The A1 at Black Cat has suffered congestion for many years and was last upgraded when the A421 to the west was upgraded. The A428 is a proposed new dual carriageway heading east from Black Cat. The inset to the top left of the image above shows the three level grade separated junction that has been published as part of the preferred route.
The project strategy is to provide a free flow link from the A421 and new A628 and reduce congestion at the existing A1 Black Cat junction.
The current solution requires significant land take and forms a significant part of the whole scheme budget due to the complexity of the works required.
John Bowes was asked to review the whole A428 scheme at a value management workshop where he provided a number of safety and cost reduction ideas. Following this he also felt that a more cost effective solution could be provided at the Black Cat interchange.
John developed two ideas, one that did not grade separate the A421 and A428 link and one which fully complied with the scheme objectives.
The image above details the alternative layout which removes the grade separation of the A1 and increases the size of the at grade roundabout to provide capacity and improve buildability. It also reduces land take by around 50%, allowing the existing businesses and a grade 1 listed building to be retained. The solution also had the following benefits:
The solution was shared with Aecom and Skanska to evaluate as part of the due diligence being undertaken as it is handed over from Aecom to Skanska at Stage 5 when they will be responsible for delivering the design and construction as the DIP for the scheme.
This page will be updated when the outcome is known.
