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.Stack interchanges are made up of many overpasses.

History

The world's first railroad overpass 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.

The first overpass in India was opened on 14 April 1965 at Kemps Corner in Mumbai. The 48 feet (15 m) long bridge was constructed in about seven months by Shirish Patel at a cost of ₹17.5 lakh (equivalent to ₹6.1 crore or US$900,000 in 2016).

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.