The concept car with the cumbersome designation XP-883 was nothing more than an experiment relegated to history, but it worked a lot like the Toyota Prius and Saturn Vue plug-in hybrids the two companies are working on today. It was sufficiently ahead of its time for Popular Science to call it "radical" and ask, "wouldn't it be great to have a car that changed from electric drive for use around town to gasoline power for highway driving?"

"It makes so much sense," the magazine wrote in July, 1969, "that we feel they're missing a bet if they don't put it in production

The XP-883 looked like an Avanti hatchback or the AMC Gremlin's prettier sister. At 122.2-inches long, 57.3-inches wide and 46.3-inches high, it was a little bigger than a Smart ForTwo and a little smaller than a Honda CRX. It had a fiberglass body for light weight, but just what it weighed has been lost to history.

Priustoric: GM Builds a Plug-In Hybrid ... in 1969 | Autopia from Wired.com