The Customized Bus (CB) system is a demand-responsive transit model aimed at addressing critical urban mobility challenges such as traffic congestion, environmental concerns, and insufficient public transport coverage in low-demand areas. Introduced in China in 2013, the CB system utilizes advanced digital platforms to design flexible routes and schedules tailored to groups with similar travel demands. This chapter examines the operational characteristics, user behavior, and market orientation of CB services, highlighting their potential as a complementary solution to traditional public transport (PT) and a sustainable alternative to private vehicles. Despite offering personalized and efficient transit services, CB systems encounter challenges in cost management, demand forecasting, and sustaining user loyalty. Understanding spatial–temporal demand patterns, passenger loyalty determinants, and the influence of the built environment on travel behaviors is crucial for optimizing the effectiveness and sustainability of the Customized Bus system.