Police were called to the A689 at Crook just after 1am on Tuesday (December 10) to reports of a crash involving one vehicle.
A 32-year-old man was pronounced dead at the scene.
Police have now launched an investigation into the incident.
They said: “Enquires are now ongoing and officers are particularly keen to speak to anyone with dashcam footage of the incident.
“Anyone with information is asked to contact the Serious collision investigation unit on 01913752996 or email sciu@durham.police.uk quoting incident number 18 of December 10.”
