Overpass
An overpass (called a flyover in the United Kingdom and most Commonwealth countries) is a bridge, road, railway or similar structure that crosses over another road or railway. An overpass and underpass together form a grade separation.[1] Stack interchanges are made up of many overpasses.
North America
In North America, 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 bears left. Such a ramp may be built as a right or left exit. A cloverleaf or partial cloverleaf contains some 270 degree loops, slowing traffic and such loops are difficult to construct with more than 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.
Pedestrian
A pedestrian overpass allows pedestrians safe crossing over busy roads without impacting traffic.
Railway
Railway overpasses are used in North America to replace at-grade crossing as a safer alternative. Using overpasses allows for unobstructed rail traffic flow from mixing with vehicular and pedestrian traffic.
First railroad flyover
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]
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Overpasses near Barcelona -
Overpass in Washington, D.C. -
Sandgate Flyover, New South Wales, where two main railway lines pass over two dedicated coal lines -
Flyover on Keelung Road in Taipei -
New York State Thruway overpass -
Pedestrian overpass, I-64, St. Louis, Missouri. This overpass is located at the St. Louis Science Center.
See also
References
- ^ Henry K. Evans (1950). "Read the ebook Traffic engineering handbook by Institute of Traffic Engineers". ENGINEERING HANDBOOK, Second Edition 1950. New Haven, Connecticut: Institute of Traffic Engineers. Retrieved 2010-10-09.
- ^ Turner, J.T. Howard (1977). The London Brighton and South Coast Railway 1. Origins and formation. London: Batsford. p. 249. ISBN 0-7134-0275-X.
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