The M25 has been closed in Kent after a two-vehicle crash in the early hours.
The accident involved a lorry with a crane attached and a road sweeper on the anti-clockwise carriageway between junctions five and four, police said.
The motorway was closed in both directions shortly after the crash at about 05:10 BST but the clockwise carriageway has since reopened.
Diversions have been put in place but motorists are advised to expect delays and avoid the area.
Jennie Schofield, who got caught in the tailbacks, said the traffic was "backing up as far as you can see".
Kent Fire and Rescue Service said four fire engines were sent to the scene and crews used hydraulic cutting equipment to rescue one of those involved in the crash.
A spokesman for South East Coast Ambulance Service said: "Ambulance crews attended the scene and were joined at the scene by the air ambulance service."
The driver of the road sweeper was taken to Kings College Hospital by road with serious injuries.
Highways England said the "extensive clean-up" was likely to take several hours, but traffic trapped in the tailback on the anti-clockwise carriageway was being released.