Abstract:With the rapid advancement of urbanization, the development of a coordinated and sustainable urban transportation system has become a critical objective for promoting transportation equity and enhancing public well-being. The proliferation of digital transportation technologies has facilitated the emergence of various transportation applications and virtual services, including realtime information retrieval, travel navigation, ticket booking, and electronic payment. Meanwhile, innovative mobility solutions such as Mobility On Demand (MoD), Shared Mobility (SM), Autonomous Vehicles (AV), and Urban Air Mobility (UAM) are progressively reshaping modern travel ecosystems, fostering the evolution of integrated transportation systems across urban and intercity contexts. Furthermore, Mobility as a Service (MaaS) has evolved beyond its initial goal of reducing private car dependency into a comprehensive and seamless transportation network. By integrating public transit with shared mobility, autonomous transport, and other intelligent transportation modes, MaaS consolidates transportation information acquisition, travel service reservations, mobile payment systems, and multi-modal coordination. Through a unified digital interface and centralized payment mechanism, MaaS enhances connectivity between diverse transportation modes, facilitating seamless transfers and on-demand mobility customization, thereby increasing public transit utilization, advancing multi-modal travel, and improving overall travel efficiency and flexibility.To advance the digitalization of public transportation and enhance mobility efficiency in urban and metropolitan areas, MaaS-based intelligent systems have emerged as a crucial component of public transport infrastructure. While integrated travel solutions effectively reduce private vehicle reliance, extend travel distances, and enhance convenience, the digitalization of transportation services does not equitably benefit all population groups, raising concerns regarding transportation equity. Disparities in mobility choices, access to transport resources, and regional differences exacerbate inequalities in digital travel services, contributing to a mobility divide in integrated transportation systems. Although MaaS has the potential to enhance transportation equity by integrating multiple platforms and reducing service fragmentation, its design and implementation, if inadequately managed, may inadvertently reinforce existing disparities in mobility access.To optimize intelligent mobility systems and promote regional transportation equity, this study integrates the MaaS development framework to examine the relationship between integrated travel and transportation fairness. Specifically, it explores the core theoretical underpinnings of this relationship, synthesizes existing research methodologies, analyzes key challenges and determinants of multi-modal travel equity, and investigates future research directions in the digitalization of public transportation. This research aims to provide insights and recommendations for developing a human-centered, low-carbon, and sustainable intelligent mobility system.While integrated travel systems enhance travel efficiency and adaptability, ensuring equitable access to transportation resources, particularly for vulnerable populations, is imperative to prevent the deepening of mobility disparities. MaaS platforms offer significant potential for delivering personalized and inclusive travel solutions. Existing research employs various data collection techniques, including surveys, travel diaries, and expert interviews, alongside quantitative methodologies such as descriptive statistics, Pearson correlation coefficients, Logit models, and machine learning algorithms (e.g., XGBoost) to analyze travel behaviors and mode selection. Equity assessments of integrated travel often incorporate measures such as the Gini index and perceivedaccessibility scales to evaluate disparities in mobility access. These studies underscore the necessity of balancing service efficiency with equity considerations in transportation planning. Research findings indicate that intelligent mobility systems face critical challenges in spatial accessibility and the accommodation of marginalized populations. Digital mobility services exhibit higher spatial coverage in urban centers compared to suburban and rural areas, disproportionately benefiting high-density communities over lower-density ones. Furthermore, these services provide significantly greater coverage for work-related commuting than for non-commuting and multi-modal activity-based travel. Socio-demographic disparities are also evident, as women, older adults, low-income individuals, those with lower educational attainment, non-car owners, and caregivers traveling with young children are less likely to benefit from digitalized mobility services compared to men, university graduates, and car owners. Future research on public transportation digitalization should adopt a comprehensive and multidimensional approach, incorporating factors such as built environment characteristics, transportation infrastructure, temporal dynamics, socio-economic conditions, digital connectivity, and external disruptions such as the COVID-19 pandemic. Advancing research in this domain necessitates methodological innovation, including the development of enhanced computational models to assess integrated travel equity, improved quantification and empirical validation of key influencing factors, and refined environmental and social impact assessments of multi-modal mobility systems. Future investigations should prioritize the holistic evaluation of mobility equity, leveraging emerging technologies and analytical frameworks to improve assessment accuracy. Key areas of inquiry include travel mode diversification, accessibility assessment, environmental and social externalities, green mobility adoption, and transportation user satisfaction—each of which holds critical implications for evidence-based policy design. This study aims to explore the intricate relationship between integrated travel and transportation equity, critically examining the role of digitalized public transport systems in mitigating or exacerbating mobility disparities. By offering theoretical insights and policy recommendations, this research seeks to contribute to the optimization of intelligent public transportation systems, the promotion of socially inclusive and equitable mobility solutions, and the enhancement of travel opportunities for vulnerable and underserved populations.