Early plans to build tunnels as part of Highways England’s A417 “missing link” between Gloucester and Swindon was always “very questionable” due to the cost, according to Highways England South West regional delivery director Nick Aldworth.
Local campaign groups and MPs spent years fighting for the road to be put in a tunnel due to environmental concerns.
However, speaking at NCE's Future of Roads conference, Aldworth said that while tunnelling was considered as an option early in the development of the scheme, cost-wise it would have always posed challenges.
“At the start of RIS1 we had up to 30 potential routes and were talking about potential for tunnels and we didn’t do everything we should have done to set expectations," he said.
“A tunnel would have been very expensive - the value for money business case for a tunnel in this area would have been very questionable and I think it would have made it more difficult to make improvements to this road. So I would have started that one differently having had a chance.”
Last month the Planning Inspectorate accepted Highways England’s planning application for the project,which will ease congestion and improve safety on the route.
The project is valued between £250M and £500M and is an alternative to the M5/M4 route via Bristol. The missing link itself is a 5km stretch of single-lane carriageway on the A417 between the Brockworth bypass and Cowley roundabout in Gloucestershire.
It causes problems for road users, with congestion frequent and unpredictable. This means motorists to divert onto local roads to avoid tailbacks – but these roads were not built to accommodate high levels of traffic. Poor visibility and other factors lead to frequent accidents along this section of road.
The scheme has been in the pipeline for 30 or 40 years and last month's planning approval is the furthest it has progressed, Aldworth said, adding that he is “proud” of the work that has been achieved on the scheme.
“This was a good project for how we managed to work with the key stakeholders,” he said. “It was a good example of collaboration and joint working.”
However the plans have not been without controversy.
According to Highways England, it would enable users of the Cotswold Way National Trail and Gloucestershire Way to safely cross the road.
However Transport Action Network said the plans for the crossing and the road itself would scar the Cotswolds area of natural beauty.