With accelerating urbanization, climate crises, and technological advancement, cities face increasing pressure on mobility systems, positioning digital transformation as a key driver of sustainable and inclusive urban development. This study evaluates various dimensions of the urban mobility system and how they are changing in the context of digitalization. First, we analyzed key digital solutions in city mobility and concluded that they increase the efficiency of transportation systems, reduce operating costs, and support environmental protection. Second, we examined partial operational and economic indicators of urban mobility and demonstrated the need for a comprehensive approach to assessing urban mobility quality. We then reviewed complex indices of city mobility and proposed a composite Index of Urban Mobility Quality, which combines both objective and experiential data, such as average trip time and user dissatisfaction with the transportation system. The practical part consists of two parts: (i) analysis of the relationship between transport inefficiency and key parameters of urban mobility, including travel time, carbon dioxide (CO2) emissions, and fares. The results revealed a strong empirical link between inefficient urban transport, prolonged travel times, and increased CO2 emissions, highlighting critical barriers to sustainable and inclusive mobility; (ii) calculation of the Index of Urban Mobility Quality for 137 cities, identifying those where targeted digital interventions are most urgently needed. The analysis also highlights cities whose experience can serve as benchmarks for smart mobility performance. Overall, the results provide a practical tool for prioritizing investments in transport digitalization and addressing inefficiencies often overlooked in conventional smart city rankings. Ultimately, the study contributes to bridging the persistent gap between technology-centric models of smart cities and citizen-centric approaches to mobility.