The examples and perspective in this article deal primarily with the English-speaking world and do not represent a worldwide view of the subject. (January 2011) (Learn how and when to remove this template message)
A route (or road) number is an identifying numeric (or alphanumeric) designation assigned by a highway authority to a particular stretch of roadway to distinguish it from other routes and, in many cases, also to indicate its classification (e.g. motorway, primary route, regional road, etc.), general geographical location (in zonal numbering systems) and/or orientation (north-south v. east-west). The numbers chosen may be used solely for internal administrative purposes; however, in most cases they are also displayed on roadside signage and indicated on maps.
In the United Kingdom, road numbers consist of a number up to 4 digits, prefixed with the letters A, B, C or D, but only A and B classifications are signed as being such, whereas C and D classifications are used for internal use by local authorities and government, and then numbered according to the zone in which it is located. For example, the historical main road from London to Edinburgh is called the A1, the "A" in Britain indicates a first class route, classified as more important than "B" roads. The A2, A3, A4, and A5 also radiate out from London (in clockwise order) to points around the coast. All classified roads starting in the zone between the A1 and the A2 begin with the figure 1 (A137, B1412, etc). Scotland is similarly divided into zones by the A7, A8 and A9 which radiate out from Edinburgh.
Motorways are classified as "special roads", and consequently are numbered differently, but in a similar manner. Motorways are either M-class or A(M) class. M-class motorways are labelled in the form Mx, as a higher grade of motorway, and A(M) roads are labelled in the form Ax(M), as upgraded A roads designations, where x is the designation of the road, dependent on the zone. For example, the M25 is the London Orbital Motorway, and the A1(M) is the upgraded A1 dual carriageway.
In the United States, numbered highways belong to one of three to four 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 highways. Some states have other systems as well, either a system of numbered county highways 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 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 3,000 miles (4,800 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. The now defunct U.S. Route 66, known as the "Mother Road", was a cultural touchstone that inspired literature, songs, and other media.
The Interstate Highway System, indicated by a red and blue shield with white numbers, is a system of entirely 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 indicates that the highway connects to another Interstate at both ends (forming loops).
The numbering system for state highways 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", "Business", or "Bypass" can be added to a sign to indicate such a situation.
The Trans-Canada Highway system is made up of federally maintained highways, and is the only system that uses route numbering that spans multiple provinces. The provincial highways are assigned numbers by their respective provinces.
All provincial highways are 'Primary Highways'. They are divided into two series', and sub-series'.
Owing to the mountainous terrain in the province, route numbers are assigned on a mostly ad hoc basis, and vary between west-east and south-north routes. They currently span from 1-118, except for Hwy 395 which is a counterpart of US 395. Some routes are grouped in numerical patterns (e.g. Highways 9, 11, 13, 15, 17, and 19 are North-South routes with values increasing by increments of two moving West). British Columbia formerly had "400 series" of highways similar to Ontario, but that scheme was dropped in 1973.
Provincial Trunk Highways (PTH) are divided into two series'.
Provincial highways are divided into three series'.
Provincial highways are divided into three series'.
Provincial highways are divided into five series'.
Provincial highways are divided into four classes.
Provincial highways are divided into three series'.
Provincial highways are divided into three classes. Odd numbers refer to routes that are generally perpendicular to the Saint Lawrence River. Even numbers refer to routes that are generally parallel to the Saint Lawrence River.
Provincial highways are divided into three series', and sub-series'.
There are currently eleven territorial highways in the Northwest Territories. All eleven are named, eight are numbered 1-8, and two are winter roads.
There are a number of roads and highways in Nunavut, none are yet numbered.
There are currently fourteen territorial highways in Yukon. All fourteen are named and numbered 1-11, 14-15, & 37.
Route numbering in Malaysia is fairly simple.
In Australia, road routes are allocated along sections of named roads, often along parts of multiple roads. Unlike many other countries, most highways in Australia tend to be referred to only by their names. State road authorities have separate numbering systems, for internal use only.
The first route marking system was introduced to Australia in the 1950s. National Routes were assigned to significant interstate routes - the most important road links in the country. National Route 1 was designated to a circular route around the Australian coastline. A state route marking system was designed to supplement the national system, for inter-regional and urban routes within states. When the National Highway system was introduced, National Routes along it became National Highway routes with the same numbers, but with distinctive green and gold route markers. Alphanumeric routes were introduced in Tasmania in 1979, and during the 1990s, planning began for nationally consistent route markings, using the alphanumeric system. Alphanumeric routes have been introduced in most states and territories in Australia, partially or completely replacing the previous systems.
In 1955, the Australian National Route Numbering System was introduced to simplify navigation across Australia. The National Route Numbers are marked by white shields that are present in directional signs, distance signs or trailblazers. The general rule was that odd-numbered highways travel in north-south directions and even-numbered highways in east-west directions, with only a few exceptions. National Route 1 was assigned to a network of highways and roads, which together linked all capital cities and coastal towns circumnavigating the mainland. The National Route system initially linked the centres of towns and cities and terminated at the junction of other national routes, however many bypasses have been constructed since then. National Routes often terminated at the metropolitan city limits rather than the individual city centres.
In 1974, the federal government assumed responsibility for funding the nations most important road links, with the introduction of the National Highway. These highways were marked with distinctive green and gold route marker shields instead of the plain National Route shield. Though the National Highway system has been superseded in subsequent legislation, National Highway route markers are still used on many of the routes. Additionally, National Highways and National Routes have been phased out, or are in the process of being phased out, in all states and territories except Western Australia, in favour of the alphanumeric system.
Important urban and inter-regional routes not covered by the National Highway or National Route systems are marked under the State Route system. They can be recognised by blue shield markers. They were practically adopted in all states by the end of the 1980s, and in some states, some less important National Routes were downgraded to State Routes. Each state has or had its own numbering scheme, but do not duplicate National Route numbers in the same state, or nearby routes in another state. As with the National Routes and National Highways, State Routes are being phased out in most states and territories in favour of alphanumeric routes. However, despite the fact that Victoria has fully adopted alphanumeric routes in regional areas, state route numbers are still used extensively within the city of Melbourne as a part of its Metropolitan Route Numbering Scheme.
In the 1990s in Sydney and Brisbane, urban route numbering system were streamlined under the Metroad scheme. Metroad route numbers were assigned to the key navigational corridors, along ring and radial routes, and marked by distinctive hexagonal shields. Most Metroads have been completely or partially replaced with alphanumeric routes in Brisbane, and they have been fully replaced in Sydney.
Tasmania introduced an alphanumeric route numbering system in 1979, based on the British system from 1963. The new system aimed to upgrade the signing of destinations, including previously unmarked roads, and to simplify navigation by allowing visitors to follow numbered routes. National Highway 1 was retained as the only route without an alphanumeric designation. In the 1990s Victoria and South Australia also overhauled their systems. While South Australia discarded the National and State Route Numbering Systems, those shield-based schemes were retained in the Melbourne metropolitan area as the Metropolitan Route Numbering Scheme. The route numbers used in the alphanumeric schemes were generally inherited from the original National Route Numbering System, with only a few exceptions, and prefixed with letters denoting their grade. For example, Western Freeway is M8 until Ballarat and continues beyond as A8 Western Highway. They are not used extensively in the Melbourne metropolitan area where the blue-shield metropolitan route system is retained for most routes. The National Highways were retained, but with the route numbers changed to alphanumeric designations.
New South Wales and the Australian Capital Territory[a] introduced the alphanumeric system from early 2013. Before being officially announced, new road signs were fitted with such numbers and then being "coverplated" with the existing route number. However, the new system does not distinguish between the former National Highways and other routes.
Alphanumeric routes have also been introduced for many major highways and urban routes in Queensland, although many other roads retain markers from the National Route, National Highway, State and Metroad numbering systems. According to the New South Wales Roads and Maritime Services, the Northern Territory has similarly begun converting their numbered routes to alphanumeric routes, with a "progressive replacement" scheme that sees alphanumeric route markers introduced only when signs are replaced. There are no plans to introduce an alphanumeric route numbering system in Western Australia.
In the alphanumeric systems, a letter denoting the route's construction standard and function is prefixed to the route number, creating an alphanumeric route designation. One of four letters may be used:
Bundesstraßen are national highways, their numbers consist of the letter B and a number:
West Berlin once had its own Bundesstraßen with letters.
State roads are roads operated by the German federal states. They are called Landesstrasse or Staatsstrasse (in Saxony and Bavaria). They are labeled by an initial L or S and a one- to four-digit individual number (e.g. S2 or L240). The federal states sustain their own numbering systems with individual styles of number shields used.
Some countries, such as Brazil, number their national highways by direction. (BR1xx = North/South highways, BR2xx = East/West, BR3xx = 'Diagonal' (i.e. NW/SE or NE/SW)).
Most States and Territories in Australia are moving to an alpha-numeric road numbering system.
Main Roads has chosen to retain the shield numbering system