A one-way road in Abingdon will be opened to two-way traffic on Sunday.
Stratton Way has been a one-way dual-carriageway for more than 30 years but will become a two-way road as part of a £3.1m highways project in the town centre.
Traffic planners hope the changes will reduce congestion in Stert Street and High Street by funnelling vehicles from Oxford Road along the redesigned Stratton Way.
Motorists have been warned to expect delays during the transition period, but police are not expecting any major problems.
Right turns into and out of Bath Street at its junction with Stratton Way will be banned and new traffic signals at either end of Stratton Way are already operational.
The changes are part of the Oxfordshire County Council's Abingdon town centre improvement scheme, aimed at increasing traffic flow and improving facilities for pedestrians and cyclists.
David Robertson, the council's cabinet member for transport, said residents had been fully consulted about the changes. He said: "Our aim is to manage traffic flow and make life more pleasant for every road user, from pedestrians through to motorists.
"In the short term, there has been disruption for people. We apologise for that and we are grateful for the understanding people have shown.
"Obviously it will take time to bed down, but the new arrangement should be judged over the longer term."
Once the Stratton Way project is complete, work will focus on the installation of traffic signals on the approach over Abingdon Bridge near Hales Meadow car park. Abingdon Chamber of Commerce has welcomed the road changes to Stratton Way.
Chamber president Jill Carver said: "It is a good move because it means traffic that just wants to go through Abingdon will not impact on the retail area.
"That will make the shopping experience in Abingdon better and hopefully increase footfall."
A spokesman for Thames Valley Police said: "As with anything new, we will pay attention to it but we are not anticipating any problems."
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