An overpass is a bridge
A bridge is a structure built to span physical obstacles such as a body of water, valley, or road, for the purpose of providing passage over the obstacle...

, road
A road is a thoroughfare, route, or way on land between two places, which typically has been paved or otherwise improved to allow travel by some conveyance, including a horse, cart, or motor vehicle. Roads consist of one, or sometimes two, roadways each with one or more lanes and also any...

, railway or similar structure
Structure is a fundamental, tangible or intangible notion referring to the recognition, observation, nature, and permanence of patterns and relationships of entities. This notion may itself be an object, such as a built structure, or an attribute, such as the structure of society...

 that crosses over another road or railway. An overpass and underpass together form a grade separation
Grade separation
Grade separation is the method of aligning a junction of two or more transport axes at different heights 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...


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
At-grade intersection
An at-grade intersection is a junction at which two or more transport axes cross at the same level .-Traffic management:With areas of high or fast traffic, an at-grade intersection normally requires a traffic control device such as a stop sign, traffic light or railway signal to manage conflicting...

. 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
Cloverleaf interchange
A cloverleaf interchange is a two-level interchange in which left turns, reverse direction in left-driving regions, are handled by ramp roads...

 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.


A pedestrian overpass
Pedestrian separation structure
A pedestrian separation structure is any structure that removes pedestrians from a vehicle roadway. This creates a road junction where vehicles and pedestrians do not interact.This can be considered a type of grade separation structure on the road....

 allows pedestrians safe crossing over busy roads without impacting traffic.

First railroad flyover

The world's first railroad flyover was constructed in 1843 by the London and Croydon Railway
London and Croydon Railway
The London and Croydon Railway was an early railway which operated between London and Croydon in England. It was opened in 1839 and in July 1846 it merged with other railways to form a part of the London Brighton and South Coast Railway ....

 at Norwood Junction railway station
Norwood Junction railway station
Norwood Junction railway station is in South Norwood in the London Borough of Croydon in south London, in Travelcard Zone 4.The station is managed by London Overground and trains operated by Southern and London Overground .-History:...

 to carry its atmospheric railway
Atmospheric railway
An atmospheric railway uses air pressure to provide power for propulsion. In one plan a pneumatic tube is laid between the rails, with a piston running in it suspended from the train through a sealable slot in the top of the tube. Alternatively, the whole tunnel may be the pneumatic tube with the...

 vehicles over the Brighton Main Line
Brighton Main Line
The Brighton Main Line is a British railway line from London Victoria and London Bridge to Brighton. It is about 50 miles long, and is electrified throughout. Trains are operated by Southern, First Capital Connect, and Gatwick Express, now part of Southern.-Original proposals:There were no fewer...

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