United States Numbered Highways - System Details

System Details

See also: List of United States Numbered Highways

In general, U.S. Routes do not have a minimum design standard, unlike the later Interstate Highways, and are not usually built to freeway standards, although some stretches of U.S. Routes do meet those standards. Many are the main streets of the cities and towns through which they run. However, new additions to the system must "substantially meet the current AASHTO design standards". As of 1989, the United States Numbered Highways system has a total length of 157,724 miles (253,832 km).

Except for toll bridges and tunnels, very few U.S. Routes are toll roads. AASHTO policy says that a toll road may only be included as a special route, and that "a toll-free routing between the same termini shall continue to be retained and marked as a part of the U.S. Numbered System." Although U.S. Route 3 meets this obligation, as in New Hampshire, it does not actually follow tolled portions of the Everett Turnpike. However, four toll roads in the system follow this:

• U.S. Route 51 uses part of the Jane Addams Memorial Tollway in Illinois; the old road is Illinois Route 251.
• U.S. Route 278 uses the tolled Cross Island Parkway in South Carolina; the old road is U.S. Route 278 Business.
• U.S. Route 412 uses the Cimarron Turnpike in Oklahoma; the old road is U.S. Route 64.
• U.S. Route 412 uses the Cherokee Turnpike in Oklahoma; the old road is Alternate U.S. Route 412.