New signs have been installed warning drivers they could be caught speeding by a police helicopter armed with a radar detection device.
Essex County Council have put up more than 20 signs around the county telling drivers that police are watching from the sky.
The aircraft is equipped with a "skyshout" public address system which can warn drivers of a pursuit.
The council said the Essex Casualty Reduction Board put forward the plan.
Board chairman Norman Hume said the signs were primarily aimed at motorcyclists.
'Expensive camera'
"We are seeing accidents in Essex dramatically reduced as a result of our intervention and education campaign, but we need to make more of an impact on motorcycle accidents," he said.
"There is a perception that it is sometimes easier for motorcyclists to evade detection of offences because of the speed they travel at.
"We feel that signs warning of the likelihood of detection by air will be an extra incentive - particularly for motorcyclists, and all motorists - to drive safely and help us to reduce accidents further."
Adam Pipe, Essex Police's Traffic Management Officer, added police were keen to use new techniques to "reduce the number of people killed and seriously injured on the roads".
"Use of the force helicopter will enable officers to obtain video evidence of offences including excess speed," he added.
The TaxPayers' Alliance said the helicopter - thought to cost about £1,000 an hour to run - would be "a very expensive speed camera".
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