Fringford Road, which runs between Fringford and Caversfield on the edge of the town, was due to shut on Monday, January 8.
But householders have now been told the closure will not take place until Tuesday, February 6.
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It was originally expected to reopen after work was completed on March 23, meaning it is estimated it will be closed until sometime in April.
The closure is due to work at the junction with the A4095 Southwold Lane with the county councillor for Bicester North, Donna Ford, revealing the change of plan was made during the Christmas break.
She said: “We have confirmed the road space for this and are in the process of amending the temporary traffic regulation order (TTRO) to reflect this.
“We have planned for letter drops in the surrounding area to be performed in the next fortnight and advanced warning signs to be erected prior to works commencing on site.”
The alternative route for traffic will be via the A4421 Skimmingdish Lane, the A4095 and vice versa.
There will be exemptions for emergency services and for access to homes on the closed section of the road.
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This comes after it was announced last year there will be a £10.7 million restructuring scheme for the nearby Banbury Road roundabout.
In October it was decided at a county council meeting that a speed hump will be installed at the junction between Southwold Lane and Fringford Road as well as introducing 30mph speed limits on the approach to the roundabout.
The speed limits will be enforced on Banbury Road, Bicester to Aynho Road, Lords Lane, Fringford Road and Southwold Lane.
The roundabout will become a signalised crossroads which moves cyclists in front of vehicles at an intersection, making it safer for those on bikes.