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Handbook for Estimating Transportation Greenhouse Gases for Integration into the Planning Process

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FHWA's Handbook for Estimating Transportation Greenhouse Gases for Integration into the Planning Processis designed for State Departments of Transportation (DOTs) and metropolitan planning organizations (MPOs) of all sizes and capabilities to understand possible approaches for analyzing greenhouse gas (GHG) emissions in the planning process. It helps users understand:

The Handbook describes methods that can be used for:


Fuel-based Methods

Fuel-based methods typically rely on fuel sales data and involve calculating carbon dioxide (CO2) emissions based on the carbon content of each fuel. Tools such as EPA's State Inventory Tool or State Inventory Projection Tool can be used to produce estimates of CO2 by fuel type. Results can be refined in a variety of ways, including allocating emissions to vehicle types or geographic areas.

VMT-based Methods

Vehicle miles traveled (VMT)-based methods involve estimating the quantity of vehicle travel and then connecting this information to an estimate of emissions using emissions factors or an emissions model like EPA's Motor Vehicle Emissions Simulator (MOVES) model, which is the preferred approach. VMT estimates can be developed relying on vehicle, household, and land use data; using data from the Highway Performance Monitoring System (HPMS); or using a network-based travel model. Emissions of CO2 and other GHGs can take into account a wide range of factors, including the mix of vehicle types, travel speeds, operating conditions, and temperature.

Alternative GHG Estimation Approaches

Other emissions estimation methods include:

Specific Transportation Strategy Analysis Methods

"Off-model" analyses may be used to analyze the effects of strategies that are not well accounted for in standard travel forecasting methods, such as:

Additional Considerations

In addition to direct emissions from motor vehicles, planners may consider:

Selecting A Method

The Handbook helps the user select an appropriate GHG analysis method, considering issues such as:

There are a number of key factors that affect the appropriate selection of a methodology. The diagram poses three questions to the analyst: 'What is the goal of the analysis?' 'What data, tools, and resources do we have available?' and 'What variables do we want to analyze?' The diagram presents potential answers to each question to help analysts narrow down their methodolgy selection. Click image for full text description.

For each methodology, the Handbook provides references to manuals, technical resources, models, and tools, and includes examples from State DOTs and MPOs that have used these methodologies.

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The Handbook and other related resources can be found at:

More information on FHWA's climate activities is available at:

Updated: 4/2/2014
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