A man is in hospital with life-threatening injuries after he was found lying on the carriageway of the M4 motorway.
Emergency services were called to the scene near junction 45 in Swansea shortly after 06:30 GMT on Sunday.
A section of the M4 was closed in both directions for around two hours while investigations took place.
South Wales Police previously described the incident as a "serious collision".
A police spokesperson said: "Emergency services were called following a report of a man lying on the carriageway of the M4 near junction 45.
"The injured man has been taken to the University Hospital of Wales with what are described as life-threatening injuries."
The Welsh Ambulance Service said it sent two ambulances to the scene before transporting the injured man to hospital.