Editing Route number (section)

===United States===

{{Further|Numbered highways in the United States}}
<gallery mode="packed" heights="65" caption="Common route number shields used in the United States" style="float:right; margin-left:1em; border:1px #aaa solid; font-size:88%; line-height:130%">
File:I-10.svg|alt=Interstate 10 route marker|{{nowrap|Interstate 10}}
File:US 50.svg|alt=US. Route 50 route marker|US {{nowrap|Route 50}}
File:Elongated circle 1.svg|alt= Delaware Route 1 route marker|Delaware {{nowrap|Route 1}}<ref group=lower-alpha>Other states including Iowa, Kentucky, Mississippi, and New Jersey also use the default circle marker. All other states have their own designs.</ref>
File:Essex County 609.svg|alt= County Route 609 route marker|County {{nowrap|Route 609}} (Essex County, New Jersey)
</gallery>
In the [[United States]], numbered highways belong to one of three or more systems of numbered routes, depending on the state. There are two national-level route numbering systems, the older [[United States Numbered Highway System]] laid out in 1920s, and the newer [[Interstate Highway System]] started in the 1950s. Additionally, every state in the U.S. maintains its own set of numbered [[state highway]]s. Some states have other systems as well, either a system of numbered [[county highway]]s or secondary state highways. A few cities also have numbered city highways; for example, the city of [[Charlotte, North Carolina]], maintains [[Charlotte Route 4]].

The U.S. Highway System, indicated by a white shield with black numbers, is based on a numbering grid, with odd routes running generally north–south and even routes running east–west. Primary routes have a one- or two-digit number, and are supplemented by [[spur routes]] that add a hundreds digit to their parent route. Routes increase from east-to-west and north-to-south, such that [[U.S. Route 1]] follows the [[Atlantic Seaboard fall line]], while [[U.S. Route 101]] does the same at the Pacific Ocean Coast. Likewise [[U.S. Route 2]] runs near the [[Canada–United States border|Canadian border]], while [[U.S. Route 98]] follows the [[Gulf Coast]]. Major cross-country routes end in either a "1" or a "0". For example, [[U.S. Route 20]] is a route that runs over {{convert|3000|mi|km}} from [[Boston, Massachusetts]], to [[Newport, Oregon]], while [[U.S. Route 41]] spans the country from [[Miami, Florida]], to the [[Upper Peninsula of Michigan]]. Routes like [[U.S. Route 141]] and [[U.S. Route 441]] branch off U.S. Route 41. [[U.S. Route 66]], known as the "Mother Road", was a cultural touchstone that inspired literature, songs, and other media from its creation in 1926 until it was superseded by segments of the Interstate Highway System. Parts of the road have been designated "Historic Route 66".<ref>{{Illinois road map |year = 2007 |access-date = May 26, 2012 }}<!--ref copied from U.S. Route 66 article--></ref>

The Interstate Highway System, indicated by a red and blue shield with white numbers, is a system of entirely [[controlled-access highway|freeways]] (unlike the U.S. Highway System, which is mostly undivided surface roads). The Interstate System is also based on a grid, with east–west routes bearing even numbers and north–south routes bearing odd numbers. In order to prevent confusion with the earlier U.S. Highway System, however, the Interstates are numbered in the opposite direction, such that the lowest routes numbers are in the south and west, and the highest numbers in the north and east. Major routes end in either a "0" or a "5"; for example [[Interstate 10]] spans the country from [[Jacksonville, Florida]], to [[Santa Monica, California]], while [[Interstate 35]] goes from the Mexican border to the Great Lakes. Like with U.S. Highways, subsidiary routes are numbered by adding a hundreds digit to the parent route. Because of the large number of these routes, three-digit numbers may be repeated within the system, but unique to each state. Additionally, the parity of the hundreds digit tells the nature of the spur route: odd hundreds digits like [[Interstate 393]] only connect to the system at one end (forming "spurs"), while an even hundreds digit like [[Interstate 440 (North Carolina)|Interstate 440]] indicates that the highway connects to another Interstate at both ends (forming loops).

The numbering system for [[state highway]]s varies widely from state to state. Each state decides how to number its own routes. Some maintain systems similar to the national road systems, based on a grid. Others number highways regionally, with similar numbers occurring in the same area of the state. Still others have no discernible system, with no connection between a route's location and its number.

In addition to numbers, route numbers also use suffixed letters and banners appended to the tops of signs to indicate alternate routes to the main highway. For example, [[U.S. Route 1A]] is the name given to many highways which are either older alignments of [[U.S. Route 1]] or provide an alternate route either around or through a city along U.S. Route 1's route. Banners are sometimes used to indicate alternate routes. Words like "[[Alternate route|Alternate]]", "[[Business route|Business]]", or "[[Bypass (road)|Bypass]]" can be added to a sign to indicate such a situation.