The big advantage of carbon fiber is that it is one-fifth the weight of steel yet just as strong and stiff, which makes it ideal for structural or semi-structural components in automobiles. Replacing half the ferrous metals in current automobiles could reduce a vehicle's weight by 60 percent and fuel consumption by 30 percent, according to some studies. The resulting gains in fuel efficiency, made in part because smaller engines could be used with lighter vehicles, would also reduce greenhouse gas and other emissions by 10 percent to 20 percent.

All of this would come with no sacrifice in safety, as preliminary results of computer crash simulations show that cars made from carbon fiber would be just as safe - perhaps even safer - than today's automobiles. Today's Formula 1 racers are required by mandate to be made from carbon fiber to meet safety requirements.

Oak Ridge news report

Other lightweight materials not being used much are aircraft aluminum, titanium, and magnesium alloys. The same result could be achieved with conventional steel construction, by making more 1- and 2-seat vehicles instead of the standard 4- or 5-seats.