This section provides an overview of the Energy and Greenhouse Gas Emissions (GHG) topic as it relates to transportation and describes a range of programs, policies, case studies and other resources related to energy consumption and mitigation of greenhouse gas emissions from the transportation sector. Issues include the following:
GHG emissions from transportation accounts for about 27% of GHG emissions in the U.S., second only to electricity generation (31%) (2013 USEPA). Within the transportation sector, light-duty vehicles were the largest category (60%) and medium- and heavy-duty trucks made up the second largest category (23%). From 1990-2013, GHG emissions in the transportation sector increased more in absolute terms than any other sector (i.e. electricity generation, industry, agriculture, residential, or commercial). (U.S. Transportation Sector Greenhouse Gas Emissions 1990-2013, U.S. EPA)
Transportation energy and climate change are closely intertwined since GHG emissions are a directly related to energy consumption. Global transportation energy demand is expected to increase substantially without implementation of aggressive policies, and could potentially be the fastest-growing end-use sector. (See p. 603 of IPCC Fifth Assessment Report WG III Chapter 8.)
For the most part, efforts to meet energy use reduction goals also will reduce transportation’s GHG emissions.
GHG Reduction Strategies
Strategies to reduce transportation GHG emissions and energy include the following:
New York State DOT’s Climate Change and Energy Initiative is an example of the wide range of efforts transportation agencies are taking to reduce greenhouse gas emissions and reliance on petroleum products.
Transportation agencies use a variety of methods to estimate GHG emissions and analyze GHG reduction strategies, including the following examples:
FHWA has developed a handbook detailing a variety of step-by-step procedures to help transportation agencies of all levels of technical capability evaluate the GHG implications of their plans.
For states with modeling expertise and advanced analytic needs, FHWA has produced the Energy and Emissions Reduction Policy Analysis Tool (EERPAT). The tool is designed to “assist state transportation agencies with analyzing greenhouse gas reduction scenarios and alternatives for use in the transportation planning process, the development of state climate action plans, scenario planning exercises, and to measure the reduction potential of various transportation strategies to meet state greenhouse gas reduction goals and targets.” EERPAT is based on the GreenSTEP model developed by the Oregon DOT.
Tools are also available to support analysis of GHG emissions associated with the construction and maintenance of transportation facilities. FHWA’s Infrastructure Carbon Estimator is a spreadsheet tool that estimates the lifecycle energy and GHG emissions based on simple data inputs related to projects or transportation plans. For
projects with detailed engineering analysis, the National Cooperative Highway Research Program (Project 25-25/Task 58) developed a spreadsheet-based calculator tool, the Greenhouse Gas Calculator for State Departments of Transportation (GreenDOT). The tool estimates CO2 emissions from state DOT construction, maintenance, and operations, including emissions from electricity used in roadways, on-road vehicle fleets, emissions from off-road equipment, and embodied energy in materials used during construction.
In 2016, the White House Council on Environmental Quality (CEQ) issued final guidance for how federal agencies should consider GHG emissions and climate change in project-level National Environmental Policy Act (NEPA) documentation.
The guidance urges agencies to quantify an action's projected direct and indirect GHG emissions, taking into account available data and suitable GHG quantification tools. It also recommends that agencies use projected GHG emissions as a proxy for assessing potential climate change effects when preparing a NEPA analysis for a proposed agency action. For more information, link to the final guidance.
In 2008, Washington State DOT (WSDOT) first issued guidance for addressing project-level GHG emissions in environmental documentation, including a standard process and template. WSDOT has separate guidance on climate change evaluations on impacts of climate change to transportation infrastructure. The WSDOT Environmental Procedures Manual provides direction to project teams on addressing climate change and project-related GHG emissions in EAs and EISs.
The FHWA Climate Change Mitigation web page has resources related to GHG emissions and mitigation in transportation.
Also see related topics on the Center website, including: Air Quality, Health and Human Environment, and Sustainability and the AASHTO Resilient and Sustainable Transportation Systems Program.
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