These signs can detect when signals are being transmitted by a mobile telephone inside a auto, and then flashes a symbol of a mobile phone with a line through it to remind drivers not to use their handsets while behind the wheel.
The UK's first road signs which will electronically detect and warn drivers who are using mobile phones have been introduced.
The roadside system, which is being piloted in Norfolk, picks up the signal in the vehicle and activates a warning sign of a phone with a red line through it, the BBC reports.
Westcotec also says it can't differentiate between legal calls made by passengers and when it's the driver being a baddie, which is presumably why an advisory road sign is all it offers.
Officials have worked with Dereham company Westcotec to develop the system which will flash a warning signal to drivers, similar to those for speeding, if a phone is being used in the vehicle.
"We are delighted to have been able to partner with Westcotec to trial this new technology across Norfolk".
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"Hopefully, as time goes on it will become as socially unacceptable as drink driving".
The move comes amid increasing concerns over the risks posed by drivers using mobile phones at the wheel.
The system will initially be used at sites in Attleborough, Holt, Norwich and Toftwood.
Iain Temperton, team manager for road safety at the county council, described it as "cutting-edge technology" which would be used as an "educational tool" throughout Norfolk to try and tackle the problem.
Insp Jonathan Chapman, of Norfolk Roads Policing unit, said: "Any scheme which prevents this kind of behaviour is welcomed".