When it comes to the dangers of driving while high on marijuana, the data isn't entirely clear—and that's becoming more of a worry as states legalize pot, the AP reports. "Anytime a driver has their ability impaired, it is a problem," notes a boss at the Governors Highway Safety Association. But weed-toking drivers show marked differences from those who drink alcohol: Those who've smoked frequently seem very aware of it. They often drive slowly and ensure space between them and other cars in an effort to stay safe, the AP notes. And indeed, studies on the dangers of such driving are "highly inconclusive," says an expert.
They range from showing triple the risk of crashing to apparently showing a decreased risk. Currently, Colorado and Washington, the only states where recreational pot is legal, have set a THC intoxication level of five parts per billion, but there's no quick way to test a pulled-over driver for the psychoactive ingredient. What's clear in Washington is that since the drug was legalized, some 25% more drivers are testing positive for it—but accident and arrest numbers haven't shown a matching increase, the AP notes. "Right now we have a patchwork system across the nation regarding mandatory drug testing following highway crashes," says a former highway safety official; transportation officials are investigating the issue.