Model and algorithm for discrete network equilibrium design problem

This paper studies a new form for discrete network design problem. The new model is different form the traditional bi-level programming model. In the new model, not only expanding the capacity of the existing congested links or adding new links to the network is to considered, but also the levels of links improvement is considered. The upper model is a traditional mathematics optimization problem, while the lower is a user equilibrium condition stated by variational inequality (VI). Then an algorithm of the model is proposed, numerical experiments indicate that the proposed algorithm is effective in practice and has the potential for solving larger network design problems.