THE IMPACT OF PUBLIC TRANSPORTATION ON THE REDUCTION OF GREENHOUSE GAS EMISSIONS IN THE UNITED STATES

Greenhouse gases (GHGs) contribute to global warming and climate change by trapping heat in the Earth’s atmosphere. The U.S. Environmental Protection Agency (EPA) states that transportation accounted for 28.4% of the total GHG emissions in 2022, making it a significant contributor. Decreasing personal vehicle travels can help reduce GHG emissions, and using public transportation is a viable way to achieve it. This study evaluates the impact of public transportation on reducing GHG emissions in the U.S. This study included 292 urban areas with public transportation services, divided into two groups based on whether the metropolitan population is over or under one million. The data for GHG emissions was based on the Road Transportation sector of the Emissions Database for Global Atmospheric Research (EDGAR), with a 0.1° by 0.1° resolution. Public transportation usage was based on passenger miles traveled (PMT) via public transportation in the National Transit Database (NTD) published by the Federal Transit Administration of the U.S. Department of Transportation. This study also considers workers commuting to work using private vehicles from the American Community Survey (ACS) of the U.S. Census. The findings from regression analysis indicate that: (1) public transportation usage reduces GHG emissions, although the effect is minimal; (2) commuting to work using private vehicles increases GHG emissions, which has a greater impact than public transportation usage; and (3) both factors explain more variance in GHG emissions in urban areas with populations over one million compared to those with populations under one million. These findings align with existing literature, demonstrating that public transportation usage can decrease GHG emissions by 0.77% in urban areas with populations over one million and by 1.03% in those with populations under one million.