I enjoy driving with my windows down when the weather is nice and when I don't care what my hair looks like. It's been beautiful outside recently, and my hair is much too long to look good anyway, so I've been doing lots of driving with the windows down.
I've noticed an interesting phenomenon which occurs during my drive home between 5:00 and 5:30 p.m. each day. When I drive with the windows down, I get to breathe lots of... no, not car exhaust (although I'm sure I'm getting some of that as well), but cigarette smoke. I guess that all the smokers who work downtown need a cigarette on their commute home. And, of course, they blow all the smoke out their car windows--after all, who wants to keep all that smoke in the car where they'd have to breathe it in?
Another thought on secondhand smoke... If I ever get lung cancer, I know of a couple bowling alleys that are on the top of my Lawsuit List.