A number of vehicles have been damaged by youths throwing rocks and stones at traffic from footbridges crossing the A1(M) in County Durham.
In the latest incident, a 45-year-old man suffered cuts and was left "extremely shocked" after a large rock smashed through his car windscreen.
A spokesman for Durham Police said that the incidents had taken place on Thursday evening and last night.
"A number of cars have been damaged by youths throwing objects off the footbridges over the A1(M) northbound," he added.
The footbridges were in the Bowburn and Coxhoe areas, near Durham City.
Police are appealing for witnesses, in particular anyone who can help identify those responsible to call Durham serious crime team on the 101 non emergency number.
Extra police patrols will now operate in those areas.
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