A man died in an incident that shut the M4 westbound between Junction 47 and 48 near Swansea.
South Wales Police said that a grey Audi Q3 had collided with a local man, who died from his injuries at the scene.
The collision is understood to have happened at around 4pm and the motorway was closed for around six hours.
The force said it thanked people for their patience and understanding.
A spokesman said: "South Wales Police would also like to speak with any witnesses to the collision, any person who may have dash cam footage of the incident or anyone who witnessed the manner of driving prior to the collision.
"Please could witnesses contact the Roads Policing Unit at Lakeside Police Station on 101 quoting occurrence 1900441957."
