A 20-month government study of drivers in 2013 and 2014 found no evidence that marijuana use leads to higher risk of getting into a car accident. However, more testing is planned and safety advocates still say it is dangerous to drive after smoking significant amounts of pot. Marijuana users in the study were about 25 percent more likely to be involved in a crash than drivers with no evidence of marijuana use, but the National Highway Traffic Safety Administration said this was mostly due to other factors, including the fact that more younger men are involved in crashes. Still, “You can’t say that driving while stoned is not a risk. We know it debilitates the ability to drive safely,” former acting NHTSA Administrator David Kelley said.