A stretch of trunk road currently undergoing upgrade work could be designated as a motorway, Highways England has said.
The agency is almost halfway through a £1.5bn project to re-route 21 miles of the A14 in Cambridgeshire.
The new A14(M) would be on an 18-mile section of the road between the Cambridge M11 junction and Huntingdon, if government approves the proposal.
This would make the road safer, the agency said. It is due to open in 2020.
The change would create an unbroken motorway link between London and Peterborough, via the M11, new A14(M) and A1(M).
Highways England project director David Bray said: "Creating a motorway link between the A1(M) and the M11 will mean motorists and hauliers carrying goods across the country will be able to travel more smoothly and safely, while local and slow moving traffic will benefit from the new routes we are introducing."
Slow moving traffic, including farm machinery and mopeds, would be banned from the 18-mile stretch.
Road signs would change from green to blue and the motorway would have variable speed limits.
A three-mile stretch of the A1 from Alconbury to Brampton would also receive motorway status under the proposal.
The section north of that, from Alconbury to Peterborough, already has motorway status.
Highways England will put the request to the Planning Inspectorate this winter.
If approved, transport secretary Chris Grayling would take the final decision on the change of designation towards the end of 2019.
The A14 through Suffolk, Cambridgeshire and Northamptonshire links the Port of Felixstowe to The Midlands, M1 and M6.