A teenage car passenger suffered cuts when a brick thrown from a bridge smashed through the vehicle in which she was travelling.
Police received a number of reports of objects being thrown at cars driving along the A303 on Sunday afternoon.
The 17-year-old girl was travelling westbound at Norton when the brick smashed the window.
The broken window and flying glass fragments slashed her face and ear. Police appealed for information.
Pc Claire Villalard said: "This is incredibly dangerous and stupid and anyone throwing stones at cars from a bridge should be under no illusion as to the potential consequences.
"A stone thrown at traffic travelling at speed could cause massive damage to a vehicle and fatal injuries to those travelling in the car, either as a direct cause of the missile or by the vehicle swerving to avoid it."