The Port Eglinton Viaduct carries a new 6 lane section of the M74 motorway over the West Coast Mainline railway in Glasgow, Scotland.  It has a main span of 138m and a total length of 750m.  There are two 3 lane carriageways that are structurally independent and each carriageway is supported by a pair of open-top steel box girders, curved both in plan and in elevation and with a composite reinforced concrete deck slab.  The two separate carriageway structures were assembled to one side of the span and then launched 170m across the railway into final position using strand jacks for movement control and rollers for support and guidance. 2 No computer controlled 418 tonne capacity strand jacks were used for the operation, one to pull and one to restrain, with both strand jacks gripping a single line of strand as shown in the photograph below. The first carriageway structure was launched into final position during a series of 24 No 2.5 hr night time possessions of the railway line in February 2010. The second carriageway structure was launched in late May 2010.. Each launched carriageway structure is 200m long and weighs over 4000 tonnes.  DLT had 2 subcontracts to Cleveland Bridge UK, who supplied and erected the steelwork for main contractor Interlink JV.  The first was to provide construction engineering services associated with the launch, and the second was to supply strand jack equipment, operators and the launch master.  The engineering services included 3D FEA of the structures at all stages of the launch, design of all temporary works including the articulated roller support and guidance systems, and preparation of the engineering method statement and control data.  The structures were moved by back-to-back 418t pulling and restraining strand jacks operating on a continuous cable running from one end of the launched structure to the other.