100 mpg and zero emissions?

SpaceShipOne designers pocketed $10,000,000 for building a craft capable of carrying 3 people to 100km above the earth, a project that led to Virgin Galactic. Sir Richard Branson may be regarded by some as slightly crazy, but he does have a tendency to follow through on these projects.

So, it’s arguable that the Auto X-prize will yield some sort of similar result, fast-tracked (one of the competition requirements is that submissions must be able to be marketed, not just concept cars).

100 mpg, zero emissions. I wonder if any Detroit based companies are going to pitch their hat in the ring on this one?