NationMaster - Encyclopedia: Grade separation

Grade separation is the process of aligning a junction of two or more transport axes at different heights (grades) such that they do not disrupt the flow of traffic on one another when they cross. This is achieved by building bridges over or tunnels under the crossing site, allowing roads, railways and canals to pass another without interrupting the flow of traffic. 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. ... A junction, when used in the context of traffic is a place where several traffic routes cross, eg. ... A grade (or gradient) is the pitch of a slope, and is often expressed as a percent tangent, or rise over run. It is used to express the steepness of slope on a hill, roof, or road, where zero indicates level (with respect to gravity) and increasing numbers correlate to... This article is about the edifice (including an index to articles on specific bridge types). ... A disused railway tunnel now converted to pedestrian and bicycle use, near Houyet, Belgium A tunnel is an underground passage. ... This article or section does not cite its references or sources. ... It has been suggested that this article or section be merged with Channel (geography). ...

In North American terminology, a junction which is grade-separated is an interchange, as opposed to an intersection which is not grade-separated; a lack of grade separation is described as "at-grade". High-capacity freeway interchange in Los Angeles, California. ... 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). ...

Roads

The term is most widely applied to describe a road junction where the direct flow of traffic on one or more of the roads is not disrupted. Instead of a direct connection, traffic must use on and off ramps (United States, Australia, etc.) or slip roads (United Kingdom, Ireland, etc.) to access the other roads at the junction. The road which carries on through the junction can also be referred to as grade separated. In the field of road transport, a road junction is a place where two or more roads either meet or cross. ... In the field of road transport, a road junction is a place where two or more roads either meet or cross. ...

Typically, large freeways, highways, motorways or dual carriageways are chosen to be grade separated, through their entire length or for part of it. Grade separation drastically increases the capacity of a road compared to an identical road with at-grade junctions. For instance, it is very uncommon to find an at-grade junction on a British motorway; it is all but impossible on a U.S. Interstate Highway, though a few do exist. A freeway is a type of highway that is designed for safer high-speed operation of motor vehicles through the elimination of at-grade intersections. ... Category: ... Motorway symbol in UK, France and Ireland. ... This early German Autobahn uses a dual carriageway design. ... A complete listing of motorways in the United Kingdom. ... The Dwight D. Eisenhower National System of Interstate and Defense Highways, commonly called the Interstate Highway System, is a network of freeways (also called expressways) in the United States. ...

If traffic can traverse the junction from any direction without being forced to come to a halt, then the junction is described as fully grade separated or free-flowing.

Weaving

Weaving is a consequence of having too many grade separated junctions on a road in a short distance, where traffic wanting to leave the grade-separated road at the next junction has to fight for road space with traffic which has just entered from the previous one.

This situation is most prevalent either where junction design places the on-slip to the road before the off-slip at a junction (for example, the cloverleaf interchange), or in urban areas with lots of close-spaced junctions (the Coventry ring road is a particularly notorious example). 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 Precinct in Coventry city centre. ... A beltway (American English), ring road or orbital motorway (British English) is a circumferential highway found around many cities. ...

Weaving can be alleviated by using collector/distributor roads to separate entering and exiting traffic. 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. ...

Types

These junctions connect two roads, but only one is fully grade-separated: A stack interchange is a free-flowing junction between two or more roads that allows turning in all directions. ... A cloverleaf interchange is a two-level interchange in which right turns (in countries that drive on the left) are handled by loop ramps. ...

These junctions connect three or more roads: A typical diamond interchange A diamond interchange is a common type of road junction. ... The parclo interchange (short for partial cloverleaf interchange) is a successor to the cloverleaf interchange. ... A typical Single Point Urban Interchange. ... It has been suggested that Cycle facilities at roundabouts be merged into this article or section. ...

These junctions terminate one road into another: For other Spaghetti Junctions, see Spaghetti Junction (disambiguation) Spaghetti Junction (officially Gravelly Hill Interchange) is junction 6 of the M6 motorway in Birmingham, England, and is so named for its impressive system of intertwined loops and ramps. ...

High-capacity freeway interchange in Los Angeles, California. ... High-capacity freeway interchange in Los Angeles, California. ...

Railways

Attempts have been made to increase the capacity of railways by making tracks cross in a grade-separated manner, as opposed to the traditional use of flat crossings to change tracks. A grade-separated rail interchange is known as a flying junction and one which is not a level junction. In U.S. railroad practice, a flying junction is a track configuration in which merging or crossing railroad lines provide track connections with each other without requiring trains to cross over in front of opposing traffic. ... In U.S. railroad practice, a flying junction is a track configuration in which merging or crossing railroad lines provide track connections with each other without requiring trains to cross over in front of opposing traffic. ... In U.S. railroad practice, a level junction (or in the United Kingdom a flat junction) is a railway junction that has a track configuration in which merging or crossing railroad lines provide track connections with each other that require trains to cross over in front of opposing traffic at...

One of the earliest examples of this type was one the Nickel Plate Road through Cleveland, Ohio, United States, completed in 1910; one of the most recent and complex is the Sandgate Flyover at Sandgate, New South Wales, Australia. The most frequent use of flying junctions are on the former Pennsylvania Railroad main lines that are now part of the Northeast Corridor and Keystone Corridor owned by Amtrak. The most complex of the junctions, near the Philadelphia Zoo, handles train traffic for Amtrak, SEPTA, New Jersey Transit, Norfolk Southern, CSX Transportation, and Conrail. Categories: Defunct railroad companies of the United States | Illinois railroads | Indiana railroads | Missouri railroads | New York railroads | Ohio railroads | Pennsylvania railroads ... Nickname: The Forest City Motto: Progress and Prosperity Location in Cuyahoga County, Ohio, USA Coordinates: Country United States State Ohio County Cuyahoga Founded 1796 Incorporated 1836 Mayor Frank G. Jackson (D) Area - City 82. ... 1910 (MCMX) was a common year starting on Saturday (see link for calendar) of the Gregorian calendar or a common year starting on Sunday of the 13-day slower Julian calendar. ... A - Rail Flyover at Sandgate Old Arrangements, New South Wales) A flyover is to be constructed at Sandgate, New South Wales. ... Sandgate can be: Sandgate, Kent Sandgate Castle Sandgate, Queensland Sandgate, New South Wales, a suburb of Newcastle, New South Wales Sandgate, Vermont This is a disambiguation page — a navigational aid which lists other pages that might otherwise share the same title. ... Capital Sydney Government Const. ... 1893 map The Pennsylvania Railroad (AAR reporting mark PRR) was an American railroad that was founded in 1846 and merged in 1968 into Penn Central Transportation. ... Most of the NEC is owned by Amtrak (those sections shown in red). ... For details about the Amtrak-owned piece, see Philadelphia to Harrisburg Main Line. ... Acela Express in West Windsor, NJ Amtrak Cascades service with tilting Talgo trainsets in Seattle, Washington Amtrak train in downtown Orlando, Florida Amtrak (AAR reporting marks AMTK and AMTZ) is the brand name of the National Railroad Passenger Corporation, created on May 1, 1971 as the United States intercity passenger... The Philadelphia Zoo, located in Fairmount Park on the west bank of the Schuylkill River in Philadelphia, was the first zoo in the United States. ... For the abbreviation SEPTA, see SEPTA. A septum, in general, is a wall separating two cavities or two spaces containing a less dense material. ... The New Jersey Transit Corporation (NJ Transit) is a statewide public transportation system serving the state of New Jersey, and Orange and Rockland counties in New York. ... Norfolk Southern Corporation (AAR reporting mark NS) NYSE: NSC is a US publicly-traded stock corporation based in Norfolk, Virginia. ... CSX Transportation (AAR reporting mark CSXT) is a Class I railroad in the United States, owned by the CSX Corporation. ... Conrail 6114, a GE Dash 8-40CW, leads a train westbound out of Altoona, Pennsylvania. ...

Personal rapid transit

Personal rapid transit systems also exhibit grade separation where the transit guideway has been elevated to cross road other transport axes throughout its network. Artists rendering of SkyTran, a proposed PRT design. ...

Advantages and disadvantages

Roads with grade separation generally allow traffic to move freely, with less interruptions, and at higher overall speeds; hence why speed limits are typically higher for grade-separated roads. In addition, less conflict between traffic movements reduces the capacity for accidents. A road speed limit is the maximum speed allowed by law for road vehicles. ... A car accident in Yate, near Bristol, England, in July 2004. ...

Grade-separated junctions are however large, and costly. Their height can be obtrusive, and combined with the large traffic volumes that grade-separated roads attract, tend to make them unpopular to nearby landowners and residents. New grade-separated road plans can receive significant opposition from NIMBY groups for these reasons. The United States suffered an extended period of anti-grade separation protests known as the freeway and expressway revolts. NIMBY (an initialism for Not In My Back Yard) is an acronym for the phenomenon in which residents oppose a development as inappropriate for their local area, but by implication do not oppose such development in anothers. ... The Freeway Revolts (sometimes expressway revolts) refer to a phenomenon encountered in the United States in the 1960s and 1970s, where planned freeway construction in many U.S. cities was halted due to widespread public opposition; especially of those whose neighborhoods would be disrupted or displaced by the proposed freeways. ...

Grade-separation is expensive, time-consuming and requires significant engineering effort compared to provision of an at-grade intersection.

See also

Categories: Junction types | Transport infrastructure An intersection of roads. ... High-capacity freeway interchange in Los Angeles, California. ... A cloverleaf interchange is a two-level interchange in which right turns (in countries that drive on the left) are handled by loop ramps. ... A typical diamond interchange A diamond interchange is a common type of road junction. ... High-capacity freeway interchange in Los Angeles, California. ... Plan of rejected diverging diamond interchange in Findlay, Ohio A diverging diamond interchange is a rare form of diamond interchange in which the two directions of traffic on the non-freeway road cross to the opposite side on both sides of the bridge at the freeway. ... The parclo interchange (short for partial cloverleaf interchange) is a successor to the cloverleaf interchange. ... High-capacity freeway interchange in Los Angeles, California. ... Schematic of a freeway-under SPUI in a country where traffic drives on the right. ... A stack interchange is a free-flowing junction between two or more roads that allows turning in all directions. ... Three-level diamond diagram A three-level diamond is a type of highway interchange where through traffic on both main roads is grade-separated from intersections which handle transferring traffic. ... 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). ... A box junction is a traffic control measure designed to prevent gridlock at busy road junctions. ... A continuous flow intersection, also called a CFI, is an at-grade intersection that moves the turn conflict (to the left where traffic drives on the right and vice versa) out of the main intersection. ... A crossroads (the word rarely appears in singular) is a road junction, where two or more roads meet (there are three or more arms). ... Hook turn sign, Melbourne A hook turn is a special right-turn manouvre required in parts of Melbourne, Australia. ... A typical jughandle setup, with one standard jughandle and one reverse jughandle A jughandle is a type of ramp or slip road that changes the way traffic turns left (when driving on the right). ... A typical Michigan left setup. ... Sketch of a Quadrant Roadway Intersection A quadrant roadway intersection includes an extra roadway between two legs of the intersection. ... It has been suggested that Cycle facilities at roundabouts be merged into this article or section. ... At a superstreet, all traffic on the side road must turn right, where it can access a U-turn ramp. ... T Intersection Sign in Taiwan with no more road straight ahead T Intersection Sign in Taiwan with side road on the left T Intersection Sign in Taiwan with side road on the right Y Intersection Sign in Taiwan A 3-way junction (or 3-way intersection) is a type of... A traffic circle is an intersection with a circular shape and, usually, a central island. ...

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