Birse Civils will start its £113m contract to upgrade the last remaining single carriageway section on the A11 in January.
The Fiveways to Thetford dualling and improvement scheme will widen 5.5 miles of the A11 – a key route between the M11 and Norwich – and build a new 3.6 mile bypass around the village of Elveden.
Roads Minister Stephen Hammond said: “The start of construction in January shows our commitment to deliver much-needed improvements to the UK’s infrastructure now.
“The new bypass and widening of the A11 will bring significant benefits for the economy, road users, and local people, by improving road safety and removing the bottlenecks.”
During November and December, preparatory works will continue, including archaeological surveys, completion of the track upgrade on the Elveden Estate, construction of the site office and access improvements for vehicles.