Alternate route - AbsoluteAstronomy.com

An official alternate route is a special route in the United States

United States

The United States of America is a federal constitutional republic comprising fifty states and a federal district...

that provides an alternate alignment for a highway

Highway

A highway is any public road. In American English, the term is common and almost always designates major roads. In British English, the term designates any road open to the public. Any interconnected set of highways can be variously referred to as a "highway system", a "highway network", or a...

. They are loop roads and found in many road systems in the United States including the U.S. Route system and various state route systems

State highway

State highway, state road or state route can refer to one of three related concepts, two of them related to a state or provincial government in a country that is divided into states or provinces :#A...

. Alternate routes were created as a means of connecting a town (or towns) desired to be on a route which had been routed differently to put another important town or city on the route.

Originally, the term for these routes was "optional"; but in 1959, the American Association of State Highway and Transportation Officials

American Association of State Highway and Transportation Officials

AASHTO, the American Association of State Highway and Transportation Officials, is a standards setting body which publishes specifications, test protocols and guidelines which are used in highway design and construction throughout the United States...

(AASHTO) changed the designation to "alternate". In some cases where needed, an additional business route

Business route

A business route in the United States and Canada is a short special route connected to a parent numbered highway at its beginning, then routed through the central business district of a nearby city or town, and finally reconnecting with the same parent numbered highway again at its...

exists as a third alignment (this was the case with former Alternate US 71 which bypassed Joplin, Missouri

Joplin, Missouri

Joplin is a city in southern Jasper County and northern Newton County in the southwestern corner of the US state of Missouri. Joplin is the largest city in Jasper County, though it is not the county seat. As of the 2010 census, the city population was 50,150...

).

AASHTO defines and specifies that alternate routes of the U.S. Route system should have the following behavior:

An "Alternate Route" shall be considered a route which starts at a point where it branches off from the main numbered route, may pass through certain cities and towns, and then connect back with the regular route some miles distant. Since it is the purpose of the U.S. numbered system to mark the best and shortest route available, an alternate route should be designated only where both routes are needed to accommodate the traffic demand, and when the alternate route has substantially the same geometric and structural design standards of the main marked routing. It is recommended that in case an alternate route is marked, that the shorter and better constructed route be given the regular number and the other section designated as the "Alternate Route". It is further recommended that the Highway Department erect signs at the junction points of the regular and alternate routes giving the distance between the cities or points concerned... In no instance should an alternate routing be used for the purpose of keeping an obsolete section on the U.S. numbered system after a new routing has been constructed and available to traffic.

In at least one case, the banner "Optional Route" was retained when a second alternate route existed. One example of this occurred in Kansas City, Missouri

Kansas City, Missouri

Kansas City, Missouri is the largest city in the U.S. state of Missouri and is the anchor city of the Kansas City Metropolitan Area, the second largest metropolitan area in Missouri. It encompasses in parts of Jackson, Clay, Cass, and Platte counties...

with U.S. Route 40

U.S. Route 40

U.S. Route 40 is an east–west United States highway. As with most routes whose numbers end in a zero, U.S. 40 once traversed the entire United States. It is one of the original 1920s U.S. Highways, and its first termini were San Francisco, California, and Atlantic City, New Jersey...

which had an alternate and an optional route simultaneously.

In some US states, an alternate route will be designated by adding an "A" after the number instead of a sign marked "Alternate" above it. Example: "US 69A" means "Alternate US 69".

See also