not unusual, but uncommon. i've seen them used on fleet trucks so that tires wouldn't develop the habit of walkin' off. the last 18 inch wheel i can remember seeing was a custom built g.m.c. step van thathad a hudraulic bucket setup mounted on the top. a person could walk thru the "cab" part, in directly into the bucket or platform, then the thing elevated so a guy could change streetlight bulbs.
like i said......not common. neither was the 409 in it. (that part, i kept!)
