چكيده به لاتين
In order to satisfy the needs, the human must have access to places where his required services or goods are supplied, and the transportation network has an essential role in creating such access. Each regime of developing the transportation network results in a different distribution of outcomes over different geographical regions. In recent years, researchers have devoted more attention to the distribution of the advantages of transportation decisions among different groups, and recognize social equity as one of the three objectives of sustainable transportation. Hence, it is very important to incorporate equity in transport network development, due to its severe influences on economic life, social activity, and future developability of different regions. In this study, after a review of the viewpoints of several economic systems about social equity, mathematical formulations for the transportation network design problem are constructed considering seven influential approaches to social equity besides the classic strategy of total travel time minimization. Afterward, by solving the models for a single case problem, the results are analyzed comparatively. All approaches are formulated as bi-level integer programming models and solved with a novel two-step genetic algorithm. An accessibility variable is utilized as the distributable advantage. Also, in this research, a ranking of the different social equity approaches has been performed. The outcomes of running the developed models over the inter-provincial road network of Iran show that the “utilitarian” approach, gives the maximum amount of total accessibilities for the society as a whole, ignoring how the benefits are distributed among regions. The “Rawlsian” approach has paid the most attention to maximizing the advantages of the poor regions. The scenario of “Egalitarianism in the final advantages”, is the most successful approach in orientation toward an average (i.e. making the final values of accessibilities as close as possible), but in terms of increasing the society’s total advantages is not successful. The scenario of “equality in added benefits”, tries to distribute the added accessibility values as equal as possible, hence it has caused the least deviation from the existing situation and approximately kept the current gap among regions. In terms of increasing the total benefits of society, this approach has been the worst of all. The scenario of “limiting the gap among final benefits”, besides its effort to maximize total benefits of the society, tries to limit the gap among post-design regional accessibilities and has been able to lay among the best methods in decreasing the proportion of the reach-to-poor accessibility values. The approach of “limiting the added benefits”, has kept the proportion of the minimum-to-maximum added benefits at a desirable level. Finally, the “Sadr” approach, a composite method concerning the three measures of society benefits, the poor people benefits, and gap decrease, has been able to gain good or excellent success in all targets. As a result of a multicriteria ranking of all equitable road network design approaches, the first and the second ranks are being shifted between the two Sadr and utilitarian scenarios. A sensitivity analysis on the rankings is done too, by changing the criteria weights. Finally, researchers have suggested policymakers to utilize Sadr scenario as a comprehensive approach in solving real problems.
