A brick was thrown from a Halifax flyover and smashed the window of car being driven by police staff.
The incident happened on September 25 at 10.40pm as the object was thrown from Burdock Way and smashed the rear window of the car below the flyover.
An officer who goes by the name Traffic Dave on Twitter, posted: "A brick was lobbed from Burdock Way #Halifax at colleagues who were in the vehicle underneath the flyover at the time."
No-one was injured in the incident.
It was the second time in one day the officer reported such an incident online.
Police officers reported being "bricked" and having rocks thrown at them while making an arrest in Bradford.
Officers were deployed to the Skinner Lane area of Manningham shortly before 6pm.
They were arresting someone suspected of drug driving.
Duty inspector Carlton Young said: "They stopped somebody and gone through to make an arrest.
"Somebody was throwing stones at them."
No further arrests were made in relation to the incident.
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