Officers are seeking to identify a young man who may have been a witness to a serious collision in Horsham.
It follows a collision between a blue Ford Fiesta and a pedestrian in Rusper Road, near the junction with Northdown Close, at approximately 9.30pm on October 16.
The pedestrian, a 29-year-old man, suffered serious injuries.
A 19-year-old man was later arrested on suspicion of causing serious injury by dangerous driving, and remains on bail as the investigation continues.
Now officers investigating are looking for a possible witness to the incident, shown in CCTV images from a nearby shop, to come forward.
He is described as a young white man with short brown hair, wearing a black T-shirt with a white trim collar and sleeves trim, blue jeans, and white Nike trainers.
Anyone who can identify him or who recognises him is asked to report it to Sussex Police online or call 101 and quote Operation Grimsby.