 In addition in the late-1960s, GM directed their GM and Pontiac divisions to develop concept mini-cars called "commuter car" for urban drivers.GM developed a gasoline-electric drive hybrid the XP-833 and the Pontiac X-4 a rear-wheel drive mid-engine car that was powered by a radical X-shaped aircraft type air-cooled two-stroke radial engine where the standard crankshaft was replaced by a unit called a Scotch yoke.While the GM car was fully tested the Pontiac concept was not.