Q2 Z2,(Q2) Z2(Q2) - Institute for Water Resources - U.S. Army

function and the drag-force function. Both of these have been esti-
1.....ted, and their forms are well known in the railroad engineering
lItcrature. The tractive-effort function is taleen over from the lit-
erature without modification. The drag-force function, however, is
modified to include variables such as number of cars, number of loco-
motives, gradient of terrain, and degree of track curvature.
Given these two functions, one can determine the cruising speed ,
of a train as a function of many interesting variables. The cruis-
ing speed of a train multiplied by the cargo tonnage of the train .
gives the ton-miles per hour produced by that vehicle, ignoring ac-
celeration, deceleration, and delays and assuming that the train
operates at full throttle. The implications and importance of these
assumptions are discussed in Chapter V. No analysis of delays is .
provided in this chapter. A discussion of acceleration and decelera-
tion, along with some estimating equations, is presented but no use
is made of them in the remainder of the chapter. It may be noted .
that the rail linehaul process function, exclusive of delays and,ac-
celeration-deceleration, is similar to the original tow process func-
tion of Howe. That is, it is incomplete in several respects but may
be used to provide insights into rail freight operations.
The chapter proceeds to investigate various productivity rela-
tionships of the rail freight train. Under certain simplifying as-
sumptions, it is found that the marginal productivity of the car in-
put is'monotouu decreasing. It is further shown that the marginal
productivity of the locomotive input diminishes. The marginal prod-
ucts of both inputs remain positive within the ranges considered.
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