| Summary: | The increasing availability of battery-electric buses (e-buses) as a sustainable alternative for public transportation has sparked considerable interest in recent years. With a notable decrease in lithium-ion battery prices, e-buses have become a competitive option in terms of the total cost of ownership when compared to diesel buses. This trend is driven by a growing awareness of the environmental impact of the transportation sector, which accounts for a significant portion of global CO2 emissions. Transit Authorities at the forefront of this transition are facing important challenges to scaling up their operations, starting with the selection of their charging infrastructure and battery-electric-bus equipment. The problem is generally approached as a cost optimization problem that fails to represent system uncertainties comprehensively, undermining the capacity of solutions to guarantee high service levels to the public. This research contributes to this regard by analyzing and comparing eight infrastructure and equipment scenarios from cost and service level perspectives, using the city of Chicago as a case study. First, an e-VSP is solved for each charging configuration to find efficient robust schedules that can withstand the uncertainties of travel time and energy demand. Then, each scenario undergoes a single-charger failure simulation to assess the operational impact of energy supply disruptions. The simulation quantifies the daily number of buses at risk of breakdown (i.e., depleted battery) as a proxy for service level degradation. Finally, the life-cycle costs of each scenario are calculated according to their infrastructure and scheduled operation and compared along the reported bus breakdowns at failure. The study finds that charging configurations favoring the concentration of power capacity (i.e., chargers at depot only) can better withstand operational uncertainties when compared to decentralized charging configurations that favor network coverage (i.e. on-route charging). The failure assessment corroborates this finding by reporting a critical degradation of service levels (i.e. multiple trip cancellations) on charging networks presenting single-charger charging stops. Ultimately, this research concludes that the selection of the charging configuration will depend on the transit agency budget and risk profile, since the higher reliability provided by the centralization of power capacity comes at a higher life-cycle cost, even when accounting for the effects of innovation in battery technology.
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