Local industry sources told the Enquirer Costain is gearing-up to start preparatory work shortly on one of the last major bottlenecks in the county.
Taylow Woodrow was originally lined-up for the job but is understood to have failed to agree a price with client Highways England.
One source said: “The job was going to Taylor Woodrow but there has been a change and now Costain will be main contractor.”
The Highways England project has been in the pipeline for several years and is now the only remaining stretch of single carriageway on the A30 between Camborne and the M5 at Exeter.
Development consent has been given to upgrade the road from a single to dual carriageway which includes construction of a 12.5 km new off line section and a new grade separated junctions at Chiverton and Carland Cross, and Chybucca.
The majority of the existing A30 will be retained as a local route.