J. P. Setu

J. P. Setu — formally the Digha-Sonpur Rail-cum-Road Bridge — is a twin-deck Ganges crossing connecting Digha (in northern Patna) to Sonpur (in Saran district north bank). Named after Jayaprakash Narayan, the Bihar-born Gandhian leader, the bridge consists of two parallel structures: a rail bridge (opened 2016) and an immediately adjacent road bridge (opened to public traffic in February 2017).

The rail bridge is a key link in the Patna–Sonpur–Hajipur–Muzaffarpur corridor, providing the second-shortest rail route between South and North Bihar and reducing freight transit by ~80 km via the previously circuitous Mokama-Hajipur route. The road bridge handles NH-19 traffic and ~30,000 vehicles/day.

Construction began in 2002 and dragged on for 15 years due to design revisions, contractor changes, and 2008 funding cuts. Total cost: ~₹3,000 crore between the two structures. The bridge has 36 PSC spans of 123 m each on the rail alignment, and 24 longer spans on the road alignment to accommodate a different pier spacing optimised for road loading.

A notable feature: the rail bridge piers are designed for an 18 m river-bed scour event, accounting for the Ganga's seasonal channel migration — one of the largest scour design depths used in Indian railway practice.