We often associate high-density cities with car-free life, and rightly so. But the concentration of businesses and residents also makes roads more crowded. That’s why dense, transit-friendly cities like New York have longer commute times than sprawling, transit-deficient cities like Phoenix. Think of it this way: New York has fewer cars per capita, but even fewer roads per capita. And building mass transit, contrary to popular belief, doesn’t generally reduce traffic congestion. (Neither, by the way, does the expansion of roads.) Growth produces traffic, and urban growth produces even more.
With that in mind, consider the unusual case of Arlington County, Virginia. Just across the Potomac River from Washington, D.C., home to the Pentagon and National Airport, Arlington has grown rapidly over the past half-century. Like many inner-ring suburbs, its population exploded between 1940 and 1960, from 57,000 to 163,000. But then, after a period of decline in the 1970s, it grew again, from 153,000 in 1980 to 227,000 today.
That second spurt of growth did not look much like the first: The new Arlington reached for the sky, with clusters of high-rise buildings that today give the county a more impressive skyline than the squat panorama of the capital. What’s more, population numbers don’t tell half the story. Office space in America’s fourth-smallest county has expanded from about 6 million square feet in 1960 to about 40 million today — making it a greater employment center than downtown Dallas or downtown Denver.