Supersize The Automobile.(Special Report; POINT OF VIEW)(Cover story)

Light, strong materials can make a car efficient and safe without having to make it small and expensive.

Some people may interpret Tata Motors' small Nano car as a sign of a new green esthetic that favors small cars. The presumption is that the Western style of supersized, muscle-bound, gas-guzzling, climate-harming cars may shrink to more sensible sizes, inspired by Tata's Gandhian frugality. Although the Nano gets good gas mileage--20 kilometers to the liter, by Tata's reckoning--it could do that without being small. Weight (not size) accounts for three fourths of the energy needed to move a car. Light but strong materials can therefore make a car very efficient without having to make it small or costly.

These two attributes--light and small--sometimes get confused for one another. In 1997, the U.S. National Highway Traffic Safety Administration issued a report purportedly showing that light cars are less safe for all road users than heavy ones. Though widely cited, the report rested on a false assumption--that size and weight are equivalent. They're not. In 2002, Dynamic Research Inc. took the same data but separated the effects of size and weight. This revealed that, weight being equal, size protects passengers; size being equal, more weight kills more people.

The way to save lives and oil and money, all at the same time, is to make cars relatively big, which is comfortable and protective, without making them heavy, which is hostile and inefficient. Achieving lightness only by making cars smaller, without improving their materials and design, degrades safety because passengers have less "crush space" to protect them. (Of course, makers of light and relatively small cars like Honda are already masters of crashworthiness.) Achieving lightness through improved design and lighter and strong materials can improve safety at any size. How do Formula One drivers generally walk away from seemingly devastating high-speed crashes? Mainly because their cars are made of ultralight carbon-fiber composites that can absorb six to 12 times more crash energy per kilogram than steel.

The heavier the car, the more fuel it needs to make it go, and the more carbon it emits. The typical car today wastes 94 percent of its fuel energy in its engine's losses and idling, its transmission, and its tires and air resistance. Only 6 percent of the fuel energy accelerates the car. In turn, the driver is only one twentieth of the total mass; the rest is the steel car itself. A mere three tenths of 1 percent of fuel energy goes into moving the driver. After 120 years of engineering effort, that's not a gratifying result.

Good design and advanced materials can help us out of this trap. Using a good hybrid engine roughly doubles a typical car's efficiency. We can then redouble efficiency by using advanced materials to halve the weight, ...