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Grade separation

Type of road junction / From Wikipedia, the free encyclopedia

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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 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 (or overpasses, also called flyovers), tunnels (or underpasses), or a combination of both can be built at a junction to achieve the needed grade separation.

An example of the potential complexity of grade separation, seen in the Jane Byrne Interchange in Chicago
Seven various overpasses for grade separation in Spain near Barcelona
Rail-rail grade separation in Xiaoshan, China
The concept of grade separation includes all transport modes, such as a simple pedestrian bridge over rail tracks.

In North America, a grade-separated junction may be referred to as a grade separation[1][2] or as an interchange – in contrast with an intersection, at-grade, a diamond crossing or a level crossing, which are not grade-separated.