A man has died after his car crashed on the M25 in Hertfordshire.
Both carriageways were closed from 0300 GMT between J21a and J22 near St Albans after the Mercedes car crashed and the driver died at the scene.
Chief Insp Donna Pierce said: "We're investigating the circumstances of this collision and have had to close the road whilst we do this.
"I would like to hear from anyone who believes they witnessed this collision or saw the car prior to the incident."
The road reopened in the early afternoon after being closed for about nine hours.