MOTORISTS are being warned they could be caught speeding by a police helicopter armed with a radar detection device.

More than 20 signs are being put up across the county telling drivers police are watching from the sky.

Essex County Council – which is putting up the helicopter warning signs – says the aircraft is equipped with a “Skyshout” public address system which could be used to “warn of a detection”.

Norman Hume, chairman of the Essex Casualty Reduction Board, which aims to lower road casualties, said: “We are seeing accidents in Essex dramatically reduced as a result of our intervention and education campaign but need to make more impact on motorcycle accidents.

“There is a perception it is sometimes easier for motorcyclists to evade detection of offences because of the speed they travel at.

“We feel signs warning of the likelihood of detection by air will be an extra incentive for motorcyclists in particular, and all motorists, to drive safely.”

The police helicopter is equipped with a special number plate recognition device which can read vehicle number plates from 700 ft and has radar speed detection.

But, a campaign group said the idea represented a “bizarre” use of public money. The TaxPayers’ Alliance said the helicopter – at a cost of about £1,000 an hour to run – would be “a very expensive speed camera”. A spokesman added signs warning motorists of a helicopter was “possibly not the best way to encourage drivers to keep their eyes on the road”.

The signs are being trialled on the B184 from Ongar to Dunmow, the B1057 from Great Dunmow to Finching-field and the B1012 Lower Burnham Road.