THE projected cost of dualling a key route in Somerset has risen by around 80 per cent – and work may not begin until 2021.

Highways England, which manages Britain’s motorways and major A-roads, is expected to announced its preferred route for dualling the A358 between Taunton and Ilminster by the end of spring.

But a report by the National Audit Office (NAO) has found the cost of the project has risen dramatically above the original estimates, and may not deliver value for money for taxpayers.

Highways England has said it is committed to delivering a scheme which is value for money and will assess all options for improving this route before it makes a final decision.

The NAO’s report, which was published on Monday (May 20), focusses primarily on the efforts to dual the A303 near Stonehenge.

But it also makes reference to Highways England’s two ongoing schemes in Somerset – the dualling of the A358, and the dualling of the A303 between Podimore and Sparkford.

When Highways England originally consulted on the A358, it had intended to begin construction in March 2020, with an estimated budget of £251m.

To keep costs down, the agency took only the cheapest option for the route out to public consultation – and then had to hold a second consultation exercise when residents and local councils said they weren’t happy.

At the second consultation, the strongest public support was for the most expensive route – which, if approved, would push the scheme’s total cost to £452m, around 80 per cent higher than originally anticipated.

The report said: “This is significantly above Highways England’s operational planning budget for this project, meaning it may be required to consider lower-cost alternatives which could result in fewer benefits.

“Early assessments of the lower-cost alternatives indicate that it may only generate 97p in benefits for every £1 spent, which the Department for Transport (DfT) considers poor value for money.”

As a result of the additional consultations, the scheme is now more than 12 months behind schedule, with construction now expected to start in the summer of 2021 and be completed three years later.

Highways England has said it assesses the value for money of its schemes in line with DfT guidance, and that it would continue to review the cost before any final decisions were taken.

Programme leader Andrew Alcorn said: “Before we announce the preferred route, we must make sure we present the best possible solution for the A358.

“This requires a great deal of assessment work based on the balance of cost, economics and impact.

“We aim to confirm the target date for the construction work to begin when we announce the preferred route.”

The scheme to dual the A303 between Podimore and Sparkford has also seen its budget increase, from £120m to £171m – a rise of 43 per cent.

However, full funding for this scheme was approved in November 2018, and the NAO has said this increase “remains within the current operational planning budget of Highways England.”

A final decision on the A303 scheme is expected at the end of 2019, with construction expected to begin in March 2020 and last until June 2023 – four months longer than was originally hoped.