Work on a new junction to cut congestion around Great Yarmouth will begin 18 months sooner than expected.
Improvements to the Vauxhall and Gapton Hall roundabouts are included in a timetable announced for major works on the A47 betwen Yarmouth and Peterborough.
It also includes dualling the A47 between North Tuddenham and Easton, further east between Blofield and North Burlingham, along with junction improvements at the Thickthorn Interchange with the A11.
Further west at Peterborough, the work involves dualling a busy stretch between Wansford and Sutton, and improving the Guyhirn junction with the A141 between March and Wisbech.
Preferred routes for each of the A47 upgrades were announced in August following public consultations earlier in the year.
Until now, the date given for all of the schemes was between 2020 and 2021.
But works to dual parts of the A47 near Norwich have also been put back a year in the latest timetable.
Improvements to the junctions at Yarmouth were expected to be completed between 2019 and 2020 but have now been brought forward to between 2018 and 2019.
Works to improve the A11 Thickthorn junction near Norwich and the Guyhirn junction near Peterborough, which include widening the bridge over the River Nene, will start between 2020 and 2021.
Work to dual the A47 between Wansford and Sutton are also expected start around that time.
Dualling the A47 between Blofield and North Burlingham and from North Tuddenham to Easton, will start between 2021 and 2022.
Jim O'Sullivan, Highways England chief executive said: 'Our update today is a sensible and responsible way to deliver major national investment in road infrastructure.
'It will keep our roads moving, deliver a lasting legacy for the country and ensure best value for money for the taxpayer.'
Six consultations into the £300 million A47 upgrades were held between March and April this year.
Some 1,447 people had their say, with 1,333 attending the 19 public events.
The six projects are part of a £15bn investment in motorways and major A roads, with £3bn invested in the east of England.
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