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Exit number

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Exit numbers on Interstate 4 in Volusia County, Florida. In this case, mile-based exits 111A and 111B had been sequential exits 53CA and 53CB, as the 'OLD 53CA' tab shows.
On a road with distance-based exit numbering, the exit number (shown here on a gore sign) matches a nearby mile or kilometer marker.

An exit number is a number assigned to a road junction, usually an exit from a freeway. It is usually marked on the same sign as the destinations of the exit, as well as a sign in the gore.

Exit numbers typically reset at political borders such as state lines[citation needed]. In some areas, such as New Jersey (and its New Jersey Turnpike), the numbers are a part of popular culture; a clichéd greeting is "what exit?"

Some non-freeways use exit numbers. Typically these are rural roads built to expressway standards[citation needed], and either only the actual exits are numbered, or the at-grade intersections are also numbered. An extreme case of this is in New York City, where the Grand Boulevard and Concourse and Linden Boulevard were given sequential numbers, one per intersection. A milder version of this has been recently used on the West Side Highway, also in New York, where only the major intersections are numbered (possibly to match the planned exits on the cancelled Westway freeway). Another case is the Nanaimo Parkway in Nanaimo, British Columbia carrying BC Highway 19, where all exits are numbered though all except one are at-grade intersections. Some other intersections on BC Highway 19 outside Nanaimo are also given numbers.

As a means of educating motorists, some state highway maps include a brief explanation of the exit numbering system on an inset. Iowa DOT maps from the 1980s and 1990s included a picture or drawing of a milepost and briefly described how Iowa had included milepost references near interchanges on the map.

Sequential numbers

The first exit numbers were sequential[citation needed]. This type of exit numbers usually begins with exit 1 at the beginning of the road; each subsequent exit is given the next number. The first implementations gave each ramp its own number, even when two ramps existed for two directions of a road[citation needed]; later implementations used directional suffixes, as in 15N/15S or 15E/15W[citation needed], and current U.S. practice is to use 15A/15B. In France and Japan, decimals are used, as in 15.1 and 15.2.

Toll roads, especially those using tickets, lend themselves nicely to sequential numbering, as each toll plaza gets its own number. Problems arise when exits are added. For instance, an exit between 15 and 16 would typically be 15A[citation needed]. On the New York State Thruway, an exit was added between 21 and 21A, leading to the sequence 21 - 21B - 21A - 22. In Florida, 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 15AA and 15AB.

Occasionally sequential exits are renumbered due to added exits. For instance, the Hutchinson River Parkway in New York was renumbered so that its northernmost exit, 27, became 30. However, the Merritt Parkway, which continued its exit numbers in Connecticut, was not renumbered, and the sequence now jumps from 30 down to 27 (the interchange on the state line had two exit 27s, and now has exits 30 and 27).

The Atlantic City-Brigantine Connector in Atlantic City, New Jersey uses letters without numbers for its exits; it has many exits in a short distance, and the South Jersey Transportation Authority may have wanted to avoid sequential numbers.

Distance-based numbers

An exit sign (kilometer-based) on Autoroute 640 in Quebec
An exit gore sign on Autoroute 35 in Quebec

As more highways were built, the limitations of sequential numbering became clear[citation needed], and states began to experiment with distance-based (mile-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 on Interstate 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; this is often impossible and exits are given sequential or directional suffixes, just as with sequential numbers.

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, the integer exit number can be determined by rounding up, rounding down, or rounding to the nearest integer. Many jurisdictions prefer to avoid an exit 0. 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 are British Columbia provincial highway 1 on the mainland, Interstate 70 in Wheeling, West Virginia along the West Virginia-Ohio border, and Interstate 65 in two locations: at its terminus with Interstate 10 in Mobile, Alabama, and just north of the Ohio River in Jeffersonville, Indiana.

In areas that use the metric system, distance-based numbers are by kilometer rather than mile. A few highways, such as Delaware Route 1 and Interstate 19, have been renumbered from miles to kilometers, even in areas that typically use miles.

Distance-based numbers have several advantages. They match the mileposts along the road; it is thus easy to calculate how far one has to go. Additionally, most new exits don't need letter suffixes, as in a sequential system[citation needed].

On the other hand, there are some disadvantages to changing from a sequential system. Businesses and motorists have to adapt to the changes, and it costs money to replace the signs (as well as for temporary "old exit" tabs to ease the transition). Additionally, some argue that it is pointless to change to mile-based numbers, as the numbers would have to be replaced again if and when the U.S. switches to the metric system. Ontario's Highway 401 changed to a mile-based system from a sequential system of exit numbers, then had to switch to a kilometre-based system when Canada metricized.

United States

Interstate Highways

Old mile tabs on I-295 in Rhode Island; several other New England states and Colorado did this

The use of exit numbers on the Interstate Highway System became mandatory in 1971. California was able to get a waiver because they had already built most of their freeways; However, some freeways in Los Angeles County got junction numbers: Interstate 10 was the only freeway in the county that had a complete set of junction numbers. Interstate 5, US 101 and then CA 11 (now IH/CA 110) were numbered for short distances from Downtown Los Angeles. Freeway connections were unnumbered; and junction numbers were only shown on plates, not on gore signs. The Cal-NExUS program began in 2002 to completely number California's junctions.[1] Out of the 50 states and district in the United States with signed Interstate Highways, eleven still use all or some sequential numbering schemes, most in the northeast:

Most other states began with sequential numbers and switched over later. Here is a list of these switches, in the order that they happened:

  • Colorado - Used dual mile/junction plates into the mid 1970s; initially used sequential numbering.
  • Indiana - Around 1980
  • Iowa - May have had sequential numbers on Interstate 80 in the early 1970s.
  • Ohio - between 1972 and 1974 (though the Ohio Turnpike continued to carry both systems until 2000)
  • Mississippi - 1980s
  • Virginia - Early 1990s
  • Georgia - began January 4, 2000 [2]
  • Pennsylvania - began April 2001 on Interstates and all highways of the Pennsylvania Turnpike system.
  • Florida - began January 28, 2002, now complete. [3]
  • California - began January 2002 - California was the only state not to have exit numbers or mileposts, because most of their highway system was built prior to the federal requirement. Before adopting statewide exit numbering, California relied on its system of county-based mileposts on all highways, without having explicitly numbered exits.
  • Maine - early 2004 (experimented with dual exit/mile tabs in the 1970s)
  • New York has been debating converting to mileage-based exit numbering since 2000, but no decision has yet been made.

Two highways (Interstate 19 in Arizona and Delaware Route 1) have metric numbering, because they were constructed during the time when the U.S. was thought to be completely converting to metric. Delaware Route 1 currently uses standard milepost when the metric-based posts were replaced.

Other highways

Exit numbering on non-Interstate highways is less consistent. For example, Texas, a state with mile-based exit numbering, uses sequential numbering on U.S. Route 75 between downtown Dallas and the Oklahoma border.

In Illinois, the entire Illinois Tollway system and Interstate 294 in the Chicago area do not number their exits at all.

Minnesota distance-numbers its exits on Interstates, but leaves other freeways or expressways with unnumbered exits. The sole exception is US 52's freeway portion through Rochester, which received mileage-based exit numbers in 2004 as part of a major widening project.

New York and most New England States post junction numbers on express highways of any significant length, despite designation. Occasionally level junctions have posted numbers-this can be seen in New York and Connecticut (CT 9).

New Hampshire does not assign numbers to exits to Interstates (with the exception of Interstate 393 in Concord, being Exit 15W off Interstate 93). For example, Interstate 293's southern exit from I-93 is between exits 5 and 6, but is not numbered; NH-101 Eastbound, however, despite being an interstate grade freeway, is assigned Exit 7. NH-101's own exit to Interstate 95 in Hampton is between exits 12 and 13, but is also not numbered.

Pennsylvania's non-Interstate highways, especially those making up the Pennsylvania Turnpike system, used sequential exit numbers prior to 2001, but has since converted to the mileage-based system. The Northeast Extension, opened in 1957, originally had a unique system in which the mileposts were separate from that of the mainline turnpike, starting at milepost A0.0 (the mainline turnpike went from 0 to 359), but used the sequential exit numbers 31 to 39 (the mainline turnpike went from 1 to 30). Upon the conversion to the mile-based system, the mainline turnpike uses the distance of I-76 from the Ohio state line to New Jersey (as I-276), while the Northeast Extension was converted in 2000-2003 using the mileage based on the southern junction of I-476 (with I-95 in Chester), with the southernmost Northeast Extension exit being numbered as Exit-20, using the I-476 mileage instead of Exit-333A or Exit-334 on the east-west mileage, thus making the highways separate, but distinct systems despite the use of the common ticket system. Additionally, freeway sections can have independent mileposting systems that apply exclusively to the freeway: an example of this being the Robert Casey Highway-US 6 extending northeast of Scranton, which has mileposts reflecting the length of the freeway section. Conversely, the US 22 Lehigh Valley Thruway through Allentown and Bethlehem has no junction numbering, but does have mileposts that reflect the appropriate distance from the state line.

Oklahoma posts junction numbers on its tollway system.

In Connecticut there are several inconsistencies in exit numbering. Three freeway segments for US 7 have three different methods for numbering exits. The southernmost section from Interstate 95 in Norwalk to just north of the Merritt Parkway, uses mileage-based exit numbering. The second segment from Wooster Mountain to Interstate 84 in Danbury has three unnumbered exits, while the third segment from Interstate 84 to US 202 in Brookfield has inconsistently-numbered sequential exits (where Exit 13 is the southernmost exit with I-84; Exit 11 is the next exit, and Exit 12 marks the present northern terminus of this freeway segment at US-202). The other inconsistency occurs with the Merritt/Wilbur Cross Parkway system. Unlike other freeways the Merritt Parkway continues the exit numbering started by the Hutchinson River Parkway in New York instead of resetting at the state line. The Wilbur Cross Parkway continues using the Merritt Parkway's sequence following its junction at Exit 54 in Milford. The Wilbur Cross Parkway terminates at Interstate 91 (Exit 68), and follows the Berlin Turnpike to Hartford as a 4-lane surface road. When the Wilbur Cross Parkway resumes as a freeway in Hartford, the first exit is Exit 85. The Wilbur Cross exit numbering continued on Interstate 84 (then designated I-86) to the Massachusetts border, where the last exit in Connecticut was Exit 106. When I-86 was redesignated I-84 in 1983, exits were renumbered to reflect the sequence for I-84 instead of the Wilbur Cross Parkway.

West Virginia has only one non-interstate with junction numbers-US 22 at Weirton.

Canada

Of all the provinces in Canada, only two use sequential numbers: Nova Scotia and Newfoundland and Labrador. The northern territories, Yukon Territory, and PEI use no exit numbers, as there are no freeways or expressways in the territories. Prince Edward Island only has a few short freeway segments. Nova Scotia also numbers level junctions on designated express highways.

New Brunswick, Quebec, Ontario, Alberta and British Columbia used kilometre-based exit numbers on most expressways in those provinces.

  • Ontario has the oldest exit number system, which started posting exit numbers in the 1960s initially, sequential junction numbers were posted on Kings Highway 401. Most short freeways do not have exit numbers, and until about 2000 (with Highways 11 and 69/400), incomplete freeways also did not have exit numbers.
  • Quebec has the second oldest system, and the only junction numbering system to use mile-based junction numbering before the Canadian metric conversion in the mid 1970s.
  • Alberta has the newest exit number system. The province started posting exit numbers on Highway 2 in 2004, and has extended the system to Highway 1.

Taiwan

Taiwan exit sign prior to 2006
Taiwan exit sign

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.

New Zealand

New Zealand began introducing exit numbers in 2005. It uses a distance-based numbering system. The distance to the exit is measured from the origin of the highway. That is:

  • State Highway 1 (Northern motorway) measured from the origin of SH1 at Cape Reinga
  • State Highway 16 (Northwestern Motorway) measured from the origin at the Port
  • State Highway 20 (Southwestern Motorway) measured from the origin at SH1

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 1km 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.

The Philippines

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. Freeway signage, exit tabs, and kilometer-posts are nearly identical in appearance to American freeway signage.

Japan

The main expressway system uses sequential numbering; Metropolitan Expressway systems also use sequential junction numbeing, usually appended with the expressway number expressed thusly: 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.

Australia

Uses distance based numbering on a section of National Route 1 northwest of Brisbane.

South Africa

Uses distance based numbering on main motorways.

Great Britain and Continental Europe

Most European countries use sequential numbering schemes. Spain uses distance based numbering; Italy does not number junctions, but at one time referred to junctions on the Autostrada Del Sole by number, and published same on toll tickets; though these may not have been posted on signs.

Early exit numbers

See also

References

  1. ^ Cal-NExUS, Possible Questions and Answers
  • Signs Numbering Exits Installed on Parkways, New York Times April 24, 1938 page 26
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