In many countries, these roads are numbered to easily tell them apart. These numbered highways are usually called routes. The United States includes a system called the Interstate Highway system, controlled by AASHTO, where major north/south routes are odd numbered and east/west are even numbered. In Canada, routes that are in the 400s are freeways. In China, types of routes are separated by the first letter of the route; "G" for national road, "S" for provincial road and "Y" for rural roads.