Commuters using the A428 between Bedfordshire and Cambridgeshire could save up to 90 minutes on their journeys every week using a new 10-mile dual carriageway linking the Black Cat roundabout to the Caxton Gibbet roundabout.
Both roundabouts would also be upgraded into free-flowing junctions under plans unveiled on Monday by Highways England and a new junction would be added at Cambridge Road, near St Neots.
The project would replace the only remaining section of single carriageway between Milton Keynes and Cambridge.
In February, Highways England announced the preferred choices from an earlier public consultation in 2017 which included three route options for the new dual carriageway and three options for improving the Black Cat roundabout.
Now, the details behind that announcement are being put to the public for consultation before the final plans go forward for planning consent early next year. An eight-week consultation launched on Monday is an opportunity for drivers, business owners and local people to get involved and help shape the plans.
Highways England A428 programme lead, Lee Galloway said: "The current A428 carries twice the traffic it was designed for and cuts through small communities and villages. It can get painfully congested - in fact it is in the worst 20 per cent of roads for delays in the whole country. Our plans will make a real difference, improving people's journeys, reducing rat running on local roads and better linking the two key economic hubs of Milton Keynes and Cambridge, with economic benefits being felt across the whole region.
"People's input has been essential in getting us to this stage, and I am looking forward to hearing what people think about our plans."
Transport secretary Chris Grayling, said: "These important upgrades will not only relieve congestion but will also link businesses and communities helping to boost the region's economy and make a real difference to people's lives.
"This is part of the Government's £15billion road investment strategy to improve our motorways and major A roads helping get motorists to their destinations quickly, easily and safely."
The project team will be hosting eight consultation events across the area, and in addition, a mobile visitor centre will visit popular locations and pop up events will be held in Milton Keynes and Bedford shopping centres. Each will give people the opportunity to find out more about the proposals, explore the project using visualisations and put any questions directly to the project team.
People can respond to the consultation by going online at www.highwaysengland.co.uk/a428. Copies of the consultation booklet are also available at local council offices and libraries.
The consultation runs eight weeks and closes on Sunday, July 28.