Wiltshire Council has been granted approval from the Department for Transport (DfT) to take forward plans to improve junction 17 of the M4 as part of the Major Road Network (MRN) programme.
The council previously submitted its outline business case (OBC) to the DfT, which sets out in detail the full costs and benefits of the scheme, which will increase capacity at this busy junction.
Approval of the OBC by the DfT allows the council to work to develop the full business case (FBC). Work will now progress towards the development of the full design for the project, with the aim of creating a more reliable, less congested, and better-connected transport network. Once the FBC has been approved by DfT, construction can begin.
In total, DfT has indicated that once the FBC is confirmed it will allocate £26.087m for the completed scheme, against the total cost of £31.937m, with the council providing the remaining budget. In the meantime, the interim DfT funding will enable the council to progress the scheme from the preliminary stage, through detailed design and on to procurement to identify a contractor, prior to the submission of the FBC.
The MRN scheme is separate to the recent Chippenham Gateway project, which has altered the junction and caused some concerns among local communities. The junction has been designed to accommodate traffic once the new development is occupied and to mitigate impacts on the M4. To help resolve queueing in the short term, the council is carrying out traffic modelling to attempt to persuade National Highways that returning the A350 northbound lane designations back to their previous arrangements would improve the junction performance.
Cllr Nick Holder, Cabinet Member for Highways, said: We know that there have been increased queues at junction 17 following the Chippenham Gateway project, which is why we’re working with National Highways to try to find a medium-term solution, while we work on the Full Business Case for our Major Road Network project to further develop our plans to improve the junction.”
It is fantastic news for Wiltshire that we have received approval from DfT for our outline business case. This is a key strategic junction for Wiltshire, which provides the vital link between the motorway network and the A350, connecting the towns in the west of the county, including Chippenham, Melksham and Trowbridge. It also provides a link to Malmesbury and the A429 in the north, along with local access to the B4122.
If approved, the MRN scheme will increase capacity at the junction to ensure it is fit to serve the county for many years to come, meeting our Business Plan commitment to have well-connected communities.
Work will now begin on the FBC phase, and it is expected to be submitted to DfT by summer 2026. If it all progresses as planned, work on the scheme would start in winter 2026 and would be completed by the end of 2027.
