A system for sensing the presence, position and type classification of an occupant in a passenger seat of a vehicle, as well as for sensing the presence of a rear-facing child seat therein, for use in controlling a related air bag activator control system to enable, disable or control inflation rate or amount of inflation of an air bag. The sensor system employs sensor fusion, a process of combining information provided by two or more sensors (24, 26), each of which "sees" the world in a unique sense. In a preferred embodiment, infrared sensor inputs (78) and ultrasonic sensor inputs (79) are combined in a microprocessor by a sensor fusion algorithm (80) to produce an occupancy state output signal (85) to the air bag controller.