A multi-vehicle crash on the M1 caused delays of almost an hour and miles of traffic on the motorway.
Highways England has warned motorists of the delays on the northbound carriageway of the M1 between junction 15 and 15A.
The motorway is now open.
A highways spokesman said: "There are 50 minute delays on the approach to this incident spanning seven miles back to J14.
"Average speeds on the approach to 15 are 11 mph.
"Please approach with caution."
The northbound entry slip was also closed to allow emergency services access to the scene of the accident.