It is worth noting that the presentation of the variational inequality formulations of the
fixed demand models given above was in the context of single mode (or single class) transport
networks. However, in view of the generality of the functions considered (cf. (18)), the
modeling framework described above can also be adapted to multimodal/multiclass problems
in which there are multiple modes of transport available and/or multiple classes of users, each
of whom perceives the cost on the links of the network in an individual manner. Dafermos in
(1972) demonstrated how, through a formal model, a multiclass traffic network could be castinto a single-class network through the construction of an expanded (and, again, abstract)
network consisting of as many copies of the original network as there were classes. The
application of such a transformation is also relevant to telecommunication networks.