An overpass (called an overbridge or flyover in the

United Kingdom The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom (UK) or Britain, is a country in Europe, off the north-western coast of the continental mainland. It comprises England, Scotland, Wales and North ...

and some other

Commonwealth A commonwealth is a traditional English term for a political community founded for the common good. Historically, it has been synonymous with "republic". The noun "commonwealth", meaning "public welfare, general good or advantage", dates from the ...

countries) is a

bridge A bridge is a structure built to span a physical obstacle (such as a body of water, valley, road, or rail) without blocking the way underneath. It is constructed for the purpose of providing passage over the obstacle, which is usually somethi ...

road A road is a linear way for the conveyance of traffic that mostly has an improved surface for use by vehicles (motorized and non-motorized) and pedestrians. Unlike streets, the main function of roads is transportation. There are many types of ...

railway Rail transport (also known as train transport) is a means of transport that transfers passengers and goods on wheeled vehicles running on rails, which are incorporated in tracks. In contrast to road transport, where the vehicles run on a pre ...

or similar structure that crosses over another road or railway. An ''overpass'' and '' underpass'' together form a

grade separation In civil engineering (more specifically highway 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 tran ...

Stack interchange 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 e ...

s are made up of several overpasses.

History

The world's first railroad flyover was constructed in 1843 by the

London and Croydon Railway The London and Croydon Railway (L&CR) was an early railway in England. It opened in 1839 and in February 1846 merged with other railways to form the London Brighton and South Coast Railway (LB&SCR). Origins The Croydon line and other railways Th ...

Norwood Junction railway station Norwood Junction railway station is a National Rail station in South Norwood in the London Borough of Croydon, south London and is in Travelcard Zone 4. It is down the line from . The station is managed by London Overground and trains are oper ...

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 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 a ...

. Traffic engineers usually refer to the latter as a ''

''. 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

pedestrian overpass A footbridge (also a pedestrian bridge, pedestrian overpass, or pedestrian overcrossing) is a bridge designed solely for pedestrians.''Oxford English Dictionary'' While the primary meaning for a bridge is a structure which links "two points at a ...

allows traffic to pass without affecting

pedestrian A pedestrian is a person traveling on foot, whether walking or running. In modern times, the term usually refers to someone walking on a road or pavement, but this was not the case historically. The meaning of pedestrian is displayed with ...

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 crossing over or under using an Overpass#Railway, overpass ...

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), also known as heavy rail or metro, is a type of high-capacity public transport generally found in urban areas. A rapid transit system that primarily or traditionally runs below the surface may be c ...

systems use complete grade separation of their

rights of way Right of way is the legal right, established by grant from a landowner or long usage (i.e. by Easement#Easement by prescription, prescription), to pass along a specific route through property belonging to another. A similar ''right of access'' ...

to avoid traffic interference with frequent and reliable service. Railroads also use balloon loops and flying junctions instead of

flat junction A level junction (or in the United Kingdom a flat crossing) 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 ...

s, 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 coast of northeastern 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 ci ...

Cumberland Highway.jpg, Cumberland Highway overpasses a street in

Sydney Sydney ( ) is the capital city of the state of New South Wales, and the most populous city in both Australia and Oceania. Located on Australia's east coast, the metropolis surrounds Sydney Harbour and extends about towards the Blue Mountain ...

Los Angeles Freeway Interchange.jpg, A high-capacity

stack interchange 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 e ...

: the

Judge Harry Pregerson Interchange The Judge Harry Pregerson Interchange is a stack interchange near the Athens and Watts communities of Los Angeles, California, United States. It is the interchange of the following routes: * * The interchange permits traffic entering the interc ...

Los Angeles Los Angeles ( ; es, Los Ángeles, link=no , ), often referred to by its initials L.A., is the largest city in the state of California and the second most populous city in the United States after New York City, as well as one of the world' ...

SandgateRailOverpass.JPG,

Sandgate Flyover The Sandgate Flyover is a grade-separated railway flyover that carries the Main North line across the Kooragang Island line, located in Sandgate, in the City of Newcastle local government area of New South Wales, Australia. Description Situa ...

, 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 Taipei (), officially Taipei City, is the capital and a special municipality of the Republic of China (Taiwan). Located in Northern Taiwan, Taipei City is an enclave of the municipality of New Taipei City that sits about southwest of the n ...

. Overpass-NYThruway-355.25-c.jpg,

New York State Thruway {{Infobox road , state = NY , type = NYST , alternate_name = Governor Thomas E. Dewey Thruway , maint = NYSTA , map = {{maplink, frame=yes, plain=yes, frame-align=center, frame-width=290, type=line, stroke-width=2, type2=line, from2=New Yor ...

overpass Pedestrian overpass.JPG, Pedestrian overpass, I-64, St. Louis,

Missouri Missouri 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 is bordered by eight states (tied for the most with Tennessee ...

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

Sion Panvel Highway The Sion Panvel Expressway is a 25 km Indian highway located entirely in the state of Maharashtra, that connects Sion in Mumbai with Panvel, via Navi Mumbai. It is one of the busiest and most important roads in the Mumbai Metropolitan Reg ...

India India, officially the Republic of India (Hindi: ), is a country in South Asia. It is the seventh-largest country by area, the second-most populous country, and the most populous democracy in the world. Bounded by the Indian Ocean on the so ...

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 in

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 has a population of 107,337. The city was named after David Burbank, w ...

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

Athens Athens ( ; el, Αθήνα, Athína ; grc, Ἀθῆναι, Athênai (pl.) ) is both the capital and largest city of Greece. With a population close to four million, it is also the seventh largest city in the European Union. Athens dominates ...

General Holmes Drive from aircraft window.jpg, Sydney airport taxiway going over a major road.

References