HS2 has passed a major construction milestone with the completion of the last of more than 2,700 giant deck segments for the project’s highly complex Delta Junction, a vast triangular network of viaducts on the northern outskirts of Birmingham.
The massive concrete units—each weighing up to 85 tonnes—have been produced at a temporary, purpose‑built outdoor precast facility beside the M42 near Kingsbury in Warwickshire. Once manufactured, the deck segments are transported by road to nearby construction sites, where they are lifted into place to form the spans of the new viaducts.
A Critical Engineering Node on the HS2 Route
Delta Junction is considered one of the most technically challenging sections of the HS2 Phase One route. It will guide high‑speed trains across major motorways, local roads, rail lines, rivers, and floodplains, requiring a sophisticated network of interlinked viaducts at Coleshill and Water Orton/River Thame.
These structures rely heavily on the precision‑engineered segments produced at Kingsbury. To date, around three‑quarters of the 2,742 deck segments have been installed, with crews recently completing deck assembly for the Coleshill viaducts. The key spans for the Water Orton 1 and 2 viaducts—crossing the A446—have also been successfully delivered.
With the final segment now completed, the Kingsbury site will shift focus to manufacturing over 1,200 concrete deck slabs required for Birmingham’s Curzon Approach Viaducts.
Industry Leaders Celebrate a Major Achievement
HS2 Ltd’s Head of Delivery, Caroline Warrington, said:
“Casting these enormous segments on site, close to the viaducts, helps us deliver a quality product and reduce disruption for road users. It’s great to see the final segments complete and I’d like to thank everyone involved in the manufacturing process.
“With this part of the work finished, the team can begin to focus on the deck slabs for the approach viaducts which will carry the railway into central Birmingham.”
Over the last three-and-a-half years, Kingsbury’s 55,000 m² precast yard has produced up to eight segments per day, each standing 3.5m tall and ranging between 7m and 11m wide depending on whether they support single or double track. In total, the units will form more than six kilometres of viaduct deck.
The works are being delivered by HS2’s main West Midlands contractor, Balfour Beatty VINCI (BBV), which also operates a dedicated Skills Academy on site to support local recruitment and training.
BBV’s team leader for Kingsbury, Laura Arrieta, commented:
“Watching the final segment roll off the production line at our precast yard in Warwickshire was a huge moment for the team. We’ve successfully delivered 2,742 viaduct segments over three-and-a-half years – an incredible achievement that we can all be proud of.
“This outdoor facility will now be repurposed to produce over 1,200 concrete deck slabs that will help form the Curzon Approach viaducts, using the same highly skilled and experienced team.”
Engineering Challenges Continue Across the Route
The Delta Junction viaducts are assembled using an incremental cantilever method, with temporary steel cables supporting each new segment until a full span is completed. Permanent post‑tensioned cables are then threaded through the hollow cores to strengthen the structure.
Despite this major milestone, significant work remains across the 140‑mile route between London and Birmingham. HS2 Ltd Chief Executive Mark Wild is leading a comprehensive reset to ensure the remainder of the project is delivered more efficiently and at the lowest reasonable cost.
Image credits: HS2
