The Interstate Highway System is officially known as the 'Dwight D. Eisenhower National System of Interstate and Defense Highways' in his honor. It was inspired in part by Eisenhower's own Army experiences in World War II, where he recognized the advantages of the autobahn systems in Germany, Austria, and Switzerland. Commemorative signs reading "Eisenhower Interstate System" and bearing Eisenhower's permanent 5-star rank insignia were introduced in 1993 and are currently displayed throughout the Interstate System. Several highways are also named for him, including the Eisenhower Expressway (Interstate 290) near Chicago and the Eisenhower Tunnel on Interstate 70 west of Denver.
If it is possible to answer this question, answer it for me (else, reply "unanswerable"): What is the formal name of the Interstate Highway System?
Dwight D. Eisenhower National System of Interstate and Defense Highways