List of Interstate Highways
Three-digit Interstates are spur or loop Interstates that usually are in big cities and areas outside of cities.  The last two digits of a three-digit Interstate are always the number of the route it is related to.  If the first digit is odd (1, 3, 5, 7, or 9), the Interstate is usually a spur route while if the first digit is even (2, 4, 6, 8, or 0), the Interstate is usually a loop route.