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Signaling and operation on the Washington Metro system involves train control, station identification, train signaling, signage, and train length. As with any working railroad, communication between train operators, dispatchers, station personnel and passengers is critical. Failures will result in delays, accidents, and even fatalities. It is therefore important that a comprehensive signal system operated by a central authority be in place. This gives individual train and station operators the information they need to safely and efficiently perform their tasks. == Train control == Metro was designed to use an Automatic Train Control (ATC) system, which comprises three sub-systems. Automatic Train Protection (ATP) protects trains by separating them so as to avoid collision. Automatic Train Supervision (ATS) routes trains and assists in maintaining adherence to schedule.〔 Together, these two sub-systems provide input to the train's cab signals and to a third sub-system, Automatic Train Operation (ATO), which can control the trains directly.〔 Since a train collision in 2009 caused by an ATC malfunction, Metro has not used the ATO sub-system. The Automatic Train Protection sub-system uses coded track circuit technology originally supplied by Rochester, New York-based General Railway Signal when the line was constructed in the 1970s. It is a life-critical system that provides a continuous stream of information to the train regarding the maximum safe speed via the running rails. Speed commands are designed to ensure trains maintain a safe stopping distance from any obstruction and do not exceed the speed limit for any segment of track. The system stops trains in advance of any other train traffic, and before stop signals at interlockings. The cab signalling system relies on track circuits to detect track occupancy, and thus send the appropriate speed code.〔〔.〕 Although the ATP system was designed to be fail-safe, the track circuit control equipment on which it relies has been prone to parasitic oscillations which can cause the system intermittently to fail to detect the presence of a train.〔 This resulted in the 2009 collision, after which Metro began to operate all trains manually.〔 The Automatic Train Supervision sub-system provides for headway management and proper interleaving of trains at junctions by speeding up or slowing down trains.〔.〕 The system works via a series of track mounted balises, which function as information beacons transmitting a speed code to the train as it passes overhead. Its designers intended its function to be non-vital, and for this reason its design is not fail-safe.〔 At no point can the ATC system override the maximum speed limit enforced by the cab signal system. Automatic Train Operation controls trains so that, between stations, they will move at the speed specified by the automatic train protection and automatic train supervision sub-systems. All Metro trains are manned by train operators who work the doors, make station announcements, and supervise the train. The train operator also can control whether the train operates in automatic mode or manual mode. From November 17, 1995 until January 6, 1996, Metro management required its employees to use the automatic mode at all times. During the Blizzard of 1996, however, there was a collision on January 6 that occurred when the ATS system failed to pick up proper instructions from the wayside communication system during a snowstorm, and defaulted to the highest speed.〔 This speed would have been safe during dry weather, but because of ice or snow, trains required additional stopping distance, which was not provided for by the ATC system. Since the June 2009 collision, Metrorail operators have been operating the trains exclusively in manual mode. The automatic train protection system still limits the maximum speed of every train that is in revenue service. An automated announcement system will be equipped on the 7000-series rolling stock and is planned to be added to the 5000- and 6000- series rolling stock once rehabilitation of those train cars is complete. Non-revenue tracks (storage tracks, tail tracks, yard tracks) are not equipped with ATC. Green signs with letters reading “START ATC” and “END ATC” mark the beginning and ending respectively of ATC territory. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Washington Metro signaling and operation」の詳細全文を読む スポンサード リンク
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