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. Some stretches of U.S. Routes do meet those standards. Many are designated using the
main streets of the cities and towns through which they run. New additions to the system, however, must "substantially meet the current
AASHTO design standards". •
US 51 uses part of the
Jane Addams Memorial Tollway in
Illinois; the old road is
Illinois Route 251. •
US 278 uses the tolled
Cross Island Parkway in
South Carolina; the old road is
US 278 Business. The tolls were removed in July 2021. •
US 301 is a toll road through
Delaware; the former routing is a free road and uses several Delaware state routes. •
US 412 uses the
Cimarron Turnpike in
Oklahoma; the old road is
US 64. • US 412 also uses the
Cherokee Turnpike in Oklahoma; the old road is
US 412 Alternate.
Numbering U.S. Routes in the
contiguous United States follow a grid pattern, in which odd-numbered routes run generally north to south and even-numbered routes run generally east to west, though three-digit spur routes can be either-or. However, some exceptions exist within the two-digit routes. These primarily occur when a route does not definitively run in a single direction. For example,
US 35 runs northeast–southwest; it is signed east–west in Ohio, but north–south everywhere else. Usually, one- and two-digit routes are major routes, and three-digit routes are numbered as shorter spur routes from a main route. Odd numbers generally increase from east to west;
US 1 follows the Atlantic Coast and
US 101 follows the Pacific Coast. (US 101 is one of the many exceptions to the standard numbering grid; its first "digit" is "10", and it is a main route on its own and not a spur of US 1.) Even numbers tend to increase from north to south;
US 2 closely follows the Canadian border, and
US 98 hugs the Gulf Coast. The longest routes connecting major cities are generally numbered to end in a 1 or a 0; however, extensions and truncations have made this distinction largely meaningless. These guidelines are very rough, and exceptions to all of the basic numbering rules exist. The numbering system also extended beyond the borders of the United States in an unofficial manner. Many Canadian highways were renumbered in the 1940s and 1950s to adopt the same number as the U.S. Route they connected to – mostly in the western provinces. Examples include
British Columbia's highways
93,
95,
97, and
99;
Manitoba's highways
59,
75, and
83; or Ontario King's Highway
71. The reverse happened with
U.S. Route 57, originally a Texas state highway numbered to match
Mexican Federal Highway 57. In the 1950s, the numbering grid for the new Interstate Highway System was established as intentionally opposite from the U.S. grid insofar as the direction the route numbers increase. Interstate Highway numbers increase from west-to-east and south-to-north, to keep identically numbered routes geographically apart in order to keep them from being confused with one another, Not all spurs travel in the same direction as their "parents"; some are connected to their parents only by other spurs, or not at all, instead only traveling near their parents. Also, a spur may travel in different cardinal directions than its parent, such as
US 522, which is a north–south route, unlike its parent
US 22, which is east–west. As originally assigned, the first digit of the spurs increased from north to south and east to west along the parent; for example,
US 60 had spurs, running from east to west, designated as
US 160 in
Missouri,
US 260 in
Oklahoma,
US 360 in
Texas, and
US 460 and
US 560 in
New Mexico. AASHTO guidelines specifically prohibit
Interstate Highways and U.S. Routes from sharing a number within the same state. Each state manufactures their own signage, and as such subtle variations exist all across the United States. Individual states may use cut-out or rectangular designs, some have black outlines, and California prints the letters "US" above the numerals. One- and two-digit shields generally feature the same large, bold numerals on a square-dimension shield, while 3-digit routes may either use the same shield with a narrower font, or a wider rectangular-dimension shield. Special routes may be indicated with a banner above the route number, or with a letter suffixed to the route number. Signs are generally displayed in several different locations. First, they are shown along the side of the route at regular intervals or after major intersections (called
reassurance markers), which shows the route and the nominal direction of travel. Second, they are displayed at intersections with other major roads, so that intersecting traffic can follow their chosen course. Third, they can be displayed on large green
guide signs that indicate upcoming interchanges on freeways and expressways. its current policy is to deny approval of new split routes and to eliminate existing ones "as rapidly as the State Highway Department and the Standing Committee on Highways can reach agreement with reference thereto". ==History==