Due to the complexity of core-periphery interactions, transportation systems in metropolitan regions necessitate the development of multi-dimensional and context-specific evaluation models. This study aims to develop a sustainable transportation system evaluation model, focusing on the Tehran metropolitan region. A mixed-method (qualitative-quantitative) approach was employed. In the qualitative phase, 41 selected articles were identified through a systematic review and meta-aggregation across six domestic and international databases, based on the thematic intersection of sustainability, transportation, and metropolitan regions, to extract relevant indices. In the quantitative phase, the model was validated using Structural Equation Modeling (SEM) with the participation of 530 experts, each possessing relevant postgraduate qualifications and a minimum of five years of executive experience in Tehran's urban management. The primary innovation of this research lies in shifting the analytical scale from the "city" to the "metropolitan region" and the formulation of integrative indicators. The findings resulted in the identification of three dimensions, nine components, and 53 sub-components. The results, with an adequate model fit (GOF = 0.832), revealed that the "economic dimension" ($\beta = 0.674$), "environmental factors" ($\beta = 0.481$), and the "social dimension" ($\beta = 0.329$) play the most significant roles in the evaluation, respectively. These results suggest that policymaking in Tehran should shift from the physical management of the core city toward "regional integration" and the strengthening of traffic deterrent factors.