Technically, it is illegal to open a door without first making sure it's safe to do so. If you're going to count on drivers actually doing this (not to mention kids in back seats opening driver-side rear doors), you're insane.

Some people have implied or even explicitly claimed that sometimes it's impossible to avoid riding in the door zone. I don't understand this. What could possibly prevent you from merging left? It's not like parked cars suddenly appear out of nowhere right next to you. If you believe that sometimes it's unavoidable, you will inevitably end up riding in door zones.

If you understand that it is never acceptable to ride in door zones, you will find a way to avoid them, always. Works for me...