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

were used to reduce yard expenses to .1 gross ton-mile basis. Later,
it was assumed "that any shipment under analysis is normal in t'le
sense that it approximates the 1947 to 1950 averages of having 3,0(o
ross ton-miles of freight moved for every road mile of diesel engine
operations and requiring one diesel engine yard hour for every
gross ton-miles of freight traffic." 35
These assumptions were used
to translate the yard engine and road engine maintenance figures into
gross ton-mile equivalents.
It is possible even within the context of the MPSZ work to avoid
making such assumptions. For example, MPSZ provide equations from
which can be estimated yard time. 36 If one does not necessarily wish
to relate all costs to a gross ton-mile basis, the original estimat-
ing equations can be used rather than the aggregate figures of Table
5.8. In most cases, they will be no different because the gross ton-
mile is the predominant output variable used, but in some cases, for
example, road engine maintenance, other variables are included in the
estimation, necessitating either assumptions such as those used by
MPSZ or actual values for a particular situation.
While it is possible to use MHZ results without some of their
assumptions, it is not possible to use them and avoid the central-
tendency aspect mentioned above. One way to avoid this problem is
to provide an alternative cost estimation procedure for some or all
of the components of total operating expenses. Clearly one of the
69,000
most important of the cost categories is train expenses. It is pro-
posed, therefore, to estimate train expenses by use of the rail pro-
.
cess function and direct costs for crew and fuel. The train expenses
177