Two motorists in Kent escaped injury after objects were thrown at their vehicles in two separate incidents.
A group of teenagers threw a brick from a bridge over the M2, just before the Medway service area, on Thursday.
It hit the bottom of the windscreen of a car being driven coastwards by a 25-year-old woman, smashing the glass.
In the second incident, at 0055 GMT on Friday, a 40-year-old man was driving his lorry down Four Elms Hill towards Strood when it was hit by a sand bag.
Police said it shattered the windscreen and dented the roof.
'Reckless behaviour'
The offenders were seen on the bridge in Upchat Road by the victim.
Officers are appealing for witnesses to either of the incidents to come forward.
A police spokesman described the behaviour displayed by the offenders as reckless and dangerous.
"Both drivers are extremely fortunate that they did not receive any injuries during these incidents and they were able to stop their vehicles safely," he said.