The significant engineering feat involved launching the final section of the 4750-tonne structure above the north and southbound carriageway at junction 4/4a. Giant hydraulic jacks were used to position the viaduct while traffic continued to flow below, minimising disruption for motorists.
This milestone means both M6 South viaducts are now structurally complete. The east deck, completed in 2025, will carry high-speed trains towards London's Old Oak Common and Euston stations. The west deck, moved into place on Saturday, 24th October, will serve trains heading to Birmingham's Curzon Street Station and northern destinations including Manchester, Liverpool, and Glasgow.
Constructed from weathering steel and supported by concrete piers, the parallel viaducts stand just 100 millimetres apart. Raised embankments will be formed on either side. Both structures are 320 metres long, with the west deck assembled and launched in four stages and the east deck in three, adapted to site constraints.
The launch process involved adding steel sections to the rear of the structure and propelling it forward using strand jacks. The weight of the deck is fully supported on concrete piers at either side of the carriageway during the final push, allowing traffic to flow.
“"These viaducts straddle some of the busiest sections of motorway in the country, which is why we adopt innovative techniques that allow construction to continue without closing the carriageway whenever we can. We have made great progress this year and I thank motorists and local communities for their patience."
Engineers from HS2’s construction partner, Balfour Beatty VINCI, completed the final launch of the west deck in nine hours, moving the steel deck 76 metres at an average speed of twelve metres per hour. While the M6 remained open, the M42 M6 link road was closed for a safety exclusion zone and reopened 25 hours ahead of schedule on Saturday, 24th October.
“"Two neighbouring viaducts that run parallel to each other now span the busy M6 motorway near Chelmsley Wood, after the west deck was safely and successfully moved into its final position over the weekend. It’s a huge moment for Balfour Beatty VINCI and HS2, concluding a major programme of work above the M6 – in extremely challenging weather conditions."
Parapet installation works for the Water Orton viaduct above the M42 were postponed due to strong winds. This has rescheduled closures for J6 to 9 northbound and J9 to 7 southbound from Friday, 30th October to Monday, 2 November 2026. In 2027, HS2's motorway construction will focus on a rail-over-road structure near Coleshill.
