A KEY motorway junction in Somerset could have to be upgraded twice in the space of five years if plans to dual the A358 are given the go-ahead.

Somerset County Council is currently undertaking an upgrade of Junction 25 of the M5 near Taunton, which is due to be completed in 2021.

Under proposals put forward by Highways England, the new dualled A358 between Taunton and Ilminster would connect onto the existing Junction 25 roundabout, rather than joining the M5 at a new junction further to the south.

The council has said this additional part of the roundabout can be added later, with the dualling expected to be completed by the summer of 2024.

Alun Griffiths, the contractor carrying out the Junction 25 upgrade, said the work currently being done was designed to stand on its own regardless of the progress of the A358 dualling.

A spokesperson said: “The current upgrade of Junction 25 is a standalone scheme which offers benefits to both congestion and the local economy while the wider A358 improvement scheme is developed.

“Work currently underway will be an essential building block for later improvements.”

Now that the preferred route has been announced, Highways England will stage a further round of public consultation, with the dates to be confirmed shortly.

Once this is over, detailed plans will be submitted to the Planning Inspectorate, and public hearings will be held over a six-month period where local concerns will be addressed and debated.

After this, the transport secretary Chris Grayling MP will have a further six months to make a final decision on whether the dualling should go ahead.

On the current timetable, the new road is expected to be finished by the summer of 2024.

The dualling announcement has been welcomed by Councillor David Hall, Somerset County Council’s cabinet member for economic development, planning and community infrastructure.

Speaking on June 27, he said: “We have always been supportive of the need to improve the A358 as a key element of the end-to-end upgrade of the A303/ A358/ A30 corridor.

“This scheme will bring considerable economic benefits to the south west and UK, and we are extremely pleased to see it progressing.

“Now that the government has announced its preferred route, we will work closely with Highways England to make sure that local issues are considered and addressed in the detailed design process.”

Both Somerset West and Taunton Council and South Somerset District Council have welcomed the plans, but have asked for more detail on the local mitigation – including the upgrades to the Southfields roundabout near Ilminster and the existing junctions between the A358 and local roads.

Benet Allen, deputy leader of Somerset West and Taunton Council, said: “The scheme meets with long-held community aspirations for a Henlade bypass and could remove nearly 90 per cent of vehicular movements out of Henlade, which has to be welcomed.

“It also ensures direct access to the Nexus 25 strategic employment site, which is great news since the link was not part of the original proposals.

“In  the longer term, our Local Plan review presents an opportunity to consider the need for future improvements to junction capacity at Taunton to support the town’s growth.

“We cannot comment on mitigation until we have seen the detailed proposals and fully understand the implications and impacts of the detailed alignment.”

A spokesman for South Somerset District Council added: “The principal of dualling the A358 is welcome, particularly from the perspective of the economic development of South Somerset.

“However, it is too early to offer further comment, particularly with regard to mitigation, and we await specific design details with interest.

“We will engage fully with our communities and neighbouring authorities to ensure any concerns are addressed before submitting any response.”