Road signs that know when a mobile phone is being used in a moving vehicle are being installed in Norfolk, in a bid to tackle usage behind the wheel.
The system, which can tell the difference between active phone calls and other activities based on the strength of a signal and how long it lasts, flashes up a red warning signal to drivers when it detects a call.
The technology cannot yet log number plates or be used to help catch offending drivers, but it is hoped it will act as a deterrent.
Holding a phone while driving was outlawed in the UK in 2003 but 23% of people admitted to taking a call in last year's RAC Report on Motoring.
Inspector Jonathan Chapman from Norfolk Roads Policing said: "This scheme is a good example of how we can work with local authorities to make using a mobile phone whilst driving as socially unacceptable as drink or drug-driving.
"Any scheme which prevents this kind of behaviour is welcomed. Using a mobile phone at the wheel is one of the fatal four road offences which can have devastating consequences if it causes a fatal or serious collision.
"We will be using the information provided by Norfolk County Council's road safety team to help us target drivers in the future but the message is simple - leave your phone alone whilst you're behind the wheel."
Norfolk County Council's road safety team have worked with speed and warning sign specialists Westcotec on deploying the next-level signs, which are a first for UK roads.
The system is able to simultaneously detect bluetooth signals so that anyone legally in a call via their car's speakers is not wrongly issued a warning.
Although the signs are unable to log offending number plates, such a feature is being considered for development in the future. There is also no facility for the signs to record footage.
For now, a counter will keep track of phone usage on the road to help authorities understand driver habits.
Diane Steiner, deputy director of public health said: "Our priority in public health is to make Norfolk a healthy and safe place to live and the new technology enables us to provide a reminder to drivers who may be using their handset whilst driving.
"Whilst this is still not a perfect science, the new generation of sign is significantly more accurate and reliable than the first."