New road signs in the UK can electronically detect and warn drivers who are using mobile phones.

According to a Telegraph report, "These signs can detect when signals are being transmitted by a mobile telephone inside a car, 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 road signs work by using a scanner to detect the radio signals emitted when someone in the car is connected to a call, with this data used to illuminate a sign further down the road."

The report notes that the scanner can pick up both mobile phone radio signals and Bluetooth signals, and differentiates between the two. So, those using Bluetooth for a hands-free connection, will not be warned by the sign, as if the scanner picks up a Bluetooth signal, it will disable the light.

The first of three electronic signs was introduced in Norwich, Norfolk.

The new technology powering the signs was developed by Norfolk County Council's Road Safety team in partnership with vehicle sign technology local company Westcotec.