A man has been killed trying to cross the M25 close to the Dartford Tunnel.
Motorists are being told to expect severe delays
Police officers were already at the scene when the person ran across the carriageway and was hit by a van at about 0500 BST on Saturday.
The incident has been referred to the Independent Police Complaints Commission (IPCC) but the reason for the referral has not been revealed.
The anti-clockwise carriageway between Darenth and Littlebrook was closed for six hours.
A spokesman for the IPCC said: "At 5am this morning a young man was killed on the tunnel approach road, A282, near Bow Arrow Lane, Dartford.
"Kent Police officers had been called to the scene and it is reported that the male pedestrian ran across the motorway and was hit by a van."
The vehicle was not a police van, the IPCC spokesman added.