A road network design model considering horizontal and vertical equity: Evidences from an empirical study

Most of the models for solving the transportation Network Design Problem (NDP) often neglect equity goals that, assuming the societal function of transportation systems, should play an important role. The NDP should be addressed to solutions in which the outcomes of the design (costs and/or benefits) are distributed as fairly as possible among the potential users or class of users. In this paper, an Equity Based NDP is proposed, where the optimal layout of a road network is determined by minimizing the total system cost under flexible equity constraints while taking into account the route choice behavior of network users. The considered equity goals are represented by a proper outcome indicator, specified for uncertain and/or approximate variables. The consequent NDP model is then a multi-objective fuzzy programming model that allow determining the most equitable solution aiming at reducing the realization costs according to a set of constraints. An application of the proposed method is given to solve the equity network design optimization and the results are discussed.