may proceed. When it is straight out from the post horizontally, the
train must stop. The position of the signal between straight up and
straight out, approximately a 45 angle, means that the train may
proceed with caution and at a reduced speed. If the signal is in any
other than the three named positions, the train must stop. A signal
imperfectly displayed or the absence of a signal at a place where a
signal is usually shown must be reported promptly to the train
This measure protects against defective signals
endangering the movement of trains. During nighttime operations, the
semaphore also has lights that can be seen as the arm is raised or
The appearance of these lights at night is also shown in
b. The color light signal has three lights of different colors:
red, yellow, and green.
It is similar to traffic-control lights at
An example of this signal is shown in figure
2.8 also. When the light is red, the train must stop. A green light
means that the train may proceed; the yellow light permits it to
proceed at a reduced speed and with caution. As a safety precaution,
two or more lights burning at the same time or all lights out mean
c. The position light signal is used
throughout the world today. This type of fixed signal is likely to
be present in a theater of operations. Yellow lights arranged in a
circular pattern around a central light burn in rows representing
semaphore-arm aspects. Thus, as shown in figure 2.8, a vertical row
means proceed; a horizontal row, stop; and a diagonal row, proceed
with caution and at reduced speed.
With this signal, it is the
position of the lights rather than the color that denotes the
indication. Again, any combination of lights in positions other than
those stated above means stop.
As an additional safety precaution, the engineman and the head
brakeman observe the signals as they are approached, and both state
the meaning they convey. For example, as a train approaches a signal
indicating proceed, the engineman says "signal up" or "green board, "
and the head brakeman looks at the signal and repeats what the
engineman has said. This is a double-check for safety. Also, if for
any reason the engineman should become disabled, the brakeman knows
the status of the last signal the train passed.
d. Color signal indications are standard for all railroads. The
results that can occur from failure to comply with signals are so bad
that railroaders learn the signals early and unfailingly comply