List of Interstate Highways
There are 70 primary Interstate Highways in the Interstate Highway System, a network of controlled-access freeways in the United States. They are assigned one- or two-digit route numbers, whereas their associated "auxiliary" Interstate Highways receive three-digit route numbers. Typically, odd-numbered Interstates run south-north, with lower numbers in the west and higher numbers in the east; even-numbered Interstates run west-east, with lower numbers in the south and higher numbers in the north. Highways whose route numbers are divisible by "5" usually represent major coast-to-coast or border-to-border routes (ex. I-10 travels from Santa Monica, California, to Jacksonville, Florida, traveling from the Pacific to Atlantic oceans). Additionally, auxiliary highways have their numbering system where a different number prefixes the number of its parent highway.
List of business routes of the Interstate Highway System
The Interstate Highway System of the United States, in addition to being a network of freeways, also includes a number of Business Routes assigned by the American Association of State Highway and Transportation Officials. The routes are signed with green shields resembling the Interstate Highway shield. The word is used instead of , and, above the number, where the state name is sometimes included, the word or appears. A business loop has both ends as its "parent", while a business spur has a "dangling end", sometimes running from the end of the Interstate to the downtown area.