Abstract: The invention is a sensing and indicating device for determining the presence of a second vehicle near to a first vehicle and indicating the presence of the second vehicle. A sensor is positioned and electrically connected between the light socket and the light bulb contained within a light assembly and protected by a lens. The sensor transmits to an indicator adjacent the operator of the first vehicle, by a visual indication in the operator's sight or by an audio indicator. The sensor can be replaced, transferred to another vehicle or retrofitted to a vehicle.