<p>Public transportation systems are essential for advancing social equity and sustainable urban growth. This study examines the spatial accessibility of Tehran’s subway network, focusing on vulnerable age groups, including the elderly and individuals under 18. Using a combination of the gravity-based accessibility index, Gini index, and Lorenz curve, the research quantifies disparities in subway access across Tehran’s statistical blocks. Data from the city’s subway network, statistical blocks, and street networks were integrated into Geographic Information Systems (GIS) to accurately assess proximity and access levels. The analysis measured the distance from the centroid of each block to the nearest subway station within an 833-meter threshold, using train frequency data to calculate the gravity index. Population data from the Iranian Statistical Center was then used to compute the Gini index and Lorenz curves, assessing equity in access across different population groups. The findings reveal significant inequalities in subway accessibility, particularly in the peripheral neighborhoods where a large portion of the population resides. There are pronounced challenges for vulnerable age groups in accessing the subway system, making it difficult for them to get to their destinations. The study underscores the need for expanding subway coverage to suburban areas and improving feeder services to enhance accessibility. Additionally, improving connectivity between subway lines, upgrading pedestrian infrastructure, and offering reduced or free fares for vulnerable age groups are recommended to foster a more inclusive and equitable transport system. Future research should incorporate more detailed socio-economic data and explore multiple accessibility metrics for a deeper understanding of transportation equity.</p>