Anunsigned highway is ahighway that has been assigned aroute number, but does not bear road markings that would conventionally be used to identify the route with that number. Highways are left unsigned for a variety of reasons, and examples are found throughout the world. Depending on the policy of the agency that maintains the highway, and the reason for not signing the route, the route may instead be signed a different designation from its actual number, with small inventory markers for internal use, or with nothing at all.
There are a variety of cases where roads are officially designated, but have no markings to show that designation. Many highway maintenance agencies assign some form of number to all highways, bridges, and other features they maintain for tracking and inventory purposes. However, policies vary regarding how and when to publicly post these assigned numbers. Several highway maintenance agencies have multiple numbering systems for the different classes of routes they maintain (freeways, expressways, rural roads, etc.). In such cases, one or more class of numbers may be reserved for minor routes and these may or may not be signed. Often roads that serve as a connector to a major highway are signed to show the connection to the major road, rather than the road's actual designation. Some highways are not signed to avoid multiple designations, such as when the entire route runsconcurrent with other highways. There are several instances where a route has officially been given a name by government agencies, and is signed with that name, but the route is also assigned a number by the highway maintenance agencies as to fit in their maintenance and inventory systems. Another common reason to not sign a highway is where the highway is government maintained, but is of little value to the general public.
Road sign alongInterstate 70 in Utah signaling traffic destined for the towns ofSigurd andAurora to exit the freeway. The road at this exit is officially designatedSR 259, a short connector; however, the sign instead showsSR 24, the highway at the other end of the connector.
Highway maintenance agencies with multiple numbering systems
The Kentucky parkway system of former toll roads were initially signed exclusively with their names, although all carry an unsigned designation over 9000.
Road signs forU.S. Route 50 inBowie, Maryland. The empty spaces next to the US 50 shields were reserved forInterstate 595 shields, which US 50 is concurrent with. However, the shields were never added, and I-595 remains unsigned.
There are numerous cases in the United States where the same physical roadbed has designations in theInterstate Highway System,U.S. Highway system and the state route system. In many cases one or more of the official designations is omitted.
Many examples exist in thewestern United States where an Interstate highway runs concurrent with a U.S. or state highway, but only the Interstate designation is signed, though any route that becomes unsigned in these situations will still be signed on many road maps and atlases. Examples includeU.S. Route 6 which is unsigned while concurrent withInterstate 70 throughoutColorado andU.S. Route 77 withInterstate 35E through theDallas metropolitan area.
The Interstate Highway System includes highways outside thecontiguous United States. While the ones inHawaii are signed similar to those in the contiguous United States, those inAlaska andPuerto Rico are signed with their state/territory route designation, not Interstate Highway shields.
In the states ofAlabama,Florida, andTennessee, every US Highway is concurrent with an unsigned state highway for its entire length. Similarly, in the states of Florida andGeorgia, every Interstate Highway is concurrent with an unsigned state highway for its entire length. In Tennessee, the state highway route number is signed along the green mile marker signs that display mileage within each county.
There are a small number of cases where a highway briefly crosses a political boundary, but is only signed with its designation on one side of that political boundary. Examples include theAlaska Highway which crosses the boundary of the Canadian province ofBritish Columbia andYukon Territory several times. Although the highway has different numbered designations on each side of the border, the signs along the highway only change designation at one point. Another example isWashington State Route 41, the unsigned designation for a brief portion of the highway signedIdaho State Highway 41 that crosses the state line.
TheEast Los Angeles Interchange is a case where a highway is unsigned with a conflict between the state and federal definition of a highway. The state definition ofInterstate 10 has a discontinuity with a stub freeway proceeding west from the northern part of this interchange towardsU.S. Route 101,[2] while the federal definition of I-10 is contiguous.[3] The discrepancy is resolved by having westbound signage at the interchange follow the federal definition. Driving westbound, I-10 is signed proceeding towards the main portion of interchange concurrent withI-5, while the I-10 stub is signed instead as US 101.
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