Evaluation of subway systems in CO2 emissions: Comparative analysis of emissions from cars, buses and subways

Abstract

The transportation sector is responsible for a portion of the global emissions of carbon dioxide (CO2). Scientific studies published on CO2 emissions by passenger transport systems treat basically results involving only the emissions related to fuel consumption of cars and buses. As for subways, usually emissions related to the generation of electrical energy needed to provide the traction force of the trains are considered. No specific or standardized publications on other approaches to calculate emissions for subways were identified. Thus, this study aims to provide a scientific contribution to the general study of CO2 emissions by subways, conceptually defining five approaches of calculations and conducting a comparative analysis of CO2 emissions by cars, buses and subways. The result of this research allowed to quantify the actual contribution of subways on the reduction of total emissions from the transportation sector. In the traction power of trains approach, it was concluded that the subways of São Paulo and Rio de Janeiro emit 63.5 times less than cars and 8 times less than buses.