Highways Agency bosses have now reopened a slip road on to the A34 outside Oxford.
Drivers suffered heavy delays this morning after line-painting work at the Botley interchange over-ran because of the hot weather.
There were heavy tailbacks after contractors kept the slip road to the northbound carriageway of the A34 closed after working there overnight.
The closure forced traffic heading north to divert south on the dual carriageway and drive to the Hinksey Hill interchange before travelling north.
Roger Jones, a spokesman for the Highways Agency, said: "The slip road was fully reopened shortly after midday."
During the rush-hour, there were major tailbacks on the A34 and on the A420 approaching the Botley interchange.
Stuart Thompson, a spokesman for the Highways Agency, said resurfacing and line-painting work over-ran due to the hot weather.
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