A350 road

A controversial £33 million bypass around Westbury was initially proposed in 1997, with public consultation and a selection of route options proposed in 1999. Wiltshire County Council's Environment and Transport Committee selected the Eastern Route (though it was the least popular) as the 'preferred route' in 2001, because the Council said that it offered the best and lowest cost way of relieving traffic congestion in the town centre. The council submitted an initial planning application during 2005. The council said that the government indicated that it was in favour of the project in 2006.[6] The Council presented a further planning application in 2007.

The council's selected route (shown on this Google overlay map) would pass to the east of the town.[7] The council expected it to reduce traffic through Westbury, create more space for cyclists and pedestrians, and improve journey time reliability on the A350 by two minutes. It would also provide a new access road to the West Wilts Trading Estate, though not to the other Westbury trading estates, or the railway station or the designated Future Intermodal Freight Terminal.[6] The scheme, would, by the council's own forecasts, cause increased heavy goods vehicle flow through other West Wiltshire communities, such as Southwick, which already have over twice the HGVs of Westbury. The eastern bypass route is supported by the 'Westbury Bypass Now' group.[8]

The council's route, which runs close to the Westbury White Horse, two Sites of Special Scientific Interest, near Salisbury Plain and through a Special Landscape Area, is not included in the Regional Transport Priority for South West England.[9] The route has been described as 'highly intrusive' by the council's landscape officer.[10] It attracted opposition from various environmental and local groups including the White Horse Alliance, the Campaign to Protect Rural England, Woodland Trust, Friends of the Earth, Campaign for Better Transport[11] and Wiltshire Wildlife Trust.[12]

The scheme was 'called in' in 2007. An Inquiry into the scheme was held in July 2008. It was adjourned until September–October after objectors noticed that some figures for lorry counts were out by 100%. The inquiry ended in the autumn of 2008. The decision was with John Denham the Secretary of State for Communities and Local Government.[13] The planning inspectors recommended refusal of planning permission for Wiltshire Council's eastern Westbury bypass scheme.

A scheme has been proposed since 2015 to improve the A350 West Ashton/Yarnbrook junction to ease traffic flows at a noted bottleneck. This will involve the construction of a new relief road to replace the section north of the junction. Three new roundabouts are also proposed, to connect with the A363 Westbury Road, a link to Yarnbrook village and one at the existing West Ashton Road.[14]

In 2020, the government said £135m could be available to bypass Beanacre, north of Melksham, and provide a new route east of the town.[15] Wiltshire Council consulted with the public in late 2020 and early 2021 on a number of options, including short and long routes to the east and west of the town, taking into account local traffic and east–west movements as well as the north–south primary route.[16]

In June 2021, Wiltshire Council's cabinet resolved to progress an eastern route that starts to the north of Beanacre and meets the A3102 and A365 before rejoining the current A350 south of the town, beyond Bowerhill. A shortlist of options around this route will again be subject to public consultation.[17]

Wiltshire Council have been awarded money to complete the dualling of the Chippenham bypass, meaning nearly 6.5 miles of continuous dual carriageway. There is also funding for a scheme to completely signalise the M4 Junction 17 roundabout and build a left turn lane between the A350 and the westbound M4.

The A350 from the M4 to Warminster has been designated as part of the new Major Road Network, a network of secondary roads which are not classed as Strategic but are classed as locally or regionally important.[18] In addition, Highways England (now National Highways) are developing a South Coast to M4 route strategy which reports in late Summer 2022. The current preferred route is the A36 to Bath, then the A46 to the M4. Due to the traffic situation in Bath, Highways England may propose de-listing the current route and adopting the A350 instead; this may release funding for further works between Poole and the M4.[19]