HS2’s complex civil engineering programme will shift up a gear this summer, as it prepares to deliver its biggest programme of work yet over the motorway network.

The construction schedule, which starts in June, will see three huge structures built over busy sections of the M42 and M6 in the West Midlands. 

In one operation, a twin box will be built above both carriageways of the M42 near Birmingham Business Park – allowing the railway to be constructed over the top. Additionally, two single-track viaducts will be extended over the M42/M6 Toll near Water Orton and a twin-track viaduct will be installed over the M6 near Chelmsley Wood. 

HS2 and its civil engineering partner, Balfour Beatty VINCI (BBV), have spent more than a year planning the motorway crossings, in conjunction with National Highways.

The six-month schedule was initially planned with nine closures, but the team has synchronised most of the work on the twin box structure and the Water Orton viaducts into the same weekends. This planning means the total number of motorway closures has reduced from nine down to six. 

To minimise impacts on commuters at peak traffic times, junction closures will only take place from 9pm on Friday evenings through to 5am on Monday mornings.  

Agnes Usciak, HS2 senior project manager for the works, said: “The progress we’re making on the viaducts and structures next to the M6 and the M42 is already clear to see, and over the next six months, we’ll start bridging the gaps above the carriageways.

“It’s been a huge team effort to condense this vast programme of work into just six weekend closures, and I’d like to thank all our partners for their co-operation and support. Safety will always be our number one priority, which is why we need to divert traffic away from the carriageway while we conduct these vital works.”

The M42 overhead works begin on the evening of Friday, 26 June 2026, with the installation of the roof deck for the twin box. This 300-metre-long structure will allow the high-speed line to be built over the M42. Once complete, vehicles will drive through the box, while trains travel above.

At the same time, engineers in nearby Water Orton are preparing to extend two single-track viaducts that will carry high-speed trains into Birmingham Curzon Street and the rolling stock depot at Washwood Heath.

Instead of continuing with the cantilever construction method, the viaducts will be prefabricated in sections adjacent to the carriageway – removing the need for further closures. Once fully assembled, they will be moved into position using self-propelled modular transporters and locked into place above the piers. This significantly reduces the installation time and means engineers can complete the works in just four weekends. This programme of work will commence at 9pm on Friday, 24 July 2026.

The final construction challenge – the installation of the M6 South Viaduct West – requires just one weekend motorway closure, as two stages of the fully restrained slide process will take place over live traffic, eliminating the need to close the carriageway. The single weekend closure will commence at 9pm on Friday, 21 August 2026.

Oliver Shore, project director at Balfour Beatty VINCI, said: “We achieved a UK first last year, when we slid a viaduct into place over a live motorway, and we’re delighted to be given the opportunity to repeat the process again this year over the same stretch of the M6.

“Engineering innovations and extensive planning have played a major role in our approach to this vast programme of work, above the M6 and M42, and we’ve made every effort to minimise impacts for motorists and communities.”

In the coming weeks, HS2 and BBV will host a series of community events, in conjunction with National Highways, to ensure residents, businesses, and commuters are aware of the planned closure dates and the approved diversion routes that will be put in place.  Find out more here.