An old alignment is an historical routing of a route, either existing or dead. For instance, some old U.S. routes remain as weed-covered paths that do not resemble major highways any more, even though they were at one time significant transportation corridors. Old alignments may also consist of a frontage road or residential street that was bypassed by a newer or wider alignment later.
A loop route is a Three-Digit Interstate highway with an even prefix that loops around a city or urban area, including most beltways. Georgia and Texas both incorporates Loops as auxiliary state routees / highways. A prime example is Georgia Loop 10 encircling Athens as a freeway.
The National System of Defense and Interstate Highways was created in 1956 in concept as a system of superhighways that would connect all major metropolitan areas. Much of the system as originally conceived was completed, and much work today involves maintaining and upgrading the existing system. However, as population has increased, the need for additional high-capacity routes resulted in additions to the network. Many of these routes, such as the [...]
In the mid-1980s, Nevada renumbered all of its state routes to a clustering system whereby similarly numbered routes would be clustered within a county or city.
In 1935-1936, most of the U.S. routes within the state of Wyoming were renumbered to allow for more route continuity and to eliminate shorter routes entirely within the state's boundary. This resulted in the elimination of U.S. 87E, 87W, 116, 185, 216 and 420.
In 1964, the state of California decided to eliminate or curtail most of the U.S. routes within its borders. This action was intended to reduce route-numbering confusion for U.S. routes parallel to new Interstate highway corridors, but it also resulted in the creation of several lengthy state routes that replaced the original U.S. routes. Some of the routes eliminated in 1964 were U.S. 40, 60, 66, 70, 80, 91, 99, [...]
Due to the high priority corridor system and acts of Congress, some routes have been identified as future interstate highway corridors. These corridors are not to receive a formal Interstate designation until they meet Interstate construction standards. They are often signed with sporadically placed green signs touting the route as a Future Interstate.
County level roads in Minnesota that are eligible for funding from the County State Aid Highway Fund. Some variation in signage for CSAH and County Roads in Minnesota may be found where CSAH routes use the standard blue and gold pentagon and County Roads use the white square.
A routed highway that is maintained at the county level. These roads are mostly signed on a pentagon shield with yellow text on blue background. Variations exist such as where Wisconsin uses lettered rectangles for county trunk highways, West Virginia with circle shields for their county routes and Missouri's lettered routes posted on square markers.<br> County routes originated in 1958 with the formation of the California County Route Marker Program. [...]
A designation the state of Georgia applies to certain state routes. These highways basically connect one to another and include"CONN" within the highway shield design. South Carolina also utilizes Connector routes for both U.S. and state highways, but does not sign these in the field.