An overpass, called an overbridge or flyover (for a road only) in the United Kingdom and some other Commonwealth countries, is a bridge, road, railway or similar structure that is over another road or railway. An overpass and underpass together form a grade separation. [1] Stack interchanges are made up of several overpasses.
The world's first railroad flyover was constructed in 1843 by the London and Croydon Railway at Norwood Junction railway station to carry its atmospheric railway vehicles over the Brighton Main Line. [2]
In North American usage, a flyover is a high-level overpass, built above main overpass lanes, or a bridge built over what had been an at-grade intersection. Traffic engineers usually refer to the latter as a grade separation . A flyover may also be an extra ramp added to an existing interchange, either replacing an existing cloverleaf loop (or being built in place of one) with a higher, faster ramp that eventually bears left, but may be built as a right or left exit.
A cloverleaf or partial cloverleaf contains some 270 degree loops, which can slow traffic and can be difficult to construct with multiple lanes. Where all such turns are replaced with flyovers (perhaps with some underpasses) only 90 degree turns are needed, and there may be four or more distinct levels of traffic. Depending upon design, traffic may flow in all directions at or near open road speeds (when not congested). For more examples, see Freeway interchange.
A pedestrian overpass allows traffic to pass without affecting pedestrian safety.
Railway overpasses are used to replace level crossings (at-grade crossings) as a safer alternative. Using overpasses allows for unobstructed rail traffic to flow without conflicting with vehicular and pedestrian traffic. Rapid transit systems use complete grade separation of their rights of way to avoid traffic interference with frequent and reliable service.
Railroads also use balloon loops and flying junctions instead of flat junctions, as a way to reverse direction and to avoid trains conflicting with those on other tracks.
An intersection or an at-grade junction is a junction where two or more roads converge, diverge, meet or cross at the same height, as opposed to an interchange, which uses bridges or tunnels to separate different roads. Major intersections are often delineated by gores and may be classified by road segments, traffic controls and lane design.
The Queen Elizabeth Way (QEW) is a 400-series highway in the Canadian province of Ontario linking Toronto with the Niagara Peninsula and Buffalo, New York. The highway begins at the Canada–United States border on the Peace Bridge in Fort Erie and travels 139.1 kilometres (86.4 mi) around the western end of Lake Ontario, ending at Highway 427 as the physical highway continues as the Gardiner Expressway into downtown Toronto. The QEW is one of Ontario's busiest highways, with an average of close to 250,000 vehicles per day on some sections.
A cloverleaf interchange is a two-level interchange in which all turns are handled by slip roads. To go left, vehicles first continue as one road passes over or under the other, then exit right onto a one-way three-fourths loop ramp (270°) and merge onto the intersecting road. The objective of a cloverleaf is to allow two highways to cross without the need for any traffic to be stopped by traffic lights. The limiting factor in the capacity of a cloverleaf interchange is traffic weaving.
King's Highway 427, also known as Highway 427 and colloquially as the 427, is a 400-series highway in the Canadian province of Ontario that runs from the Queen Elizabeth Way (QEW) and Gardiner Expressway in Toronto to Major Mackenzie Drive in Vaughan. It is Ontario's second busiest freeway by volume and the third busiest in North America, behind Highway 401 and Interstate 405 in California. Like Highway 401, a portion of the route is divided into a collector-express system with twelve to fourteen continuous lanes. Notable about Highway 427 are its several multi-level interchanges; the junctions with the QEW/Gardiner Expressway and Highway 401 are two of the largest interchanges in Ontario and were constructed between 1967 and 1971, while the interchanges with Highway 409 and Highway 407 were completed in 1992 and 1995, respectively.
In civil engineering, grade separation is a method of aligning a junction of two or more surface transport axes at different heights (grades) so that they will not disrupt the traffic flow on other transit routes when they cross each other. The composition of such transport axes does not have to be uniform; it can consist of a mixture of roads, footpaths, railways, canals, or airport runways. Bridges, tunnels, or a combination of both can be built at a junction to achieve the needed grade separation.
A single-point urban interchange, also called a single-point interchange (SPI) or single-point diamond interchange (SPDI), is a type of highway interchange. The design was created in order to help move large volumes of traffic through limited amounts of space efficiently.
A partial cloverleaf interchange or parclo is a modification of a cloverleaf interchange.
In the field of road transport, an interchange or a grade-separated junction is a road junction that uses grade separations to allow for the movement of traffic between two or more roadways or highways, using a system of interconnecting roadways to permit traffic on at least one of the routes to pass through the junction without interruption from crossing traffic streams. It differs from a standard intersection, where roads cross at grade. Interchanges are almost always used when at least one road is a controlled-access highway or a limited-access divided highway (expressway), though they are sometimes used at junctions between surface streets.
Reid Highway is a 23-kilometre (14 mi) east-west highway and partial freeway in the northern suburbs of Perth, Western Australia, linking North Beach with Middle Swan. As part of State Route 3, it forms half of Perth's outer ring road along with Roe Highway, which it joins onto at its eastern terminus.
A directional interchange, colloquially known as a stack interchange, is a type of grade-separated junction 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, have the highest vehicle capacity, and vehicles travel shorter distances when compared to different types of interchanges.
A junction is where two or more roads meet.
A subway, also known as an underpass, is a grade-separated pedestrian crossing running underneath a road or railway in order to entirely separate pedestrians and cyclists from motor or train traffic.
The Third Ring Road, or The Third Ring, is a beltway around central Moscow, Russia, located between the Garden Ring in the city centre and the Moscow Ring Road (MKAD).
In the field of road transport, a turnaround is a type of junction that allows traffic traveling in one direction on a road to efficiently make a U-turn typically without backing up or making dangerous maneuvers in the middle of the traffic stream. While many junction types permit U-turns, the term turnaround often applies to road junctions built specifically for this purpose.
Interstate 70 (I-70) is an Interstate Highway that is located in the Commonwealth of Pennsylvania in the United States. It runs east to west across the southwest part of Pennsylvania and serves the southern fringe of the Pittsburgh metropolitan area.
County Route 97 (CR 97) is a north–south expressway in Suffolk County, New York, in the United States. It runs from an intersection with CR 85 in Bayport just west of Blue Point on the south shore of Long Island to a junction with New York State Route 25A (NY 25A) in Stony Brook on the island's north shore. A 5-mile (8.0 km) section of the route from Holbrook to Farmingville is a freeway, while the remainder of the road is an expressway with at-grade intersections. CR 97 is known as Nicolls Road, named after 17th-century colonial Governor Richard Nicolls.
An unused highway is a highway or highway ramp that was partially or fully constructed, but went unused or was later closed or part of a future expansion. An unused roadway or ramp may often be referred to as an abandoned road, ghost road, highway to nowhere, stub ramp, ghost ramp, ski jump, stub street, stub-out, or simply stub.
U.S. Route 24 (US 24) in Indiana runs east from the Illinois state line to Huntington. At Huntington, US 24 turns northeast and runs to Fort Wayne; it then runs concurrently with Interstate 69 (I-69) and I-469 to bypass the city before entering Ohio at the state line east of Fort Wayne. The segment of US 24 between Logansport and Toledo, Ohio, is part of the Hoosier Heartland Industrial Corridor project of the Intermodal Surface Transportation Efficiency Act.
The North–South Motorway is a partially complete motorway traversing the inner western suburbs of Adelaide, from Waterloo Corner in the north to Bedford Park in the south. Progressively constructed in stages since 2010, once complete it will replace the adjacent South Road as Adelaide's main north–south roadway. It will form the central section of the North–South Corridor, being flanked north and south by the Northern Expressway and Southern Expressway, respectively. It is designated part of route M2.
Terminology related to road transport—the transport of passengers or goods on paved routes between places—is diverse, with variation between dialects of English. There may also be regional differences within a single country, and some terms differ based on the side of the road traffic drives on. This glossary is an alphabetical listing of road transport terms.
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