The multiobjective equilibrium network design problem revisited: A simulated annealing approach

In this paper we present a model for continuous multiobjective optimal design of a transportation network. The model presented here explicitly incorporates user equilibrium constraints and takes the form of a difficult nonlinear, nonconvex mathematical program. The user equilibrium constraints form a finite set of nonlinear, albeit nonconvex, inequalities, and give rise to a single level mathematical program, as opposed to the now standard mathematical programming/variational inequality representation which leads to a bilevel formulation of the equilibrium network design problem. We show that simulated annealing is ideally suited for solving multiobjective versions of the equilibrium network design problem articulated in this fashion. We employ the ‘weighting’ method together with simulated annealing to generate the Pareto optimal set. A numerical example is provided to demonstrate the efficacy of this solution methodology.