An Update on Public Transportation's Impacts on Greenhouse Gas Emissions (2021)

Below is the uncorrected machine-read text of this chapter, intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text of each book. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.

1   Transportation is a major source of the greenhouse gas (GHG) emissions that are causing climate change (U.S. EPA 2020d). As communities work to cut emissions and become more resilient, they are looking to public transportation as a climate action strategy. This report provides updated national analysis of public transportation’s role as a climate solution by documenting public transportation’s 2018 GHG impacts. Public Transportation’s GHG Emissions Impacts Public transportation in the United States saved 63 million metric tons of carbon dioxide equivalent (MMT CO2e) emissions in 2018—the equivalent of taking 16 coal power plants offline for a year (U.S. EPA 2020c). This study examined public trans­ portation’s impacts on GHG emissions by calculating the difference between transit vehicle GHG emissions (12 MMT of CO2e) and GHG reductions associated with transit (Figure 1). • Transportation Efficiency GHG Savings: The GHG emissions saved by passengers riding transit rather than using personal vehicles: 9 MMT CO2e in 2018. Transit passenger surveys show 33% of transit passenger miles would otherwise be replaced by personal vehicle miles (APTA 2020). • Land Use Efficiency GHG Savings: The GHG emissions saved by the broader impact of transit on vehicle miles traveled (VMT) in the community: 66 MMT CO2e in 2018. Even residents who do not ride transit themselves save GHGs because transit creates land use efficiencies, such as through shorter driving trips, fewer driving trips, and more trips on foot or by bicycle. • Net Impact: 12 MMT CO2e emitted – 75 MMT CO2e reduced = 63 MMT CO2e. S U M M A R Y An Update on Public Transportation’s Impacts on Greenhouse Gas Emissions

2 An Update on Public Transportation’s Impacts on Greenhouse Gas Emissions This study takes into account the full life cycle of transportation fuels (see Figure 1), as follows: • Direct CO2e emissions at the vehicle. • Indirect CO2e emissions from power plants and hydrogen production facilities. • Upstream CO2e from fuel production and distribution. Public Transportation’s VMT and Fuel Impacts Communities with public transportation avoided 148 billion miles of personal vehicle travel in 2018 through transportation efficiency and land use efficiency savings, or 5% of the 3 trillion total U.S. vehicle miles that year (FHWA 2019a). Transit vehicles traveled 4.7 billion miles in 2018, and the average transit vehicle had 12 passengers (FTA 2020a). Public transportation helped avoid 6.6 billion gallons of gasoline use in 2018 through transportation efficiency and land use efficiency savings, and transit vehicles used signi­ ficantly less energy than that—837 million gallons of fossil fuels, 49 million gallons of biodiesel and ethanol, and 6.7 billion kilowatt hours (kWh) of electricity (FTA 2020a). Public Transportation’s Individual Impacts Public transportation helps passengers reduce their carbon footprint. An individual riding transit in 2018 contributed 55% fewer GHGs per mile than would have been done through driving or ridehailing alone (0.23 kg CO2e per transit passenger mile versus 0.51 kg CO2e per mile for a single­occupancy private vehicle). Even at a U.S. average automobile occupancy of 1.67 passengers per trip, the GHG emissions of personal vehicle travel were higher than the transit average on a per­passenger­mile basis (0.23 kg CO2e per transit passenger mile versus 0.30 kg CO2e per mile for an average occupancy private vehicle). Figure 1. GHG impacts of public transportation in 2018.

Summary 3   The most carbon­efficient transit mode on a per­passenger­mile basis was rail­based transit, which transported 60% of passenger miles in 2018. Buses varied in emissions efficiency depending on fuel, technology, operations, and occupancy. Electric and bio­ diesel buses had the lowest GHG emissions per passenger mile in 2018. Passengers on ferries and vans had higher emissions profiles, but those modes only accounted for 5% of passenger travel. Transit Agency Contributions to GHG Emission Reduction and Sustainability Transit agencies are increasingly taking climate actions. Transit GHG emissions have fallen over the past 15 years on both an overall basis and a per­passenger­mile basis. Even those agencies that are not setting specific GHG targets are pursuing fuel efficiency and cost savings that can bring GHG savings. Transit agencies are adopting lower­carbon vehicle technologies and fuels, such as hybrids, regenerative braking, biofuels, and electric vehicles. The growth of electric buses in recent years has been notable and especially benefi­ cial as the use of more carbon­intensive grid electric power sources like coal has lessened while solar and wind have grown. A continuation of these trends will enable transit to be a low­carbon solution to meeting transportation needs into the future. This will be even more true if ridership and occupancy increase over time. However, decreases in ridership, whether due to COVID­19 creating lasting disruptions in our travel patterns or scaling back of transit service, will shrink transit’s climate benefits. A scenario of potential transit GHG savings to 2030 and 2050 was developed to show how transit climate action can grow impacts. That said, GHGs are not the only metric by which transit success should be judged. In addition to benefiting the climate, transit provides essential mobility and access to communities that are otherwise made vulnerable by age, income, disability, neighborhood disinvestment, or other forces that may also put them on the front lines of climate dis­ ruption. Planning for a sustainable, resilient future must include public transportation that serves community needs. Research Approach The emissions calculations in this analysis are based on data for transit vehicles, energy use, and passengers reported in the National Transit Database (NTD) of the FTA (FTA 2020a). The GHG calculation methods follow best practices from the American Public Transportation Association (APTA 2018), the U.S. Environmental Protection Agency (U.S. EPA 2020d), and the GHG Protocol [World Business Council for Sustainable Development (WBCSD) and World Resources Institute (WRI) 2004], as documented in Chapter 2 and the appendices of this report. The land use efficiency GHG savings were modeled using household travel survey data from 28 regions using a structural equation model documented in the methodology. The emissions values in this report include direct, indirect, and upstream GHG emis­ sions associated with vehicle travel. • Direct GHG Emissions are the carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) emissions that occurred at the vehicle when fuel was consumed. • Indirect GHG Emissions occurred at the power plant when electricity was produced or in the process of producing hydrogen.

4 An Update on Public Transportation’s Impacts on Greenhouse Gas Emissions • Upstream Emissions, sometimes referred to as “well­to­pump” emissions, are the GHG emissions that occurred during fuel production and distribution. Thus, the emissions values presented here are “well­to­wheels” values or the full life­ cycle GHG emissions associated with using a fuel. In 2018, public transportation in the United States used 49 million gallons of biodiesel fuel and 47,000 gallons of ethanol. The CO2 emitted by these fuels is considered “biogenic” by major GHG accounting standards because it is sourced from plant matter and part of the natural carbon cycle. In 2018, transit use of biodiesel and ethanol emitted 0.5 MMT biogenic CO2. The emissions calculations presented here do not include the GHG impacts of transit operations, which may represent 5% to 35% of transit agency GHG emissions (McGraw et al. 2010, Southworth et al. 2011). This is an area worthy of further research. Transit agencies report their activity data to the NTD each year, so the GHG calcula­ tions in this report could be repeated annually as part of the database compilation process, which would provide transit agencies and communities necessary data to manage climate impacts. Project Resources The GHG analysis presented here is meant to be a resource for transit agencies, decision makers, communities, and other public transportation and sustainability stakeholders. This information can be used to guide decision making toward lower­carbon fuels, technologies, and operations improvements as well as demonstrating the importance of transit rider­ ship and occupancy as a climate solution. The analysis in this research project is also meant to provide the information necessary to communicate public transportation’s important role as a climate solution. To those ends, tools for communication and ideation have been created as part of this project. These supplementary materials can be obtained by going to www.TRB.org and searching for “TCRP Research Report 226”: 1. Three one-page factsheets that present key findings regarding transit as a climate solution. 2. A PowerPoint slide deck summarizing these findings and the research they are based on with the infographics and charts used in this document and a template for transit agencies to add their own data for climate communications. 3. A simple spreadsheet tool that provides this study’s 2018 GHG impact findings by transit agency and allows users to apply several of the future scenarios to see how their transit agency’s GHG impacts change with electrification, clean power, and ridership increases.