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Train order operation, or more accurately timetable and train order operation, is a largely obsolete system by which the railroads of North America conveyed operating instructions before the days of centralized traffic control, direct traffic control, and the use of track warrants conveyed by radio. The system used a set of rules when direct communication between train dispatchers and trains was limited or non-existent. Trains would follow a predetermined operating plan, known as the timetable, unless superseded by train orders conveyed to the train from the dispatcher, through local intermediaries. Train order operation was a system that required minimum human overhead in an era before widespread use of technology-based automation. It was the most practical way for railroads with limited capital resources, or lines with limited traffic, to operate. To this day, a large number of short lines, heritage railways, and railroad museums continue to use Train Order operation for the aforementioned reasons. Train order operation has been almost completely replaced by more modern operating methods. The Long Island Rail Road in New York is the last major railroad in North America to use a "traditional" Train Order operating practice on parts of its Greenport and Montauk Branches, as well as Train Order forms for non-standard operation on the remainder of its system. While the last traditional long hand train order form was issued on September 3, 2012, timetable and train order operating practices remain in effect. The second to last train order holdout, the Chicago South Shore and South Bend Railroad, had retired its system in 2011. == North American usage == ''Timetable and train order operation'' was widely used on North American railroads that had a single ''Main Track'' with periodic passing sidings. Timetable and train orders were used to determine which train had the right of way at any point along the line. A train which had the right of way over another train was said to be the superior train. Trains could be superior by right, by class or by direction.〔http://www.wx4.org/to/foam/sp/train_orders/primers/to_primer1.html〕 While a train dispatcher could establish "right" via train orders, the operating timetable established scheduled trains, their class and the superior direction. The "class" designation of a train equates to its priority with passenger trains having the highest, freight trains having less and Extra (unscheduled) trains having the least. In case of trains of the same class meeting the superior direction would then apply. On single track rail lines, the timetable specifies (explicitly or implicitly) the points at which two trains would meet and pass. It would be the responsibility of the inferior train to clear the main track a safe time before the superior train is scheduled to pass. The timetable thus provides the basic framework for train movement on a particular portion of the railroad. However, variations in traffic levels from day to day, unforeseen delays, the need to perform maintenance, and other contingencies required that railroads find a way to deviate from their established schedules. Deviations from the timetable operation would be enacted through train orders sent from the train dispatcher to block operators. These orders would override the established timetable priorities and provide trains with explicit instructions on how to run. Train orders consisted of two types, Protection and Authority. Protective train orders would be used to ensure that no trains would be at risk of colliding with another along the line. Once the protective orders had been delivered to block operators (who might in turn pass them on to the train crews), an authority could be issued to a train to move over the line where protection had been established. Normally the timetable established both protection and authority for scheduled trains so train orders were only used for extra trains, which were not in the timetable, and scheduled trains moving contrary to their normal authorities. Timetable and train order operation supplanted earlier forms of timetable only and line-of-sight running. The ability for a single dispatcher to issue train orders was enabled by the invention of the electric telegraph in the 1840s. The earliest recorded usage of the telegraph to convey train orders in the United States came in 1851 on the Erie Railroad and by the time of the American Civil War, nearly every railroad had adopted the system. Over time the telegraph gave way to the telephone as the preferred method of communication, and by the 1970s this function was carried out primarily by two-way radio. With the advent of radio communications, timetable and train order operation began to fall out of favor as direct traffic control and centralized traffic control (CTC) became more common on major carriers. CTC enabled dispatchers to set up meets remotely and allowed trains to proceed entirely on signal indication. Where signals were not present, DTC and the related track warrant control allowed dispatchers to directly inform trains what they were to do instead of needing to work through intermediaries or have the train crews figure things out for themselves. 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「train order operation」の詳細全文を読む スポンサード リンク
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