A tanker carrying liquid petroleum gas (LPG) overturned on the M25, causing disruption for motorists driving around the Kent/Surrey border.
It was travelling clockwise when the accident happened near Clacket Lane services at about 0900 GMT.
The M25 was closed in both directions between junctions five and six and did not reopen until 1600 GMT.
The M26 westbound was also closed between junction 2A and the M25/A21.
Kent Police said the closures were caused by the extra time and care needed to deal with the LPG that was being carried in the tanker.
Diversions were in place via the A25 and A22, and motorists were warned to expect long delays.
No-one was injured in the accident.