Good news for commuters: better and faster rapid transit

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.