Traffic is now flowing on one lane of the southbound carriageway of the M40 following an earlier accident.
The carriageway was closed shortly after 5.30pm when a 4x4 car and trailer overturned between junctions seven and six.
Emergency services were called to the scene, but no passengers were trapped.
One lane is now open to traffic, though vehicles had been backed up to junction nine at Bicester.
A Highways Agency spokesman said: “The traffic was bad immediately after the incident, but I understand it is moving quite smoothly now and most of this has cleared.”
It is not known when the other two lanes will reopen.
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