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U.S. Department of Transportation U.S. Department of Transportation Icon United States Department of Transportation United States Department of Transportation

Improving Efficiency and Energy Security of Transportation and Reducing Emissions

A man installing solar panels on a roof
Installing solar roof on an airport on Nantucket, MA (PSNH photo)

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


  • 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 



  • 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 



  • 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