Abstract: A vehicle surveillance system has a plurality of side-light units mounted on opposite sides of a truck, bus, train or a similar long vehicle. The side-light units form an RF communication network on the vehicle. Each side-light unit comprises a day-running light source, a sensor for defining a surveillance zone on the side of said vehicle, said the sensor being arranged to detect an object or a movement of an object within the surveillance zone, and an RF transmitter which is controlled by said sensor and arranged to transmit an RF detection signal from said side-light unit. Existing day-running side-light units of a vehicle may be replaced with the inventive vehicle day-running side-light units.