We emphasize that the above network equilibrium framework is sufficiently general to also
formalize the entire transportation planning process (consisting of origin selection, or destination
selection, or both, in addition to route selection, in an optimal fashion) as path choices
over an appropriately constructed abstract network or supernetwork. This was recognized
by Dafermos in 1976 (in the context of separable link cost functions) in her development of
integrated transportation network equilibrium models in which location decisions are made
simultaneously to transportation route decisions (see also Boyce (1980)). Further discussion
can be found in that reference as well as in the books by Nagurney (1999, 2000) and Nagurney
and Dong (2002a, b) who also developed more general models in which the costs (as
described above) need not be separable nor asymmetric.