Fair enough, but in the linked article the example would not meet even your test of "Look like cars and function like cars"...because the thing is basically a l

Fair enough, but in the linked article the example would not meet even your test of "Look like cars and function like cars"...because the thing is basically a luge-position with an aero-fairing. This was the starting point of my comment--its not a "car" really in any sense--because it fails the technical/legal/regulatory (not obvious) in addition to the practical/function (more obvious).