The Department for Transport (DfT) has approved plans by Wiltshire Council to take forward proposals 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.