3.3. ROLLING STOCK
When planning for rolling stock, a planner thinks in terms of
the types and numbers of railway cars required to move freight. In
most military operations, freight movement is in one direction only,
from a port or base depot to a railhead in the forward area of a
theater. Occasionally freight may be moved from a port to a point on
the same division and unloaded, and different freight picked up there
and moved on forward by the same train. This kind of freight
movement is commonly referred to as a setout and fillout operation.
However, the net division tonnage remains approximately the same.
Regardless of the kind of operation, there must be enough cars to
maintain continuity of car loadings and movements. How many are
enough? The following paragraph explains how to make an estimate of
rolling stock requirements accurately enough for broad planning
3.4. ESTIMATING ROLLING STOCK REQUIREMENTS
Each railway car has a rated capacity, normally stenciled on its
side, given in pounds. For example, a boxcar with 80,000 stenciled
on its side has a rated capacity of 80,000 pounds or 40 short tons.
However, for planning purposes, the carrying capacity or average
payload of that car is 40,000 pounds (20 short tons) or 50 percent of
its rated capacity. There is a good reason for using only half of
the rated capacity of cars in planning. If you packed a boxcar full
of lightweight bulky cargo such as blankets, the payload would weigh
far less than the rated capacity. If, however, you packed the car
with ammunition, the payload weight would be much nearer or might
even exceed the rated capacity. Therefore, a good average figure to
use for payload in planning is 50 percent or onehalf the rated
capacity of all freight cars except tanks cars. The capacity in
gallons and tons is stenciled on their sides. If a tank car holds
10,000 gallons of water it will hold 10,000 gallons of any other
liquid, and it can be loaded to its content capacity if the weight of
the liquid does not exceed the maximum tonnage capacity of the car.
Use the rated capacity for tank cars.
Once you know the average payload of the cars you have, you must
find the number of cars needed to transport the end delivery tonnage.
This is referred to as 1 day's dispatch (DD), or the number of cars
dispatched from the port or base of operations in a day. It is also
the number of cars that run over the first division each day. In
broad planning, 1 day's dispatch is considered the same for all