What's the first thing you notice about the United States after returning from a long trip abroad? Some say the fast food. Some say the rudeness. Most people I know say the space. As in, we've got a lot of it.

The U.S. is blessed, or cursed, with an abundance of livable real estate, and Americans are constantly inventing new ways to use it. After the urban revolution and the second World War, families spent most of the last half-century moving out to the suburbs, sub-suburbs, exurbs, and ex-exurbs, until metro areas resembled large spills on U.S. maps.

Between 1970 and 2000, the share of families living in suburbs in the U.S. grew from 38 to 50 percent. The trend accelerated in the housing boom, as families flowed into the suburbs of the Sun Belt. Texas and California -- sunny, suburban, sprawling -- led the nation in total population growth. Arizona and Nevada -- same trio -- led the country in percent growth.

As a matter of cultural and political necessity, our roads and gas are cheap. Suburban culture requires lots of driving, and lots of driving begs cheap fill-ups. When you're feeling indignant about gas breaking $4 a gallon, think of Europe. And shudder.

Europe is blessed with many things: history, art, coastline ... but not space. Its roads were mostly built before cars, which makes them bad at handling traffic. If the U.S. has a strong incentive to make gas cheap, Europe has an equally strong incentive to pull families closer to its cities, push up the price of gas, and generally make life miserable for the driving set. Elizabeth Rosenthal explains in the New York Times:

Geography, economics and culture have already combined to discourage driving in Europe, while in the US population growth in the 2000s concentrated in the suburbs of sunbelt states, at least before gas prices made the drive into work prohibitively expensive

Cities including Vienna to Munich and Copenhagen have closed vast swaths of streets to car traffic. Barcelona and Paris have had car lanes eroded by popular bike-sharing programs. Drivers in London and Stockholm pay hefty congestion charges just for entering the heart of the city. And over the past two years, dozens of German cities have joined a national network of "environmental zones" where only cars with low carbon dioxide emissions may enter.

We're a long way from $4 gas taxes, congestion pricing, and environmental zones. But there are all sorts of subtle ways we can make our metros less like Vegas and more like Vienna. We can raise the gas tax, cap the mortgage interest deduction (to stop subsidizing large exurban homes), and mix zoning to welcome residential buildings into downtown areas. We've chosen to build out rather than build up, exposing ourselves to broken housing bursts and gas spikes. In the long run, making life difficult for drivers just might make life easier for everybody.

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