Skanska has completed the installation of the main steel beams for the new flyover at the A428 Black Cat junction, marking a significant milestone in the delivery of the £1bn road improvement scheme between Bedfordshire and Cambridgeshire.
The wider A428 project will upgrade around 16km of highway between the Black Cat roundabout near St Neots and the Caxton Gibbet roundabout, creating a new dual carriageway designed to improve capacity, safety and journey reliability.
A total of 15 steel beams were transported to site under police escort before being lifted into position during a single-day operation using a 650-tonne crane. The installation forms the primary structural support for the new flyover, which will carry traffic over the redesigned junction.
Ten pairs of beams, each measuring approximately 38m in length and weighing around 60 tonnes, were installed across the western and central sections of the structure. A further five beams, each around 18m long and weighing approximately 30 tonnes, were positioned on the eastern side of the flyover.
The flyover represents the final major structure within the improvement programme and will connect directly to the new 16km dual carriageway once construction is complete.
With the steelwork now in place, construction teams will begin work on the bridge deck before completing the permanent structural connections between the beams and the reinforced concrete supports.
Because the flyover crosses the junction at an angle, temporary steel support frames known as Megashores were installed during the lifting operation to stabilise the beams while permanent connections are completed. These temporary supports will be removed later this year once the structure has been fully secured.
The completion of the beam installation also allows work to begin on excavating a new underpass beneath the A1, another key element of the junction redesign.
Construction at the Black Cat junction has been carried out while maintaining traffic on the surrounding road network. Skanska said extensive planning, phased traffic management and carefully sequenced road switches have enabled work to progress while minimising disruption, with the majority of the most intensive construction activities taking place during daylight hours.
Foundation works for the flyover and associated secant retaining walls were delivered by Cementation Skanska. At the peak of construction, the specialist contractor operated four piling rigs across three separate structures.
The overall scheme includes two new major junctions and 32 structures, including 18 bridges, and is scheduled to open to traffic in spring next year.
National Highways, which is delivering the project, said the upgrade will reduce congestion, improve journey time reliability and road safety, while strengthening transport links between communities and employment centres across the region.
Skanska project manager Neil Davison said: “The installation of these bridge beams marks a major milestone for the A428 Black Cat to Caxton Gibbet project and is a testament to the dedication and commitment of the entire integrated project team.
“Careful planning and the successful delivery of multiple traffic management phases have enabled us to create safe working areas and prepare for the next stage of construction. This has required close coordination between our structures team, supply chain partners and many other specialists working across the site.”
