Mixed electric bus fleet scheduling problem with partial mixed-route and partial recharging

Given the goal of reducing emissions and saving energy, an increasing number of transit agencies have proposed electrification plans for public transport buses. The two fundamental challenges to adopting electric vehicles in transit operations are the purchase of appropriate electric vehicles to establish the bus fleet and the creation of an efficient schedule and recharging plan. This paper examines the multi-depot and multi-vehicle type electric vehicle scheduling problem with partial mixed-route strategy and partial recharging policy. The partial mixed-route strategy proposed in this paper allows multiple transit routes to operate in a more cost-efficient way. Moreover, it takes into account the bus allocation problem of the transit network fleet to meet the parking restrictions of each depot. The problem is formulated in a mixed-integer programming model, and an adaptive large neighborhood search (ALNS) algorithm with new mechanisms specific to the problem is proposed to apply the model in a more efficient manner. The dataset of a real transit network in Nanjing is used for case study, and the performance of ALNS is tested by using randomly generated instances from the dataset. The results show that the proposed method is effective in finding high quality solutions and adopting partial recharging policy can reduce the fleet size and the total cost while providing advantages depending on the operational parameters of the schedule. In addition, comparison of two schedules using different partial mixed-route strategies shows that there may be two sides of adopting mixed-route scheduling.