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

N b
from
Given Q, C t' and C b and knowing the number of barges in the tow,
then the cost per ton-mile of a to trip, C, may be determined
tm .
C tm -
C t + N b C b
Q
(4.48)
Note that the cost per ton-mile given by Equation (4.48) refers
only to a point-to-point movement. Such a cost, therefore, does not
take into consideration any adjustments in the barging firm's other
transportation activities. If the firm, for example, had to divert
barges from some other traffic to make a . given trip, then the real
cost per ton-mile might not be reflected in the cost per ton-mile
for the point-to-point movement. Moreover, a change in the depth of
a waterway, for example, would affect the cost per ton-mile of the
point-to-point barge movement over that waterway, but might also af-
fect the operations on other waterways as well. The effect of these
other adjustments would not be reflected in the point-to-point cost
per ton-mile over the improved waterway.
In order to determine the cost per ton-mile of the firm's opera-
tions, one would need to know the entire distribution of tow trips
undertaken by the firm. In addition, to know the change in the firm's
costs due to a waterway improvement, one would again need information
on the firm's entire activities. In order, therefore, to know firm
costs as opposed to individual trip costs, the tow process function
must be incorporated into a scheduling model of the barging firm.
Simple scheduling problems, such as contract carriage, can be handled
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