Airport accessibility assessment and shuttle bus scheduling across socioeconomic groups

Airport accessibility is a critical factor influencing air travel behavior, particularly for low-income travelers who face both economic and transit-related constraints. This study proposes the Fairness Airport Accessibility Metric (FAAM), a novel measure that captures disparities in accessibility across income groups by incorporating variations in travel options and behavioral responses. Building on this metric, we develop a dual-perspective, two-stage Airport Bus Scheduling and Allocation Model that reflects the differing priorities of public stakeholders. The government-led model first maximizes accessibility to ensure fair transit access across income groups, then minimizes operational costs under fairness constraints. The operator-led model, in contrast, begins by minimizing costs while maintaining baseline accessibility, and subsequently improves accessibility within those budgetary limits, capturing the trade-off between fairness and efficiency from both policy and operational standpoints. To validate the framework, we conduct a case study in Hong Kong, using actual flight schedules from Hong Kong International Airport (HKIA) combined with a synthetically constructed public transit network. The case study confirms significant spatial and income-based disparities in current airport accessibility and demonstrates the necessity of differentiated planning for diverse socioeconomic groups. Numerical experiments reveal that over-prioritizing low-income users can lead to underutilized system capacity, while favoring high-income users may improve overall efficiency but widen accessibility gaps. A balanced, fairness-driven weighting scheme provides inclusive service delivery without compromising operational feasibility. The findings highlight the importance of integrating income-responsive transit planning, fairness-aware scheduling algorithms, and targeted fare policies. Together, these strategies provide a scalable and adaptable framework for designing airport ground access systems that are both socially inclusive and operationally sustainable.