Design and Performance Improvement of Metro Feeder Bus Lines Using a Metaheuristic Algorithm: A Case Study of Tehran Metro Line 3

Public transportation plays a critical role in promoting sustainable urban development by offering mobility solutions that are efficient, equitable, and environmentally responsible. It encompasses a wide range of transit modes, which are generally classified into mass transit systems—such as metro and rail services—and non-mass transit systems, including buses, minibuses, and other forms of road-based public transport. As cities expand and mobility demands grow, the complexity of managing and integrating various transport modes also increases. One of the key challenges in the planning and operation of public transport systems lies in ensuring seamless integration between these modes, particularly through the design and optimization of feeder networks that connect local bus services to major mass transit infrastructure.
This study focuses on improving the operational efficiency and user attractiveness of Tehran’s public transportation system by enhancing the feeder bus services connected to three specific stations—Abdol Abad, Shahrak-e Shariati, and Zamzam—located on Metro Line 3. The primary objective is to increase metro ridership and improve the overall effectiveness of public transport usage by optimizing the sub-network of feeder lines servicing these metro stations. Improving connectivity and reducing transfer times between feeder and metro systems is considered crucial for encouraging the use of public transit, particularly in densely populated urban areas like Tehran.
To achieve this goal, a structured four-step methodology was adopted. Initially, the feeder routes relevant to the three metro stations were identified through data collection and analysis of existing traffic patterns. Subsequently, two improvement strategies were formulated and applied: (1) uniform improvements applied across the entire feeder routes, such as reducing headways and enhancing vehicle availability; and (2) targeted enhancements focused on selected high-demand stops, including limited-stop service and priority routing. These strategies were translated into multiple operational scenarios, which were then simulated using the EMME/2 transportation planning software, a recognized tool for multimodal transport analysis.
Each scenario was evaluated based on four key performance metrics: the total number of trips made using public transport, the number of boardings on Metro Line 3, the ratio of public transport trips to the number of vehicles (fleet size), and the ratio of metro boardings to the number of deployed feeder buses. The results reveal that reducing headways on feeder bus routes generally leads to an increase in both public transport trips and metro boardings. However, in some cases, this strategy created unintended competition between feeder buses and the metro, which did not necessarily result in higher metro ridership.
Among the various scenarios analyzed, those that implemented limited-stop feeder services showed the highest effectiveness in encouraging multimodal travel behavior and promoting better utilization of both bus and metro systems. Conversely, scenarios that increased the number of feeder buses without allocating dedicated lanes led to greater traffic congestion and reduced overall service quality.
From a policy and planning standpoint, this research underscores the importance of clearly defined objectives and appropriately weighted performance indicators in selecting the most effective operational scenarios. The insights provided can support transport planners and decision-makers in enhancing the integration of feeder systems with metro services, ultimately contributing to the overall sustainability and quality of urban public transportation networks.