Planning, good sense, and caution go a long way to compensate for physical impairment. Weed is different from booze in that booze increases risk taking, which makes driving such a danger. But that doesn’t mean weed doesn’t impair in some material way compared to baseline.

Your average driver on alcohol: goes 100 miles per hour into a tree

Your average driver on weed: drives 5 miles per hour to the taco bell drive thru