The Bus Scheduling Problem. The bus scheduling problem of Example 2.3-8 provides
an interesting modeling situation in AMPL. Of course, we can always use a twosubscripted parameter,similar to parameter a in the Reddy Mikks model in Section 2.4.2
(Figure 2.16), but this may be cumbersome in this case. Instead, we can take advantage of
the special structure of the constraints and use conditional expressions to represent them
implicitly