Book excerpt: From Acadia and Great Smoky Mountains to Zion and Mount Rainier, millions of visitors tour America's national parks. While park roads determine what most visitors see and how they see it, however, few pause to consider when, why, or how the roads they travel on were built. This illustrated book highlights the qualities of park roads, details the factors influencing their design and development, and examines their role in shaping the national park experience--from the Blue Ridge Parkway and Skyline Drive to Glacier National Park's Going-to-the-Sun Road, Yellowstone's Grand Loop, Yosemite's Tioga Road, and scores of other scenic drives.