I think the real question is "do you think your driving is negatively effected by smoking?"
Personally, I smoke almost every time I get in the car. If I'm going on a road trip, I smoke every 50 miles or so. I love driving. I love driving high. I love cruising down the highway with my sunroof open on a sunny day and my music cranked toking a bowl...
Truthfully I just enjoy being high while doing most things in life...it turns the mundane into the slightly more interesting, and the interesting into the freaking awesome.
I don't think my driving is negatively affected while I'm high either. If anything I'm more relaxed behind the wheel, meaning I'm less aggressive and less easily agitated by all the shitty drivers around me. I don't excessively speed. It almost eliminates my road rage.