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Encyclopedia > Interchange (road)
High-capacity freeway interchange in Los Angeles, California.
High-capacity freeway interchange in Los Angeles, California.

In the field of road transport, an interchange is a road junction that typically utilizes grade separation, and one or more ramps, to permit traffic on at least one road to pass through the junction without crossing any other traffic stream. It differs from an intersection, at which roads cross at grade. Interchanges are almost always used when at least one of the roads is a freeway, though they may occasionally be used at junctions between two surface streets. ImageMetadata File history File links Download high resolution version (2032x976, 497 KB) Freeway interchange in Los Angeles, California. ... ImageMetadata File history File links Download high resolution version (2032x976, 497 KB) Freeway interchange in Los Angeles, California. ... Los Angeles and L.A. redirect here. ... Disruptions in organized traffic flow can create delays lasting hours. ... A junction, when used in the context of traffic is a place where several traffic routes cross, eg. ... An example of a four-level stack interchange in the Netherlands. ... Mountain road with hairpin turns in the French Alps For other uses, see Road (disambiguation). ... In the field of road transport, an intersection is a road junction where two or more roads either meet or cross at grade (they are at the same level). ... An at-grade intersection is a junction at which two or more transport axes cross at the same level (or grade). ... Interstate 80 (Eastshore Freeway) in Berkeley, California: a typical American freeway (MUTCD definition) A freeway, also known as a highway, superhighway, autoroute, autobahn, autostrada, dual carriageway, expressway, Autosnelweg or motorway, depending on the country of discussion, is a type of road designed for safer high-speed operation of motor vehicles...

Contents

Terminology

Approaching a freeway exit.

Note: The descriptions of road junctions are for countries where vehicles drive on the right side of the road. For countries where driving is on the left the layout of the junctions is the same, only left/right is reversed. Image File history File linksMetadata Download high-resolution version (2000x1500, 1753 KB) Mercedes-Benz Station Wagon exiting with turn signal on I, the creator of this work, hereby release it into the public domain. ... Image File history File linksMetadata Download high-resolution version (2000x1500, 1753 KB) Mercedes-Benz Station Wagon exiting with turn signal on I, the creator of this work, hereby release it into the public domain. ... The Trikke is a Human Powered Vehicle (HPV) This article is about the means of transport. ...  drive on right  drive on left Traffic going in opposite directions should be separated in such a way that they do not block each others way. ... Layout, in publishing, is the process of arranging editorial content, advertising, graphics and other information in a manner that creates an effective presentation. ...

  • A freeway junction or highway interchange (in the US) or motorway junction (in the UK) is a type of road junction, linking one motorway to another; to other roads; or sometimes to just a motorway service station. In the UK, all junctions on a motorway with other roads are numbered - the first being called "Junction 1", etc. In the US, interchanges are either numbered according to cardinal interchange number, or by mileage.
  • A highway ramp (as in exit ramp and entrance ramp) or slip road is a short section of road which allows vehicles to enter or exit a freeway (motorway).
  • A directional ramp always tends toward the desired direction of travel. This means that a ramp that makes a left turn exits from the left side of the roadway (a left exit). Left directional ramps are relatively uncommon as the left lane is usually reserved for high-speed through traffic. Right ramps are almost always directional.
  • A non-directional ramp goes in a direction opposite to the desired direction of travel. Many loop ramps (as in a cloverleaf) are non-directional.
  • A semi-directional ramp exits a road in a direction opposite from the desired direction of travel, but then turns toward the desired direction of travel. Many 'flyover ramps' (as in a stack) are semi-directional.
  • A U-Turn ramp leaves the road in one driving direction, turns over or under it and rejoins in the opposite direction.

Weaving is an undesirable situation in which traffic veering right and traffic veering left must cross paths within a limited distance, to merge with traffic on the through lane. In the worst circumstances, a large portion of through traffic must change lanes to stay on the same roadway. Weaving creates both safety and capacity problems. Some interchanges use collector/distributor roads to deal with weaving--while doing so does not eliminate the problem entirely, it separates the weaving traffic from the freeway's main lanes, thus improving traffic flow. Some areas that had such bad junctions have gone through the expensive process of "unweaving the weave" to improve traffic flow. Motto: (Out Of Many, One) (traditional) In God We Trust (1956 to date) Anthem: The Star-Spangled Banner Capital Washington D.C. Largest city New York City None at federal level (English de facto) Government Federal constitutional republic  - President George Walker Bush (R)  - Vice President Dick Cheney (R) Independence from... Motorway symbol in UK, France and Ireland. ... A motorway service station is a place where drivers can leave a motorway to refuel, rest, or take refreshement. ... Interstate 80 (Eastshore Freeway) in Berkeley, California: a typical American freeway (MUTCD definition) A freeway, also known as a highway, superhighway, autoroute, autobahn, autostrada, dual carriageway, expressway, Autosnelweg or motorway, depending on the country of discussion, is a type of road designed for safer high-speed operation of motor vehicles... Motorway symbol in UK, France and Ireland. ... Overpass in East Potomac Park, Washington, D.C. Flyover in Miami Beach, Florida An overpass (In UK, India, Hong Kong flyover) is a bridge, road or similar structure that crosses over another road. ... A collector/distributor road, often abbreviated as C/D road, is a one-way road next to a freeway that is used for some or all of the ramps that would otherwise merge into or split from the main lanes of the freeway. ...


The German Autobahn system splits Autobahn-to-Autobahn interchanges into two types - Autobahnkreuz (AK, translates as motorway cross), a crossing of two Autobahns (or something more complicated), and Autobahndreieck (AD, translates as motorway triangle), an interchange where one of the Autobahns ends. It has been suggested that German Autobahns be merged into this article or section. ...


Complete interchanges

A complete interchange has enough ramps to provide access from any direction of any road in the junction to any direction of any other road in the junction.


Barring u-turns, a complete interchange between two freeways requires eight ramps, while a complete interchange between a freeway and another road (not a freeway) requires at least four ramps. Using u-turns these numbers can be halved to four and two respectively, by making cars that want to turn left pass by the other road first, then make a u-turn and turn right. The use of u-turn ramps is common in less wealthy countries.


The general rule today is that freeways should have at least one mile between interchanges to prevent excessive weaving between entering and leaving traffic. Unfortunately, most older freeway interchanges do not follow this rule (and are congested as a result).


Types of interchanges

Between two freeways

A compact highway interchange (Circle Interchange) in Chicago, Illinois,USA.
A compact highway interchange (Circle Interchange) in Chicago, Illinois,USA.
A typical cloverleaf interchange with collector/distributor roads
Stacked interchange near Den Haag (The Hague), Netherlands.
Stacked interchange near Den Haag (The Hague), Netherlands.
Stack Interchange in Farmington, Connecticut, USA.
Stacked interchange in Los Angeles, California, USA.
Stacked interchange in Los Angeles, California, USA.
Trumpet interchange near Arnhem, Netherlands
Trumpet interchange near Arnhem, Netherlands
  • A cloverleaf is a two-level interchange in which left turns are handled by loop ramps. To go left, vehicles first pass either over or under the other road, then bear right onto a one-way ramp that loops 270 degrees to the right and then merges onto the intersecting road. (In countries where cars drive on the left, this is a left turn.) The major advantage of cloverleafs is that they require only one bridge, which makes such junctions cheap if land is plentiful. A major problem with cloverleafs is weaving (see definition of weaving, above). Cloverleafs also have a considerable land consumption which means that while they are common in the United States, Canada (mainly parclos), Germany, and Netherlands, only four such junctions are found in the land-scarce United Kingdom, with just one on the motorway network (partial cloverleaf exists where the M25 meets the M40 west of London). In Germany the standard design is to separate all turning traffic into a parallel lane so that the extra road space minimizes the problem of weaving. Collector-distributor roads are similar, but are separated from the main freeway lanes by a divider. Collector-distributor roads can be seen at the junction of Interstate 64 and Interstate 295 east of Richmond, Virginia, USA. Cloverleafs are often seen in urban highways within cities that grow out instead of up.
  • A stack is an interchange in which left turns are handled by semi-directional flyover ramps. In order to go left, vehicles first turn slightly right (on a 'right-turn' ramp), then go left on a ramp which goes over (or under) both freeways and connects to the 'right-turn' ramp in the opposite quadrant of the interchange. A stack interchange, then, has two pairs of left-turning ramps, which can be "stacked" in various configurations above or below the two through routes. Stacks do not suffer from the problem of weaving associated with cloverleafs, but require massive construction works. A basic stack involves roads on four levels, but in stacks including ramps for direct movement between high occupancy vehicle lanes, even more levels of stack can be needed; the interchange between Interstate 105 and Interstate 110 in Los Angeles County, California, is a five-level stack. This is not only expensive, but also unsightly, leading to considerable NIMBY opposition. Large stacks with multiple levels are sometimes referred to as Mixmasters in the United States.

Yet another example is the junction of Interstate 787 and US 9/US 20 in Albany, New York. [4] Image File history File links Metadata Size of this preview: 800 × 600 pixelsFull resolution (2592 × 1944 pixel, file size: 1. ... Image File history File links Metadata Size of this preview: 800 × 600 pixelsFull resolution (2592 × 1944 pixel, file size: 1. ... This article or section does not cite any references or sources. ... Nickname: Motto: Urbs in Horto (Latin: City in a Garden), I Will Location in the Chicago metro area and Illinois Coordinates: , Country State Counties Cook, DuPage Settled 1770s Incorporated March 4, 1837 Government  - Mayor Richard M. Daley (D) Area  - City  234. ... Official language(s) English[1] Capital Springfield Largest city Chicago Largest metro area Chicago Area  Ranked 25th  - Total 57,918 sq mi (149,998 km²)  - Width 210 miles (340 km)  - Length 390 miles (629 km)  - % water 4. ... Image File history File links No higher resolution available. ... Image File history File links No higher resolution available. ... A collector/distributor road, often abbreviated as C/D road, is a one-way road next to a freeway that is used for some or all of the ramps that would otherwise merge into or split from the main lanes of the freeway. ... Stacked highway interchange near The Hague, Netherlands Source and ©: picture archive of the ministry of traffic (V&W), Netherlands, 1983. ... Stacked highway interchange near The Hague, Netherlands Source and ©: picture archive of the ministry of traffic (V&W), Netherlands, 1983. ... Coordinates: , Country Netherlands Province South Holland Area (2006)  - Municipality 98. ... Image File history File linksMetadata Download high-resolution version (2080x1552, 769 KB) Interstate 84 and Route 9 overlapping in a half-used stack interchange. ... Image File history File linksMetadata Download high-resolution version (2080x1552, 769 KB) Interstate 84 and Route 9 overlapping in a half-used stack interchange. ... Farmington is the name of some places in the United States of America: Farmington, Arkansas Farmington, California Farmington, Connecticut Farmington, Delaware Farmington, Illinois Farmington, Iowa Farmington, Kentucky Farmington, Maine Farmington, Michigan Farmington, Minnesota Farmington, Mississippi Farmington, Missouri Farmington, New Hampshire Farmington, New Mexico Farmington, New York Farmington, Pennsylvania Farmington, Utah... Official language(s) English Capital Hartford Largest city Bridgeport Largest metro area Hartford Area  Ranked 48th  - Total 5,543[2] sq mi (14,356 km²)  - Width 70 miles (113 km)  - Length 110 miles (177 km)  - % water 12. ... Los Angeles, California. ... Los Angeles, California. ... Flag Seal Nickname: City of Angels Location Location within Los Angeles County in the state of California Coordinates , Government State County California Los Angeles County Mayor Antonio Villaraigosa (D) Geographical characteristics Area     City 1,290. ... Official language(s) English Capital Sacramento Largest city Los Angeles Largest metro area Greater Los Angeles Area  Ranked 3rd  - Total 158,302 sq mi (410,000 km²)  - Width 250 miles (400 km)  - Length 770 miles (1,240 km)  - % water 4. ... Trumpet highway interchange near Arnhem, Netherlands Source and ©: picture archive of the ministry of traffic (V&W), Netherlands, 1984. ... Trumpet highway interchange near Arnhem, Netherlands Source and ©: picture archive of the ministry of traffic (V&W), Netherlands, 1984. ... Arnhem ( ) (South Guelderish: Èrnem) is a city and municipality in the east of the Netherlands, and capital of province Gelderland. ... A cloverleaf interchange is a two-level interchange in which right turns (in countries that drive on the left) are handled by loop ramps. ... The parclo interchange (short for partial cloverleaf interchange) is a successor to the cloverleaf interchange. ... Motorway symbol in UK, France and Ireland. ... The M25 motorway looking south between junctions 14 and 15, near Heathrow Airport. ... The M40 motorway is a motorway in the English transport network that connects London to Birmingham. ... This article is about the capital of England and the United Kingdom. ... Wikimedia Commons has media related to: Interstate 64 Interstate 64 (abbreviated I-64) is an Interstate Highway in the eastern United States. ... Interstate 295 (abbreviated I-295) is an eastern bypass of Richmond and Petersburg as well as a northern bypass of Richmond. ... Nickname: Motto: Sic Itur Ad Astra (Thus do we reach the stars) Location in the Commonwealth of Virginia Coordinates: , Country State County Independent City Government  - Mayor L. Douglas Wilder (I) Area  - City 62. ... A stack interchange is a free-flowing junction between two or more roads that allows turning in all directions. ... A permanent, separated high-occupancy vehicle lane on I-91 in Connecticut A high occupancy vehicle (or HOV) is any vehicle with a driver and one or more (or sometimes two or more, or three or more) passengers. ... Interstate 105 (abbreviated I-105) is an interstate highway that runs east-west in southern Los Angeles County, California. ... “Harbor Freeway” redirects here. ... Los Angeles County is a county in California and is the most populous county in the United States. ... NIMBY (an acronym of Not In My Back Yard) describes the phenomenon in which residents oppose a development as inappropriate for their local area, but by implication do not oppose such development in anothers. ... This article does not cite any references or sources. ... Interstate 696 (abbreviated I-696) is an interstate highway entirely within the U.S. state of Michigan. ... Mound Rd. ... Country United States State Michigan County Macomb County Incorporated 1957 Government  - Type Council-Strong Mayor  - Mayor Mark A. Steenbergh Area  - City  34. ... Interstate 95 is 42 miles long in the state of Rhode Island. ... U.S. Route 6 is a main route of the U.S. Highway system, running east-northeast from Bishop, California to Provincetown, Massachusetts. ... “Providence” redirects here. ... Wikimedia Commons has media related to: Interstate 4 An old shield in Orlando, Florida Interstate 4 (abbreviated I-4) is a 132. ... This article does not cite any references or sources. ... Nickname: Location in Hillsborough County and the state of Florida. ... Interstate 787 (abbreviated I-787) is a 9. ... United States Highway 9 is a north-south United States highway in the states of Delaware, New Jersey, and New York in the United States. ... United States Highway 20 is an east-west United States highway. ... Location in Albany County and the State of New York Coordinates: , Country United States State New York County Albany Founded 1614 Incorporated 1686 Government  - Mayor Gerald D. Jennings (D) Area  - City  21. ...

  • A variation appropriate when the freeways meet at an angle is the cloverdirectional interchange, which has cloverleafs for the sharp left turns (less than 270° turning) and adjacent semi-directional ramps for the gentle left turns, one inside and one outside the junction. This design is compact and has no serious drawbacks. Other variations of half-cloverleaf-half-directional interchanges include the cloverstack (in which the stack ramps pass over the cloverleaf loop ramps) and the cloverturbine (where two turbine ramps surround the cloverleaf ramps. Other variations have three directional ramps and one cloverleaf loop.

A junction with two adjacent cloverleafs is sub-optimal and will be the result of a previous junction improvement subject to land restriction. There are also variations with three cloverleaf loops and one directional ramp (usually a turbine ramp).

  • A trumpet is an interchange traditionally used where one freeway terminates at another freeway; it involves at least one loop ramp connecting traffic either entering or leaving the terminating freeway with the far lanes of the continuous freeway. These junctions are also useful for toll roads as they concentrate all entering and leaving traffic in a single stretch of road, where toll booths can be installed. Double Trumpet interchanges can usually be found when a toll road meets another toll road or a freeway.
  • A Directional T provides for high-speed ramps in all directions at a three-way interchange. A semi-directional T does the same, but some of the splits and merges are switched to avoid ramps to and from the passing lane.
  • Hybrids, variations and rare types

This article or section does not cite any references or sources. ... This article or section does not cite any references or sources. ... Interstate 80 (Eastshore Freeway) in Berkeley, California: a typical American freeway (MUTCD definition) A freeway, also known as a highway, superhighway, autoroute, autobahn, autostrada, dual carriageway, expressway, Autosnelweg or motorway, depending on the country of discussion, is a type of road designed for safer high-speed operation of motor vehicles... Diagram showing lanes and road layout, with Irish road markings. ...

Between a freeway and a non-freeway road

  • Diamond interchange
  • Cloverleaf interchange
  • Parclo interchange (partial cloverleaf - sometimes called a folded diamond when only four ramps, in two quadrants, are used)
  • Single Point Urban Interchange
  • Roundabout interchange--this uses a single roundabout or traffic circle which spans the freeway with two over/underpasses (either above or below the freeway). These are very common in the UK, Ireland and France, but almost unknown in the rest of Europe and the United States. Such junctions can be improved by adding a flyover for straight-through traffic on the non-freeway, creating a stacked roundabout.
  • Dumbbell interchange - this is similar to a diamond except that it uses roundabouts rather than signals or stop signs where the ramps meet the non-freeway road.
  • Inner diamond interchange -- this type of interchange allows opposing left turns to proceed concurrently where the ramps meet the surface street due to all four ramps meeting at a single intersection either above or below the freeway median, just as if it were an intersection of two surface streets. However, all of the ramps enter and exit the freeway from the innermost passing lanes, creating the potential for confusion to people not familiar with the area. The only known freeways in the U.S. to have such an interchange are Interstate 290 in Chicago, Illinois at the Austin Avenue and Harlem Avenue interchanges, Interstate 244 in Tulsa, Oklahoma at the Sheridan Avenue and Memorial Drive interchanges, and New York State Routes 9A, 100 at 117, and U.S. Route 422 (Benjamin Franklin Highway) at Bingaman St/E. Lancaster Ave in Reading, Pennsylvania.

A typical diamond interchange A diamond interchange is a common type of road junction. ... A cloverleaf interchange is a two-level interchange in which right turns (in countries that drive on the left) are handled by loop ramps. ... The parclo interchange (short for partial cloverleaf interchange) is a successor to the cloverleaf interchange. ... A typical Single Point Urban Interchange. ... A roundabout interchange is an interchange between a freeway and a minor road. ... A roundabout or rotary is a type of road junction (or traffic calming device) at which traffic enters a stream around a central island after first yielding (giving way) to the circulating traffic. ... Columbus Circle, New York City, NY; site of the first traffic circle in the United States completed in 1905 DeSoto Fountain sits in the center of a traffic circle in the city of Coral Gables, Florida. ... For other uses, see Europe (disambiguation). ... Route 9A is a 47. ... Junction Location I-87 0. ... Junction Location US-9 0. ... This U.S. Highway article needs to be cleaned up to conform to both a higher standard of article quality and accepted design standards outlined in the WikiProject U.S. Highways. ... , Reading (IPA:) is the county seat of Berks County, Pennsylvania and the center of the Greater Reading Area. ...

See also

Wikimedia Commons has media related to:
Road junctions

Image File history File links Commons-logo. ... A free-flow interchange is an interchange in which all roads are grade-separated, and where no movement from one road to another requires the driver to stop for traffic (for example, the interchange may not include traffic lights or roundabouts). ... An example of a four-level stack interchange in the Netherlands. ... A junction, when used in the context of traffic is a place where several traffic routes cross, eg. ... In the field of road transport, an intersection is a road junction where two or more roads either meet or cross at grade (they are at the same level). ... An unused highway may reference a highway that was partially or fully constructed but was unused. ...

External links

Types of road junctions
Interchanges
(grade separated)
Cloverleaf - Diamond - Directional T - Diverging diamond - Parclo - Trumpet
SPUI - Stack - Three-level diamond - Raindrop - Roundabout interchange - Quadrant roadway
Intersections
(at-grade)
Box junction - Continuous flow - Hook turn - Jughandle - Michigan left
Quadrant roadway - Roundabout - Superstreet - 3-way junction - Traffic circle - Bowtie

  Results from FactBites:
 
Interchange (road) - Wikipedia, the free encyclopedia (1382 words)
In the field of road transport, an interchange is a road junction that utilizes grade separation, and one or more ramps, to permit traffic on at least one road to pass through the junction without crossing any other traffic stream.
A highway ramp (as in exit ramp and entrance ramp) or slip road is a short section of road which allows vehicles to enter or exit a freeway (motorway).
A trumpet is an interchange traditionally used where one freeway terminates at another freeway; it involves at least one loop ramp (for traffic leaving the terminating freeway) whose overpass is shared by traffic connecting to the terminating freeway.
Interchange - Wikipedia, the free encyclopedia (303 words)
In the UK an interchange is a transport node for more than one form of transport; see also intermodal passenger transport.
In Australian rules football, interchange refers to a group of players in a sporting team that can be subsituted into a match, replacing players coming off the ground.
The level of interchange is determined by many different factors according to the way the transaction occurred and the type of card used.
  More results at FactBites »

 
 

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