• Public transportation systems are pivotal in fostering sustainable mobility within green cities by addressing key environmental and societal challenges. This study highlights the significance of public transportation in promoting sustainability in green cities. It explores various factors including modal shift, mass transportation, integrated networks, transit-oriented development, emission reduction, active transportation infrastructure, and technological advancements. Public transportation plays a crucial role in encouraging people to switch from private vehicles to sustainable modes of transport, resulting in reduced carbon emissions and less traffic congestion. Mass transportation efficiently moves a large number of individuals in a single vehicle, leading to lower energy consumption and a smaller carbon footprint compared to individual cars. Integrated transportation networks offer seamless travel experiences and decrease reliance on private vehicles by incorporating buses, trains, ferries, and cycling infrastructure. Transit-oriented development reduces long commutes, lessens car dependency, and improves accessibility to public transportation and active transport. Public transportation systems, especially electric or hybrid buses and trains, contribute to the reduction of greenhouse gas emissions and the enhancement of air quality. Active transportation infrastructure, such as pedestrian pathways and bike lanes, encourages walking and cycling for short trips, resulting in reduced emissions and the promotion of healthier lifestyles. Technological advancements in public transportation, such as smart ticketing, real-time information, optimized routes, and electric vehicle charging, enhance user experiences, operational efficiency, and environmental impact reduction.