"Wherever an alternate route is not suitable for its own unique two-digit designation, standard procedure assigns the unqualified number to the older or shorter route, while the other route uses the same number marked by a standard strip above its shield carrying the word 'Alternate'."Most states adhere to this approach. However, some maintain legacy routes that violate the rules in various ways. Examples can be found in California, Mississippi, Nebraska, Oregon, and Tennessee. In 1952, AASHO permanently recognized the splits in US 11, US 19, US 25, US 31, US 45, US 49, US 73, and US 99.