<p>The urban bus system is an important part of the urban transportation system. Buses commute daily between terminals and depots, generating a large number of deadhead kilometers, thus increasing carbon emissions. Current bus-to-depot allocation methods lack the consideration of management requirements during the optimization process and are unable to provide intuitive comparison of different schemes for effective decision making. In this study, we present BusAllocVis, an interactive visual analytics system designed to optimize bus-to-depot allocation schemes to reduce carbon emissions from bus operations. First, a carbon emission calculation model for electric buses is defined. Then, different bus-to-depot allocation schemes are calculated that can consider different management preferences and minimize carbon emissions from deadhead kilometers. Finally, multiple visual views are designed to provide an intuitive explanation and comparison of different allocation schemes. The results of the case study and the task-based user study have demonstrated the effectiveness of our system in identifying the suitable allocation schemes for practical application scenarios.</p> Graphical Abstract <p></p>