Engineering works to enable high speed trains to cross the M6 came to a successful close this weekend, as the second HS2 viaduct was installed near Chelmsley Wood.
The final section of the 4750-tonne structure was launched above the north and southbound carriageway (junction 4/4a) using giant hydraulic jacks while vehicles travelled below – minimising disruption for motorists.
The milestone means that both M6 South viaducts are now structurally complete. The east deck, which will carry high-speed trains towards HS2’s two London stations – Old Oak Common and Euston, was completed in 2025. The west deck, which was successfully moved into place on Saturday, 24th October, will carry trains towards Curzon Street Station in Birmingham city centre and destinations in the north, including Manchester, Liverpool and Glasgow.
The parallel structures, which stand just 100 millimetres apart, were constructed using weathering steel and are supported by a series of concrete piers. Raised embankments will then be formed either side of the viaducts.
Both viaducts are 320 metres long, but they were assembled and launched slightly differently due to the constraints of the site. The west deck was launched in four incremental stages, and the east deck in three.
For each launch, additional steel sections are added to the rear of the structure and the whole deck is propelled forward using strand jacks. By the final launch, the weight of the steel deck is fully supported on concrete piers at either side of the carriageway, which means the ‘last push’ can be safely executed while maintaining traffic flows.
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.”
It took engineers working for HS2’s construction partner, Balfour Beatty VINCI, just nine hours to complete the final launch of the viaduct’s west deck. In that time, the steel deck moved forward 76-metres, at an average speed of twelve metres per hour.
While the M6 stayed opened to traffic throughout the weekend, the M42 M6 link road was closed to provide a safety exclusion zone. It reopened 25 hours ahead of schedule at 9pm on Saturday, 24th October.
Russell Luckhurst, the Balfour Beatty VINCI engineer leading the delivery of this work, said:
“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.”
As strong winds affected large parts of the UK at the weekend, the Water Orton viaduct parapet installation works - above the M42 - were postponed for safety reasons.
This programme of work has now been rescheduled to the following weekend. As a result, J6 to 9 northbound and J9 to 7 southbound will be closed from 9pm on Friday, 30th October to 5am on Monday, 2 November 2026.
Looking ahead to 2027, HS2’s motorway construction programme will centre around the triple box – a rail‑over‑road structure that will carry four HS2 railway tracks over the M42 near Coleshill. HS2 is working closely with National Highways to agree the schedule of works.
