The darling/courageous/who-knows-what Mrs. Lottie B. Ellison of Rawls Falls (say that ten time fast), Mississippi, was awarded a patent (#1,323,177, to be exact) in 1919 for her design of a passenger-side door that would accommodate a third front-seat rider without causing discomfort to other occupants. The door consisted of a retractable bottom section which, when flipped up, allowed an extra rider to sit on the floor while resting his/her feet on the outside running board.
Sounds like every teenager we know.
While we are on the subject, this 1943 cartoon was titled “You’re the man, Jones, who said car pooling wouldn’t work!”