A police officer was knocked down by a motorbike rider who he had stopped for dangerous driving.
Cleveland Police said the officer suffered bruising and swelling when the bike was ridden at him on Springholme Terrace in Stockton at about 18:40 GMT on Wednesday.
The officer had stopped the bike after he spotted it being driven dangerously along Yarm Road, the force said.
Police are appealing for information on the rider.
Ch Supt Alison Jackson said: "Assaulting an officer is completely unacceptable and this behaviour will not be tolerated."