“There is no such thing as a weed Breathalyzer, no biological factor that indicates whether someone is impaired by cannabis at the moment you test them—not blood or urine or hair or breath or spit. While every state prohibits driving under the influence of weed, no state has found a reliable way to sort the stoned from the sober. Like Washington, some states have implemented the 5-nanogram-per-milliliter threshold, but cannabis pharmacokinetics are so variable that even if two people share a joint, one person might dip below that level within two hours and the other might stay above it for the rest of the week. Stoned driving is therefore one of the biggest unresolved sticking points in the long slide toward legalizing marijuana in the US—a Kafkaesque quandary with no clear solution.” Wired: Driving While Baked? Inside the High-Tech Quest to Find Out. Two roads diverged in a wood, and I—I got really paranoid and went back home to eat Cool Ranch Doritos…