Cambridge police officers are appealing for help to trace a black BMW after the driver failed to stop following a collision with a police motorbike today.
The collision happened at about 4pm on the M11.
The driver failed to stop at the scene and enquiries are ongoing to trace them.
The officer suffered serious but not life-threatening injuries in the incident. He is being treated by paramedics at the scene.
The M11 is currently closed southbound between junctions 10 and 11.
Anyone with any information should call police on 101.