A woman who was found injured by the side of the M3 motorway remains in hospital in a critical condition, police have said.
Officers are investigating how the woman came to be on the hard shoulder between junctions one and two at Chertsey at 0300 GMT on Monday.
She was taken by ambulance to St George's Hospital in Tooting, south London, with serious head injuries.
Surrey police have appealed for witnesses to come forward.
Det Insp Paul Burrill said he wanted to hear from any motorists on the M3 or near the Littleton Lane Bridge who had seen anything unusual.