Skanska footage shows A1 underpass taking shape seven metres below Black Cat roundabout

Skanska has released drone footage of the A1 underpass it is building seven metres beneath the Black Cat roundabout in Bedfordshire, the final phase of National Highways' A428 scheme, due to open in mid-summer 2027.

The contractor said the work is taking place in a tightly constrained and congested area, with traffic continuing to move around the site.

According to Skanska, the free-flowing underpass will improve journeys through the junction and help ease congestion. Vehicles using the scheme's new 10-mile dual carriageway will cross above it on a bridge.

Dan Trathen, Project Director, said in the Skanska release: "Delivering work of this scale in such a challenging environment requires detailed planning, close coordination and strong collaboration across the project team and supply chain."

He added: "Through that combined effort, the new Black Cat junction is steadily taking shape."

The timetable

National Highways said most of the scheme will open in spring 2027, including the new 10-mile A421 dual carriageway between Black Cat junction in Bedfordshire and Caxton Gibbet in Cambridgeshire.

The underpass will follow in mid-summer 2027. Until then, A1 traffic will continue to use the Black Cat roundabout, the client said.

National Highways also said the team found a higher than expected number of unrecorded underground services at the junction, including water, gas and telecommunications, which had to be safely moved.

The scheme

National Highways describes the project as a billion pound scheme to improve journeys between Milton Keynes and Cambridge.

Skanska is responsible for design and build. The dual carriageway will link the A1 and A421 Black Cat roundabout with the A428 Caxton Gibbet roundabout, and the scheme includes 18 bridges and three junctions, according to the contractor.

In a 2025 release marking the approach to the halfway point, Skanska said the new road would replace the only stretch of single carriageway between the M1 near Milton Keynes and the east coast ports of Felixstowe and Harwich.

At that stage, the contractor said the A1 carriageway was being lowered to pass beneath the new junction while work progressed on the A421 flyover bridge. The project team had lifted 84 bridge beams into place on six structures and laid 60,000 tonnes of asphalt across Black Cat roundabout, Cambridge Road junction, Eltisley and Caxton Gibbet roundabout.

The Planning Inspectorate's record shows development consent for the scheme was granted on 18 August 2022.

What happens next

National Highways said it will provide a further update, including confirmed opening dates, in early 2027.