If you think modern cars burn too much gas, well, you’re right—but don’t blame automotive engineers. For years, they’ve made cars more efficient in ways obvious and subtle: tweaking transmissions, futzing with camshafts, and refining engine architectures. In a recent paper, the MIT economist Christopher Knittel reported that from 1980 to 2006, the fuel economy of the U.S. fleet should have gone up by 60 percent.

Instead, fuel economy increased by only 15 percent. The reason is simple: cars got more efficient, but they also got bigger. Much of the technological progress of the past three decades has been squandered. Electric cars aren’t necessarily the answer, either. The Nissan Leaf, laden with a 660-pound battery, weighs 3,385 pounds. (The Toyota Prius weighs 3,042 pounds.)

Lighter cars are a no-brainer solution—and new materials suddenly make it possible to shave weight without sacrificing safety. (One reason consumers like big cars is that they perceive them, often erroneously, to be safer.) Most cars are made of steel and aluminum, but several companies have released concept cars built with a carbon fiber–reinforced polymer, which is extremely light and stiff.

Taking a different tack is a company called Edison2. Its Very Light Car seats four adults and weighs just over 800 pounds, thanks to a composite body, while its chassis is made of less expensive, easy-to-recycle chromoly steel. The car is optimized for lightness—the aluminum shifter knob, for example, is two-tenths of an ounce, barely heavier than a cough drop. An electric version of the car has garnered an official EPA rating of 245 mpg equivalent.

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