Originally Posted by ItsJustMe

The ones moving at 35 mph are only moving 15 mph relative to you going 20. Someone opening a car door into you is throwing an immovable, relatively sharp and pointy hunk of steel right into your face. Worse yet, it's hinged so that when you hit it, it swings open, takes you with it, and throws you under traffic.

The moving cars are in traffic and can see you and make adjustments. The person opening the door does not (is supposed to but doesn't).

I think until you're actually doored, you don't know how much it can hurt. I have not been either hit or doored, but I have a friend who has been doored (but never hit). He was lucky enough to not be thrown into traffic, but he had a broken arm, a broken clavicle, and had 2 surgeries to put his face back in order. He now stays out of the door zone (and in the traffic lane) and in 10 years since that incident has not had a problem.