Driven by concerns over global warming and the prospect of tougher restrictions, automakers worldwide have moved up a gear in the race to build the ultimate clean car.

Honda's FCX-V3 runs on hydrogen and produces no greenhouse-causing waste.

Japanese firms enjoyed success in energy efficiency and low nitrogen oxide emissions in the 1970s and 1980s, but the ongoing competition represents a fundamentally new ball game -- a shift from gasoline to cleaner energy sources.