Modularity-Enabled Partial Express Operations in Zone-Based Flexible Feeder Transit

Abstract

Flexible transit services are widely used as many-to-one feeders in rural and suburban areas with intermediate demand, yet their flexibility often induces substantial in-vehicle travel-time penalties due to cumulative deviations. This study investigates whether modular vehicles enabling in-vehicle transfers can support partial express operations that mitigate such penalties without external transfers. We develop an analytical model for a zone-based feeder system with checkpoints, capturing re-partitioning of service zones as express units depart. Performance is evaluated using an integrated generalized-cost framework capturing operator and user costs, including walking and riding. Results across a structured design space of demand densities and service-area geometries indicate that modular express operations can reduce total generalized cost in various configurations, primarily driven by peak riding-cost reductions of approximately 19–22%. The findings highlight the potential of modular coupling and in-vehicle transfers as an operational enhancement for flexible feeder systems under intermediate demand conditions.