and models for modern big business, so too the railway timetable was adapted to myriad uses, such as schedules for buses, ferries, airplanes, radio and television programs, school schedules and factory time clocks. The modern world was ruled by the clock and the timetable. 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. 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 lowest. 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 pass them to 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,