Mahatma Gandhi Setu (also called Gandhi Setu or Ganga Setu) is a bridge over the river Ganges connecting Patna in the south to Hajipur in the north of Bihar. Its length is 5,575 metres (18,291 ft) and it is one of the longest river bridges in India. It was inaugurated in May 1982 by the then Prime Minister, Mrs Indira Gandhi, inauguration took place at north end of the bridge located in Hajipur viewed by thousands of people.
The bridge was approved by the Central Government in 1969 and built by Gammon India Limited over a period of ten years, from 1972 to 1982 with total expenditure of Rs 87.22 crore at that time. . It was built to connect North Bihar with the rest of Bihar and part of national highway 19 (NH19). . Before this bridge was constructed, Rajendra Setu, opened in 1959, was the only link to North Bihar. Since then, the Vikramshila Setu has also been built across the Ganges. Two more rail-cum-road bridges are currently under construction, between Digha and Sonepur and at Munger.
The bridge consists 45 intermediate spans of 121.065 metres (397.19 ft) each and a span of 65.530 metres (214.99 ft) at each end. The deck provides for a 7.5 metres (25 ft) wide two lane roadway for IRC class 70 R loading with footpaths on either side. The cantilever segmental construction method was adopted to construct this mega bridge. Each span has two cantilever beams on both sides which are free to move at the ends. It has two lanes one upstream and the other downstream each with a width of around 6m. Both the lanes are also free from each other and are not connected anywhere. It was constructed by using 3 meter pre-casted parts being joined at both ends to complete the span. The Spans are connected by using a Protrusion which is free to move longitudinally also along the river flow. In upwards and downwards direction it is such that it allows vibration to transfer smoothly to the next span while vehicular movement without much discreteness.
In recent times, the bridge has been witnessing major traffic chaos and accidents due to exceeding number of vehicles passing over it and regularly over loading the structure. Bihar Government is planning to build two Pontoon bridges in parallel to it, in order to ease traffic.