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Anexit number is a number assigned to aroad junction, usually an exit from afreeway. It is usually marked on the same sign as the destinations of the exit. In some countries, including the United States and Canada,[1] it is also marked on a sign in thegore.
Exit numbers typically reset at political borders such asstate or provincial lines.[1]
Some non-freeways use exit numbers. An extreme case of this was in New York City, US, where theGrand Concourse andLinden Boulevard were given sequential numbers, one per intersection (neither boulevard has had exit numbers since 2011). A less extreme version was used on theWest Side Highway, also in New York, where only the major intersections are numbered, possibly to match the planned exits on the cancelledWestway freeway. Another case is theNanaimo Parkway inNanaimo, British Columbia, Canada,Highway 19, where all exits are numbered, though all except one areat-grade intersections. Some other intersections on Highway 19 outside Nanaimo are also given numbers.As a means of educating motorists, somestate highway maps include a brief explanation of the exit numbering system on an inset.Iowa DOT maps from the 1970s and 1990s included a picture or drawing of amilepost and briefly described how Iowa had included milepost references near interchanges on the map.
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Sequential exit numbering usually begins with exit 1 at the beginning of the road; each subsequent exit is given the next number. Letter suffixes are commonly used when new exits are added. For example, on theNew York State Thruway, an exit was added between 21 and 22, and was given the number 21A. Subsequently, a new exit was added between 21 and 21A, leading to the sequence 21 – 21B – 21A – 22. InFlorida, some new exits got the suffix C, so that if it had or acquired separate exits for the two directions, they would be 15CA and 15CB rather than 15AB. There are also occurrences of this happening on the New Jersey Turnpike; the original interchanges opened in 1951, with newer exits as recently as 1982. On theBaltimore Beltway, there is an exit 12B-C (MD 372), as well as 12A (US 1). There is also an exit 8A (I-895) and an exit 8 (MD 168).
Some sequential exits are renumbered (remaining sequential) due to added exits. For instance, theHutchinson River Parkway inNew York was renumbered so that its northernmost exit, 27, became 30. However, theMerritt Parkway, which continued the Hutchinson's exit numbers inConnecticut, was not renumbered. This means theRoute 120A interchange is numbered 27 in Connecticut and 30 in New York.
TheAtlantic City-Brigantine Connector inAtlantic City, New Jersey, uses letters (without numbers) for its exits; it has many exits in a short distance, and theSouth Jersey Transportation Authority may have wanted to avoid numbers, as theAtlantic City Expressway's lowest numbers (mile-based) are in Atlantic City.
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As more highways were built, states and countries began to experiment withdistance-based (mile-based orkilometer-based) exit numbers. The first mile-based system known was implemented on the Garden State Parkway in New Jersey in the late 1950s. Michigan also implemented mile-based junction numbers onInterstate 94 in the 1960s. In this system, the number of miles from the beginning of the highway to the exit is used for the exit number. If two exits would end up with the same number, the numbers are sometimes modified slightly; unless there are too many in proximity, and exits are given sequential or directional suffixes, just as with sequential numbers. Distance based numbering is the norm for most highways in the United States and Canada. Many jurisdictions in North America began switching to distance based in the 1980s, with some projects still ongoing currently to convert towards a distance based system. These are further complemented by mile markers or KM markers.
An exit can be numbered by where the exit in the direction of increased mileage leaves the freeway, or by where the road that the exit serves crosses the freeway (which is occasionally ambiguous). From this number, theinteger exit number can be determined by rounding up, rounding down, or rounding to the nearest integer. Many jurisdictions prefer to avoid an exit 0.[a] To this end, the numbers are either rounded up to get the exit number, or any exit that would get the number 0 is instead numbered 1. Examples of highways with an exit 0 areBritish Columbia Highway 1 on the mainland,Interstate 70 inWheeling, West Virginia, along the West Virginia–Ohio border, andInterstate 90 on the Montana side of the Idaho–Montana border.
Some freeways' exit number starts from an advanced number (i.e. higher than 1). One reason for starting with a number higher than 1 is that the maintaining agency expects that the highway will be extended. For example,Ontario Highway 400 starts at 20 because it was expected that the southern end of the highway would extend to downtown Toronto (which was never built). Another reason to use a higher number is that the freeway is branching off from another freeway. An example isBritish Columbia Highway 5, which branches offBritish Columbia Highway 1 and starts at 170.
In areas that use themetric system, distance-based numbers are by kilometer rather than mile. A number of highways have kilometer-based exit numbers, even in areas that typically use miles; an example of this is withInterstate 19 in the US state of Arizona.
Distance-based exit numbering is used in Queensland, although there is not a consistent approach for defining the datum. For example, exit numbers may increase from south to north or north to south.
Victoria and New South Wales have partially implemented sequential exit numbering on selected urban motorways. For instance, the M31 Hume Motorway in New South Wales has exit numbering between Prestons and Campbelltown.
Most European countries use sequential numbering schemes. Spain uses distance-based numbering on its Autovias, but not on its Autopistas. Austria, the Czech Republic, Hungary and Slovakia use distance-based schemes. A number of European countries (including the Netherlands, Belgium and France) do not number motorway intersections, apparently because one cannot "exit" the motorway there. Countries like Germany and Switzerland number interchanges, but instead of the usual exit symbol, they are given a specific interchange symbol.
Italy uses sequential numbering on the ring roads for some cities, including the ring road of Rome (GRA) and Milan (Tangenziali). At one time, it referred to junctions on theAutostrada del Sole[4] by number, and published same on toll tickets; though these may not have been posted on signs.
Both the United Kingdom and the Republic of Ireland use sequential numbering systems, with the junction number indicated by a white number in a black square in the corner of signs. In the United Kingdom they are frequently referenced in the media as the number with "J" on front of it, with for example Junction 58 being referred to as "J58"; as such this abbreviated term has entered popular usage. If a junction is newly constructed between two existing junctions, it is normally allocated the number of the lower of the two junctions, with the letter "A" attached, followed by "B", then "C" (and so on). For example, a new junction opened between Junctions 86 and 87 would become Junction 86A, and if a new junction opened between Junctions 86A and 87, it would be Junction 86B.
In the Republic of Ireland, junction numbers have existed since the opening of the first section of theM50 motorway in 1990.[citation needed] Since 2005 have been given greater prominence on road signs. With the development of theinter-urban motorway network in the 2000s, theNational Roads Authority adopted a numbering scheme for the inter-urban roads that saw Junction 1 be designated as that road's junction with the M50 in most cases.[citation needed] This has meant renumbering of existing junctions on some motorways, most notably theM7 motorway. Non-motorway dual carriageways forming part of major inter-urban roads also have junction numbers; however, only grade-separated interchanges are numbered.
Countries like Germany and Denmark do not number exits on single carriageway routes that are open only to motorised traffic.
Of the provinces that have numbered exit signs on their highways, the majority either use distance based or have switched to using distance based systems. Some highways may also supplement their roads with kilometer-based distance markers at specific intervals on the side of the road.
Sequential numbers are used only inNova Scotia, andNewfoundland and Labrador.
The territories ofYukon,Nunavut, andNorthwest Territories use no exit numbers, as there are nofreeways orexpressways in the territories.
Prince Edward Island does not use exit numbers. The only limited access highway runs between New Haven and North River (part of the Trans Canada Highway), which features two interchanges, both unnumbered. The Albany Corner interchange nearBorden-Carleton is the only other grade-separated exit.
Exit numbers were introduced to major Hong Kong routes in 2004, in conjunction with the re-organization of the route numbers. A sequential numbering scheme is used.
The main expressway system uses sequential numbering; Metropolitan Expressway systems also use sequential junction numbering, usually appended with the expressway number expressed thus: 5-1; 5-2, etc. There are multiple toll expressways not operated by the major national syndicates or the Metropolitan Expressway Authorities that have no junction numbering scheme.
New Zealand began introducing exit numbers in the Auckland region in 2005. It uses a distance-based numbering system. The distance to the exit is measured from the origin of the highway. That is:
There is no exit zero. If there is an exit within 1.499 km of the origin, Exit 1 is used. Exit 2 would be between 1.500 and 2.499 km of the origin. Subsequent 'exit zones' are at 1 km intervals. Letter suffixes are added at multi-exit interchanges, or where two or more exits exist within the same exit zone. For example, State Highway 1 (Southern Motorway) has an Exit 429A (Symonds St), Exit 429B (Wellesley St) and Exit 429C (Port). Instead of replacing existing ramp and link signs, the exit numbers were added as supplementary information. Thus drivers can navigate either by exit number or name. Exit numbers are only used for exits that may be used by all vehicle types. Bus- or emergency vehicle-only exits would not be numbered.
Exit numbers are not used outside the Auckland region.
Metric distance-based numbers are used on the tollways radiating from Manila. Supplemental "A" and "B" designations are appended to signage at the ends of slip roads.
Uses distance based numbering (in kilometers) on main motorways. Letter suffixes are added at multi-exit interchanges, an example being the Buccleuch interchange inJohannesburg.
Exit numbers are reset on the borders of the provinces as they were until 1994. This means that exit numbering may change in the middle of a province.
One exception to the usual distance based numbering is the southern portion of the M4 inDurban, which uses sequential numbering.
Taiwan uses distance-based exit numbers in kilometers. If two exits are located within the same kilometer mark, the Roman letters are appended to differentiate the exits. Taiwan did experiment with sequential exit numbers with National Freeway No. 1 for a couple of years, but abandoned the experiment in 2004.
Prior to 2006, Taiwan exit signs were generally near replicas of their US counterparts. However, the exit signs now not only indicate the distance number, but they also display the Chinese code-name for the interchange.
