Another term for the
short bus, usually ridden by children with handicaps of some sort of the other.
My youngest brother had mild cerebral palsy as a child and was forced to wear a helmet and ride the short bus. My evil middle brother made a sign out of a large piece of plywood that said "Welcome Tard Cart" and placed it on our lawn in the wee hours of the morning so it would be there when the short bus drove up to our house. He got in a decent bit of trouble for that one.
I know it sounds cruel, and is derogatory, but he was the first one who would defend our youngest brother and beat many a person within an inch of their life for picking on him.