In road transportation in the United States, a special route is a road in a numbered highway system that diverts a specific segment of related traffic away from another road. They are featured in many highway systems; most are found in the Interstate Highway System, U.S. highway system, and several state highway systems. Each type of special route possesses generally defined characteristics and has a defined relationship with its parent route. Typically, special routes share a route number with a dominant route, often referred as the "parent" or "mainline", and are given either a descriptor which may be used either before or after the route name, such as Alternate or Business, or a letter suffix that is attached to the route number. For example, an alternate route of U.S. Route 1 may be called "Alternate U.S. Route 1", "U.S. Route 1 Alternate", or "U.S. Route 1A". Occasionally, a special route will have both a descriptor and a suffix, such as U.S. Route 1A Business.