When It Comes to Pot, a 'Big Concern' About Driving

Figuring out when it's safe to drive after marijuana consumption remains a challenge
By Jenn Gidman,  Newser Staff
Posted Feb 17, 2024 5:30 AM CST
Just Smoked a Joint? When It's Safe to Drive Is Murky
Stock photo.   (Getty Images/agafapaperiapunta)

Amid increasing marijuana legalization over the past two decades or so, both medicinal and recreational, has come a spike in accompanying car accidents. According to a 2021 study in the American Journal of Public Health, the percentage of car-crash fatalities tied to cannabis was just 9% in 2000; in 2018, it bumped up to 21.5%—and contributing to the problem is that it's not exactly clear for cannabis users when it's safe to get behind the wheel after smoking a joint or downing an edible, reports the Wall Street Journal. "It's a big concern," Jane Metrik of Brown's Center for Alcohol and Addiction Studies tells the paper. "There's more people on the roads driving after they used cannabis or as they're smoking or vaping."

The Journal notes that "pot affects you differently than alcohol, can linger in your system for longer, and it can be harder to figure out when it's safe to drive." Drivers with THC in their system, however, in general tend to drive more slowly; the drug also affects how well they stay in their lane, how far they stay behind other drivers, their reaction time, and judgment overall. Currently, a dozen states have a "zero tolerance" rule when it comes to THC in one's system, whereas other states have set a THC limit of 2 nanograms to 5 nanograms per milliliter of blood.

A study released last year by UC San Diego found that field sobriety tests may not be adequate to test for THC impairment in drivers, per the Times of San Diego. "While cannabis can be impairing, the effects vary for each individual," study co-author Thomas Marcotte said at the time. The Times also notes that "unlike the association of blood alcohol concentrations with impairment, THC blood concentrations do not correlate with driving performance." There's been some recent good news on that front, however: Marijuana Moment reported last month that a new testing method with a 96% accuracy rate has emerged, though researchers want to try it out on a larger sample. More on that here. (More marijuana stories.)

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