There are unwritten rules in these parts, where snow falls frequently between December and March (sometimes November to April), and comes in large quantities.
When you leave your house after a snowfall, you clear off your car in its entirety. You don't leave big snowcakes on your roof or your trunk, because those are bound to come off in chunks, and splat all over the windshield of the car behind you. It's unsafe.
This is how NOT to abide by unwritten rules:
Check out THAT snowpatty.
I took this photo from the driver's seat of my car earlier this week. Don't worry, we were at a complete stop as cars tried to finagle around towering snowbanks while pulling out onto the main street. This guy, of course, was trying to turn left across all the traffic. OF COURSE.