A14 Cambridge to Huntingdon to open in the spring
A £1.5bn road improvement scheme is expected to be completed six months ahead of schedule.
Work on the 21-mile (34km) route between Cambridge and Huntingdon began in November 2016 and was due to be finished by the end of 2020.
However, Highways England has announced it will be fully open to traffic "this spring".
It said journeys between Cambridge and Huntingdon could be up to 20 minutes faster on the new road.
Part of the project, a 12-mile (19km) bypass between the A14 at Swavesey and the A1 at Brampton, opened in December, a year ahead of schedule.
The scheme also includes widening the A1 between Brampton and Alconbury and the existing A14 between Swavesey and Milton, and improving the junctions at Bar Hill, Swavesey, Girton, Histon and Milton.
Highways England said the A14 was used by 85,000 drivers every day, including 21,000 hauliers.
The improvement works will be delivered on budget and "more than half a year early", the organisation said.
Highways England said it would open fully "this spring", but was not able to give an exact month or date.
Roads Minister Baroness Vere said: "I'm delighted that the A14 upgrade will open ahead of schedule, not only meaning drivers will benefit from quicker and safer journeys sooner, but also ensuring that key access between the region's ports and the West Midlands will be boosted."