean a bump up to criminal court. Canada looked at decriminalization a long time ago but once Conservatives got elected the whole idea went up in smoke ;) With that being said, what constitutes an impairment threshold will also depend on which side of the political Isle (chasm) that you sit. The problem with testing for blood levels of marijuana is getting a person to a qualified lab and getting the blood work drawn and run. IIRC Marijuana has a fairly long serum 1/2 life so testing expediency might not be an issue but are you going to detain every suspect during the time it takes to confirm blood levels? Urine tests are cheap, quick and easy to administer but all they provide is a yes/no answer. THC tends to accumulate in adipose so i can see the court defense now..... my client is a former marijuana smoker who just went on a crash diet or the famous Canadian snowboarder who kept his Olympic Gold medal by claiming a failed test was due to "passive" 2nd hand smoke. (Aren't all marijuana smokers passive? LOL) This will be an interesting legal maze to navigate."

  • ToolGuy 9 miles a day for 20 years. You didn't drive it, why should I? 😉
  • Brian Uchida Laguna Seca, corkscrew, (drying track off in rental car prior to Superbike test session), at speed - turn 9 big Willow Springs racing a motorcycle,- at greater speed (but riding shotgun) - The Carrousel at Sears Point in a 1981 PA9 Osella 2 litre FIA racer with Eddie Lawson at the wheel! (apologies for not being brief!)
  • Mister It wasn't helped any by the horrible fuel economy for what it was... something like 22mpg city, iirc.
  • Lorenzo I shop for all-season tires that have good wet and dry pavement grip and use them year-round. Nothing works on black ice, and I stopped driving in snow long ago - I'll wait until the streets and highways are plowed, when all-seasons are good enough. After all, I don't live in Canada or deep in the snow zone.
  • FormerFF I’m in Atlanta. The summers go on in April and come off in October. I have a Cayman that stays on summer tires year round and gets driven on winter days when the temperature gets above 45 F and it’s dry, which is usually at least once a week.
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