A350 Chippenham Bypass Improvements (Phase 4 and 5)

The A350 Chippenham Bypass phases 4 & 5 scheme includes the following improvement works:

Bumpers Farm Roundabout improvements

We will be adding additional lanes and highway capacity on the A420 approaches and exits in both directions. We'll also be adding additional lanes on A350 northbound approach to the roundabout. Traffic signals will be Provided on each of the A420 and A350 arms, and signal-controlled pedestrian and cycle crossings will be added to the northern A350, and eastern A420 arms.

Phase 4 dualling (Chequers to Lackham)

We will be widening the A350 to two lanes in both directions, between Chequers and Lackham roundabouts, and the Phase 4 works will tie into the new roundabout at the Southpoint development.

Phase 5 dualling (Bumpers Farm to Cepen Park South)

We will be widening the A350 to two lanes in both directions between Bumpers Farm and Cepen Park South roundabouts. This is the section which passes the rugby club.

Lackham roundabout capacity enhancements

The scheme is anticipated to complete the dualling of the A350 from the M4 to Lackham Roundabout. There will be some minor changes at the Lackham roundabout to improve traffic flows there.

The scheme will benefit around 24,000 vehicles a day by helping to relieve congestion on the A350 Chippenham Bypass, building on previous phases to remove the remaining restrictions that can cause blockages during peak travel times. The key benefits include:

Local Benefits

• improvements at Bumpers Farm Roundabout will reduce peak time queuing on Bumpers Way and allow easier exit onto the roundabout
• increased road capacity along the A350 Chippenham Bypass, which will:
  • help deter traffic from using alternative parallel routes on the local road network such as the B4528 Hardenhuish Lane and B4528 Hungerdown Lane
  • help support the local economy by improving connections
• alterations to the local public rights of way network will improve safety for those accessing the countryside
• improvement in journey-time reliability along the bypass and a reduction in congestion, which will:
  • support future growth in the town and help achieve the economic competitiveness and growth ambitions
  • contribute towards reducing greenhouse gas emissions and address the negative impacts on safety, security, health, and quality of life
• reduction in the frequency of collisions along the bypass and parallel routes

Regional Benefits

• improvement in journey-time reliability along the bypass and a reduction in congestion, which will:
  • help preserve the route's key role as part of the advisory freight route network
  • reduce transport costs for businesses and transport operators and encourage inward investment to the A350 Growth Zone

The tables below shows predicted traffic flows and queue length at Bumpers Farm Roundabout for the AM and PM peak hours, based on a computer traffic simulation model. The figures in bold demonstrate a significant reduction in projected queue lengths with the scheme.

The new dualled sections of the A350 will generally have a national speed limit, which is appropriate given the strategic importance of the route, and the role the A350 plays within the wider highway network.

However, speed limits will be reduced at various locations in response to factors including:

• safety
• the exiting bypass layout and design constraints
• the relatively close proximity of some junctions
• the need to include for Public Rights of Way changes and crossing locations

In general terms, the relatively straight dual carriageway sections of the bypass will be subject to national speed limit. However, reductions to 40 / 50mph will be introduced where appropriate.

The key upgrades being made at Bumpers Farm Roundabout include:

• increased capacity through adding an additional lane on the approach of both the eastern and western arms of the A420, and to the approach on the A350 northern arm (two to three lanes)
• adding an additional lane on the exits of both the eastern and western arms of the A420 (one to two lanes)
• adding traffic signals on the A350 and A420 arms to better manage traffic flow
• adding signal-controlled crossings on the eastern A420 and northern A350 arms

Benefits for Bumpers Way traffic

Currently, during afternoon peak periods, significant traffic queuing occurs along Bumpers Way as traffic seeks to leave the industrial/business area. This is due to the dominant A350 southbound traffic flow restricting access onto the junction from both the A420 and Bumpers Way.

To improve this situation, the scheme will include traffic sensors on the Bumpers Way approach. The sensors will detect stationary traffic, and when a large queue is identified, the timings of the traffic signals system at the roundabout will be adjusted to help generate gaps in the traffic flow and ease the traffic movement out of Bumpers Way. The sensors will be calibrated on-site to ease the Bumpers Way queuing issue, whilst maximising traffic flows through and around the junction.

The existing A350 crossing to the north of the roundabout will be upgraded to be traffic signal-controlled. It will be located between two roundabouts which are relatively close together. Traffic speeds will naturally tend to be lower and better controlled here, which will improve the safety for those using the crossing. The new facilities will also tie in and supplement the existing routes.

The current crossing at the end of Drake Crescent is well-used. The new dual carriageway will cut off access at his location, so we will be replacing this facility with a new crossing to the south of the Cepen Park South Roundabout.

The new crossing will be signal-controlled and placed between two roundabouts where the traffic speed is naturally lower; therefore, enhancing the safety for people wishing to access to the countryside from the residential areas.

We will also be ensuring that connections to existing public routes are maintained and new ones are provided where needed, both to the residential area and to the existing rights of way network west of the A350.

The current crossing of the A350 at the Rugby Club will be cut off by the new dual carriageway.

To ensure the public rights of way connection is maintained, the pedestrian route will be diverted south on both sides of the A350 and will cross over at the existing Frogwell Footbridge. This will provide for a safer crossing facility.

Styles and fences will be replaced by gates where possible to aid accessibility.

An existing pedestrian desire line exists along the alignment of Saltersford Lane, just to the north of the Railway bridge. This informal crossing location will be affected by the new dual carriageway construction.

A connection will be provided between the Saltersford Lane area and Easton Lane which has recently been closed to vehicular traffic and is now a safe pedestrian and cycle link across the A350.

Advanced Works are being undertaken across the A350 Phase 4-5 dualling site.  These works focus on vegetation clearance outside of the bird nesting season, and some initial earth moving work.  Undertaking these advanced works now helps avoid delays to the construction of the main scheme which is anticipated to start later this year.

The scheme includes for various areas of landscape planting works across the Phase 4-5 site.

The A350 Chippenham Highway Improvements will involve building new carriageways alongside the existing road between Bumpers Farm Roundabout (A420) and Cepen Park South Roundabout, and between Chequers Roundabout (A4) and Lackham Roundabout. The new carriageways will be to the west of the existing road, and within the existing highway boundaries on land originally acquired for that purpose. The bridges along the route were constructed to facilitate this dualling. The scheme also includes alterations to Bumpers Farm Roundabout. 

Tenders have been invited for the construction of the scheme, with a view to starting construction in 2024 and completing in 2025.

The scheme cost is estimated to be £31.909 million, and DfT have allocated £26.625 million to the scheme. The remaining funding is expected to be provided by the Council from the Community Infrastructure Levy contributions.

A policy of selective improvements to the A350 has been included in the council's development plans for many years, including in the current Wiltshire Core Strategy. These have been subject to extensive public consultation.

The A350 Chippenham Bypass was the subject of a planning application, statutory orders and a public inquiry in the 1990's for the full dual carriageway scheme. Initially it was constructed as a single carriageway, but land was included to facilitate the future dualling which has been taking place in recent years.

A public engagement exercise was held during winter 2022/23 to provide the opportunity for residents, businesses, and others to comment on the latest proposals.

Various roadworks by developers and public utilities are proposed in the area, including the Southpoint development at Showell Farm, and the proposed dualling work will be coordinated with them to reduce congestion and avoid unnecessary abortive work.

Appropriate and safe traffic management measures will be set up to reduce the impact of construction as much as possible. Inevitably there will be some disruption to traffic especially at peak times, but careful consideration will be given to the timing and phasing of works to keep these to a minimum.

Yes. There can be long delays for traffic leaving Bumpers Farm Estate, especially in the evening peak periods. The scheme will increase the size of the roundabout and traffic lights will be installed to control traffic and make it safer and easier to leave the estate at busy times.

Low Noise Surfacing on the new A350 north-bound carriageway between Sandown Drive Roundabout and Bumpers Farm Roundabout will be provided which will result in the majority of nearby receptors experiencing no change or a minimal change in noise.

There will be a concrete safety barrier separating the northbound and southbound carriageways, which is also expected to help limit the traffic noise which local residents experience.

There is currently a left in - left out junction between Drake Crescent and the A350, which will remain. The signing will be improved by the addition of yellow backing boards for the 'Junction ahead' signs. The street lighting in the vicinity of the junction will be upgraded, and the visibility of the merge and diverge tapers will be improved.

The new dual carriageway layout will remove the potential for high-speed head on collisions and it will be possible for traffic to safely overtake slower vehicles accessing or leaving Drake Crescent.

It is not proposed to include pedestrian and cyclist routes alongside this section of the A350 as there are better and safer routes through the adjacent residential areas. There will be crossing facilities, particularly near Bumpers Farm, which will be developed as part of the design process.

Yes. The Full Business Case, as submitted to DfT can be accessed below:

A350 Chippenham Phase 4 / 5 - Full Business Case (PDF) [7MB] (opens new window)

Appendix A - Strategic Dimension (PDF) [85MB] (opens new window)

Appendix B - Economic Dimension (PDF) [41MB] (opens new window)

Appendix C - Commercial Dimension (PDF) [1MB] (opens new window)

Appendix D - Financial Dimension (PDF) [897KB] (opens new window)

Appendix E - Management Dimension (PDF) [4MB] (opens new window)

Between November 2022 and February 2023, we asked residents and businesses in the Chippenham area, and wider A350 users, to share their views on phases 4 and 5 of plans to turn the remaining single carriageway sections of the A350 at Chippenham into dual carriageways. 

Following the feedback from the engagement event we have produced the report below which highlights the responses received to the questionnaire and additional comments around the scheme. 

A350 Chippenham Phases 4 and 5 - Public Engagement Report (OpenDocument text format) [2MB] (opens new window)

Appendix B - Public Engagement Questionnaire (OpenDocument text format) [22KB] (opens new window)

Appendix C - Public Engagement Webinar Q&A (OpenDocument text format) [101KB] (opens new window)

Appendix D - Chippenham Town Council Response (OpenDocument text format) [41KB] (opens new window)

We also held an online webinar about the scheme on Wednesday 11 January 2023, taking attendees through the  Appendix A - Public Engagement Booklet (PDF) [7MB] (opens new window) , and answering questions.

Watch a video of the webinar (opens new window)

Following the publication of the Factual Public Engagement Report we have considered the findings as the scheme design has progressed. Those considerations, and the response to the Public Engagement exercise is detailed within the A350 Chippenham Phases 4 & 5 - Public Engagement Report Response (July 2023) (OpenDocument text format) [2MB] (opens new window) .

At this stage, no firm proposals have been developed for the section of the A350 to the south of Lackham Roundabout and around Lacock, and no significant upgrades or changes are currently programmed. 

That said, it may be that as part of the Local Plan review, upgrades to this section of the A350 are identified as being required over the longer term. This may include for the dualling of this section with associated junction improvements,  in a similar vein to the ongoing progressive upgrade works that have come forward along the A350 corridor over recent years. 

It should also be noted that National Highways are currently undertaking a strategic North-South connectivity review. Their study encompasses the Wiltshire geographic area and includes the A350 as a key route. The outcomes of that study may have implications for the status of the A350 and whether, and when, further upgrade works come forward. The Highway Authority will monitor the performance of the network, and if issues arise, will seek to bring forward improvement work as necessary and as funding allows.