Two police officers were taken to hospital after the driver of a transit van reversed into their duty vehicle and fled the scene.
Police are appealing for information after the incident in the early hours of Saturday in Ravensthorpe, Dewsbury.
Huddersfield CID would like to speak to anyone who witnessed the collision on Huddersfield Road in Ravensthorpe at 1.07am.
It took place after a police car pulled up behind a Ford Transit van which had stopped.
A passenger fled from the vehicle, which then reversed into the stationary police car before fleeing the scene.
Both officers in the car, a police constable and special constable, were injured and taken to hospital as a result of the collision.
A female police constable received injuries to her foot while a female special constable was treated for whiplash injuries.
Both have been discharged from hospital.
Superintendent Oz Khan of Kirklees District Police , said: “Police enquiries are ongoing today in to what has been a serious incident in which two of our officers have been injured in the early hours of this morning.
“Incidents such as these highlight the dangers officers can face while trying to carry out their duties and keep communities safe.
“It is fortunate they were not more seriously injured and we are doing all we can to locate and arrest those responsible.
“We would like to speak with anyone who saw the collision itself or a white Ford Transit driving in the Huddersfield Road area of Ravensthorpe.
“Information can be given to Kirklees CID on 101 or anonymously, to the independent Crimestoppers charity on 0800 555 111.”