divisions of railroad between the port and the railhead. Also, all

divisions are assumed to have the same train density and the same

number of cars per train, because the bulk of all cargo moved in a

theater is through freightfrom port to railhead.

To find the number of cars, by type, required for 1 day's

dispatch, divide the number of short tons to be transported in each

type of car by the average payload of these cars. An example of how

to determine 1 day's dispatch is given in paragraph 3.5.

When you know the number of cars in 1 day's dispatch, you can

determine the total number of cars required for the entire operation.

To do this, you must first know the turnaround time, the total

estimated number of days required from the time a car is placed for

loading at its origin, moved to its destination, unloaded, and

returned to its origin. Such time is computed as follows: allow 2

days at origin, 2 days' transit time for each division (1 for forward

and 1 for return traffic), and 1 day at destination. This method,

rather than an actual hourly basis, is used to allow for delays due

to switching at terminals and way stations and rehandling of trains

in transit. The total number of cars required for the operation is

determined by multiplying 1 day's dispatch of each type of car by the

turnaround time. Then, to the total number required, add 10 percent

to each type of car as a reserve to allow for contingencies such as

routine maintenance, bad order cars, operational peaks, and delays.

3.5. EXAMPLE OF DETERMINING ROLLING STOCK REQUIREMENTS

Assume that you are planning a rail operation in a theater of

operations. The railroad is the same hypothetical threedivision,

singletrack, standardgage rail line discussed in paragraph 2.17 of

chapter 2. You are not doubleheading or adding more sidings. The

line reaches from a port to a railhead in the forward area of the

theater. You have already determined that the end delivery tonnage

for the railroad is 2,177 short tons. From your intelligence data

you find that the tonnage is to be moved on the following basis: 50

percent of the EDT will be shipped in boxcars, 40 percent in

gondolas, and 10 percent in flatcars. The three types of cars are

all U. S. Army rolling stock with rated capacities of 40 short tons,

or carrying capacities (payload) of 20 STON each. Your problem is to

find how many cars, by type, are required to operate the railroad.

First, you must find a value for 1 day's dispatch (DD). This

computation is important, because subsequent switch engine

requirements are based on 1 day's dispatch. Remember that in broad

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