Despite being unable to pick up whether the driver is using the phone, it is hoped it will act as a deterrent to people making calls behind the wheel.
The technology picks up the phone signal in the vehicle and activates a roadside warning sign of a mobile with a red line through it.
Being initially tested in Norfolk, the system cannot record footage.
However, it is designed to pick up whether the phone is being used hands-free or via a vehicle's Bluetooth system and as a result will not trigger the sign.
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