The government says work to dual the last single section of carriageway of the A11 through Norfolk and Suffolk will be finished in two years.
Transport minister Norman Baker said the new nine-mile stretch between Fiveways and Thetford should be completed by December 2014.
He made the announcement during a debate in parliament.
Preliminary work on the scheme, expected to cost £131m, has already begun.
During the debate in the House of Commons, Mr Baker said: "The massive improvement on the A11 between Fiveways and Thetford will be delivered by December 2014, so Norwich will finally get the road that it has perhaps been after for some time."
It is hoped the main works to transform the road will begin between January and March next year.
The road will be closed for several nights during November to allow workers to clear the sides of the road where it will be dualled.
Since June, the Highways Agency has carried out preliminary work including installing fencing and animal protection work.
Archaeological surveys are also being done near How Hill Tumulus and between Chalk Farm and the B1106.