The '57 Chevy was still a year away when the launch of the interstate highway system kicked U.S. car culture into high gear. But six decades later, changing habits and attitudes suggest America's romance with the road may be fading. After rising almost continuously since World War II, driving by U.S. households has declined nearly 10 percent since 2004, with a start before the Great Recession suggesting economics is not the only cause. "There's something more fundamental going on," says Michael...