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Exit number
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Exit number
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. In some countries, including the United States and Canada, it is also marked on a sign in the gore.
Exit numbers typically reset at political borders such as state or provincial lines.
Some non-freeways use exit numbers. An extreme case of this was in New York City, US, where the Grand Concourse and Linden Boulevard were given sequential numbers, one per intersection (neither boulevard has had exit numbers since 2011). A less extreme version was 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, Canada, Highway 19, where all exits are numbered, though all except one are at-grade intersections. Some other intersections on 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 1970s 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 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 the New 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. 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 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 the Baltimore 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, the Hutchinson River Parkway in New York was renumbered so that its northernmost exit, 27, became 30. However, the Merritt Parkway, which continued the Hutchinson's exit numbers in Connecticut, was not renumbered. This means the Route 120A interchange is numbered 27 in Connecticut and 30 in New York.
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 numbers, as the Atlantic City Expressway's lowest numbers (mile-based) are in Atlantic City.
As more highways were built, states and countries began to experiment with distance-based (mile-based or kilometer-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; 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, 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 Highway 1 on the mainland, Interstate 70 in Wheeling, West Virginia, along the West Virginia–Ohio border, and Interstate 90 on the Montana side of the Idaho–Montana border.
Hub AI
Exit number AI simulator
(@Exit number_simulator)
Exit number
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. In some countries, including the United States and Canada, it is also marked on a sign in the gore.
Exit numbers typically reset at political borders such as state or provincial lines.
Some non-freeways use exit numbers. An extreme case of this was in New York City, US, where the Grand Concourse and Linden Boulevard were given sequential numbers, one per intersection (neither boulevard has had exit numbers since 2011). A less extreme version was 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, Canada, Highway 19, where all exits are numbered, though all except one are at-grade intersections. Some other intersections on 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 1970s 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 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 the New 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. 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 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 the Baltimore 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, the Hutchinson River Parkway in New York was renumbered so that its northernmost exit, 27, became 30. However, the Merritt Parkway, which continued the Hutchinson's exit numbers in Connecticut, was not renumbered. This means the Route 120A interchange is numbered 27 in Connecticut and 30 in New York.
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 numbers, as the Atlantic City Expressway's lowest numbers (mile-based) are in Atlantic City.
As more highways were built, states and countries began to experiment with distance-based (mile-based or kilometer-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; 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, 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 Highway 1 on the mainland, Interstate 70 in Wheeling, West Virginia, along the West Virginia–Ohio border, and Interstate 90 on the Montana side of the Idaho–Montana border.
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