The new dual carriageway in Bedfordshire will get the go-ahead following a deal with developers to contribute to the project, which will cost around £200m including land costs.
Civil servants at the Department for Transport issued a letter yesterday confirming the decision to proceed with land acquisition and construction orders.
Developers planning 5,000 homes in Houghton Regis will pay £45m towards the construction project with Central Bedfordshire Council putting in a further £5m.
The £70m construction project is the final stage in a wider scheme awarded to a Costain-Carillion joint venture under an early contractor involvement deal back in 2010.
Both firms will deliver a 2.3-mile, two-lane dual carriageway running east from the A5 north of Dunstable to join the M1 at a new Junction 11a south of Chalton.
The scheme is intended to improve journey times by removing the need for long distance traffic to travel on the A5 through Dunstable.