The £105m Fiveways to Thetford dualling and improvement scheme will widen 5.5 miles of the A11 – a key route between the M11 and Norwich.
Birse will also build a new 3.6-mile bypass around the village of Elveden, from Chalk Hall Farm to Thetford roundabout.
The A11 widening project is part of a £3.3bn investment in major road improvements in England during this spending review period and the second major road scheme to start work this month.
Work to widen the A453 in the East Midlands got underway last week.
Roads Minister Stephen Hammond said: “The Government is committed to giving this country the first-class infrastructure we need, and the A11 is another example of how we are delivering projects that will boost the economy, especially in the East of England.
“We are investing more than £2bn in road projects over the next two years, with the Highways Agency developing and starting work on 19 major projects, including improvements to the A11.
“Once completed, these schemes will add around 250 miles of additional lanes for drivers, easing congestion, creating jobs and supporting homeowners and businesses alike.”
The Highways Agency started work earlier this month on another major road improvement, with Laing O’Rourke main construction getting underway to widen the A453 in the East Midlands.
A seven-mile rural section of the road from M1 Junction 24 to the A52 Nottingham Ring Road will be upgraded to a dual carriageway at a cost of £150m.
The scheme also includes widening the 1.5-mile urban section through Clifton, near Nottingham, to a four-lane single carriageway (two lanes in each direction) with new signalisation at junctions and roundabouts.
Advanced works also started this month on a scheme to provide technology-driven improvements to upgrade junctions 23 to 27 of the M25, one of Europe’s busiest motorways. Advance work is already underway on a similar scheme to improve the section of the M25 between Junctions 5 and 7.
Main construction is due to start on both schemes in spring this year, and once completed they will increase capacity and make journeys more reliable on these sections of motorway.