Speed detector warning signs

A radar speed sign is an interactive sign, generally constructed of a series of LEDs, that displays vehicle speed as motorists approach. The purpose of radar speed signs is to slow cars down by making drivers aware when they are driving at speeds above the posted limits. They are used as a traffic calming device in addition to or instead of physical devices such as speed bumps and rumble strips. The devices have been referred to by a wide variety of names, a partial list of which follows: driver feedback sign, radar signs, Vehicle Activated Sign (UK), changeable message sign, Your Speed sign, radar feedback sign, speed radar sign, radar speed display, speed feedback sign, traffic calming sign, speed display board, dynamic speed display (DSDS) or variable message sign.