Bus splitting and bus holding: A new strategy using autonomous modular buses for preventing bus bunching

Autonomous Modular Buses (AMBs) with in-motion transfer capability can be more effective in preventing bus bunching than strategies available with conventional buses, such as bus-holding and/or stop-skipping. We previously proposed bus-splitting, a novel alternative to stop-skipping that directs a modular bus to decouple into individual units when it experiences a longer than normal headway. Despite outperforming stop-skipping, bus-splitting alone cannot eliminate bunching completely since it cannot increase short headways. Therefore, we now propose an integrated strategy that combines bus-splitting with bus-holding so that headways that are both shorter or longer than required can be corrected. We conduct a macroscopic simulation based on a bus route in Hangzhou, China, to compare our combined strategy with standalone bus-splitting as well as stop-skipping combined with bus-holding. Our strategy outperforms the others in terms of reducing both the average travel cost and its variation, limiting the overhead of bus bunching to below 10% under realistic system utilization levels. A bus service adopting the proposed strategy would therefore be more cost-effective, reliable, and attractive for commuters, potentially increasing its ridership and reducing the mode share of private vehicles.