Police are appealing to trace the driver of a small or medium dark coloured hatchback which was travelling on the A19 southbound, south of the junction of Elwick Village, at around 7.55pm on Thursday 21st July.
As the car in question was heading south, there is a possibility the occupants could be from the North Yorkshire area.
The vehicle was seen in lane 1 at the time of a fatal collision in which a 71-year-old man from the Sunderland area died. Police would like to speak to the driver or occupants of the vehicle.
A 48-year-old man who was arrested on suspicion of causing death by dangerous driving remains on bail pending further enquiries.
The driver or occupants of the vehicle are asked to contact PC Alexander Nisbet on 01642 326326, quoting event number U131612.