I smoke but not when i'm driving anymore, used to be my worst habit. Get in the car spark up a lung basher.
Makes your car stink to but when you do it you don't notice it, I really notice it now when I get in a smokers car.
But still worse than a fag is a mobile phone, I was driving along eating a pear and talking on the phone (Very stupid I know but I was explaining to the misses I was going to be late back because of a roadworks on the M11), anyway she was moaning, I wasn't listening, I finished my pair and chucked it out the window.
One problem the Pear was still in my hand.
So it could be worse you could have a mobile phone lugged at you while driving.