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."