method where loaded trains run forward for a given period and then
the empty trains return toward the rear for an equal period. Manual
block operation is also used before a railway communications net is
established. Trains run from one block station to the next, having
permission from the train dispatcher and the block station agent. In
permissive block, more than one train may occupy a block at the same
time, providing they are moving in the same direction. In positive
block, only one train may occupy a block at any one time; this allows
the train to back up to the station in the rear if it is attacked.
Train order operation, started after dependable communications
are established and sidings are usable, is more efficient and
flexible than fleet or manual block. Trains are operated under
orders from the train dispatcher to block station agents. The agent
writes the order and repeats it back for accuracy. One copy is given
to the train conductor and one to the engineman. Train movements are
expedited because meeting and passing of trains can be arranged or
changed, and train rights conferred or reversed. Timetable
operation, used after rail traffic has been stabilized, is the most
efficient method. The timetable gives a train the right to occupy a
stretch of track at a specified time; it tells which train has right
over another train and which one must take the siding and where. In
a theater, timetable operation is normally used with train order and
manual block operation to provide more flexibility.
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