Bunching-Proof Capabilities of Modular Buses: An Analytical Assessment

Modular vehicles are a novel concept that allows for the coupling and decoupling of different vehicle modules and enables in-motion passenger transfers; it can potentially increase the flexibility of the transportation system. Recent studies have numerically highlighted the potential of using modular vehicles as transit buses to mitigate the bus bunching phenomenon. Building upon this, our study offers a comprehensive and systematic analytical assessment of the bunching-proof capabilities associated with modular buses. Specifically, we examine two sets of cases: those with fixed boarding capacities, where each bus stop processes only one queue for a modular platoon, irrespective of the number of modular vehicles it consists of; and those with flexible boarding capacities, where multiple queues can be served at each stop, enabling all modular units within a platoon to cater to boarding passengers concurrently. For the cases with fixed boarding capacities, we quantify the necessary conditions for successful hysteresis restoration, whereas for the cases with flexible boarding capacities, we discover a notable “bounded bunching property,” wherein the bus operation inherently restricts the ongoing deterioration of bunching. Leveraging this property, we propose an innovative proactive bunching mitigation method, called “adaptive pushing strategy,” to mitigate bus bunching more proactively. A computer simulation platform is established to validate the theoretical findings and mitigation solutions presented in this study.