The depot and charging facility location problem for electrifying urban bus services

Abstract

• The depot and facility location problem is formulated for deploying electric and diesel buses. • Cost components in the transition from diesel buses to electric ones are evaluated. • Depot locations highlight the trade-off between deadhead mileage and land cost. • The required ratio of electric buses is a key factor in the total operational cost. • The bus fleet size affects the cost and robustness of system operation. The transition from diesel-consuming buses to electric ones entails the problem of determining the locations of bus depots, charging and maintenance stations, which can directly affect the operating cost and efficiency of a bus system. The problem also involves practical concerns, including the selection of fleet size (of electric buses), land acquisition, bus allocation, and the associated deadhead mileage. This study develops an optimization model to systematically locate depots and relevant facilities for deploying mixed types of vehicles. Further, a decomposition-based heuristic algorithm is proposed to enhance computational efficiency. A case study is performed using the data of a bus operator in Taiwan. Sensitivity and scenario analyses are conducted, evaluating major cost components and identifying the factors that affect the trade-offs between them. The proposed methodology enables bus operators/planners to closely and holistically examine their decisions during the transition toward electric bus systems.