Transport planning is an important aspect of urban planning. In this regard, enhancement of public transport systems and guiding urban travels towards them has found a crucial role in traffic improvement, preventing capital waste, and achieving sustainable cities. Mashhad, Iran, the second largest city in Iran, with a population of three million, has two main systems of public transport, light rail transit (LRT) and bus rapid transit (BRT). In designing these lines, not enough attention was paid to urban sustainability principles and maximizing access. The aim of this study was to redesign the main public transport lines using the approach of accessibility enhancement. The meta-heuristic method of Ant Colony Optimization was applied for this purpose. To compare the redesigned paths with the current paths, access indicators were defined and computed in the case of two alternatives. The results show that the access indicator in the modified alternative is significantly higher than the current one.