Urban sprawl has been the defi ning quality of American urbanism for more than a half century. And now sprawl is spreading across the planet. In 1950, about one-quarter of all Americans in cities resided in the suburbs; a decade later that proportion had increased to one-third. By 1990, half of all metropolitan-based Americans were living a suburban life. 1 Today, despite the crescendo of publicity about climate change, sustainable communities, and smart growth, the fact is that, for now and for the foreseeable future, most Americans still live in the suburbs, and still commute to work by car.