Abstract: An electronic system provides traffic control and warning functions by radio transmission of signals to civilian vehicles from authorized mobile units, such as police vehicles and portable units at dangerous locations, such as the scene of an accident or road obstruction, etc., utilizing transmission within a police communications band. Transmitting circuitry carried within the mobile unit includes means for modulating the frequency modulation carrier signal radiated by an antenna with either a voice message or by preselected pulse messages. Receiving circuitry is carried within each of a plurality of civilian vehicles separate from the mobile unit, the antenna of such vehicles picking up the modulated carrier signal when the vehicle is within at least the general vicinity of the transmitting mobile unit.