be in operation, supporting combat forces and strengthening the
military effort.
Before a dependable railway communications net is established,
the manual block operation method may be used if there are passing
tracks or sidings. The railway line is divided into blocks running
from station to station. Trains operate from one station to the
next, and at each they are either cleared to proceed to the next or
held until the track to the next station is clear. The train moves
from one block to the next only when the station agent at one station
gets permission from both the station agent at the next station ahead
and the train dispatcher. Thus, the station agents are always aware
whether another train is in the block.
The two kinds of manual block operation are permissive and
positive. In permissive block operation, more than one train may
occupy a block of rail at one time if all the trains are moving in
the same direction. In positive block operation, only one train is
allowed in a rail block at any one time. This method is normally
used when the railway line is subject to guerrilla attack, enemy
action, or sabotage. If the track is blocked, this method allows the
train to back up to the nearest station. Positive block operation
would normally be used in forward areas.
With the aid of annex A, follow the moves on a railway net where
manual block operation is being used. Printed down the left side of
the annex are cutout blocks representing the six trains involved in
the operation. Cut out the blocks, and place them on the railway net
as tabulated below and as shown in figure 3.2. Now set the annex to
one side and as the text describes each train's move, change the
train to its new position.
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