HS2’s construction partner Balfour Beatty VINCI has completed the second of two viaducts carrying the new railway over the M6 at junctions 4/4a near Chelmsley Wood. The final section of the 4,750-tonne west deck was pushed into position above the north and southbound carriageways using giant hydraulic jacks, while vehicles continued to travel below.
The west deck will carry trains towards Birmingham Curzon Street and destinations in the north, including Manchester, Liverpool and Glasgow. It sits alongside the east deck, completed in 2025, which will carry trains towards Old Oak Common and Euston.
The two parallel structures are each 320 metres long and stand just 100mm apart. Built from weathering steel and supported on concrete piers, they will be joined by raised embankments on either side.
Site constraints meant the decks were launched slightly differently: the west deck in four incremental stages and the east deck in three. At each stage, new steel sections were added to the rear and the whole deck was propelled forward using strand jacks. By the final launch, the deck was fully supported on piers either side of the carriageway, allowing the “last push” to be carried out safely with the motorway open.
That final push took just nine hours, moving the deck 76 metres at an average of 12 metres per hour. The M42–M6 link road was closed as a safety exclusion zone and reopened 25 hours ahead of schedule.
Ian Clarke, Senior Project Manager at HS2 Ltd, said: “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.”
Russell Luckhurst, the Balfour Beatty VINCI engineer leading the work, described it as “a huge moment for Balfour Beatty VINCI and HS2”, completing a major programme above the M6 in extremely challenging weather.
Strong winds that weekend led to the postponement of parapet installation on the Water Orton viaduct above the M42, which was rescheduled to the following weekend.
In 2027, HS2’s motorway programme will focus on the triple box, a rail-over-road structure that will carry four HS2 tracks over the M42 near Coleshill. HS2 is working with National Highways to agree the schedule.