The Highway Act of 1956 established the United States Interstate Highway System. It was inspired by Eisenhower's experience getting from New York to San Francisco by convoy in 1919, which took 2 months, and his observation of the efficient German autobahn network during World War II. The act created 47,000 miles of interstate highways in the US to facilitate transportation and support national defense by requiring one-fifth of the miles be straight sections. The interstates also aid evacuation during natural disasters.