America would not look the way it does if our metropolitan areas had been built in an era of $4 per gallon gasoline. Plentiful and cheap energy, as much as plentiful and cheap land, has fueled the growth of the suburbs and exurbs encircling our major cities. That means energy policy and development policy must converge if the U.S. is to meaningfully confront the intertwined challenges of climate change and dependence on foreign oil.

It's often said that American families trade time for space, that they accept longer commutes, from more-distant suburbs, as the price of living in bigger houses. Census data quantify that inclination. In 1985, the average new home was 1,554 square feet. Now the average new home measures 2,267 square feet, nearly 50 percent more. Meanwhile, the average commute for people living in new homes has steadily edged up from 22 minutes (13 miles) in 1997 to 24 minutes (15 miles) today.

But from both directions, high energy prices are undermining the time-for-space trade-off. Soaring gasoline prices are swelling the cost of lengthy commutes. And rising electricity prices are inflating the tab for heating and cooling large homes. "People are getting squeezed on both ends," says Reid Ewing, a research professor at the University of Maryland's National Center for Smart Growth. "The model is dysfunctional. It assumes low energy prices that we will never see again."

The social costs of the time-for-space model are mounting, too. Sprawling development has been a major contributor to the unrelenting growth in the number of miles Americans drive each year. And that growth enormously complicates the challenge of reducing both our dependence on foreign oil and our emissions of carbon dioxide and the other gases linked to global warming.

Washington hasn't put nearly enough pressure on automakers to improve their vehicles' fuel efficiency. Even so, the average car gets 40 percent more miles per gallon now than it did in 1980. Yet our reliance on foreign oil, and the amount of carbon dioxide our cars pump into the atmosphere, is greater now than then. The reason: The total vehicle miles traveled on American roads have doubled since 1980. That's more than triple the pace of the nation's population growth.

In their recent book, Growing Cooler, Ewing and four co-authors calculate that if the number of miles we drive remains constant, the increase in fuel-efficiency standards Congress mandated in 2007 would cut U.S. greenhouse-gas emissions from cars and trucks by nearly one-quarter through 2030. But, in fact, they project that emissions won't decline at all over that period, because an expected increase of nearly 50 percent in miles traveled will offset the efficiency gains. The same dynamic could prevent better fuel efficiency from reducing our reliance on foreign oil. "If we don't change the way we live, the way we build our communities ... we are going to fall way short of our goal of energy independence," says Sen. Thomas Carper, D-Del.

Carper is the rare political leader who acknowledges that confronting our energy challenges may require changes in everyday life. Most discussion of these problems assumes technological salvation, as if tomorrow's solar panels and hydrogen fuel cells will seamlessly power the same lifestyle as coal and oil do today. Yet without new development patterns that slow the rising demand for gasoline and electricity, even technological breakthroughs may not sufficiently reduce our greenhouse-gas emissions or thirst for oil.

Americans won't all live in high-rises or abandon the exurbs to tumbleweed. The question is whether future development will tilt toward closer-in and compact communities that better link home, work, and shopping. High energy prices already may be encouraging that shift: Home prices appear to be falling more in exurbs than in neighborhoods closer to major cities.

Both Carper and Ewing think that Washington could accelerate the transition to more-sustainable development in next year's highway bill by equalizing the treatment of mass transit and highway construction. (Washington pays only 50 percent of the bill for transit projects compared with 80 percent for highways.) Both also want to promote smart growth with revenue from any future cap-and-trade climate-change legislation. These are small initial steps toward reassessing the gasoline-fueled, highway-enabled pattern of sprawling development that reshaped America during the last half of the 20th century, but appears increasingly incompatible with our energy and environmental needs in the 21st.

This article appeared in the Saturday, August 2, 2008 edition of National Journal.

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