Rule 4 of TM 55-200 provides that:
Each timetable, from the moment it takes effect, supersedes the
previous timetable. All trains operating on schedules not provided for in
the new timetable will secure valid authorization from the dispatcher to
continue their runs and do so as extra trains.
Right is conferred by train order, and class and direction by timetable-
-the basic roots of dispatching theory and practice.
The dispatcher, to
accomplish his objective, can change the order of precedence of these
governing rules to suit a particular operation. All rule books, no matter
where you may be railroading, contain a section of rules outlining the
method of determining the superiority of trains.
This section of the
operating rules, as well as those in appendix III, should be consulted the
moment you are assigned to any railroad operating task, whether it be in
train or engine service, in any phase of dispatching work, or in any rail
supervisory capacity involving the movement of road trains.
As a student of train dispatching, you are reminded that this entire
reference text is intentionally general; it cannot be construed as being
standard for all railroads for all conditions of train operation. The rules
that establish superiority, however, are standard on all American railroads
and are identical to those in military use. Operational procedures based on
fundamental rules and practices that might be suitable in peacetime
railroading may be totally inadequate in a theater of operations.
dispatcher has broad powers in handling trains, but he must stay within the
limits of operating policy dictated by higher authority. The timetable, the
established rules, and the particular dispatching policy always govern; they
must be examined before assuming that all the fundamentals outlined here