Assessment of Population Decentralization Policies in Tehran Metropolitan Area through Multi-Criteria Decision-Making Approaches

The rapid expansion of Tehran metropolitan area and the growing concentration of population and economic activities in this region have generated extensive environmental, social, and economic challenges. This study aims to propose effective strategies for population decentralization in the Tehran metropolitan region in order to promote regional sustainable development. To this end, key indicators of sustainable development were identified across three dimensions—economic, social, and environmental—and weighted using the Analytic Hierarchy Process (AHP). Subsequently, policy alternatives including polycentric development, strengthening of new towns, regulatory policies, and capital relocation were evaluated through the Technique for Order Preference by Similarity to Ideal Solution (TOPSIS). The findings reveal that polycentric development, with the highest closeness coefficient (0.83), emerged as the most effective strategy. Strengthening new towns (0.65) and regulatory policies (0.52) ranked next, while capital relocation, with the lowest score (0.29), was identified as the least effective option. The results indicate that adopting a polycentric development approach and enhancing the functional role of surrounding cities can reduce demographic and spatial pressures on Tehran, foster spatial–population balance, and improve sustainability indicators. Ultimately, the study recommends that future regional planning policies in Iran place greater emphasis on the concurrent development of secondary urban poles, thereby paving the way for sustainable development and the enhancement of quality of life at the national level.