A man has been questioned on suspicion of causing death by dangerous driving, after a crash in which an off-duty police officer died.
Detective Constable Bob Keylock was killed at Deddington, near Banbury, on 19 November when his car left the road and hit a tree.
A 21-year-old man from the Deddington area has been questioned and released on bail.
The police on Wednesday night stopped drivers exactly a week after the crash, in an attempt to find witnesses.
The crash happened at around 2320 GMT when Det Con Keylock's silvery-blue Rover 75 left the road.