If anything I think it makes you a safer driver, when you smoke they always seem to have a window open so more fresh air coming into the car preventing nodding off behind the wheel.
If you knock the tip of the ciggie off on the indicator stalk it really makes you alert while trying to avoid burning your nether regions.
Never seen an accident caused by smoking...all the other things,sat nav, radio tuning, mobile phones, sex, have.
GB was really great when we were a nation of smokers, when you was working you would have a smoke break and lots of work problems would be thought out and resolved. We were happier, you would just say to any problem,SOD IT lets go and have a smoke. Most of the great thinkers were pipe smokers.
The west has gone backwards since the drive against smoking, whereas the countries of lots of smokers,China etc , have thrived.
My wife smokes about 5 cigs a day but never in the car and I used to smoke 40 to 50 a day and stopped 23 years ago and now weigh 3 stone more. I know the health issues have been proved but I still miss smoking.