HE0914 A350 Chippenham Duelling Scheme April 2023

he A350 is one of the most important routes in Wiltshire. It is a primary north-south route with regional significance connecting the south coast with the M4 and onwards to Bristol and the Midlands.

In Wiltshire it passes around the principal settlements of Chippenham and Trowbridge via the town of Melksham and on to Westbury and Warminster. It has been a longstanding priority to improve north-south connectivity along the A350, and Wiltshire Council has been progressively bringing forward the dualling of the A350 Chippenham bypass.

Over recent years three major capital schemes (Phases 1, 2 and 3) have been brought forward to improve capacity and safety on the route, largely funded through successful Department for Transport (DfT) and/or Local Enterprise Partnerships (LEP) funding bids. Most recently, an Outline Business Case (OBC) bid was made to DfT for funding to bring forward a scheme to complete the dualling of the A350 bypass at Chippenham.

In the spending review in October 2021 the government announced that it would allocate funds for a scheme to dual the remaining single carriageway sections of the A350 route round Chippenham. The project was also included within the list of forthcoming infrastructure projects as part of The Growth Plan 2022 published in September 2022.

Wiltshire Council and its consultants Atkins are now pressing forward to complete the design of the remaining Phases 4 and 5 of the scheme, and preparing the Full Business Case (FBC). Subject to the FBC being approved by the DfT, it is anticipated that construction works will be undertaken during 2024 and 2025.

The scheme is likely to include for the following key elements Phase 4 dualling: widening the A350 over a total distance of some 1.5km to dual 2-lane between Chequers roundabout and Lackham roundabout. The dualling would take place within the existing wide highway verge to the west of the current carriageway.

Phase 5 dualling: widening the A350 over a total distance of some 1.75km to dual 2-lane between Cepen Park South roundabout and Bumpers Farm roundabout. Again, the dualling would take place within the existing wide highway verge to the west of the current carriageway.

When implemented with Phase 4, this would extend the dualling to cover the full stretch of the A350 Chippenham Bypass. Bumpers Farm Roundabout capacity enhancements: increasing the circulatory from 2 lanes to 3; signalising 4 approach arms; increasing approach arms from A350 (S), A420 (W), A350 (N) and A420 (E) to 3 lanes; and dualling the exits onto the A420 (E) and A420 (W) and Lackham roundabout capacity enhancements: dualling the exit to the A350 north as part of the phase 4 works.

The works will be designed and built-in accordance with current standards and guidelines and will include for all key aspects of highway construction – earthworks, carriageway, footways, drainage, street lighting, signage, statutory authority (gas, water electric etc) service diversions and provision, and hard and soft landscaping works. The works will be contained within the existing highway boundary extents and there should be no requirement for additional land.

The existing bridges along this route were constructed to accommodate the additional carriageways without needing further major works, and as such there are no major structural works anticipated. The A350 route will need to remain in operation throughout the works, and as such careful traffic management considerations and phasing, particularly in connection with the Bumpers Farm Roundabout enhancements, will be required. There will be a desire to minimise impacts on traffic flows during the works and ensure that the scheme is undertaken with suitable and appropriate levels of public engagement and liaison.