2.15. CLASSIFICATION SIGNALS AND MARKERS
When flags by day and in addition lights by night are placed on
the  front   of   the   engine,   they   are   called   classification   signals,   and
are used to show what type of train it is.   When flags by day and in
addition lights by night are placed on the rear of a train, they are
called  markers.     Every  type  of  train  must  display  markers  to  qualify
as a train and to show that the train is complete.
a. Train   classification   signals.     A   regular   train   displays   no
classification   signals   in   front   unless   it   is   being   run   in   sections.
The first section of a regular train displays green flags by day and,
in addition, green lights by night on the front of the locomotive as
shown on the right in figure 2.   6.   Each section carries these same
classification   signals   except   the   last   section,   which   carries   none.
For example, if a train is being run in three sections, the first two
sections   display   the   appropriate   green   classification   signals,   and
the   last   section   runs   as   a   regular   train   showing   no   classification
signals in front.  If there are only two sections, the first displays
the   green   classification   signals,   and   the   second   does   not.     Extra
trains are not run in sections.
Figure 2.6.  Train Classification Signals.
An   extra   train   always   displays   white   classification   signals   on
the   front   of   the   locomotive   as   shown   on   the   left   in   figure   2.6.
White   flags   are   used   during   daylight   in   addition,   two   white   lights 
are used by night.
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