HS2 completes both viaducts over the M6 near Chelmsley Wood without closing the motorway

HS2 has finished building the second of its two huge viaducts over the M6 near Chelmsley Wood, completing a major piece of the high-speed line's route into Birmingham, and the motorway stayed open while it happened.

The final section of the 4,750-tonne steel deck was pushed out over the north and southbound carriageways at junction 4/4a on Saturday 24 October, using giant hydraulic jacks while traffic kept moving underneath.

Both decks now in place

With the west deck in position, both M6 South viaducts are now structurally complete. The east deck, completed in 2025, will carry trains towards HS2's two London stations, Old Oak Common and Euston. The new west deck will carry trains towards Curzon Street station in Birmingham city centre and on to destinations in the north.

The two parallel structures stand just 100 millimetres apart. Both are 320 metres long, built from weathering steel and supported on concrete piers, with raised embankments to be formed on either side.

Nine hours, twelve metres an hour

The structures were built by sliding them forward in stages. Extra steel sections are added at the back and the whole deck is pushed forward with strand jacks. By the final push, the deck was fully supported on concrete piers on either side of the motorway, so the work could be done safely without closing the carriageway.

Engineers from HS2's construction partner, Balfour Beatty VINCI, took just nine hours to complete the final launch of the west deck, moving it 76 metres at an average of twelve metres an hour.

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."

"We have made great progress this year and I thank motorists and local communities for their patience."

Ahead of schedule

The M42 to M6 link road was closed to create a safety zone during the work, but it reopened 25 hours ahead of schedule, at 9pm on Saturday 24 October.

Russell Luckhurst, the Balfour Beatty VINCI engineer who led the work, said it was "a huge moment for Balfour Beatty VINCI and HS2, concluding a major programme of work above the M6 - in extremely challenging weather conditions."

What comes next

Strong winds that weekend postponed separate parapet work on the Water Orton viaduct above the M42, which was rescheduled for the following weekend.

Looking ahead to 2027, HS2's motorway work will centre on the "triple box", a structure that will carry four HS2 tracks over the M42 near Coleshill. HS2 says it is working closely with National Highways to agree the timetable.

For Birmingham, each milestone on this stretch brings the city's new Curzon Street station a step closer to its high-speed connection, and for drivers on the M6 and M42, it means one more major job done without a full motorway closure.