A division's timetable is the authority for moving scheduled trains; it
establishes their superiority and the superior direction of the tracks. For
example, first-class trains are superior to second class.
trains--extras--are inferior to scheduled ones and have no class designator.
The superior direction is decided by the line's officials.
receive train orders from the dispatcher.
They supersede the superiority
established by the timetable. Operating rules of both civilian and military
lines are based on a standard code, to provide safe and efficient train
operation. Rules 86 and S-87 cover procedures followed by extra trains.
The four methods of dispatching are single-track, double-track,
multiple-track, and Centralized Traffic Control. Single-track dispatching,
conducted by using written train orders to tell the crew what to do, is more
complicated than double-track dispatching.
The latter depends mainly on
automatic block signals and on proper spacing of trains.
dispatcher must enforce the established current of traffic except when
single-lining or reverse movement is called for.
Train orders, too, are
used to avoid delay to top-priority trains.
Operating problems are further reduced on multiple-track lines,
especially where there are four tracks: high- and low-speed tracks for each
direction can be designated.
Some railroads make a strict distinction
between the high- and low-speed tracks, with lighter rail being used and
less roadbed maintenance being performed on the latter. Other lines make no
distinction between the two; the rail, ties, and subgrade for both are the
Centralized Traffic Control is the simplest method of dispatching and
provides the dispatcher the greatest flexibility in manipulating trains.
Small indicator lights on a control panel come on as trains reach particular
points on the line. The lighted indicators permit the dispatcher to check
the train's progress and speed.
dispatcher can give a train a proceed sign or divert it to another track.
The system is safe--the dispatcher cannot set up conflicting moves, and
restrictive signals flashed in the crew's face cannot be complied with if
there is too little time.
Among the system's advantages are reduced
maintenance-of-way costs, accelerated freight train schedules, increased
train density at times, and less delay because of fewer wait-and-meet