I watched the driver flicking his cigarette ashes out the window, figuring if he had an ashtray, he would most likely throw it out the window. I was right. Traffic was going very slowly, and I was tempted to stop and pick up the cigarette butt and return it to the person, but didn't think it would be safe to do so. I got the impression that this is a habitual thing, and would like it if someone could send him a reminder.