Police have released a picture of a traffic officer who was killed when he was hit by a lorry while helping a woman whose car had broken down on a motorway.
Pc Mark Goodlad, 41, died from his injuries following the accident on the M1 near Wakefield on Monday afternoon.
The Chief Constable of West Yorkshire Police, Sir Norman Bettison, paid tribute to the officer, saying he had made the "ultimate sacrifice" as he went to help a vulnerable motorist in the "dangerous environment of the motorway".
"Mark paid the ultimate sacrifice and we are all proud of him and are saddened by his loss," he said.
"Our thoughts and sympathy are with Mark's family. We shall try to be there for them as Mark was there for the public at large."
West Yorkshire Police are appealing for witnesses to the crash to come forward.
The accident happened on the southbound carriageway of the M1 just after Junction 39 at about 4.14pm when an orange Scania articulated heavy goods vehicle was in collision with a marked BMW X5 police vehicle and a grey Suzuki Swift.
At the time of the collision the police BMW and the Suzuki were both stationary on the hard shoulder. Pc Goodlad was between the two vehicles, assisting the 51-year-old female Suzuki driver who had a problem with her vehicle.
The woman suffered minor injuries in the incident.
A 44-year-old man, from the Oldham area, was arrested on suspicion of causing death by dangerous driving and is currently in police custody.