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A directional interchange, colloquially known as a stack interchange, is a type of
grade-separated junction A grade-separated junction is a transport junction where at least one bridge or tunnel is used to separate traffic flows (known as grade separation). Relevant articles include: * Road interchanges Interchange may refer to: Transport * Interch ...
between two controlled-access highways that allows for free-flowing movement to and from all directions of traffic. These interchanges eliminate the problems of
weaving Weaving is a method of textile production in which two distinct sets of yarns or threads are interlaced at right angles to form a fabric or cloth. Other methods are knitting, crocheting, felting, and braiding or plaiting. The longitudinal ...
, have the highest vehicle capacity, and vehicles travel shorter distances when compared to different types of interchanges. The first directional interchange built in the world was the
Four Level Interchange The Four Level Interchange (officially the Bill Keene Memorial Interchange) is the first stack interchange in the world. Completed in 1949 and fully opened in 1953 at the northern edge of Downtown Los Angeles, California, United States, it connect ...
which opened to
Los Angeles Los Angeles ( ; es, Los Ángeles, link=no , ), often referred to by its initials L.A., is the List of municipalities in California, largest city in the U.S. state, state of California and the List of United States cities by population, sec ...
traffic in 1949.


Definition

A directional interchange is a grade separated junction between two roads where all turns that require crossing over or under the opposite road's lanes of travel in order to complete the turn utilize ramps that make a direct or semi-direct connection. The difference between direct and semi-direct connections is how much the motorist deviates from the intended direction of travel while on the ramp; direct ramps are shorter and can handle higher traveling speeds than semi-direct.


Four-level stack

The four-level stack (or simply ''four-stack'') has one major freeway crossing another freeway with a viaduct, with connector flyover ramps crossing on two further levels. This type of interchange does not usually permit
U-turn A U-turn in driving refers to performing a 180° rotation to reverse the direction of travel. It is called a "U-turn" because the maneuver looks like the letter U. In some areas, the maneuver is illegal, while in others, it is treated as a ...
s. The four-level stack creates two "inverse"
dual-carriageway A dual carriageway ( BE) or divided highway ( AE) is a class of highway with carriageways for traffic travelling in opposite directions separated by a central reservation (BrE) or median (AmE). Roads with two or more carriageways which are ...
s—the turn ramps crossing the middle section have traffic driving on the opposite side of oncoming traffic to usual (see diagram for clarity).


United States

The first stack interchange was the
Four Level Interchange The Four Level Interchange (officially the Bill Keene Memorial Interchange) is the first stack interchange in the world. Completed in 1949 and fully opened in 1953 at the northern edge of Downtown Los Angeles, California, United States, it connect ...
(renamed the Bill Keene Memorial Interchange), built in
Los Angeles Los Angeles ( ; es, Los Ángeles, link=no , ), often referred to by its initials L.A., is the List of municipalities in California, largest city in the U.S. state, state of California and the List of United States cities by population, sec ...
, California, and completed in 1949, at the junction of US Route 101 (US 101) and State Route 110 (SR 110). Since then, the
California Department of Transportation The California Department of Transportation (Caltrans) is an executive department of the U.S. state of California. The department is part of the cabinet-level California State Transportation Agency (CalSTA). Caltrans is headquartered in Sacr ...
(Caltrans) has built eight more four-level stacks throughout the state of
California California is a state in the Western United States, located along the Pacific Coast. With nearly 39.2million residents across a total area of approximately , it is the most populous U.S. state and the 3rd largest by area. It is also the m ...
, notably the
Judge Harry Pregerson Interchange The Judge Harry Pregerson Interchange is a stack interchange near the Athens and Watts communities of Los Angeles, California, United States. It is the interchange of the following routes: * * The interchange permits traffic entering the interc ...
, as well as a larger number of three-level and four-level stack– cloverleaf hybrids (where the least-used left-turning ramp is built as a cloverleaf-like 270-degree loop). The stack interchange between I-10 and I-405 is a three-level stack, since the semi-directional ramps are spaced out far enough so they do not need to cross each other at a single point as in a conventional four-level stack. The first four-level stack interchange in Texas was built in Fort Worth at the intersection of
I-35W Interstate 35W may refer to: * Interstate 35W (Texas), an Interstate highway serving Fort Worth, Texas, and its suburbs * Interstate 35W (Minnesota), a Interstate highway serving Minneapolis, Minnesota, and its suburbs **The I-35W Mississippi Riv ...
and
I-30 i30, I30, i-30 or I-30 may refer to: *Interstate 30, an Interstate Highway in the southern United States *, an Imperial Japanese Navy submarine during World War II * (1940-1968), a Royal Australian Navy ''Tribal''-class destroyer *I30, a 9000 serv ...
(originally I-20) near downtown. This interchange, finished in 1958, was known as "The Pretzel" or the "Mixmaster" by locals. The original contract cost was $1,220,000.Interstate 35W, Fort Worth
/ref> Improvements to the old Mixmaster over the past 60 years include an upgrade to a Texas-style five-level stack exchange (see below). One of the first four-level stack interchanges in the northeastern United States was constructed in the late 1960s over I-84 in
Farmington, Connecticut Farmington is a town in Hartford County in the Farmington Valley area of central Connecticut in the United States. The population was 26,712 at the 2020 census. It sits 10 miles west of Hartford at the hub of major I-84 interchanges, 20 miles ...
, for the controversial I-291 beltway around the city of
Hartford Hartford is the capital city of the U.S. state of Connecticut. It was the seat of Hartford County until Connecticut disbanded county government in 1960. It is the core city in the Greater Hartford metropolitan area. Census estimates since t ...
. Most of the I‑291 beltway was later cancelled, and the sprawling stack lay dormant for almost 25 years. In 1992 the extension of
Connecticut Route 9 Route 9 is a , four-lane freeway beginning in Old Saybrook and ending at I-84 near the Farmington–West Hartford town line. It connects the Eastern Coastline of the state along with the Lower Connecticut River Valley to Hartford and the ...
to I-84 used the I‑291 right-of-way and some sections of the abandoned interchange. Several ramps still remain unused, including abandoned roadbed for I-291 both north and south of the complex. Four-level stacks are used for the interchanges between: *
I-5 Interstate 5 (I-5) is the main north–south Interstate Highway on the West Coast of the United States, running largely parallel to the Pacific coast of the contiguous U.S. from Mexico to Canada. It travels through the states of Californi ...
and SR 4 in Stockton, California; *
I-71 Interstate 71 (I-71) is a north–south Interstate Highway in the Great Lakes region, Great Lakes/Midwestern and Southeastern region of the United States. Its southern terminus is at an interchange with Interstate 64 in Kentucky, I-64 and ...
/
I-75 Interstate 75 (I-75) is a major north–south Interstate Highway in the Great Lakes and Southeastern regions of the United States. As with most Interstates that end in 5, it is a major cross-country, north–south route, traveling from St ...
and I-275 in
Erlanger, Kentucky Erlanger is a home rule-class city in Kenton County, Kentucky, United States. It had a 2010 census population of 18,368. Erlanger is part of the Cincinnati-Middletown, OH-KY-IN Metropolitan Statistical Area. History Erlanger was founded in th ...
( Cincinnati metropolitan area); *
I-71 Interstate 71 (I-71) is a north–south Interstate Highway in the Great Lakes region, Great Lakes/Midwestern and Southeastern region of the United States. Its southern terminus is at an interchange with Interstate 64 in Kentucky, I-64 and ...
and I-90/ I-490 in Cleveland, Ohio; * I-77 and
I-480 Interstate 480 may refer to: *Interstate 480 (Nebraska–Iowa), a loop through Omaha, Nebraska into Council Bluffs, Iowa * Interstate 480 (Ohio), a loop through Cleveland, Ohio *Interstate 480 (California), the former Embarcadero Freeway in San Fran ...
in Independence, Ohio (just outside
Cleveland Cleveland ( ), officially the City of Cleveland, is a city in the U.S. state of Ohio and the county seat of Cuyahoga County. Located in the northeastern part of the state, it is situated along the southern shore of Lake Erie, across the U.S. ...
); * I-77 and I-490 in Cleveland, Ohio; * I-77 and I-485 in
Charlotte, North Carolina Charlotte ( ) is the most populous city in the U.S. state of North Carolina. Located in the Piedmont region, it is the county seat of Mecklenburg County. The population was 874,579 at the 2020 census, making Charlotte the 16th-most populo ...
; *
I-65 Interstate 65 (I-65) is a major north–south Interstate Highway in the central United States. As with most primary Interstates ending in 5, it is a major crosscountry, north–south route, connecting between the Great Lakes and the Gulf ...
and I-440 in
Nashville, Tennessee Nashville is the capital city of the U.S. state of Tennessee and the seat of Davidson County. With a population of 689,447 at the 2020 U.S. census, Nashville is the most populous city in the state, 21st most-populous city in the U.S., and ...
; * I-20 and
I-459 Interstate 459 (I-459) is a bypass highway of I-59 that is an alternate Interstate Highway around the southern sides of Birmingham, Bessemer, and several other cities and towns in Jefferson County, Alabama. I-459 lies entirely within Jeffe ...
near
Birmingham, Alabama Birmingham ( ) is a city in the north central region of the U.S. state of Alabama. Birmingham is the seat of Jefferson County, Alabama's most populous county. As of the 2021 census estimates, Birmingham had a population of 197,575, down 1% fr ...
; * I-90 and I-405 in
Bellevue, Washington Bellevue ( ) is a city in the Eastside region of King County, Washington, United States, located across Lake Washington from Seattle. It is the third-largest city in the Seattle metropolitan area and has variously been characterized as ...
; * I‑110 and US 61/ US 190 in Louisiana; *
I-75 Interstate 75 (I-75) is a major north–south Interstate Highway in the Great Lakes and Southeastern regions of the United States. As with most Interstates that end in 5, it is a major cross-country, north–south route, traveling from St ...
and
US 35 U.S. Route 35 (US 35) is a United States Highway that runs southeast-northwest for approximately from the western suburbs of Charleston, West Virginia to northern Indiana. Although the highway is physically southeast-northwest, it is nomi ...
in
Dayton, Ohio Dayton () is the sixth-largest city in the U.S. state of Ohio and the county seat of Montgomery County. A small part of the city extends into Greene County. The 2020 U.S. census estimate put the city population at 137,644, while Greater D ...
; *
I-75 Interstate 75 (I-75) is a major north–south Interstate Highway in the Great Lakes and Southeastern regions of the United States. As with most Interstates that end in 5, it is a major cross-country, north–south route, traveling from St ...
and I-696 near
Detroit, Michigan Detroit ( , ; , ) is the largest city in the U.S. state of Michigan. It is also the largest U.S. city on the United States–Canada border, and the seat of government of Wayne County. The City of Detroit had a population of 639,111 at ...
; *
I-69 Interstate 69 (I-69) is an Interstate Highway in the United States currently consisting of 10 unconnected segments with an original continuous segment from Indianapolis, Indiana, northeast to the Canadian border in Port Huron, Michigan, at ...
and I-475 in Flint, Michigan; * I‑70/ I‑270 and I‑270/ I‑64 St. Louis, Missouri; * The Marquette Interchange between I-794, I-94, and I-43 in
Milwaukee, Wisconsin Milwaukee ( ), officially the City of Milwaukee, is both the most populous and most densely populated city in the U.S. state of Wisconsin and the county seat of Milwaukee County, Wisconsin, Milwaukee County. With a population of 577,222 at th ...
; and * The Zoo Interchange between I-894, I-94,
I-41 Interstate 41 (I-41) is a north–south Interstate Highway connecting the interchange of I-94 and U.S. Route 41 (US 41), located south of the Wisconsin–Illinois border at the end of the Tri-State Tollway in metropolitan C ...
, and US 41/ US 45
Milwaukee, Wisconsin Milwaukee ( ), officially the City of Milwaukee, is both the most populous and most densely populated city in the U.S. state of Wisconsin and the county seat of Milwaukee County, Wisconsin, Milwaukee County. With a population of 577,222 at th ...
. Another well-known stack interchange lies west of
Baltimore, Maryland Baltimore ( , locally: or ) is the List of municipalities in Maryland, most populous city in the U.S. state of Maryland, fourth most populous city in the Mid-Atlantic (United States), Mid-Atlantic, and List of United States cities by popula ...
, serving as the junction between I-695 and
I-70 Interstate 70 (I-70) is a major east–west Interstate Highway in the United States that runs from I-15 near Cove Fort, Utah, to a park and ride lot just east of I-695 in Baltimore, Maryland, and is the fifth-longest Interstate in the c ...
. It was originally built for a planned extension of I‑70 into the city, but because of heavy opposition, I‑70 ends at a
park and ride A park and ride, also known as incentive parking or a commuter lot, is a parking lot with public transport connections that allows commuters and other people heading to city centres to leave their vehicles and transfer to a bus, rail system ( ...
east. As a result, the road east of I‑695 sees very little traffic compared to the high volumes to and from the west. Another four-level stack interchange in the Baltimore area is located at the northeastern junction between I-695 and
I-95 Interstate 95 (I-95) is the main north–south Interstate Highway on the East Coast of the United States, running from US Route 1 (US 1) in Miami, Florida, to the Houlton–Woodstock Border Crossing between Maine and the Canadia ...
. The stack was built as part of a massive I-95 reconstruction project that includes
high-occupancy toll lane A high-occupancy toll lane (or HOT lane) is a type of traffic lane or roadway that is available to high-occupancy vehicles and other exempt vehicles without charge; other vehicles are required to pay a variable fee that is adjusted in response ...
s (HOT lanes), designed to relieve congestion between Baltimore and its northeastern suburbs. The
Springfield Interchange The Springfield Interchange, also known as the Mixing Bowl, is the interchange of Interstate 95, Interstate 395, and Interstate 495 in Springfield, Virginia, outside of Washington, D.C. The interchange is located at exit 57 on the Capital Beltw ...
, south of
Washington, D.C. ) , image_skyline = , image_caption = Clockwise from top left: the Washington Monument and Lincoln Memorial on the National Mall, United States Capitol, Logan Circle, Jefferson Memorial, White House, Adams Morgan, ...
, was rebuilt into a four-level stack to accommodate
I-95 Interstate 95 (I-95) is the main north–south Interstate Highway on the East Coast of the United States, running from US Route 1 (US 1) in Miami, Florida, to the Houlton–Woodstock Border Crossing between Maine and the Canadia ...
's transition from the
Capital Beltway The Capital Beltway is a Interstate Highway in the Washington metropolitan area that surrounds Washington, D.C., the capital of the United States, and its inner suburbs in adjacent Maryland and Virginia. It is the basis of the phrase " inside ...
to its own alignment further south into Virginia. This was necessitated by the inadequacy of the original configuration that was caused by the rerouting of I-95 onto the Beltway after its cancellation within Washington and points north. In
Lone Tree, Colorado The City of Lone Tree is a home rule municipality located in northern Douglas County, Colorado, United States. Lone Tree is a part of the Denver–Aurora–Lakewood, CO Metropolitan Statistical Area. The city population was 10,218 at the 2010 U ...
, there is a four-level stack serving
I-25 Interstate 25 (I-25) is a major Interstate Highway in the western United States. It is primarily a north–south highway, serving as the main route through New Mexico, Colorado, and Wyoming. I-25 stretches from I-10 at Las Cruces, New Mexic ...
, the eastern end of C-470 and the southern end of E-470. In
Thornton, Colorado The City of Thornton is a home rule municipality located in Adams and Weld counties, Colorado, United States. The city population was 141,867, all in Adams County, at the 2020 United States Census, an increase of +19.44% since the 2010 United ...
, there is another stack serving I-25 and E-470 at its northern end as it continues west as the Northwest Parkway.


Canada

The initial design of Highway 407 had several four-level stack interchanges planned at junctions with existing 400-series highways, but ending up only one example was built—the interchange at Highway 400 in
Vaughan, Ontario Vaughan () (2021 population 323,103) is a city in Ontario, Canada. It is located in the Regional Municipality of York, just north of Toronto. Vaughan was the fastest-growing municipality in Canada between 1996 and 2006 with its population increas ...
, which is also the only true four-level stack in all of Canada. Highway 407's other proposed four-level stacks at Highway 410 and Highway 404 were reduced to three-level cloverstack interchanges with loop ramps instead of a fourth level of semi-directional ramps. Similarly the Highway 407 interchange with Highway 427 has four levels but only two semi-directional flyover ramps (that cross each other) connecting to Highway 427 south of that junction, while two loop ramps link Highway 407 with Highway 427 north of that junction.


Europe

In Belgium, on the
Brussels Ring The Brussels Ring ( Dutch: ''Grote ring rond Brussel'', French: ''Ring de Bruxelles'') numbered R0, is a ring road surrounding the city of Brussels as well as other smaller towns south of Brussels. It is about long, with 2 or 3 lanes in each direc ...
there are four-level stack interchanges: The Grand-Bigard and Machelen interchange (only partly in use). In Germany, there is one, the Wetzlarer Kreuz. In Greece, there is also four stack interchange near Metamorfosi, which connects the A1 Highway with
Attiki Odos Attiki Odos ( el, Αττική Οδός) is a privately owned toll motorway system in Greece. The Attiki Odos motorways form the outer beltways of the Greater Athens metropolitan area. The total length of the motorways is . The Attiki Odos system ...
. In the Netherlands there is currently four-level stack interchange: the Prins Clausplein near
The Hague The Hague ( ; nl, Den Haag or ) is a city and municipality of the Netherlands, situated on the west coast facing the North Sea. The Hague is the country's administrative centre and its seat of government, and while the official capital o ...
. It forms the junction of the A4 and A12. In the United Kingdom there are four-level stacks: at the junction of the M4 and M25 near Heathrow Airport in
London London is the capital and List of urban areas in the United Kingdom, largest city of England and the United Kingdom, with a population of just under 9 million. It stands on the River Thames in south-east England at the head of a estuary dow ...
, at the junction of the M23 and M25 to the south of London, and at the junction of the M4 and M5 near
Bristol Bristol () is a city, ceremonial county and unitary authority in England. Situated on the River Avon, it is bordered by the ceremonial counties of Gloucestershire to the north and Somerset to the south. Bristol is the most populous city in ...
(the
Almondsbury Interchange The Almondsbury Interchange in South Gloucestershire, is one of the United Kingdom's largest motorway stack interchanges. The interchange is one of only three four-level stacks in the UK, spanning a range (including slip roads) of 1 km ...
). The M4/M25 junction is particularly unusual as it also has a railway line bisecting it at its lowest level. The M4/M25 junction is slightly offset so there is no point where all four levels are directly above each other. M25 (a north–south road at this junction) is offset to the east by approximately . The junction of the A19 and A66 in
Teesside Teesside () is a built-up area around the River Tees in the north of England, split between County Durham and North Yorkshire. The name was initially used as a county borough in the North Riding of Yorkshire. Historically a hub for heavy manu ...
uses a three-level variant, with a 270-degree loop allowing southbound A19 traffic to exit to the westbound A66.


Southern Hemisphere

The
Light Horse Interchange The Light Horse Interchange is a motorway interchange located in Eastern Creek, Sydney, Australia at the junction of the M4 and M7 motorways. The interchange is the largest in the southern hemisphere and was opened to traffic in December 200 ...
at the junction of the M4 and M7 is a four-level stack interchange in Sydney, New South Wales, Australia. Opened in late 2005, it is the largest in the Southern Hemisphere. The EB Cloete Interchange just outside
Durban, South Africa Durban ( ) ( zu, eThekwini, from meaning 'the port' also called zu, eZibubulungwini for the mountain range that terminates in the area), nicknamed ''Durbs'',Ishani ChettyCity nicknames in SA and across the worldArticle on ''news24.com'' from ...
, is another four-level stack interchange. The N3 is the busiest highway in South Africa and a very busy truck route. Because
Johannesburg Johannesburg ( , , ; Zulu and xh, eGoli ), colloquially known as Jozi, Joburg, or "The City of Gold", is the largest city in South Africa, classified as a megacity, and is one of the 100 largest urban areas in the world. According to Dem ...
is not located near a body of water, most of the city's exports travel through the Port of Durban. The N2 connects
Cape Town Cape Town ( af, Kaapstad; , xh, iKapa) is one of South Africa's three capital cities, serving as the seat of the Parliament of South Africa. It is the legislative capital of the country, the oldest city in the country, and the second largest ...
with Durban and serves the South African cities of Port Elizabeth, East London and
George George may refer to: People * George (given name) * George (surname) * George (singer), American-Canadian singer George Nozuka, known by the mononym George * George Washington, First President of the United States * George W. Bush, 43rd Presid ...
and the towns of
Grahamstown Makhanda, also known as Grahamstown, is a town of about 140,000 people in the Eastern Cape province of South Africa. It is situated about northeast of Port Elizabeth and southwest of East London. Makhanda is the largest town in the Makana ...
, Port Shepstone, Richards Bay and the
iSimangaliso Wetland Park iSimangaliso Wetland Park (previously known as the Greater St. Lucia Wetland Park) is situated on the east coast of KwaZulu-Natal, South Africa, about 235 kilometres north of Durban by road. It is South Africa's third-largest protected area, ...
. Two busy roads intersect at the junction. A four-level stack interchange was chosen to serve the high volumes of traffic.


Five-level stack


Texas-style stack

In
Texas Texas (, ; Spanish: ''Texas'', ''Tejas'') is a state in the South Central region of the United States. At 268,596 square miles (695,662 km2), and with more than 29.1 million residents in 2020, it is the second-largest U.S. state by ...
, many stacks contain five levels. They usually have the same configuration as four-level stacks, but
frontage road A frontage road (also known as an access road, outer road, service road, feeder road, or parallel road) is a local road running parallel to a higher-speed, limited-access road. A frontage road is often used to provide access to private drive ...
s add a fifth level. The frontage roads usually intersect with
traffic light Traffic lights, traffic signals, or stoplights – known also as robots in South Africa are signalling devices positioned at road intersections, pedestrian crossings, and other locations in order to control flows of traffic. Traffic light ...
s and are similar to a grid of nearby
one-way street One-way traffic (or uni-directional traffic) is traffic that moves in a single direction. A one-way street is a street either facilitating only one-way traffic, or designed to direct vehicles to move in one direction. One-way streets typical ...
s. A common setup is for one mainline to go below grade and another to go above grade. The intersection of the frontage roads is typically at grade or close to it. Two pairs of left-turn connectors are built above these. The Dallas–Fort Worth metroplex has several five-level stacks, most notably the
High Five Interchange The High Five Interchange is one of the first five-level stack interchanges built in Dallas, Texas. Located at the junction of the Lyndon B. Johnson Freeway ( Interstate 635, I-635) and the Central Expressway ( US Highway 75, US 7 ...
between US 75 and
I-635 Interstate 635 may refer to: * Interstate 635 (Kansas–Missouri), a connector highway between Interstate 35 in Overland Park, Kansas and Interstate 29 in Kansas City, Missouri, signed as the Harry Darby Memorial Highway * Interstate 635 (Texas) I ...
; completed in 2005 and currently the tallest interchange in the world. Others can be found at the interchanges between State Highway 121 (SH 121) and the Dallas North Tollway, SH 121 and
I-35E Interstate 35E may refer to: *Interstate 35E (Texas), a long branch route serving Dallas, Texas *Interstate 35E (Minnesota), a long branch route serving St. Paul, Minnesota See also * Interstate 35W (disambiguation) Interstate 35W may refer to: * ...
/ US 77,
I-30 i30, I30, i-30 or I-30 may refer to: *Interstate 30, an Interstate Highway in the southern United States *, an Imperial Japanese Navy submarine during World War II * (1940-1968), a Royal Australian Navy ''Tribal''-class destroyer *I30, a 9000 serv ...
and
I-35W Interstate 35W may refer to: * Interstate 35W (Texas), an Interstate highway serving Fort Worth, Texas, and its suburbs * Interstate 35W (Minnesota), a Interstate highway serving Minneapolis, Minnesota, and its suburbs **The I-35W Mississippi Riv ...
, I-30 and
President George Bush Turnpike The President George Bush Turnpike (PGBT) is a toll road running through the northern, northeastern and western suburbs, forming a partial loop around Dallas, Texas, United States. It is named for the late George H. W. Bush, the 41st president ...
and others which are technically five levels but do not fit under a Texas-style stack configuration (i.e. the extra level being located away from the central stack or existing in only one direction). The
Houston Houston (; ) is the most populous city in Texas, the most populous city in the Southern United States, the fourth-most populous city in the United States, and the sixth-most populous city in North America, with a population of 2,304,580 i ...
area has seven five-level stack interchanges along
Beltway 8 Beltway 8 (BW8), the Sam Houston Parkway, along with the Sam Houston Tollway, is an beltway around the city of Houston, Texas, United States, lying entirely within Harris County. Beltway 8, a state highway maintained by the Texa ...
: at I-10 east and west of downtown,
I-69 Interstate 69 (I-69) is an Interstate Highway in the United States currently consisting of 10 unconnected segments with an original continuous segment from Indianapolis, Indiana, northeast to the Canadian border in Port Huron, Michigan, at ...
northeast and southwest of downtown,
I-45 Interstate 45 (I-45) is a major Interstate Highway located entirely within the US state of Texas. While most Interstate routes which have numbers ending in "5" are cross-country north–south routes, I-45 is comparatively short, with the ...
north and south of downtown, and US 290 in the beltway's northwest quadrant. The newly reconstructed interchange of I-610 and I-69, with the new I‑610 northbound feeder road built underground and the new I-610 southbound feeder road overpass, is also a five-level stack interchange. Though not a Texas-style stack in the above sense, an unusual stack is nonetheless found in Houston that features more than four levels of traffic but whose fifth level exists in only one direction. In 2011, the previously four-level stack interchange between I-610 and I-10 on the city's east side gained a new (though long-planned) level of complexity with the opening of four ramps connecting the new
US 90 U.S. Route 90 or U.S. Highway 90 (US 90) is an east–west major United States highway in the Southern United States. Despite the "0" in its route number, US 90 never was a full coast-to-coast route. With the exception of a short-live ...
(Crosby Freeway) to the east, featuring direct movements for the new freeway to and from the southeast quadrant of I-610, to westbound I-10, and from eastbound I-10. It is the latter ramp which gives the interchange the fifth level, as US 90 to I-10 westbound merges onto I-10 before crossing I-610. (None of the frontage roads for these highways cross the interchange itself, and thus do not factor into the complexity of the stack.) More than 40 bridges make up the five-level stack interchange known as the Big I between
I-40 Interstate 40 (I-40) is a major east–west Interstate Highway running through the south-central portion of the United States. At a length of , it is the third-longest Interstate Highway in the country, after I-90 and I-80. From west to ea ...
and
I-25 Interstate 25 (I-25) is a major Interstate Highway in the western United States. It is primarily a north–south highway, serving as the main route through New Mexico, Colorado, and Wyoming. I-25 stretches from I-10 at Las Cruces, New Mexic ...
in Albuquerque, New Mexico. China is also home to many Texas-style stack interchanges. For example the Nanjing's Yingtian Street Elevated has one each where it intersects the Inner Ring Road twice.


Other five-level stacks

Sometimes a fifth level is added for HOV connectors. An example of this exists in
Los Angeles, California Los Angeles ( ; es, Los Ángeles, link=no , ), often referred to by its initials L.A., is the largest city in the state of California and the second most populous city in the United States after New York City, as well as one of the world' ...
, at the
Judge Harry Pregerson Interchange The Judge Harry Pregerson Interchange is a stack interchange near the Athens and Watts communities of Los Angeles, California, United States. It is the interchange of the following routes: * * The interchange permits traffic entering the interc ...
. The connector from HOV southbound 110 to HOV westbound 105 can be at the same level as the connector from mixed eastbound 105 to mixed northbound 110, but the connector from HOV southbound 110 to HOV eastbound 105 needs to be higher level, since it crosses over the former connector. Another case is where connection to nearby arterials suggests that another level may be useful, thus making the interchange more complicated but easier to use. In the Atlanta area, a side ramp forms the fifth level of the
Tom Moreland Interchange Tom Moreland Interchange, colloquially known as ''Spaghetti Junction'', is the interchange of Interstate 85 (I-85) and I-285, along with several access roads, in northern DeKalb County, Georgia, northeast of Atlanta and just to the south of No ...
, colloquially known as ''
Spaghetti Junction Spaghetti junction is a nickname sometimes given to a complex or massively intertwined road traffic interchange that is said to resemble a plate of spaghetti. Such interchanges may incorporate a variety of interchange design elements in ord ...
'', found in
DeKalb County, Georgia DeKalb County (, , ) is located in the north central portion of the U.S. state of Georgia. As of the 2020 census, the population was 764,382, making it Georgia's fourth-most populous county. Its county seat is Decatur. DeKalb County is inclu ...
.


Six-level stack

There is a six-level stack on the Yan'an East Road Interchange () in Puxi, Shanghai, with no dedicated HOV/bus/truck lanes. It is six-level stack because it is formed by two elevated highways, Nanbei Elevated Road and Yan'an Elevated Road with service roads and a
footbridge A footbridge (also a pedestrian bridge, pedestrian overpass, or pedestrian overcrossing) is a bridge designed solely for pedestrians.''Oxford English Dictionary'' While the primary meaning for a bridge is a structure which links "two points at a ...
underneath. The centrally located interchange has a central pillar known as the Nine-Dragon Pillar (). The story is that after several construction accidents, a monk suggested the nine-dragon be welcomed with a bas relief sculpture depicting the dragon. An unusual six-level stack is located at the junction between Interstate 35E and
I-635 Interstate 635 may refer to: * Interstate 635 (Kansas–Missouri), a connector highway between Interstate 35 in Overland Park, Kansas and Interstate 29 in Kansas City, Missouri, signed as the Harry Darby Memorial Highway * Interstate 635 (Texas) I ...
in
Dallas, Texas Dallas () is the third largest city in Texas and the largest city in the Dallas–Fort Worth metroplex, the fourth-largest metropolitan area in the United States at 7.5 million people. It is the largest city in and seat of Dallas County ...
, and does not contain any service or frontage roads. The interchange features two levels of highway with the top three levels consisting of direct connection ramps and HOV connectors. A single ramp leading from I-635 westbound to I-35E southbound weaves underneath the I-635 eastbound bridge, making the interchange six levels. The interchange between
I-35E Interstate 35E may refer to: *Interstate 35E (Texas), a long branch route serving Dallas, Texas *Interstate 35E (Minnesota), a long branch route serving St. Paul, Minnesota See also * Interstate 35W (disambiguation) Interstate 35W may refer to: * ...
and the
Sam Rayburn Tollway The Sam Rayburn Tollway (formerly the State Highway 121 Tollway) is a tollway operated by the North Texas Tollway Authority that runs from Grapevine to McKinney. Its frontage road are signed State Highway 121. The original portion of the to ...
in Lewisville, Texas, although similar in design to five-level stacks elsewhere in Texas, also qualifies as a six-level stack, since the ramp connecting the eastbound Sam Rayburn Tollway with northbound I-35E goes over the fifth-level ramps connecting I-35E in both directions with the Sam Rayburn Tollway. The ramp connecting the westbound Sam Rayburn Tollway with southbound I-35E is on the fourth level of the interchange, going under the fifth-level ramps connecting both directions of I-35E with the Sam Rayburn Tollway.


See also

* List of road interchanges in the United States


References


External links


Satellite image of Nanbei Elevated Road and Yanan Elevated Road six-level interchange
in
Shanghai Shanghai (; , , Standard Mandarin pronunciation: ) is one of the four direct-administered municipalities of the People's Republic of China (PRC). The city is located on the southern estuary of the Yangtze River, with the Huangpu River flowin ...
, China.
Satellite image of Interstate 105 and Interstate 110 five-level interchange
in
Los Angeles Los Angeles ( ; es, Los Ángeles, link=no , ), often referred to by its initials L.A., is the List of municipalities in California, largest city in the U.S. state, state of California and the List of United States cities by population, sec ...
.
Satellite image of Interstate 95 and Interstate 695 four-level interchange
near
Baltimore Baltimore ( , locally: or ) is the List of municipalities in Maryland, most populous city in the U.S. state of Maryland, fourth most populous city in the Mid-Atlantic (United States), Mid-Atlantic, and List of United States cities by popula ...
Maryland. {{DEFAULTSORT:Stack Interchange Road interchanges