The M25 was closed for six hours after a three-car crash which left one man dead and two others injured.
The crash took place just after 11am on Monday, and led to the motorway closing in both directions, huge tailbacks and drivers trapped in queues for hours.
Essex Police said despite the best efforts of paramedics, a 68-year-old man died at the scene. Two others were taken to hospital.
The busy motorway was closed as emergency services worked at the scene following the crash on an anti-clockwise section between Junction 28 (Brentwood) and Junction 27 (Epping).
National Highways warned that seven miles of congestion built up as drivers remained trapped for hours before slowly being released from the busy motorway.
It earlier said that an air ambulance was sent to the scene along with other emergency services.
The issue also sparked long queues on nearby roads. There were also delays on the M11 southbound, with journeys taking an hour longer than normal due to four miles of congestion on Monday afternoon.
National Highways confirmed on X that the motorway had reopened in the early evening but warned there was still congestion.
Essex Police are appealing to speak to anyone who has dashcam footage that will help with the investigation.
A spokesperson for the force said: "Please get in touch quoting incident number 400 of Monday December 16. You can let us know by submitting a report on our website or by using our online Live Chat service which is available 24 hours-a-day, seven days a week."
