Drivers using the M40 in Oxfordshire are being advised to check conditions before travelling today, Thursday, while urgent repair work is carried out to the central reservation safety barrier.
A vehicle collided with the barrier between junctions 10 (for the A43) and 9 (at Bicester) earlier this morning, damaging it and reducing its strength.
Two lanes are closed on the southbound carriageway, and one lane on the northbound carriageway.
Repair work will need to be done on around 1,600 metres of barrier, and this work is expected to last until the early hours of tomorrow morning, Friday.
Highways England will try to have an extra lane reopen on the southbound carriageway in time for the evening rush hour, but lane three will have to remain closed in both directions for safety reasons while the concrete foundations of the safety barrier set and gain strength.
For the latest information up to date traffic information, drivers should stay tuned to local radio, or follow Highways England on Twitter @HighwaysEAST.