Officers today issued this CCTV image, which shows a white van carrying potential witnesses to the fatal crash in Halton.
Garforth Academy teacher Ian Winterburn, 58, was seriously injured when he collided with a car while out cycling on December 12 and died in hospital 10 days later.
Sergeant Ann Drury, of West Yorkshire Police's Major Collision Enquiry Team, said: "At the time the collision occurred, this van was the lead vehicle waiting at the junction of Whitkirk Lane and the Ring Road and the collision happened at the side of it.
"The vehicle waited a few seconds before setting off and I feel the occupants of this vehicle will have witnessed the collision and will be able to assist the investigation."
The collision took place on the A6120 Ring Road at the junction with Whitkirk Lane, near to Colton roundabout, at 7.30am.ã€€
Mr Winterburn was cycling towards the roundabout and the silver/grey coloured Skoda Fabia was turning right into Whitkirk Lane from the ring road.ã€€
The white van in the CCTV image is shown after the collision as it turned left out of Whitkirk Lane onto the ring road.
Sgt Drury said: "We believe they will recognise themselves from the date, location and circumstances and we would like them to get in touch so we can have as full a picture as possible of what happened.
"We are also still keen to hear from anyone else who we have not already spoken to who witnessed the collision or who saw the movements of either vehicle immediately before the collision."ã€€
The driver of the Skoda, a 51-year-old woman from Leeds, has been interviewed under caution in connection with the incident.ã€€
Anyone with information is asked to contact the Major Collision Enquiry Team via 101 quoting log number 249 of December 12.