Here's what to know about the study's findings and just how much marijuana affects drivers. Have cannabis-related motor vehicle accidents, deaths increased ... affected their driving, 46.9% ...

Using a driving simulator, volunteers were subjected to situations that commonly lead to automobile accidents, once while sober, and again 30 minutes after smoking a marijuana cigarette.

He said there are no specific data on the number of impaired drivers under the influence of marijuana, as the stats are for “drugged impaired driving,” which includes marijuana.