The £90m work to dual just over 1.6 miles of the A47 between Norwich and Acle will begin in the autumn, highways bosses have confirmed.
Transport secretary Grant Shapps announced on Wednesday (June 22) that the dualling scheme between Blofield and North Burlingham could go ahead.
And National Highways - the government-owned organisation which will build the road - has confirmed work will start in October.
It says the newly dualled section is due to open to traffic in the summer of 2024.
A new two-lane dual carriageway will be built 70m south of the existing road.
Safety improvements will be made to the Yarmouth Road junction, closing the right turn and adding a dedicated lane to join the A47.
A new bridge will cross over the new dual carriageway to connect Blofield and North Burlingham, and take traffic from Blofield toward Great Yarmouth.
The east junction - a notorious crash blackspot - is also being changed, with a new two-tier junction connecting the B1140 South Walsham Road with the B1140 Coxhill Road.
Details of what the impact on traffic will be while the work is done have yet to be revealed.
But National Highways says it will organise face-to-face public information events from August, using engagement van at venues in areas which will be affected.
These will provide information about the scheme and allow officers to answer any questions people have.
National Highways will also hold online briefings in September.
The dualling between Blofield and North Burlingham will be the first of £300m A47 Norfolk projects first earmarked back in 2014.
By the autumn, decisions will have been made on two more major Norfolk A47 schemes.
Mr Shapps is due to make a decision over dualling a section between North Tuddenham and Easton in August.
As well as dualling five and a half miles of road, two new junctions would be created at the Wood Lane/Berry's Lane and Norwich Road/Blind Lane junctions. Easton roundabout would be removed.
And a decision on changes to the Thickthorn roundabout, on the edge of Norwich, is due in September.
The Thickthorn plans include a new slip road off the A11 northbound, which would take motorists beneath both roads before re-joining traffic on the A47 heading towards Great Yarmouth - eliminating the need to use the roundabout.
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