Police have released shocking CCTV footage of yobs hurling stones at traffic from a motorway bridge.
Three youths threw the missiles, which smashed the windscreen of a Post Office lorry, sending broken glass flying into the driver's eye.
The incident on June 12, in Slip End Road, Luton, is one of eight recent occasions on which rocks or stones were thrown from bridges on to moving traffic on the M1.
Three drivers have received medical treatment after glass fragments hurtled into their eyes, Bedfordshire Police said.
In one incident, an ambulance windscreen was smashed at one of the Luton motorway bridges. It was one of five cases reported in a half hour period between 7.40pm and 8.15pm on June 8.
The three youths involved in the latest incident are described as being white boys aged between about 13 and 15-years-old, all wearing hoodies.
PC Charlie Pirie, investigating, said: "There has been expensive damage caused to the vehicles involved and three drivers have needed medical treatments for glass fragments in the eye, but fortunately none of the injuries have been serious.
"However, it doesn't take much to imagine what could have happened if one of these heavy goods vehicle drivers had lost control of his lorry. Other road users would have been at extreme risk of being involved in a high speed collision and terrible consequences could have followed."