This study examines urban transportation system optimization through the lens of sustainable mobility, employing literature analysis and international case studies of Copenhagen and Singapore. It investigates critical strategies such as public transit prioritization, non-motorized network development, and renewable energy integration. The research identifies three implementation challenges: institutional barriers in policy coordination, technological limitations in system interoperability, and social acceptance gaps in behavioral adaptation. Proposed strategies include intelligent transportation management systems leveraging big data to alleviate congestion, transit-oriented development models to enhance public transport utilization, and widespread adoption of new energy vehicles to reduce carbon emissions. These solutions not only address current urban mobility challenges but also provide transferable frameworks for cities transitioning toward sustainable transportation systems, demonstrating how integrated planning and smart technologies can reconcile operational efficiency with environmental objectives.