Way back in 1980, Volkswagen built a Golf-sized experimental car dubbed VW2000. The timing was off by a few years, but the good bits were remarkably close to where we are today. The VW2000 had a prototype automatic start stop system which is becoming increasingly common today. Unlike today's systems that mainly rely on a heavy duty conventional starter or integrated starter/generator, this concept used a flywheel based system.
The system adds a second clutch between the engine and flywheel in addition to the conventional unit between the clutch and gearbox. The new clutch would disengage when the car came to a stop, allowing the flywheel to continue spinning while the engine was off. Re-engaging the clutch would allow the flywheel to restart the engine. It's an interesting idea that we'll have to look into to see why it was never adopted. Another of the idea in the VW2000 was the adoption of direct injection for the diesel engine. That, of course, is pretty much universal now in diesels and rapidly becoming ubiquitous in gas engines too. Check out the full story in Google books where all many old issues of Popular Science have been scanned.
[Source: Popular Science]