Engineers delivering HS2’s complex triangular Delta Junction outside Birmingham have reached a major construction milestone, completing four parallel viaduct decks at the Coleshill site in Warwickshire. The structures, stretching more than 600 metres, form a crucial part of the wider Delta Junction — one of the most intricate infrastructure sections on the entire high-speed rail route.
Modelled in complexity on Birmingham’s iconic Spaghetti Junction, the Delta Junction comprises a vast network of viaducts, flyovers and underpasses designed to carry HS2 over a series of challenging obstacles including major motorways, local roads, railways, rivers and floodplains.
A Key Link in the Southern Section of the Junction
The Coleshill East and West viaducts sit on the southern side of the Delta Junction. Here, HS2 lines diverge while crossing a local road and the floodplain of the River Cole, situated between the M6 and M42. Two of the newly completed decks will support the north–south four-track mainline, while two narrower structures will accommodate services connecting to the future Birmingham Curzon Street station.
Caroline Warrington, HS2 Ltd’s Head of Delivery, said:
“HS2 will transform journeys between our two largest cities, while freeing up space on the existing West Coast Main Line for more freight and local services.
“The Delta forms a key part of the project and it’s great to see it starting to come together. I’d like to thank everyone involved in the Coleshill viaducts and look forward to seeing more progress in the year ahead, as the focus turns to completing the robust kerbs and parapets.”
Precision Engineering Across a 2.4km Viaduct System
The Coleshill viaducts — totalling 2.4km — are being delivered by HS2’s main works contractor in the Midlands, Balfour Beatty VINCI (BBV). The decks are formed from 1,024 pre-cast concrete segments, each manufactured at a purpose-built Kingsbury facility and transported to site for installation.
Key engineering highlights include:
- 60-tonne, 11m-wide segments forming the central 22m deck, arranged in two parallel rows
- 44-tonne segments used for the single-track side viaducts
- Support from 54 reinforced concrete piers, each up to 12m high
- Use of a cantilever construction method, aided by temporary steel cables
- Final strengthening via post-tensioned cables installed within hollow deck sections
Simon Albarel, Section Manager at BBV, praised the team’s efforts:
*”We’re continuing to make great progress on the construction of HS2’s Delta Junction – one of the most complex sections of the entire route. Our latest milestone is the successful installation of 1,024 pre-cast segments along all the Coleshill Viaducts.
“Completing the deck assembly is another great achievement for the team, demonstrating their precision engineering and hard work over the last two and a half years.”**
Next Steps and the Wider HS2 Reset
With all deck segments now in place, teams will shift focus to installing the remaining kerbs and parapets, preparing the viaducts for their final structural form.
Across the rest of the 140-mile route between London and Birmingham, significant work continues. HS2 Ltd Chief Executive Mark Wild is leading a comprehensive project reset aimed at ensuring the remaining phases are delivered more efficiently and at the lowest reasonable cost.
Image and video credits: HS2
