Motorists are having to contend with scores of attacks a year by missile-throwing yobs, it was revealed today.
One county police force reported that more than half the attacks in its area last year involved objects hurled from bridges, according to data gathered from a Freedom of Information request by the Autoglass company.
Ten English police forces who responded to the request reported a total of 395 incidents of rocks, stones and other objects being thrown at motorists or moving vehicles during 2011.
Lancashire Police recorded 125 incidents, with the Northumbria and Nottinghamshire forces both reporting 64 instances.
Suffolk Police said 15 of their 28 incidents last year related to objects thrown from bridges.
Previous data for 2010 - from nine police forces - showed there were 457 such attacks on motorists and moving vehicles.
Autoglass made the 2011 request after two attacks on the A12 in December.
In one, Carol Manley, 57, suffered fractures to her face and ribs, and internal injuries after a lump of concrete was dropped on her vehicle from a bridge.
Another motorist, Lisa Horne, 26, escaped unharmed when a rock the size of a football smashed through her windscreen.
Autoglass managing director Matthew Mycock said: "It is horrendous that so many thugs are prepared to risk the lives of so many by targeting moving vehicles for fun.
"The alarming thing is that our findings are just the tip of the iceberg because they relate to only the reported incidents and there must be many more cases where drivers don't bother to alert the authorities."
He went on: "We know from the experience of our own technicians that missile attacks are a growing problem and a recent Autoglass survey found that a quarter of motorists have had their vehicles hit by a missile of some sort in the last five years.
"We would advise victims and witnesses to always accurately record these incidents and report them to the police to help eradicate such reckless behaviour and to save innocent UK road users from death or injury."