Abstract: A passive optical system (POS) is disclosed for detecting the presence of an object, such as a vehicle, in one or more areas of surveillance. The system includes one or more sensor tubes, each having one or more photosensitive devices arranged interiorly at one end and an opening in a wall at the other end, capable of focusing light rays emanating from a specific area of surveillance. Variations in the light rays caused by an object moving into or out of the area of surveillance cause corresponding fluctuations of the light rays impinging on the photosensitive devices, which, in turn, produce variation in a signal. The signal may be utilized to inform the driver of the host vehicle of a nearby vehicle or, when the POS is connected into a cruise control system, to manipulate the host vehicle, accordingly.