where ykna is the auxiliary flow of mode k on link a at iteration n given by an all-or-nothing
assignment based on link travel time, t kn a , and vi,kn
w is the auxiliary demand of class i
selecting mode k between O-D pair w at iteration n given by an all-or-nothing assignment
based on the generalized costs, c
i,knw .
Figure 5 shows the gaps against the iteration number for the lower-level problem and
upper-level problem, respectively. It can be seen that the solution algorithm has a good
convergence especially for the upper-level problem. It can be explained that the network
structure of the traveler’s mode choice in the upper-level problem is simpler than that of the
traveler’s route choice in the lower-level problem.