The expression

in the formula is known as the engine

factor; it represents the percent of time during a 24hour period

that a road engine is in use. It provides for the pooled use of

motive power that may make one or more trips per day over a short

division.

The three unknowns in the formula are TD (train density, found

as explained in paragraphs 2.13 and 2.14); RT (running time, found by

dividing the length of the division by the average speed); and TT

(terminal time, found by using table VI). Terminal time is that time

required for servicing and turning locomotives.

Table VI. Terminal Time Average Values

The number of road engines required must be computed for each

division separately. A detailed explanation of how to determine the

road engine requirements is presented in the following paragraph.

3.7. EXAMPLE OF DETERMINING ROAD ENGINE REQUIREMENTS

The division of railroad used in this example is the 110mile

second division given in the example in paragraphs 2.17 and 2.19. It

has a train density of 7, and the track is rated good to fair with a

ruling grade of 1.8 percent. The motive power used for road service

on this division is 0440 dieselelectric locomotives.

Since a value for TD in the formula is known, you must find

values for RT and TT. The length of the division (110 miles) divided

by the average speed gives you the value of RT. Look at table IV.

An average speed of 10 mph is given for a good to fair track with a

ruling grade of 1.5 percent or less. However, the ruling grade for

this division is 1.8 percent; therefore, the more restrictive factor

of 2.5 governs. The average speed, then, is 8 mph. The value for RT

is 14.