Isa Town Gate interchange, Bahrain

The Bahrain Ministry of Works roads directorate and Hyder Consulting undertook a national transport model in 2002 in which traffic congestion was identified and future 2021 traffic flows were estimated. Strategic improvements were identified to improve traffic flow and make allowances for future increases in traffic volumes. The Isa Town Gate interchange was an existing roundabout with a five-leg junction in an urban setting with two major highways: Sheikh Salman Highway and Al Estiqlal Highway. This paper details the design of the £66 million project from concept to tender and also expands on the construction progress. Execution of the project modified the existing Isa Town Gate roundabout into a three-level grade-separated interchange. The option chosen was a three-level grade-separated junction with a free-flow flyover and underpass for the major highway routes. The existing roundabout was replaced with a complex split-traffic signalised junction accommodating all movements. The flyover consisted of two non-parallel curved bridge decks 2·4 km long of glued segmental prestressed concrete viaducts. An overhead launching gantry was specified to minimise traffic management. The underpass was designed as a diaphragm-walled U trough but was later varied to a ground-anchored solution. Construction commenced in October 2007, and is due for completion in mid-2010.