Public Transit as a Catalyst for Emission Mitigation and Air Pollution Reduction: A Case Study in India

Rapid motorization and urbanization have made the transport sector a dominant contributor to air pollution in developing economies such as India. In this study, vehicular emission trends were investigated in Bhubaneswar, a Tier-II smart city, using a combination of questionnaire surveys, video graphic traffic analysis, and IPCC estimation methodologies during October–December 2025. A roadside survey was conducted with a sample size (N = 385), passenger car sample size (N = 520), bus trips (N = 85), and functional unit (g⋅person−1⋅km−1). Primary data regarding vehicle age, emission standards, mileage, and traffic volume were compiled to evaluate average fuel usage and total pollutant loads under estimated field-level traffic conditions. The empirical results indicate that emissions are fundamentally characterized by vehicle configuration, passenger occupancy, and fuel efficiency. Four-wheelers exhibit the highest per capita emissions (1.44 g⋅passenger−1⋅km−1 CO and 0.24 g⋅passenger−1⋅km−1 HC+NOx), primarily due to low occupancy rates. In contrast, buses demonstrate the lowest per capita emissions (0.13 g⋅passenger−1⋅km−1 CO and 0.07 g⋅passenger−1⋅km−1 HC+NOx). The study concludes that transitioning from private modes to public transit could mitigate vehicular emissions from as low as 8–15% (shift from 2W to buses) to as high as 61–80% (all shifting to bus), highlighting the need for strategic planning for sustainable public transportation infrastructure.