Thorne Road between Clay Lane and Edenthorpe is shut for the next ten weeks while work takes place to lower the carriageway.
It is part of a long-running project to improve access into Doncaster from the West Moor Link which began in 2019.
But drivers have been left frustrated by a string of diversions and delays as the project has dragged on.
The road is not expected to open until September 3.
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A Doncaster Council spokesman said: "The proposed final phase of the A18 Thorne Road improvement scheme is due to start on Saturday 25 June.
“All remaining works will be undertaken under a road closure for approximately 10 weeks.
“Pedestrian and cycle access will be maintained throughout.”
The £10.65m scheme is aimed at easing traffic bottlenecks at the railway bridge, close to the Sainsbury’s supermarket.
A Doncaster Council spokesman said: “The A18 Thorne Road and West Moor Link suffer from congestion and delays, particularly during peak times. This congestion is stifling growth and preventing housing and employment development in the area.
“The route is a key public transport corridor with over 240 buses using the link under the rail bridge each weekday.”
The new and widened bridge has already been installed.
Signed diversions will be in place throughout the course of the works while bus services will be diverted during the latest phase of work.
Full details are available HERE