Essex Police have increased patrols on and around the A12 as they continue to investigate two unsolved attempted murder cases in which concrete objects were thrown from bridges.

Harold Hill grandmother, Carol Manley, 57, suffered rib and facial fractures when a concrete block smashed through the windscreen as her husband drove the car under West Hanningfield Road bridge near Chelmsford.

She was injured around 10pm on December 1 last year.

At about 9.25pm the same night, a car passing under Fryerning Lane bridge, Ingatestone, had its windscreen smashed by a large rock.

The driver and passenger, Lisa and Stella Horne, were unharmed but badly shaken.

Essex Police said that several other incidents where vehicles had been damaged had been reported in previous years, and they had historically occurred between November and January.

Most of the incidents happened in the areas between Mountnessing near Brentwood, and Boreham near Chelsmford.

Extra patrols are now being carried out on the A12 and around rural and residential areas on either side of bridges.

Drivers using the A12 or roads and lanes leading to bridges are urged to be vigilant, especially at night, and to report any suspicious incidents or people loitering on bridges.

The Highways Agency will be putting up special information signs near A12 bridges in the Chelmsford area to help drivers give a precise location when reporting anything suspicious.

Chief Supt Simon Williams, from Essex Police, said: “Essex Police treats incidents of missiles being thrown from bridges on to the road as extremely serious, the consequences of such an act puts road users in danger of serious injury as well as significant delays on the roads

“In order to combat those that wish to put others in danger, Essex Police will be deploying additional patrols to those areas that have experienced this type of incident previously and will prosecute anybody identified as responsible.”

Anyone who sees bridge crimes in progress should dial 999 immediately, for less urgent information please call 101.