a network of U.S. highways connecting the 48 contiguous states and most of the cities with populations above 50,000, begun in the 1950s and estimated to carry about a fifth of the nation's traffic.
INTERSTATE HIGHWAY SYSTEM
Meaning of INTERSTATE HIGHWAY SYSTEM in English
Random House Webster's Unabridged English dictionary. Полный английский словарь Вебстер - Random House . 2012