Пробелы в системе межштатных автомагистралей США

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There are gaps in the Interstate Highway system, where the roadway carrying an Interstate shield does not conform to the standards set by the Federal Highway Administration (FHWA), the body that sets the regulations for the Interstate Highway System. For the most part, the Interstate Highway System in the United States is a connected system, with most freeways completed; however, some Interstates still have gaps. These gaps can be due to unconnected segments of the same route or from failure of the road to fully conform to Interstate standards by including such characteristics as at grade crossings, traffic lights, undivided or narrow freeways, or movable bridges (lift bridges and drawbridges).

True gaps are where multiple disjoint sections of road have the same Interstate highway number and can reasonably be considered part of "one highway" in theory, based on the directness of connections via other highways, or based on future plans to fill in the gap in the Interstate, or simply based on the shortness of the gap. The sections are either not physically connected at all, or they are connected but the connection is not signed as part of the highway. This list does not include different highways that share the same number, such as the two different I 76s, I 84s, I 86s, I 87s, and I 88s, which despite appearances, were always intended as distinct highways and were never intended as a contiguous route.

In North Carolina, Interstate 26 has a gap from Forks of Ivy to Asheville at exit 4A of Interstate 240. This is because not all of the parts in the gap were built to Interstate standards. As of November 2023, Interstate 26 is designated as Future I 26, US 19, and US 23. Construction on building this gap to Interstate Standards was scheduled to start in 2022.

Interstate 49 (I 49) currently has three sections: the original alignment from I 10 in Lafayette to I 20 in Shreveport, one from I 220 near Shreveport to Texarkana; and the third section from I 40 near Alma, Arkansas to I 470/I 435 south of Kansas City, Missouri. A bypass south of Bella Vista, Arkansas was completed in 2021, and existed initially as Arkansas Highway 549; the latter designation is now used on a short section southeast of Fort Smith that is several miles long. It is planned to be connected to an interstate with a project to construct a new roadway from Arkansas Highway 22 to Interstate 40 in Arkansas. I 49 from Fort Smith to Texarkana is still unbuilt. These gaps are expected to be eventually closed.

I 69 currently has several disconnected sections: the original alignment travels from Indianapolis, Indiana, to Port Huron, Michigan. A second section exists from near Evansville, Indiana, to Martinsville, Indiana south of Indianapolis. In stages from 2011 to 2018, sections of the Purchase Parkway, I 24, the Wendell H. Ford Western Kentucky Parkway, and the Pennyrile Parkway from Mayfield, Kentucky, to Henderson, Kentucky, became signed as I 69. On October 2, 2006, a segment of I 69 opened in Tunica and DeSoto counties in Mississippi; this segment has since been continued (but is not signed) through Memphis, Tennessee, to an intersection with U. S. Highway 51 on the north side. Between 2012 and 2015, a portion of U. S. Highway 59 (US 59) between Rosenberg and Cleveland, Texas, extending through Houston, became part of I 69. In South Texas, I 69's route splits into three spurs to cities on the U. S.–Mexico border, on which four segments are complete: a short segment of I 69E in Corpus Christi and another from Raymondville to the border in Brownsville; a short segment of I 69C in Edinburg and McAllen; and a very short segment of I 69W adjacent to the border in Laredo. As of 2021, projects to connect these segments are in varying stages of development. Indiana is currently working to connect the Port Huron–Indianapolis and Martinsville–Evansville sections by extending I 69 north from Martinsville to the I 465 Indianapolis loop, with construction planned to be complete in late 2024. Kentucky and Indiana expect to begin construction of the eastern bypass of Henderson and new Ohio River crossing, connecting the Mayfield–Henderson and Martinsville–Evansville sections, in 2022. Kentucky has plans to upgrade the remaining section of the Purchase Parkway and work with Tennessee to reconstruct the current interchange at the south end of the Purchase Parkway in South Fulton, Tennessee to provide a free flow connection to the existing U. S. 51 freeway to Union City, while Tennessee finished I 69 bypass of Union City. It is currently designated as SR 690. A further bypass of Troy is proposed but not yet funded, which would complete a freeway standard route from I 155 in Dyersburg to Henderson. Tennessee has deferred plans to complete the section between Dyersburg and Memphis to close the gap until the South Fulton–Dyersburg section is completed. The section from Memphis to Houston is the least developed; as of 2021, Mississippi has no current plans to extend I 69 further south, and the states of Louisiana and Arkansas have not funded construction of their portion of the proposed route (via El Dorado and Shreveport) between Mississippi and Texas, other than a two lane southern bypass of Monticello, Arkansas designed to be incorporated into I 69 at a later date. Texas has continued to fund projects to upgrade U. S. 59, U. S. 77, U. S. 281, and other routes that would eventually form parts of I 69 in South Texas and East Texas, including the I 69W/C/E spurs.

I 74 currently has five sections, the original segment heading northwest from Cincinnati, Ohio, to Davenport, Iowa; one from the Virginia–North Carolina line along I 77 south and east to a point southeast of Mount Airy, North Carolina; one traveling around High Point connecting with I 85 and reaching I 73, where the two are concurrent until Ellerbe; and from west of Laurinburg to south of Lumberton, North Carolina, at I 95. North Carolina is currently working on connecting all its sections of I 74.

The eastern I 86 has had two sections since 2006. One travels for 197 mile (317 km) from I 90 in North East, Pennsylvania (which is a town in the northwestern part of the state) to exit 61 in Waverly, New York. The second section is a 9.9 mile (16 km) stretch outside of Binghamton traveling from I 81 in Kirkwood to exit 79 in Windsor. The gap is signed as Future 86. I 86 will eventually travel from North East, Pennsylvania, to the New York State Thruway (I 87) near Harriman, New York. All the designated sections and gaps in New York are part of New York State Route 17.

As of 2023, I 99 has two sections: one from the Pennsylvania Turnpike to just south of I 80, concurrent with US 220, and one from the Pennsylvania–New York state line north to I 86 in Corning, New York, concurrent with US 15. Much of the intervening route, including the entire US 15 section between I 180 in Williamsport and the New York state line, has been constructed to freeway standards but as of yet is not signed as part of I 99. The signing of the intervening route as I 99 will be completed when the route is upgraded to Interstate standards, connecting the two segments of I 99.

Freeway gaps occur where the Interstate is signed as a continuous route, but part, if not all of it, is not up to freeway standards. This includes drawbridges where traffic on the Interstate can be stopped for vessels. This does not include facilities such as tollbooths, toll plazas, agricultural inspection stations, or border stations.

In urban and heavily developed areas, Interstates may travel along surface roads or have at grade intersections with stop signs or traffic lights. This usually happens because the Interstate started construction after the land was heavily developed and buildings such as residences and businesses and other roads would have to be removed to allow a freeway to pass through. Additionally, more developed land would have to be cleared for space to build interchanges to connect the Interstate and surface streets. This situation is extremely uncommon as Interstates are usually built around cities or through them on pre or lightly developed land. I 516 downgrades to an expressway as it heads toward its eastern terminus. The expressway features a frontage road right turn and an at grade intersection with Mildred Street close to the terminus at Montgomery Street and Derenne Avenue (SR 21) in Savannah, Georgia. Mildred Street southbound is closed by concrete barriers. I 19 between North West Street and its southern terminus at West Crawford Street at North Sonoita Avenue, in Nogales, Arizona, consists of surface streets with traffic lights. The signage of this segment is intended to help direct traffic entering from Mexico to the nearest interstate. Interstate 69E in Brownsville, Texas passes through an at grade signalized intersection with University Avenue/East Boulevard, as well as a minor intersection with Courage Street, before passing through the Brownsville – Veterans Port of Entry and crossing the Veterans International Bridge. I 70 uses part of US 30 along a surface road in Breezewood, Pennsylvania. Traffic traveling eastbound on I 70/I 76 must exit and travel a short distance on US 30 in order to continue south on I 70 heading to Hancock, Maryland. (The routing is similar for traffic following I 70 in the opposite direction: traffic traveling north on I 70 must exit and travel a short distance on US 30 in order to continue west on I 70/I 76 or to enter the Pennsylvania Turnpike.) This is one of very few instances of traffic lights on an Interstate. There was formerly a sign of a policeman pointing at drivers leaving the Pennsylvania Turnpike to enter US 30, saying, "You! Slow Down!" Local businesses have lobbied to keep the gap to avoid a perceived potential loss of business. I 676 has a surface street section at the west end of the Ben Franklin Bridge in Philadelphia, Pennsylvania, because of historically significant areas. Signage and the Federal Highway Administration consider I 676 to use the surface streets; the Pennsylvania Department of Transportation and the New Jersey Department of Transportation consider I 676 to be continuous across the Ben Franklin Bridge, even though the bridge, built in 1926, is not up to Interstate standards. This does not specifically violate Interstate standards, however, as the two separated segments of I 676 are in different states. I 78 travels along a one way pair of surface streets, 12th Street and 14th Street, in Jersey City, New Jersey, between the end of the New Jersey Turnpike Newark Bay Extension and the Holland Tunnel, which leads into New York City. Between the two aforementioned points are four signalized intersections. I 180 in Cheyenne, Wyoming is an expressway with no parts built to Interstate standard; the interchange with I 80 is a simple diamond interchange with two traffic lights on I 180. I 81 near Alexandria, New York before the Thousand Islands Bridge across the Saint Lawrence River has intersections with an off ramp leading from NY 12 and a service road connecting from the bridge toll station to a police department while also intersecting NY 12. I 587 in Kingston, New York has a traffic circle (with yield signs) at its northern terminus with the ramps leading to/from I 87.

Several Interstates in rural areas of the U. S. have minor at grade intersections (including median breaks) with farm access roads or authorized vehicle only driveways used for highway maintenance or connection to nearby utility stations. This is usually due to the lack of an old highway, the need to provide access to property that was accessed via the road prior to its upgrade to an Interstate, and the high cost to construct an interchange for the small amount of traffic that would use such a connection or to build a frontage road parallel to the freeway to the nearest interchange. I 10 in Hudspeth County, Texas has at least fifteen at grade intersections containing median breaks with minor dirt or gravel roads. I 11 in Boulder City, Nevada has an at grade intersection with an authorized vehicle only service road giving access to Buchanan Boulevard and the WAPA Mead substation. An interchange replacing this has been considered. I 15 in Wheaton Springs, California (east of Mountain Pass) has several at grade intersections with dirt roads, including one leading to a house. I 15 west of Mesquite, Nevada has an at grade intersection with Toquop Wash Road, a dirt road. Another access point to Toquop Wash Road passes under the I 15 southbound lanes and connects to the northbound lanes in the median. I 15 southbound near Cove Fort, Utah has an at grade intersection with Cinder Crater Road, an asphalt and gravel road that provides access for trucks to the Cinder Crater quarry. I 520 in Augusta, Georgia has an at grade intersection with a gravel and asphalt road that provides access to Lovers Lane. I 40 in the mountains of western North Carolina has at grade access to several dirt roads, as well as a partially grade separated interchange that lacks ramps or RIROs where roads directly connect to the I 40 carriageways. (Example)
I 40 in western Texas has eight at grade access points for cattle ranches with median breaks. I 80 westbound in western Utah in the Great Salt Lake Desert has two gravel roads that directly connect to the freeway, one accessing the Metaphor: The Tree of Utah artwork and another towards Cobb Peak. I 80 westbound in northwestern New Jersey has a RIRO providing access to Hainesburg Road at mile marker 3.4. I 94 at Fort Custer west of Battle Creek, Michigan is the only instance of an Interstate freeway in Michigan to have a gated driveway (at 44th Street), which facilitates access of military vehicles.

The northbound lanes of I 5 in Washington intersect with an at level crosswalk approximately 100 feet (30 m) south of the border with Canada. This crosswalk allows pedestrians access to a monument that is part of Peace Arch Park.

By Interstate standard, all bridges on the Interstate system must be fixed as to not interrupt the flow of traffic. Several bridges on the system, however, are movable:
I 5 crosses the Columbia River from Portland, Oregon, to Vancouver, Washington, on the Interstate Bridge, a vertical lift bridge. The Columbia River Crossing project sought to replace this bridge until being abandoned in 2013. However, in 2019, a new project was approved, scheduled to begin work in 2025. I 110 has a drawbridge across the Back Bay of Biloxi in Biloxi, Mississippi. I 64—the Hampton Roads Beltway—crosses the South Branch Elizabeth River in Chesapeake, Virginia, on the High Rise Bridge, which is a drawbridge, expected to be replaced by a larger fixed bridge. It opened in July 2022. I 264 has a drawbridge, the Berkley Bridge, crossing the Elizabeth River in Norfolk, Virginia. I 278 has a drawbridge across the Bronx River in New York City. I 280 has a vertical lift bridge, the Stickel Memorial Bridge, crossing over the Passaic River between Newark and Harrison, New Jersey. I 95/I 495 pass together as the Capital Beltway over the Potomac River on the Woodrow Wilson Bridge, a double leaf bascule span. Even though the original bridge was replaced in the 2000s, the new bridge also has a draw span, albeit with more vertical clearance resulting in fewer openings than the old bridge—about 65 per year, an average of about one every six days. I 695 has a drawbridge over Curtis Creek, south of Baltimore and just west of the Francis Scott Key Bridge. This section of the Baltimore Beltway is not part of the Interstate Highway System, however, and is officially Maryland Route 695 despite the Interstate signage on the highway.

I 422 (proposed) would have no direct freeway connection to its parent I 22, though the two routes would cross near Adamsville, Alabama.

Auxiliary Interstates (also known as three digit Interstates) are intended to connect to their parent either directly or via a same parented Interstate (like I 280 in California being connected to I 80 via I 680). Often, these connection gaps occur to eliminate concurrencies between other three digit routes. Freeway gaps (signed or unsigned) that officially connect auxiliary routes to the parent are excluded.

I 210 in California does not currently connect directly to I 10 or any of its spurs according to freeway signage. It was signed all the way to I 10 until 1998, when California State Route 57 replaced the portion of I 210 through Covina and San Dimas to provide a proper connection to current State Route 210. The former portion of I 210 now known as SR 57 still remains on the Interstate Highway System federally defined as Interstate 210 maintaining its connection to I 10, but it is not signed as per Caltrans tradition to sign state highways by their state definition over their federal definition. State Route 210, built as an extension to replace Route 30, connects to I 10 further east in Redlands, and California is petitioning to have that portion signed as I 210 as well. When that happens, this gap will close. I 238 does not have a parent. It was previously a part of California State Route 238 that was built to Interstate standards, and it was added to the Interstate system using the same number it had as a state highway. It was upgraded to be an auxiliary route of I 80, but no three digit combinations were available at the time the route was designated an interstate. Additionally, the exit numbers continue the mileage from the state highway instead of starting over from 1. Due to Highway revolts in New York state forcing the interstate to terminate prematurely, none of the spurs of I 78 in New York City (I 278, I 478, I 678, I 878) connect to the parent road I 78, nor is there any surface street with a state route designation with the same number that continues with a solid connection. I 78 was planned to extend southeast through New York City via the Lower Manhattan Expressway, Williamsburg Bridge and Bushwick Expressway, then east along what is now I 878 and north along what is now I 295. I 78 would have then split into two branches (the current I 295 and I 695), which would have both terminated at I 95. I 478 comes the closest, and would have intersected I 78 as part of the Westway project; this project was later canceled. I 278, the only I 78 spur to leave New York City, was planned to extend northwest to I 78 at Route 24. Since all the spurs are interconnected, only one of them needs to be eventually connected to its parent route for all of them to conform to numbering standards. I 585 in South Carolina currently does not connect directly to I 85. Until 1995, I 85 was routed along present day I 85 Business. In that year, I 85 was moved to the north to bypass Spartanburg while I 85 Business took over its former route, leaving I 585 without a connection to its parent route until upgrades to the existing US 176 highway are complete. As of July 2022, I 587 in North Carolina does not connect with its parent route, I 87. Upgrades to the existing US 264 freeway from US 64 to I 95 to Interstate standards, as well as extending I 87 via upgrades to US 64, will connect I 587 with its parent route. I 335 in Oklahoma will not have a connection with its parent route, I 35, until an extension of the road to Purcell is built. Numerous three digit Interstate routes are unsigned on some portions, leading some to think there are connection gaps. These so called connection gaps do not have internal unsigned concurrencies on other Interstate highway segments between the "parent route" and signed terminus.