Good news for clean-energy optimists: The dramatic array of lean, green driving machines on display at the Tokyo Auto Show recently provided ample evidence that humanity can, indeed, innovate its way out of environmental problems. Once every two years, major players in the auto industry convene in Tokyo to give the public a glimpse of their most futuristic automotive designs—dazzling concept cars that look borrowed from the set of The Matrix or swiped from the garage of George Jetson.

This year they all had one thing in common, aside from snazzy space-pod designs: fabulous fuel economy. And it wasn't just the hybrid-engine technology now mass-marketed in the Toyota on display. Ford, GM, Honda, Mazda and Toyota and others debuted new concepts for next-gen engines, including a rotary engine that runs on hydrogen, and a hybrid-electric engine powered by a low-pollution hydrogen cell.

Photo Credit: Joe Brown, www.popsci.com