There is a scene early in the 2006 mockumentary Radiant City that provides the key explanation to the morphology of suburban sprawl. Our favorite writer James Howard Kunstler sits on a bench in a community bike trail that is enclosed in two rows of chain link fence in order to, I presume, secure it from the high-capacity arterial road that runs alongside it. The experience is vaguely what it must have been like to patrol the Berlin Wall, had it been encircled by an expressway.