Cumbria Police officers were called to a crash on the Stainburn bypass, near Workington.
The call came in just after midnight on Sunday, April 20, with a red Volkswagen Golf involved.
A man in the Volkswagen Golf, aged in his forties, was pronounced dead at the scene.
Investigations were launched and the Stainburn bypass remains closed while enquiries continue today.
The road is expected to be closed for some hours and drivers are asked to seek alternative routes.
Police are appealing for witnesses to the collision.
Anyone with information can email officers on: SCIU@cumbria.police.uk
Alternatively, you can contact police on 101. Please refer to log one of April 20.