The chief dispatcher maintains an accurate, uptothe minute
account of what movements are actually taking place on the division.
For this purpose, the dispatchers' record of train movements is used.
Another requirement for the safe and orderly operation of trains
over a railroad is an easily understood signal system. Fixed signals
are along the railway rightofway to give directions to train
operating crews by either their position or their color. The three
most common types of fixed signals are the semaphore, the position
light, and the color light. Trains also have markers and
classification signals recognized by all railway personnel involved
in train movements.
When trains must run through radioactivecontaminated areas, the
operation should be delayed as long after an explosion as possible,
and every precaution must be taken to protect personnel from
rapidly and, when possible, avoid any stops, delays, or train meets.
While the positive block method is usually best suited for these
operations, the fleet method may be used.