Well IMO, I think that smoking pot can definitely impair driving ability. It depends on the person, but even though I consider myself fully able to, I can understand the impairment factor.

But anyway, I'm suprised nobody has mentioned the fact that a good amount of people on the road smoking or high are only on the road high, because they are driving, looking for somewhere concealed to smoke, since marijuana is illegal. If it were made legal, perhaps this would help with this issue, but its not even like its a major issue now.