The M25 was closed for about 12 hours after a crane collapsed on the motorway.
The crane toppled at Junction 27 for the M11 in Epping, Essex, at about 16:45 GMT on Friday.
It caused huge tailbacks in both directions, with more than 10 miles of near-stationary traffic.
The road is now open clockwise, but with lane closures while the central reservation is repaired. Essex Police said no-one has been seriously injured.
The anti-clockwise carriageway remains shut at junction 27.
Essex Fire and Rescue Service said six engines were sent to the scene, where traffic stretched back to Junction 29 (A127) on the anti-clockwise carriageway.
Concrete had been scattered across the motorway by the crane, making it impossible for cars to pass.
Work continued through the night to clear away debris and resurface the road.
Highways England warned motorists to avoid the area.
A spokesperson for the organisation said the road was damaged due to a diesel spillage, but specialist contractors had been brought in to get the motorway reopened.