Enhancing efficiency of transportation sources can improve energy independence and economic and functional resilience in the transportation sector while reducing greenhouse gas and other emissions. Distributed and diverse energy production and utilization can enable transportation infrastructure to function even under extreme conditions, and energy efficiency and domestic energy production reduce the need for foreign energy sources.

The U.S. DOT Volpe Center works with its sponsor agencies to identify, plan for, integrate, and evaluate the efficacy of efficiency, energy diversification, and emissions reduction projects. This includes developing a plan for the first carbon-neutral airport in the U.S., calculating and reporting pollutant emissions for various agencies, modeling future demand for low-carbon technology adoption, and modeling benefits of the Corporate Average Fuel Economy (CAFE) regulatory changes. The U.S. DOT Volpe Center also provides support to FAA for its participation in the United Nations International Civil Aviation Organization (ICAO) efforts to develop a global market-based measure to cap carbon emissions in international aviation, which took effect starting in 2021.

Research and Reports

Transit

• FTA Greenhouse Gas Emissions from Transit Projects: Programmatic Assessment    
  This programmatic assessment serves to (1) report on whether certain types of proposed transit projects merit detailed analysis of their greenhouse gas (GHG) emissions at the project level and (2) be a source of data and analysis for FTA and its grantees to reference in future environmental documents for projects in which detailed, project-level GHG analysis is not vital 
• FTA Transit Bus Electrification Tool  
  The Transit Bus Electrification Tool is a Microsoft Excel-based spreadsheet tool that allows users to estimate the partial lifecycle greenhouse gas emission savings associated with replacing standard bus fleets with low-emission or zero-emission transit buses  
• FTA’s Greenhouse Gas Emissions Estimator 3.0 
  The Transit Greenhouse Gas (GHG) Emissions Estimator (Estimator) is a Microsoft Excel-based spreadsheet tool that allows users to estimate the partial lifecycle GHG emissions generated and energy used during the construction, operation, and maintenance phases of a project across select transit modes. Users input general information about a project, and the Estimator calculates annual GHG emissions by project phase. Although the Estimator lacks the precision for projections that may be attainable by using more complex emission models or route-specific ridership estimates, it can generate early, informative GHG emissions and energy use estimates for a broad range of transit projects 

Multimodal

• Carbon Dioxide Emissions from Four Real World Inter-City Passenger Trips: A Comparison of Rail, Air, and Road Travel Modes by City Pair   
• Confluence of ITS, Complete Streets, and GHG Emissions 
• Report to Congress on Transportation Decarbonization   
  Report to Congress outlining existing and planned efforts by U.S. DOT to reduce transportation sector greenhouse gas emissions. Expected completion in Fall 2023 
• Carbon Dioxide Emissions from Four Real World InterCity Passenger Trips: A Comparison of Rail, Air, and Road Travel Modes by City Pair    
  The U.S. DOT Volpe Center provides subject matter expertise on climate change, resiliency, and sustainability in support of FRA’s priorities on climate and sustainability. Specifically, the U.S. DOT Volpe Center conducts research and analysis on greenhouse gas emissions, develops tools and resources for FRA and FRA grant applicants, and supports FRA’s efforts to demonstrate and report on the climate benefits of rail, among other activities  

Freight

• Bunker Adjustment Factor, Fuel Adjustment Factor and Currency Adjustment Factor Study  
  The U.S. DOT Volpe Center supports U.S. Transportation Command (USTRANSCOM) acquisitions’ economic price adjustments which are applied to commercially shipped DOD cargoes. The study involves analyzing the shipping industry and factors that influence vessel fuel consumption such as the significant International Maritime Organization's (IMO) 2020 and 2023 regulations that seek to economize fuel consumption and curb sulfur and carbon emissions in shipping 

Rail

• Best Practices and Strategies for Improving Rail Energy Efficiency 
  Reviews and evaluates international and U.S. passenger and freight rail industry segments for improving energy efficiency (E2) performance and attaining environmental sustainability goals 

Highways

• CAFE Compliance and Effects Modeling System: The Volpe Model 
  Estimating how manufacturers could attempt to comply with a given CAFE standard by adding technology to anticipated future vehicle fleets, and to estimate impacts of that additional technology on fuel consumption, greenhouse gas emissions, and economic costs and benefits 
• Cambridge Clean Fleet Initiative: 2030 GHG Reduction Scenarios and Proposed Target 
  On behalf of the city of Cambridge, the U.S. DOT Volpe Center: 1) develops strategies to decrease greenhouse gas emissions (GHG) from the municipal fleet; 2) establishes a 2030 fleet GHG emissions reduction target from the 2016 baseline; and 3) creates a fleet implementation plan to reach that target 
• Corporate Average Fuel Economy (CAFE) 
  Analyses to assess the costs and benefits of national fuel economy standards 
• FHWA CMAQ Emissions Calculator Toolkit  
  The Congestion Mitigation and Air Quality Improvement (CMAQ) Program provides funding to highway and transit projects that improve local air quality. Many projects, such as alternative fuel and electric vehicle purchase and electronic open-road tolling lanes, also reduce greenhouse gas emissions. The CMAQ Emissions Calculator Toolkit is an optional resource to assist DOTs, MPOs and project sponsors in the project justification process for CMAQ funding 
• Highway Renewable Energy: Photovoltaic Noise Barriers 
• Reducing Heavy Truck Fuel Consumption
  Improving vehicle fuel economy, analyzing emerging technologies and alternative fuel sources, and modeling emissions to establish fuel consumption standards 
• Renewable Energy in Highway Right-of-Way 
  Resources and workshops to assist transportation agencies in pursuing renewable energy projects such as solar
• Highway Renewable Energy: Photovoltaic Noise Barriers
  Presents state of practice and business case for photovoltaic noise barriers

Aviation

• Achieving Airport Carbon Neutrality 
  Achieving carbon neutrality typically requires the use of multiple mechanisms to first minimize energy consumption and then maximize renewable energy use. This report provides a flexible, step-by-step outline for planning and achieving airport carbon emissions reduction or neutrality  
• Aviation Environmental Design Tool 
  AEDT is a software system that models aircraft performance in space and time to estimate fuel consumption, emissions, noise, and air quality. AEDT is a comprehensive tool that provides information to FAA stakeholders on each of these specific environmental impacts. AEDT facilitates environmental review activities required under NEPA by consolidating the modeling of these environmental impacts in a single tool 
• Commercial Aviation Alternative Fuels Initiative (CAAFI) 
  A multi-organizational coalition dedicated to promoting the development and deployment of safe, green alternatives to today’s jet fuels
• ICAO Environment Report 2013: Aviation and Climate Change  
  An overview of the main developments related to aviation and the environment from 2011 to 2013
• ICAO Environmental Report 2019: Environmental Trends in Aviation to 2050   
  The U.N. International Civil Aviation Organization's triennial report on environmental progress, future trends assessment for fuel burn, emissions, and emissions reductions, and other environmental topics 
• ICAO Environmental Report 2022: Environmental Trends in Aviation to 2050   
  The U.N. International Civil Aviation Organization's triennial report on environmental progress, future trends assessment for fuel burn, emissions, and emissions reductions, and other environmental topics 
• ICAO Environmental Trends    
  Tutorial on the process by which the environmental trends assessment for ICAO is executed  
• U.S. Airport Greenhouse Gas Emissions Inventories: State of the Practice and Recommendations for Airports