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The earlier researches in the area of freight demand
were concentrated on the problem of mode competition.
Gradually the idea of analyzing the short-run freight demand
using inventory theory has been proposed and commonly
accepted. Since then, the research in freight demand analysis
has extended from only mode choice to the choice of mode as
well as shipment size. From the foreign experiences, the
choice of the mode and shipment size are decided in the
joint manner, where the choice of mode is a discrete choice,
and the choice of the shipment size is a continuous
one. Therefore, it would be useful to consider the choice of
mode and shipment size to be a joint discrete and
continuous process. The application of the joint discrete
and continuous choice model for the analysis of freight
demand is still in initial stage, there are still
many problems. Especially, how to derive the freight demand
function which is appropriate for empirical analysis is a
crucial one. Because the logistics cost function is a
complex non-linear function, it would be difficult to derive
a linear, additive demand function so that it can''t be apply to
empirical analysis. Therefore, most researchers must to
simplify the non-linear function, so that a linear model can
be developed. However, the resulting model becomes a
function of modal attributes and the basic
characteristics of the inventory theory has been ignored......
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