A cool technology of the 1950-60's national economy runs was the freewheel clutch.
The freewheel clutch was either attached to the transaxle or the wheel hub, only allowing power to be transmitted to the wheels in one direction. Like a ratchet, the wheels were driven when powered but freewheeled while gliding.
Most think of rolling resistance (RR) as being a quality of the tires and bearings, but it also encompasses friction from a spinning transmission and main clutch end. By using a freewheel clutch, you remove all the robbing friction from the axles inward.
The clutch seemed simple to design, just being a small freewheel hub you could probably pick up a McMaster-Carr spliced into an axle. You do lose reverse, but that's undesirable anyways...
- LostCause