Nine weeks of archaeological investigations are taking place on the site of the Grantham Southern Relief Road.
Allen Archaeology started work earlier this month and should complete the works on site by the end March.
The works form part of the second phase of the £81 million project which will join the B1174 to the A1 via a grade-separated junction.
Phase one of the relief road was completed in August 2016 and saw the creation of a roundabout off the B1174 and a road along Tollemache Road that leads to a second new roundabout.
Initial archaeological investigations have already been completed for phase three, and, at the beginning of January, Lincolnshire County Council’s Executive gave officers the go-ahead to pursue the necessary legal orders and land acquisitions for the project.
The relief road will link the A52 at Somerby Hill to the A1, which should reduce congestion in Grantham town centre.
Lincolnshire County Council is leading the project, with support from South Kesteven District Council, Greater Lincolnshire Local Enterprise Partnership, Homes and Communities Agency and local businesses.
Councillor Richard Davies, responsible for highways at the county council, said: “Building a major new road like the relief road involves a lot of preliminary work before tarmac can be laid.
“A major aspect of these works is carrying out a thorough archaeological investigation to protect the heritage of the area before we start building.
“Whenever you’re building a big piece of infrastructure, like Grantham Southern Relief Road, it’s incredibly important that work is carried out to gain a better understanding of the heritage and history that can be found just below your feet.
“From this, future generations then have the chance to learn and understand what was happening on-site thousands of years ago.”