Official: Cannabis use impairs driving as much as alcohol says first of its kind study while drug's legality continues to spread

A National Institute on Drug Abuse study tasked stoned participants with driving a highly sophisticated driving simulator.
 
Researchers found that after their blood levels of THC reached a certain point, the drivers weaved similarly to a driver with a BAC of .08
 
The study also found that combining cannabis and alcohol decreased motor skills even more than just one or the other