Impact of Electrification on the Required Bus Fleet Size: The Case of Overnight Depot Charging

The electrification of public transit systems, particularly the adoption of electric buses, stands as a critical strategy in the global pursuit of sustainable urban mobility. Amidst this transition, the establishment of robust charging infrastructure and the optimization of fleet size emerge as pivotal challenges for transit agencies and policymakers. This paper delves into the specific implications of overnight depot charging on the required bus fleet size, focusing on the Canadian context. By analyzing operational data from electric bus deployments in Toronto, the study investigates the impact of limited electric bus range on the fleet size requirements. The results reveal that, on average, a 34% increase in fleet size is necessary to maintain equivalent service levels compared to traditional diesel buses. In addition, the results show that the required replacement factors vary across the different seasons, indicating variable fleet size requirements based on energy consumption rates. Moreover, bus type also influences fleet size requirements, with buses featuring higher battery capacities exhibiting lower replacement factors. This study underscores the necessity of understanding these dynamics for effective decision-making in electric bus deployment. Insights derived from this research offer valuable guidance for transit agencies, policymakers, and stakeholders involved in advancing sustainable urban transportation initiatives.