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In the United States, exit numbers are assigned to freeway junctions, and are usually numbered as exits from freeways. Exit numbers generally are found above the destinations (and route number(s) ) of the exit, as well as a sign in the gore. Exit numbers typically reset at political borders such as state lines. Some major streets also use exit numbers. Freeway exits in the United States are usually numbered in two formats: distance-based and sequential.
The Federal Highway Administration (FHWA) generally requires exit numbers (mile-based or sequential) on the Interstate Highway System; the FHWA established that requirement in 1970. The Manual of Uniform Traffic Control Devices (MUTCD) encouraged use of mileposts and exit numbering by 1961. The MUTCD mandated exit numbering in 1971. The FHWA granted California an exception due to the cost of installing and maintaining additional signage. California was able to obtain a waiver because it had already built most of its freeways, although some freeways in Los Angeles County received 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 I-110/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. In 2002, the Cal-NExUS program began to completely number California's junctions. The program is not well-funded, especially because of California's budget woes, so exits are only being signed with numbers when signs need to be replaced. As the efficiency of an exit numbering system for navigational purposes depends on all exits being consistently numbered, the usefulness of the system while only some exits are numbered is limited. Originally, the initial completion date for this project was set as November 2004. The deadline was then extended to 2008. However, the 2006 edition of the California MUTCD removed any sort of compliance deadline for the exit numbers.
Nine states as of June 2008[update], mostly in the Northeast, and the District of Columbia use sequential numbering schemes on at least one highway, although the 2009 edition of the Manual on Uniform Traffic Control Devices (MUTCD) requires these jurisdictions to transition to distance-based numbering. Although a ten-year compliance period was proposed for the new edition of the MUTCD, a compliance date for this change was ultimately not adopted with the 2009 edition, meaning that the transition is accomplished through a systematic upgrading of existing signing and there is no specific date by which the change must be implemented. However, the FHWA has required that all federally funded routes with sequential numbering eventually be converted to mileage-based exit numbers. To that end, the FHWA has required each state that currently uses sequential exit numbering to submit a plan to eventually transition to distance-based exit numbers. Some of the states that currently have sequential numbering either have or intend to request a waiver from the Federal Highway Administration to retain their current numbering systems, while others have planned a gradual transition to mileage-based exit numbering over time as existing signage reaches the end of its serviceable life and is replaced.
The mile-based requirement mandates multiple exits in the same mile to use A, B, C, etc. This also applies to divided interchanges, where two exits are used for opposite directions of the road, for example on full cloverleaf interchanges. Older exit numbering schemes sometimes use cardinal directions (E, N, S, W; often E-W or N-S) depending on the directionality of the cross route(s), for example Interstate 93 in New Hampshire uses exits 15E and 15W for the cloverleaf interchange with U.S. Route 202 in Concord which is signed "east" and "west" at the interchange. Many exits in the Northeastern states which currently or formerly used sequential numbering schemes had these directional abbreviations, but most have converted to A-B schemes. (As of 2019, New Hampshire is the only state to have never used distance-based exits, including "experimental" dual exit/mile numbers/letters.)
Several exits on the New Jersey Turnpike use E and W suffixes on the portion where the roadways split (interchanges 15-18); one interchange on the eastern spur is numbered 15X, as there already was a 15E.
Several states still maintain systems other than the MUTCD-standard mileage based systems, among these are:
- Delaware – Exit numbers are sequential on I-95 and I-495. I-295 has no exit numbers at all, however, DelDOT has made a reference on a 2016 construction notice referring to the exit to I-495 north as "Exit 2".
- District of Columbia – Historically, the only exit numbers posted in the District consisted of sequential numbers on I-295. The other freeways within the District of Columbia did not have exit numbers, but in 2008 the District began posting sequential numbers on I-395. As of June 2008[update], not all interchanges had received numbers. The close proximity of the interchanges on this short freeway, coupled with the lack of space for new interchanges, renders the sequential system more practical than the mileage-based.
- Massachusetts – Sequential (experimented with dual exit/mile tabs in the 1970s). A contract (MassDOT Project 608024) to change over most highways to mileage-based has been awarded. Work was to start in January 2016 to convert all highway exit numbers, though local opposition has caused the state to halt immediate plans and re-evaluate the scheme. and the State Highway Administrator, Tom Tinlin is quoted in a Worcester Telegram & Gazette
- Maryland – The Baltimore Beltway is sequentially numbered.
- Mississippi – Exits on Interstate 69 are unnumbered.
- New Hampshire – All sequential. New Hampshire DOT has reportedly received permission to use Federal funding to convert to mileage-based, but has yet to announce a formal plan for conversion.
- New Jersey – Sequential numbering on I-676 and the New Jersey Turnpike (part of which is concurrent with I-95). Other New Jersey exit numbering is mile-based.
- New York – Mostly sequential; exceptions include I-781 (Fort Drum spur), I-890 in Schenectady, I-95 in New York City, I-99, and the Putnam County section of I-84.
The mainline of the New York State Thruway utilizes a separate exit-numbering scheme separate from its Interstates; non-Thruway sections of I-87 and I-90 each use three independent (currently sequential) exit-numbering schemes.
- Pennsylvania – Interstates are numbered by milepost with the exception of Interstate 579 and Interstate 676. Both are short urban freeways with no exit numbers at all. The Pennsylvania Turnpike Northeast Extension (I-476), 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 0.0 to roughly 359.0), 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. (Coincidentally, Exit 31 for Lansdale kept its original number being between Mile 30 and 31 when the extension was renumbered for I-476's mileage.)
- Rhode Island – Sequential, except for I-295, which has been converted to mile-based numbering as of December 2017; experimented with dual exit/mile tabs in the 1970s. Rhode Island was denied a waiver from the FHWA to retain its sequential numbering system. Rhode Island will complete its transition to mile-based exit numbers statewide by 2021. 
- Texas – Exits on completed sections of Interstate 69 around Houston are currently unnumbered, but will eventually receive mile-based exit numbers when the entire route through the state is complete.
- Vermont – Sequential, with no plans as of late 2018 to changed to mile-based. Governor Phil Scott is in discussions with the FHWA to retain its sequential numbering system.
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 has used standard mileposts since 2003 when the metric-based posts were replaced, and several exit numbers (79, 83, 86, 88, 119) do not coincide with either the milemarker nor its kilometer conversion as they are offset by miles from a kilometer-based exit. I-19 currently has all exit numbers and distances in kilometers, but speed limits in miles per hour. The road has received funding for the distances to be changed back to miles, but in response to local opposition against exit number changes, the Arizona Department of Transportation had decided to spend the money on other roads instead.
Exit numbering on non-Interstate highways is less consistent. For example, Texas, which normally uses mile-based exit numbering, uses sequential numbering on U.S. Route 75 between downtown Dallas and the Oklahoma border. Similarly, the U.S. Route 54 freeway from El Paso to the New Mexico border also uses sequential exit numbering.
- Alabama: only on U.S. Route 78 (future Interstate 22).
- In Arizona, many of its non-interstate freeways utilize exit numbers such as the freeway loops (Arizona State Highway 101 and Arizona State Highway 202) around Phoenix, U.S. Route 60 and Arizona State Route 51.
- In Arkansas, U.S. Route 67 (Future I-57), State Highway 549, and U.S. Route 70 on the Hot Springs bypass are the only non-interstate freeways to have exit numbers. Currently, I-49 from I-40 in Alma to Bentonville in northwest Arkansas follows the old numbering system off its old designation I-540. The exit numbers and mileage are derived from their distance from where the Fort Smith section of I-540 begins at the Oklahoma state line.
- California uses exit numbers on all of its non-interstate highways statewide when they are built to freeway standards. However like its interstate highways (as stated above), the state's budget concerns have caused exits on these routes to only be signed with numbers when signs need to be replaced.
- Colorado does not use exit numbers on non-interstate highways. The exception is E-470 and the Northwest Parkway, which are separate toll highways.
- Connecticut uses sequential exit numbers on longer non-interstate freeways, such as CT Routes 2, 8, 9, 11, 25, and 72, but will eventually transition to distance-based exit numbers. Exit numbers on Routes 2A, 40, 184, 349, and unsigned SR 695 are mileage-based; these changes include the eastern end of the former Connecticut Turnpike. Shorter freeway sections, such as the US-6 Windham Bypass, Route 20 (Bradley Airport Connector), and freeway sections of Route 17 lack exit numbers. Exit numbers on Route 15 (Merritt and Wilbur Cross parkways) are sequential; Route 15's exit numbers were originally a continuation of exit numbers from the Hutchinson River Parkway in New York. However, New York has since added additional exits on the Hutchinson River Parkway, so that now the Route 120A interchange on the state line is Exit 30 eastbound (Hutchinson), and Exit 27 westbound (Merritt). The Wilbur Cross Parkway, eastbound, takes over the Merritt's sequential numbering. Freeway sections of US 7 also use sequential numbering. CT 72 is scheduled to have its exit numbers changed to mile-based in 2020.
- In Delaware, U.S. Route 301 uses mileage-based exit numbers and Delaware Route 141 uses sequential exit numbers. Delaware Route 1 uses kilometer-based exit numbers despite using milemarkers since 2003 (and newer exits use numbers making no sense to either system, such as Exit 86 in Frederica not being 86 miles or kilometers from the Maryland line).
- In Florida, the Turnpike and other expressways owned and operated by the Florida Turnpike Enterprise use distance-number exits. Toll roads under the Central Florida Expressway Authority also use distance-number exits. The Lee Roy Selmon Expressway in Tampa uses a sequential-based exit numbering system. Expressways under the authority of the Miami-Dade Expressway Authority have no exit numbers.
- Georgia does not carry exit numbers on non-interstate expressways except for the Georgia 400 and Stone Mountain Freeway, which run on a sequential system, and Georgia State Route 10 Loop, running on a distance-numbers system.
- The state of Iowa uses exit numbers on non-interstate expressways, such as Iowa 163 or the non-Interstate portions of the Avenue of the Saints.
- Kentucky does not limit exit numbers to interstate highways.
- Exits on the controlled-access portion of New Circle Road (KY 4), which surrounds the urban core of Lexington, are numbered on the standard distance-based system. Numbering increases in clockwise order, starting and finishing at the interchange with Nicholasville Road (US 27) near New Circle's southernmost point.
- All roads within the state's parkway system of former toll roads (some of which have been converted to Interstates, with others in the process of conversion) use the same distance-based numbering system used on interstates.
- In addition to these instances, several smaller cities, mainly in the southeastern and south-central portions of the Commonwealth, mark traffic lights on a main commercial road with sequential numbers, usually beginning at an intersection with a primary highway:
- Berea — KY 21, starting at the I-75 interchange until KY 21 meets US 25. Numbering continues on US 25 until the road leaves the city limits. Throughout this stretch, numbering increases as one travels north.
- Corbin — US 25E, starting at the I-75 interchange at North Corbin and continuing for approximately 5 miles (8 km) until its intersection with KY 830 east of Corbin. Numbering increases as one travels east (which is signed as south on 25E).
- London has two sets of numbered lights. The Hal Rogers Parkway, starting at KY 192 (which is not numbered, as it is a flashing yellow light for parkway traffic instead of a fully controlled signal) and ending at US 25, uses increasing westbound numbering. KY 192, starting at the I-75 interchange, uses increasing eastbound numbering until the Hal Rogers Parkway.
- Manchester — US 421, starting at the Hal Rogers Parkway and increasing as one travels north through the city.
- Middlesboro — KY 74 through the downtown area, with numbering increasing as one travels west.
- Monticello — KY 90, starting at the northern end of the city and increasing until exiting the city.
- Radcliff — US 31W, also known as Dixie Highway, starting at an intersection at the city's border with Elizabethtown and increasing as one travels north until reaching the main entrance to Fort Knox.
- Richmond also has two sets of numbered lights. U.S. Route 25 Business uses exit numbers through downtown numbers lights 1–6 from KY 52 at Lancaster Avenue and the next 5 consecutive lights south; however, the lights south of the railroad tracks and north of the KY 52 multiplex are not numbered. The bypass route wrapping east around Richmond uses exit numbers from KY 876 (locally known as Eastern Bypass) east of I-75 exit 87, and continues onto Dr. Robert R. Martin Highway US 25/US 421 to I-75 exit 90; however, the traffic lights at the interstate are not numbered.
- Somerset — US 27, starting at the northern limits of the city and increasing as one travels south. The numbering continues even after the road leaves the city limits, with the final numbered intersection occurring shortly before US 27 enters the city of Burnside.
- Maine has exit numbers only on Interstates; its other limited-access highways with limited exceptions lack mile markers.
- In Maryland, there are three state highways that use exit numbers. Maryland Route 200 continues the distance-based exits from its parent Interstate 370. Maryland Route 32 has a peculiar distance-based exit set up in that the exits are numbered from east to west from Interstate 97 to Maryland Route 108 so that the eastern terminus of MD 32 starts at mile 0. Maryland Route 100 uses distance-based exits until Edwin Raynor Blvd (Exit 20).
- Minnesota distance-numbers its exits on Interstates, but leaves other freeways or expressways with unnumbered exits. The first exception was US 52's freeway portion through Rochester, which received mileage-based exit numbers in 2004 as part of a major widening project. Since then, exit numbers also started appearing on US 169 in Shakopee in 2016 and on MN-62. In 2019 exit numbers have been added on US 12 in Wayzata.
- In Mississippi, exits on non-Interstate freeways are not currently numbered.
- In Missouri, non-Interstate Highways do not have exit numbers, the exceptions being Route 364 and Route 370 in St. Charles and St. Louis counties, which use mile-based exit numbers.
- In New England, except for Maine (which assigned exit numbers based on mileage), exit numbers are posted on express highways of any significant length, regardless of designation. Some at-grade intersections have posted numbers; such as on CT 9 in Middletown.
- New Hampshire does not assign numbers to exits to junctions with Interstates (with the exception of I-393 in Concord, in which exit 15W from I-93 connected to the US 4/US 202 interchange prior to the construction of I-393). For example, I-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.
- In New Jersey, the New Jersey Turnpike and Palisades Interstate Parkway are numbered sequentially. All other highways are mile-based, except for the Brigantine Connector in Atlantic City, which uses letters for exits. Many New Jersey freeways lack exit numbers.
- In New Mexico, U.S. 84/285 between Pojoaque and Santa Fe was the first non-Interstate highway in New Mexico to use exit numbers. The NM 599 has two (mile-based) numbered interchanges: at Jaguar Drive (Exit 2) and at County Road 62 (Exit 6). The US-70/285 Relief Route around Roswell has an interchange with two exits marked "Exit A" and "Exit B." Other freeways (US-70 east of Las Cruces and NM 423 in Albuquerque) have no exit numbers due to their relatively short lengths.
- In New York, most highways in the New York City metro region of this type use sequential numbering (an exception is the Belt Parkway system, which uses directional suffixes (N, S, E, W) and alphabetical suffixes.) Expressways and freeways without interstate designations upstate have unnumbered interchanges. In addition:
- All parkways on Long Island, except the Southern State Parkway, Heckscher State Parkway, and Northern State Parkway preface exit numbers with a one or two letter prefix indicating the parkway's name. For example, exits on the Meadowbrook Parkway are numbered M1 through M10, and exits on the Sunken Meadow Parkway are numbered SM1 through SM5. Some of these exits have a letter suffix as well (usually N, S, E, and/or W).
- Some at-grade intersections (level junctions) have posted numbers; former examples are the Taconic State Parkway, NY 17, and within New York City, NY 27 along only the section of Linden Boulevard east of Kings Highway. Current examples are the Bronx River Parkway and, within New York City, NY 27 along Conduit Avenue only.
- The Taconic State Parkway formerly numbered exits and at-grade intersections sequentially by county, with a one-letter prefix indicating the county. Interchanges in Westchester County were prefixed with W (e.g., W5), Putnam with P, Dutchess with D, and Columbia with C. The Taconic Parkway received mile-based exit numbers in the summer of 2017 as part of an ongoing sign replacement project.
- Exits on the Berkshire Spur (part of which is I-90) of the New York Thruway are B1, B2 and B3, as the spur is part of the mainline ticket system. (Exits 1, 2, and 3 on the mainline Thruway are in Yonkers.)
- In North Carolina, non-interstate freeways formerly did not use exit numbers. Beginning in the 1990s, all interchanges on U.S. highways have been assigned exit numbers, either when they were constructed, or when the signage was updated. There is still an incomplete conversion, as some highways which have not been upgraded in many decades (such as portions of the U.S. 64 freeway in Nash County) lack exit numbers. Also, exit numbers have been assigned to all U.S. highway grade-separated interchanges, even when the U.S. highway is not a freeway, such as the interchange between the boulevard-grade U.S. 70 and I-540 in Wake County.
- In Ohio, exits on non-Interstate highways generally go unnumbered. However, Ohio Department of Transportation Districts 2 and 6 have begun to employ exit numbers on non-Interstates using the south or west entrance into the state or highway beginning as the point of origin, and District 3 measures them from the south or west entrance into the respective county.
- Oklahoma posts exit numbers on its turnpike system.
- Oregon originally did not post exit numbers on any of its non-Interstates. In the 1990s, the Oregon Department of Transportation began numbering most sections of its freeways with mile-based exits, starting with US-26 and OR-217 west of Portland. As of 2013, almost all Oregon freeway interchanges are numbered; new interchanges are also numbered. (These exits are based on internal limited-access road mileage; see State highways in Oregon for an explanation on these differences.)
- Pennsylvania's non-Interstate highways that have numbered exits are still numbered sequentially (such as the freeway portion of PA 28 between Pittsburgh and Kittanning) with the exception of the toll roads that are part of the Pennsylvania Turnpike system. PA 60 was one of these roads, but the numbers were converted to the mileage-based system (since reversed) in November 2009 when I-376 replaced PA 60 to Mercer County. The Lehigh Valley Thruway (US 22) through Bethlehem and US 30 between York and Lancaster have no exit numbering, but do have mileposts that reflect the appropriate distance from the Ohio border. Additionally, freeway sections can have independent milepost 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.
- Rhode Island has mile-based exit numbers on RI-99 as of December 2017 and on RI-4 as of December 2018.
- Tennessee generally does not post exit numbers on its non-Interstate freeways, with the exception of Nashville's partial beltway TN 155 (Briley Parkway).
- Texas currently has three non-interstates that use exit numbers. US 75 uses a sequential scheme. Due to a major reconstruction project in the 1990s, which combined many exits, these jump from 8B to 20B. Similarity, US 54 in El Paso uses sequential exits, starting at exit 20. SH 130 uses mile-based exits starting at 497 and decreases to 411 at its northern terminus. Exits on other freeways are based off a statewide reference system where the exit number is determined by the distance from either the northernmost (northwest corner of the Texas Panhandle, for north-south routes) or westernmost (Texas/New Mexico/Mexico tripoint, near El Paso, for east-west routes) geographic reference point in Texas.
- Utah's higher-density freeways have exit numbers, including SR-154 (Bangerter Highway), and SR-201. Ten miles of US-89 in Davis County are signed with exit numbers.
- Vermont does not use the mileage-based system on non-Interstates, with two exceptions: VT 127 and VT 289 in the Burlington area. The numbers would have been continuous if the Chittenden County Circumferential Highway were completed. The numbers start at Manhattan Drive just north of Burlington and end at Interstate 89 near Williston. Freeway sections of US-4 and US-7 in the western part of the state use sequential numbering.
- Washington state does not number most of its non-Interstate freeway exits. Two exceptions are SR-14 from Vancouver to Camas (since the 1990s) and SR-16 from Tacoma to near Gig Harbor (since 2006, possibly to extend along all of SR-16 to its northern terminus in Gorst), both milepost-based. It is unclear if other freeways will receive numbers in the future.
- West Virginia has only one non-interstate with exit numbers, the US 22 freeway in Weirton.
- Wisconsin has exit numbers on the freeway and expressway portions of US 12 WIS 16, WIS 29, WIS 64, US 41, US 45, US 51, US 53, WIS 145 and US 151.
States that renumbered exits
Many states formerly used sequential numbers, and in some cases used exit numbers sparingly, if at all. The following states have introduced mile-based exit numbering on some or all of their highways:
- California – Began widespread exit numbering in January 2002, although some exits in Los Angeles received mile-based numbers in the 1970s. California was the only state not to require exit numbers or mileposts, because most of their highway system was built prior to the federal requirement. Before adopting exit numbering, California relied on its system of county-based mileposts on all highways, without having explicitly numbered exits. Originally, the initial completion date for installing exit numbers statewide was set as November 2004. But because of California's budget concerns, exits (especially in the Greater Los Angeles and San Francisco Bay areas) have generally been numbered only when signs needed to be replaced. The state may eventually replace all older overhead signs (and thus add exit numbers) as part of an energy-saving measure: in 2014, Roads & Bridges reported that the California Department of Transportation was testing types of reflective sheeting to eliminate the need for electrical-sign lighting.
- Colorado – Initially sequential; used dual mile/sequential plates in the mid-1970s.
- Connecticut – Started a gradual transition from sequential to mileage-based exit numbers in 2015, with SR 695 and I-395 converted that year, and Route 2A in early 2016 under the same contract. The next freeways to be converted to mileage-based exit numbering will be Route 72 and SR-571 starting in 2020, Route 9 in 2021; followed by Routes 8 and 25, tentatively scheduled for conversion starting in 2022. Two short freeways whose exits were previously unnumbered, Route 184 and Route 349 in Groton received mileage-based exit numbers starting in 2018 as part of a sign replacement project that includes I-95 from New London to the Rhode Island state line (this section of I-95 will retain sequential exit numbers for the time being until signs along the entire length of I-95 are updated and ready for conversion). Route 40 has only one, sequentially-numbered, exit (Exit 1); it would not need to be "changed" to a mile-based number as it is located around milepost 1. Exit numbers on other highways will be converted to mile-based numbering over a 20-year period as existing highway signs reach the end of their serviceable life and are replaced with new signage. As highways are converted to mile-based exit numbers, sequential numbers will be posted on "Old Exit XX" placards on advance guide signs and gore signs for at least two years following the conversion.
- Florida – Began January 28, 2002; now complete. However, I-110 retained its sequential exit numbers.
- Georgia – Began January 4, 2000, now complete; no "former exit" signs were used in the renumbering. (Interstate highways only).
- Illinois formerly did not number exits on its original Illinois Tollways, including those overlaid with Interstate highways. Starting with Interstate 355 (a toll road from its inception in 1989), toll roads began to be numbered according to standard mile-based exit signage. From the 1990s through the 2010s, Illinois gradually added exit numbers to its remaining toll interstates.
- Indiana – Around 1980. Exits on I-69 between Indianapolis and the Michigan state line underwent a second renumbering in 2012, when the first portion of the I-69 extension to Evansville opened that year.
- Iowa – Adopted distance-based exit numbering in 1977.
- Maine – Early 2004 (experimented with dual exit/mile tabs in the 1970s). Sequential exit numbers were retained for two years on yellow "Formerly Exit XX" placards below advance guide signs, which have since been removed.
- Maryland - All interstates (except I-695 and I-83) use mileage-based exits except for the unsigned Interstate 595, it uses miles based on concurrent US Route 50 starting with the District of Columbia border.
- Mississippi – 1980s.
- New Jersey – Around 1970. The New Jersey Turnpike kept sequential exit numbering.
- New York – New interstates (I-781 and I-99) have mileage-based exit numbers. The state has no timeline for converting its remaining highways to mileage-based numbering, although it appears that NYSDOT and NYSTA will gradually transition to mile-based exit numbers through sign replacement projects, as evidenced by a sign replacement and exit numbering contract for the Taconic State Parkway completed in 2017, and a similar contract to replace signs and renumber exits on I-84 starting in late 2018. Bills directing the NYSDOT and the New York State Thruway Authority to renumber exits from sequential to mile-based have been introduced into the state legislature since 2008; none of which have been approved by both chambers. On routes where exit numbers are converted, "Old Exit XX" placards will be placed alongside advanced guide signs for a period of time for motorists to adjust to the new numbering system.
- North Dakota – 1980s
- Ohio – Interstate 475 was its first highway to receive mileage-based exit numbers, in October 1974. The Ohio Turnpike used both systems from January 1998 to September 2002.
- Pennsylvania – Began April 2001 on Interstates and all highways of the Pennsylvania Turnpike system. Prior to renumbering, junctions solely between two-digit interstates were not numbered (for example, the junction of I-79 and I-80). Sequential numbering skipped these junctions. Signage approaching many interchanges still includes former sequential numbers on "Old Exit XX" placards below the exit signs. Neither Interstate 579 nor Interstate 676 have exit numbers.
- Rhode Island – Transition was supposed to occur in four phases starting in 2016, with the full conversion scheduled for completion by the end of 2019. Mile-based exit numbers have been added to Route 146 as part of a sign replacement project. A second project to convert exit numbers to mile-based on I-295 and Route 99 has also been completed. A third contract has been awarded to add mile-based exit numbers to Routes 4, 78, and 403 starting in the middle of 2019. 
- Texas – late 1970s
- Utah – renumbered about 80 mile-based exits on Interstate 15 in 2005 due to surveyors' errors.
- Virginia – Early 1990s; exceptions include Route 267 (suburban Washington, D.C.), Interstate 581 (Roanoke), and Interstate 664 (Newport News - Chesapeake). I-581 and I-664 both utilize sequential exit numbers; furthermore, Exit 1 is at the highways' northern ends.
Early exit numbers
- In April 1938, the New York City Department of Parks installed exit numbers on New York City's parkways, specifically:
- Grand Central Parkway – 1 at Triborough Bridge to 11 at Kew Gardens, and on to 24 at Marcus Avenue, then continuing from 25 (Lakeville Road) on the Northern State Parkway (run by the Long Island State Park Commission, which also planned numbers on its other parkways)
- Interborough Parkway (now the Jackie Robinson Parkway) – 4 at Pennsylvania Avenue to 11 at Kew Gardens (Exits 1, 2, and 3 were intended for a formerly proposed extension to Belt Parkway)
- Henry Hudson Parkway – 1 at 72nd Street to 19 at Mosholu Parkway
- Hutchinson River Parkway – beginning with 7 in Pelham Bay Park
- As other New York-area parkways were completed, they too got numbers.
- Connecticut's Merritt Parkway (CT-15) got sequential numbers in 1948, continuing the numbers of the Hutchinson River Parkway. The Merritt Parkway's lowest-numbered exit remains Exit 27, although the "Hutch" exits were renumbered; traveling towards Connecticut, Exit 30 is encountered at the border (also the beginning of Route 15), where the number "resets" to 27 before reascending. The remainder of Route 15's exit numbers (on the Wilbur Cross Parkway and Wilbur Cross Highway) continue the Merritt sequence.
- The Pennsylvania Turnpike had sequential numbers when its first section opened on October 1, 1940, eventually using Exits 1 to 30 for the mainline from Ohio to New Jersey. When the Northeast Extension was opened in the 1950s, it numbered the exits from 31 to 38 (and later 39). Only Exit 31 retained its original number when the exits were renumbered.
- The New Jersey Turnpike had sequential numbers when it opened in late 1951. Residents of New Jersey identify with these exit numbers, and even an in-state brewery made beers named for the exit numbers.
- In the early 1950s, New Jersey's Garden State Parkway opened, probably the first road to use distance-based exit numbers.
- The Gulf Freeway (US 75, later Interstate 45) in Houston, Texas had sequential numbers by 1956. The numbering scheme started at the freeway's northern end in downtown Houston, and counted up towards the southeast and Galveston.
- Massachusetts started handing out exit numbers in the 1950s to its freeways in and around the Boston area, with an uncommon system of making sure every freeway's intersection with Route 128 was an "Exit 25", numbers increasing away from Boston. Starting in 1976, these freeways started to receive more conventional numbering. As of 2018, only the US 3 freeway retains its original numbering with the older system, to avoid exit confusion with MA 3, whose northernmost non-multiplexed numbered exit is 20.
- California Highways: Numbering Conventions – Postmiles. Accessed: July 17, 2008.
- Brown, Patricia Leigh. "Counting the way to San Jose." The New York Times, February 10, 2002, sec. WK, p. 2.
- "California Highways: Numbering Conventions Exit Numbers". Retrieved March 5, 2009.
- Proposed Amendments to the MUTCD Section 2E.27 Lines 33–41
- MUTCD 2009 Edition Introduction, Paragraphs 22 through 24 and Table I-2
- Exit Numbering, www.kurumi.com, Accessed Nov 15, 2009
- I-395 Exit Re-Numbering Will Create Problems, Montville Patch, May 16, 2013
- Röckers Meet King Tubbys Inna Fire House
- Upstate New York Roads – Interstate 890 Interchange Guide
- New interstate exit numbering system in Vermont? Scott hopes not. Vermont Digger, July 19, 2018
- Holley, Denise (March 17, 2009). "New signs on Interstate 19 courtesy of recovery funds". Nogales International. Retrieved December 29, 2009. Italic or bold markup not allowed in:
- "Florida Department of Transportation Interchange Report" (PDF). Florida Department of Transportation. November 24, 2008. Archived from the original (PDF) on February 8, 2012. Retrieved July 27, 2009.
- Taconic State Parkway to get exit numbers, The Journal News, Sep 4, 2016
- Patch, David (February 10, 2007). "ODOT extends numbered exits to noninterstates". The Blade. 157 (41). p. B1. Archived from the original on February 10, 2007. Retrieved September 28, 2009.
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- "Highway Reference (SR-154)". Utah Department of Transportation. September 10, 2018. Retrieved August 11, 2019.
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- Signs Numbering Exits Installed on Parkways, The New York Times April 24, 1938 page 26