An overpass, called an overbridge or flyover (for a road only) in the United Kingdom and some other Commonwealth countries, is a

bridge A bridge is a structure built to Span (engineering), span a physical obstacle (such as a body of water, valley, road, or railway) without blocking the path underneath. It is constructed for the purpose of providing passage over the obstacle, whi ...

road A road is a thoroughfare used primarily for movement of traffic. Roads differ from streets, whose primary use is local access. They also differ from stroads, which combine the features of streets and roads. Most modern roads are paved. Th ...

railway Rail transport (also known as train transport) is a means of transport using wheeled vehicles running in railway track, tracks, which usually consist of two parallel steel railway track, rails. Rail transport is one of the two primary means of ...

or similar structure that is over another road or railway. An ''overpass'' and '' underpass'' together form a grade separation. Stack interchanges are made up of several overpasses.

History

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.

Highway and road

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.

Pedestrian

A pedestrian overpass allows traffic to pass without affecting pedestrian safety.

Railway

Railway overpasses are used to replace

level crossing A level crossing is an intersection where a railway line crosses a road, Trail, path, or (in rare situations) airport runway, at the same level, as opposed to the railway line or the road etc. crossing over or under using an Overpass#Railway, o ...

s (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 Rapid transit or mass rapid transit (MRT) or heavy rail, commonly referred to as metro, is a type of high-capacity public transport that is generally built in urban areas. A grade separation, grade separated rapid transit line below ground su ...

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.

Gallery

Overpasses in Spain.JPG, Overpasses near

Barcelona Barcelona ( ; ; ) is a city on the northeastern coast of Spain. It is the capital and largest city of the autonomous community of Catalonia, as well as the second-most populous municipality of Spain. With a population of 1.6 million within c ...

Cumberland Highway.jpg, Cumberland Highway overpasses a street in

Sydney Sydney is the capital city of the States and territories of Australia, state of New South Wales and the List of cities in Australia by population, most populous city in Australia. Located on Australia's east coast, the metropolis surrounds Syd ...

Los Angeles Freeway Interchange.jpg, A high-capacity stack interchange: the Judge Harry Pregerson Interchange in

Los Angeles Los Angeles, often referred to by its initials L.A., is the List of municipalities in California, most populous city in the U.S. state of California, and the commercial, Financial District, Los Angeles, financial, and Culture of Los Angeles, ...

SandgateRailOverpass.JPG, Sandgate Flyover, New South Wales, where two main railway lines pass over two dedicated coal lines South entrance of Zheng Qi Overpass 20110114.jpg, Zheng Qi overpass,

Taipei , nickname = The City of Azaleas , image_map = , map_caption = , pushpin_map = Taiwan#Asia#Pacific Ocean#Earth , coordinates = , subdivision_type = Country ...

Overpass-NYThruway-355.25-c.jpg, New York State Thruway overpass Pedestrian overpass.JPG, Pedestrian overpass, I-64, St. Louis,

Missouri Missouri (''see #Etymology and pronunciation, pronunciation'') is a U.S. state, state in the Midwestern United States, Midwestern region of the United States. Ranking List of U.S. states and territories by area, 21st in land area, it border ...

. This overpass is located at the St. Louis Science Center. Sion Panvel Highway Kharghar exit.jpeg, A road sign on Sion Panvel Highway in

India India, officially the Republic of India, is a country in South Asia. It is the List of countries and dependencies by area, seventh-largest country by area; the List of countries by population (United Nations), most populous country since ...

instructing travellers to use flyover for onward journey. Burbank Ave I-5 overpass under construction in Burbank, California.JPG, Overpass under construction over

Interstate 5 Interstate 5 (I-5) is the main north–south Interstate Highway System, 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 thro ...

Burbank, California Burbank is a city in the southeastern end of the San Fernando Valley in Los Angeles County, California, United States. Located northwest of downtown Los Angeles, Burbank had a Census-estimated population of 102,755 as of 2023. The city was ...

, July 2021 Athens-Kiffisia-aerial.jpg, Round overpass in

Athens Athens ( ) is the Capital city, capital and List of cities and towns in Greece, largest city of Greece. A significant coastal urban area in the Mediterranean, Athens is also the capital of the Attica (region), Attica region and is the southe ...

General Holmes Drive from aircraft window.jpg, Sydney airport taxiway going over a major road. Welcome to New Jersey Turnpike Southbound Edgewood Road Bridge 2023.jpg, Sign welcoming drivers to the New Jersey Turnpike under the Edgewood Road Bridge in Leonia, New Jersey

References

External links

* {{Infrastructure Bridges Railway buildings and structures Road infrastructure pl:Estakada