Abstract :
Rail signal systems have traditionally been employed to prevent collision of trains while permitting them to adhere to a schedule that is adequate for moving passengers and/or freight. In today´s rapid-transit systems, however, the corollary objectives of a signal system¿namely, controlling the speed of trains, increasing the capacity of the line, and minimizing schedule disruptions caused by transient disturbances in train operations¿are critical to providing satisfactory service to passengers.
