Progress on new M4 underpass continues, as next stage of the scheme begins next week

Work to construct the Wichelstowe Southern Access (WSA), a new underpass beneath the M4, will move to stage four next week, with all associated traffic management to be removed from the motorway.

Published: Thursday, 13th May 2021

Image showing construction of WSA near M4

Since last year, work has taken place to build the outer structure of the new underpass, which once complete, will provide residents with a new access route into Wichelstowe and the 4,500 new homes it will bring.

With this structure now complete, including construction of both the north and south entrances to the underpass, the project is ready to move onto stage four, which will involve the excavation of the underpass and construction of the new road underneath the motorway above.

Since last year, a 50mph speed limit and narrowed lanes have been in place near to junction 16 of the M4 to allow the work to continue safely, without the need for any significant lane closures. Advanced engineering methods, including the construction of a specially-built embankment to redirect lanes of traffic, have ensured enough space is available on the motorway for work to continue and for drivers to continue using the road.

However, with stage four now ready to begin beneath the motorway, work has been underway over the past week to remove all traffic management associated with the scheme from the M4, including returning lanes to their original alignment and reintroducing the original 70mph speed limit.

By Saturday (15 May), all traffic management, including the temporary 50mph speed limit, is expected to be removed, significantly reducing the impact of the project on road users for the remainder of the scheme.

As well as the construction of the underpass itself, the WSA will connect to both Hay Lane and Wharf Road via a new roundabout on the south side. Work to construct the new roundabout and road layout is currently ongoing with minimal impact on road users.

Once complete, the scheme, which is being delivered by Alun Griffiths Ltd on behalf of Swindon Borough Council, will provide a fourth access into Wichelstowe, helping to support the new housing development, a new district centre and around 2,000 new jobs, by unlocking 12.5 hectares of employment land.

Councillor Gary Sumner, Swindon Borough Council’s Cabinet Member for Strategic Planning, said: “Once complete, the Wichelstowe Southern Access will provide a key access to Wichelstowe, including the new housing development, and significant employment space.

“Throughout the project, the engineering and construction work has been extremely impressive, creating the underpass beneath the motorway, without the need for any significant road closures.

“The removal of the current traffic management will reduce the impact of the works on road users even further, while allowing us to continue making progress on the scheme, a huge feat of engineering.”

Regular updates on the scheme will continue to be available via the Council’s Highways News e-newsletter at: and via the Council’s social media pages. Further details about the Wichelstowe Southern Access scheme are available on the Council’s website:

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