Police investigating a fatal road accident near Keighley are appealing for the drivers of two other vehicles to come forward.
Tahir Khan, 29, was pronounced dead at the scene of the accident on May 24.
Mr Khan, a cab driver, was driving a grey Peugeot Partner van, which was travelling along the A629 Aire Valley trunk road when it plunged down an embankment.
Officers want to speak to the drivers of a silver Toyota Hiace van and a white Suzuki Swift, which were travelling along the same road towards Silsden around 9.30am.
It is believed they may have vital information about the accident.
Sergeant Mat Tunney, of the Major Collision Enquiry Team, said: "It is likely that these drivers will have seen Tahir's van in the moments before it left the road and I would ask them to contact us immediately, so they can help us piece together the circumstances which led to the collision."
Witnesses are asked to contact the Major Collision Enquiry Team on 101.