As part of the new bridge's construction, the northbound lanes of the A1, between Harlaxton and Little Ponton, will be temporarily diverted to a new section of A1 carriageway.
Subject to suitable weather, the lane diversion starting on Monday 27 January is expected to be in place for seven months while the first half of the new bridge is built.
Cllr Richard Davies, executive member for highways, said: "Over the past four months, Galliford Try has been hard at work widening the A1 so it can be re-aligned as part of the new Grantham Southern Relief Road.
"And starting next week, we'll be moving traffic off of the A1's northbound lanes to this newly-widened section of road so we can make a start building the first half of the new grade-separated junction which will connect the trunk road with the B1174.
"Once that section is finished, we'll move over to the south side of the A1 to complete the bridge ahead of fully opening phase two up to traffic in 2021 and the whole of the relief road by Winter 2022/23.
"Once the entire relief road is complete, it will not only reduce congestion and improve journey times in and around Grantham, but it will also boost the local economy by opening the door to more homes, job opportunities and community facilities."
The Grantham Southern Relief Road project is being led by Lincolnshire County Council and supported by South Kesteven District Council, Greater Lincolnshire LEP, Highways England, Department for Transport, Network Rail, Homes England and local businesses.
For the latest news on the Grantham Southern Relief Road, visit www.lincolnshire.gov.uk/majorprojects.