A couple days ago I was driving to work and got sprayed by the car in front of me washing its windshield. This set off a chain reaction as I then had to wash my windshield in order to see and then the guy behind me had to wash his. I was annoyed at the guy in front of me, but then I realized the guy behind me was probably just as annoyed with me. So then I wondered... is there windshield cleaning etiquette? Should you do this only when you're stopped? Or maybe just wait til there's no one behind you on the road?