Auxiliary route

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In road transportation, an auxiliary route is either a spur or a loop of a parent route. The auxiliary route, sometimes called a "child route", is typically distinguished from its parent with either a specific numbering scheme (e.g. in the United States Interstate Highway System, Interstate 240 is an auxiliary route of Interstate 40) or, in the U.S., the use of auxiliary signs like "Business", "City", "Alternate", "Spur", and "By-pass".

Often the term "spur" is used as a substitute for "auxiliary", but true spurs have a unique characteristic in that they do not normally reconnect to the parent highway once separated.

In the case of U.S. state routes, auxiliaries are generally restricted to primary state routes, not secondary state routes, though Missouri has three supplemental routes which have short spur routes.

[edit] See also

• List of auxiliary Interstate Highways
• Auxiliary U.S. Route