"Cannabis alone, particularly in low doses, has little effect on the skills involved in automobile driving."
You can find studies that say anything you want to back up any points. The key thing to read in that quote is LOW DOSES. The people I referred to drink excessively. The new group will use marijuana excessively. I can't speak for everyone, and neither can you, but these usages to extremes are common things you see nowadays. They offer the prediction of the excessive overuse of marijuana leading to a whole new set of DUI drivers killing people.