Integrating passenger and freight transport in depopulated areas: key success and failure factors from Japanese case studies

In response to depopulation and aging in rural Japan, integration of passenger and freight transport (IPFT) is a promising strategy to maintain essential mobility and logistics services. Although regulatory reforms in 2017 enabled privately paid transportation (PPT) systems to incorporate cargo delivery, cases remain limited. This study examines two fixed-schedule and two demand-responsive systems within the PPT framework. Through a comparative case study, it identifies key operational and institutional factors influencing the sustainability of these services. Using international literature and original fieldwork, each case is analyzed across transport volume, integration route characteristics, and schedule coordination. Results show that in demand-responsive systems, success depends on sufficient idle vehicle capacity and operational flexibility. Conversely, fixed-schedule systems hinge on effective last-mile delivery coordination and stakeholder alignment. The ongoing Hoihoi Service and Smile Daisen Service projects illustrate how successful integration depends on vehicle utilization, institutional coordination, infrastructure readiness, and adaptive business models. This study enriches existing IPFT literature by providing empirical evidence from Japan, where such initiatives are nascent. Moreover, it offers practical implications for policymakers and operators designing sustainable mobility systems in depopulated regions. It emphasizes the need for context-specific strategies that integrate passenger and freight objectives under realistic institutional and logistical constraints.