I have yet to see a credible report that smoking pot affects your driving anymore then a cold medicine. (I would expect the cold medicine to affect driving more by nature of it being a depressant)
Folks stoned are infamous for taking forever to get somewhere as they are really aware and slower/safer.
Not that I am saying to take bong rips and drive cross country or a school bus. But I don't see the comparison between common narcotic over the counter drugs and pot + driving.
Drunk folks and tired people are the real dangers.
Hmm, but then:
I guess potheads sometimes take a hand off the wheel to grab cheeseburger bites more often then others?