Adam Viaduct

The Adam Viaduct is an under bridge located within a longer railway embankment in Wallgate, Wigan. It was constructed in 1946 by the London, Midland and Scottish Railway, with W. K. Wallace as the chief engineer and Leonard Fairclough Limited as the contractors. The structure features reinforced pre-stressed pre-cast deck units supported by in-situ reinforced concrete piers that rest on old foundations. The east side of the viaduct has pre-cast concrete parapet units along with original concrete handrails and standards.

The viaduct consists of four spans, with the end spans measuring 29 feet 9 inches wide and the center spans measuring 29 feet 4 inches and 28 feet 6 inches wide. The deck is constructed from 'I'-beams that are 32 inches deep. The small space between the top flanges of the 'I'-beams, which support the tracks, is grouted. High-tensile tie rods, tightened by nuts at each end, connect the beams to work together under live loads.

The Adam Viaduct is recognized as the earliest pre-stressed railway bridge in England, with only examples in Switzerland predating it. The London, Midland and Scottish Railway established a pioneering research institution in 1932 at Derby, where extensive testing laboratories were built in 1935. They developed the use of pre-cast concrete in the 1930s due to its strength, durability, and cost-effectiveness, allowing for quick installation on the railway line. Although pre-stressed beams were used for emergency repairs during the war, this viaduct represents their first full-scale designed application.