A man has died after his car hit a footbridge over the road linking the M25 and the M1 in Hertfordshire.
The victim, aged in his 40s, died at the scene on the A405 near Bricket Wood at about 06:45 GMT on Sunday.
Hertfordshire Police said the silver Mercedes C Class was the only vehicle involved, but it was not known why it left the Watford-bound carriageway.
The road was closed in both directions for more than nine hours on Sunday.
The northbound carriageway reopened at about 16:00 and the southbound side at about 17:00.
Sgt Ian Manley said the victim's friends and family were being supported by specialist officers and appealed for witnesses to come forward.