Carillion has bagged the contract to design and build a £57m bypass in south-west Wales.
The Welsh Government confirmed to Construction News that the contractor had been appointed for the bypass, which will run around Llandewi Velfrey in Pembrokeshire.
Currently the single-lane A40 runs through the centre of the village, which often gets heavily congested.
The 5 km bypass will comprise 2.5 km of carriageway to the north of the village and a 2.5 km section west of the village.
The bypass will then rejoin the existing A40 at the Penblewin roundabout.
Carillion’s early contractor involvement will see it prepare the necessary statutory orders to progress the project through planning.
If successful, the firm will then begin the detailed design, construction and aftercare of the road.
Construction is expected to start in the autumn of 2018 and take two years to complete.
The Welsh Government has said funding could be available for the design and construction of further schemes along the A40.
A Carillion spokesman said: “We are pleased to have been awarded this prestigious contract which continues our association with important road projects in Wales, including the Heads of the Valley programme.
”Our work is helping deliver economic benefits and create jobs.”
Elsewhere, a Carillion-led joint venture this week revealed a three-year extension to its support services deal with BT Openreach.