Many families who travel for the summer will pack up the car and jump on the highway to their destination. On this week's Please Explain, Dan McNichol, author of The Roads that Built America: The Incredible Story of the U.S. Interstate System, explains how the country's highways were planned and created, more than 50 years ago, how these roadways changed the country by connecting cities and small towns, creating the suburbs, and improving transportation of people and goods.