Dualling the remaining 42 miles of single carriageway on the A1 between Berwick and Morpeth would cost nearly £600 million.
That’s the eye-watering figure contained in an unreleased report compiled on behalf of Northumberland County Council which estimates the costs of dualling at around £14.2 million per mile.
A feasibility study looking at a range of proposals for the A1 north of Newcastle is currently being carried out, with an announcement expected in the Chancellor’s Autumn Statement.
The most likely option would identify stretches of the route for dualling such as those between Morpeth and Felton and between Adderstone and Belford.
Dualling of the full 42 miles - nine miles between Morpeth and Felton and 33 miles between Alnwick and the Scottish border - would cost £596.4 million although this figure could rise significantly higher if bridge work is required.
Converting the route to motorway standard would cost an estimated £1.5 billion, say consultants.
Northumberland County Council claims the costs of dualling would be offset by a boost to the county’s economy.
A county council report released in July and passed on to the Department for Transport (DfT) and Highways Agency stated that dualling the A1 north of Morpeth could generate £376million for the local economy. The study also estimates that transforming the road could result in the creation of 2,000 jobs and 12,000 new homes.
Council leader Grant Davey said: “Dualling the A1 has been a long cherished aim of campaigners in Northumberland and it’s great to see a ‘cross party consensus’ on how important this project would be for Northumberland as a whole but North Northumberland in particular.
“Our aim is to make a robust case to the coalition government based on how the project would drive up economic activity. It’s long overdue and with this feasibility study, we think the campaign to dual the A1 should be pushing at an open door.”
Last month, Berwick MP Sir Alan Beith said it appeared the main emerging options to be put to ministers by officials are likely to involve dualling from Morpeth to Felton, and possibly as far as the North Charlton dual carriageway, but with a less favourable rating for full dualling of sections further north.
In April, the DfT released a document outlining the study proposals for the dualling of the A1 north of Newcastle.
The scope document explained that the first part of the feasibility study, looking at the range of proposals, should have been completed by the end of July with the second part, on issues such as affordability and value for money, due to be finished by the autumn.
Speaking to the BBC, Berwick councillor Alex Gibson also raised the safety issue. His son, Alexander, 32, died in a 2011 collision.
Mr Gibson said: “If the road was dualled and had a central barrier, he would have just drifted and banged against the barrier and no other car would have been involved. They reckon he would have had about a 90% chance of being alive today.”