i watched this show on discovery about future cars. their favorite was a car that ran off compressed air. the most amazing thing as that there is potential for an alternator that would recompress air back into the tanks so that you could run forever. as it stands now the car has a 250 mile range and can hit about 90 mph and isn't all that bad looking. they use very light weight materials to build the cars and i believe the cost would be around 15k.