Works to increase capacity and improve traffic flow at the A46 Riseholme Roundabout are scheduled to begin early 2020.
The project is expected to take seven months to complete, subject to suitable weather.
As part of the scheme, an extra roundabout lane will be added, along with extra entrance and exit lanes at all approaches and exits.
The drainage system at the roundabout will also be rebuilt, along with resurfacing works and the installation of new signs and lighting columns.
Cllr Richard Davies, Executive Member for Highways and Transport, said: "This stretch of the A46 is a crucial part of the county's infrastructure and a key part of the Lincolnshire Coastal Highway.
"But drivers often face queues at Riseholme Roundabout at peak times, which can significantly affect people's journey times.
"Our research and traffic models show that making Riseholme Roundabout bigger and adding extra approach and exit lanes would be improve this issue significantly, since that's where traffic bottlenecks.
"These works will inevitably cause some disruption, but we'll be doing our absolute best to keep traffic moving and will ensure that the works will not impact on traffic flow during next year's Lincolnshire Show."
A combination of narrowed lanes, temporary traffic signals, speed reductions and night-time road closures will be used throughout the works. In addition, a right-turn ban into St George's Lane will also be in place.
The diversion route for this will be via the A15 North to the A15/A1500 roundabout back to the A15 South for a left-turn only into St George's Lane.
Cllr Davies continued: "Our original plan was to also improve the A46 Nettleham Roundabout as part of this project, but we've decided to hold-off on that part of the project for the time being.
"Instead, we're looking at developing the project into a more substantial improvement that includes potentially using that area to improve sustainable transport links in and around the city – something that has come out of new Lincoln Transport Strategy, which we'll be publishing next year."
Ruth Carver, Chief Executive of the Greater Lincolnshire LEP, said: “The A46/A15 Riseholme Junction scheme will have a positive impact on local jobs, housing and future investment.
"It is of high strategic importance and without the Greater Lincolnshire LEP's £2.4m grant contribution to the infrastructure works proposed, a number of major growth projects within Lincoln would be unable to progress.”
For more information about this and other major highways projects, visit www.lincolnshire.gov.uk/majorprojects.