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

deprecL.tion. The ,outputs were represented by (1) loaded freight car
miles, (2) carloads of freight, and (3) empty freight car miles. , The
fixed inputs were represented by (1) total tractive capacity of freight
locomotives and (2) miles of mainline track. In an alternative speci-
fication of the model, a variable was employed to measure all of the
physical capital in use by the railway firm.
in the switching process the following variables were used to ,
measure the flow of input and output services. The variable inputs
were the same as those used for the linehaui model, except, of course,
they were specified to yard operations. The outputs were represented
by (1) yard switching locomotive miles, (2) yard switching locomotive
hours, and (3) carloads of freight. The fixed inputs were (1) miles
of yard switching track, (2) total tractive capacity of yard locomo-
tives, and (3) average number of freight cars standing on line.
Two statistical models were formulated and their coefficients
estimated. In the first model, each variable input was treated as a
linear function of the fixed inputs and of the outputs. The second
,
model.was derived from the first by normalizing the variables by a
measure of capacity. .
The data consisted of observations on seventy-six Class I rail-
ways in the United States for the year 1948. All observations were
from Interstate Commerce Commission data. The coefficients of the
equations for each model were estimated by least-squares methods.
From the estimated regression coefficients (of which slightly fewer
than one-third were not significantly different from zero) elastici-
ties of factor use•were derived. The elasticity of factor use is
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