originally posted on Metroblogging Chicago

I saw this No Parking sign outside my work and wondered what the kind of sidewalk had to do with whether you could park there. I discovered that a vaulted sidewalk is a sidewalk "built over basement space originally designed for delivery and storage of coal"*. Ah... so "don't park here because the weight of your car might collapse the sidewalk down into the empty space underneath." Noted. I'm surprised there isn't just a symbol for that.