Pot-Legal States Struggle to Stem Rise in Driving While Stoned

Car crashes in the first three states to legalize recreational marijuana have soared as law enforcement and regulators struggle to define driving high, let alone determine how to fight it.

Colorado, Oregon, and Washington saw a combined 5.2% increase in the rate of police-reported crashes after legalizing recreational marijuana, compared with neighboring states where such sales are illegal, according to data compiled and analyzed by the Insurance Institute for Highway Safety. Researchers tallied crash rates between 2012 and 2016.