Transportation and Climate
Greenhouse Gas Emissions Model (GEM) for Medium- and Heavy-Duty Vehicle Compliance
EPA’s Greenhouse Gas Emissions Model (GEM) is a free, desktop computer application that estimates the greenhouse gas (GHG) emissions and fuel efficiency performance of specific aspects of heavy-duty vehicles. GEM is designed to operate on a single computer.
To request a CD of this software instead of downloading it or if you have trouble with accessibility of this software, please contact EPA.
GEM Simulation Model v2.0 (Supporting the Final Heavy-Duty Vehicle Greenhouse Gas Emissions and Fuel Efficiency Rules)
The model documentation provides details on how to install and use the model. The pdf file also contains the input files that were used to determine the stringency of the final Greenhouse Gas Emissions Standards and Fuel Efficiency Standards for Medium- and Heavy-Duty Vehicles. The downloadable installation file below contains the application executable files for the active version of the GEM for simulating vehicle compliance. Lastly, the report of the peer review of GEM v1.0 includes the comments received on the model and EPA’s responses.
- Read the user guide for model architecture, how to use the model, and inputs used to determine the final standards (PDF) (16 pp, 693K, EPA-420-B-11-019, August 2011)
- Download the executable version of GEM_Setup.exe (zip) (194MB)
- Update: An installation bug has been identified for computers using a Windows 7 operating system. Due to the security setup of the Windows 7 operating system, the GEM executable code will not run from the default installation folder of C:\Program Files(x86)\EPA\GEM or from any other folder under C:/Program Files. This bug can be avoided by clicking on Browse under "Choose Installation Location," and then selecting a different local folder into which to install the GEM.
- Please unzip the file first and then follow the GEM User Guide instruction to install GEM v2.0
- Peer Review Report and Response to Comments (PDF) (106 pp, 1.67MB, EPA-420-R-11-007, August 2011) This document contains the Peer Review Report, which is comprised of comments from four separate peer reviewers, and EPA’s response to those comments.
GEM v1.0 (Supporting the Proposed Heavy-Duty Vehicle Greenhouse Gas Emissions and Fuel Efficiency Rules)
The model documentation provides details on how to use the model, the model’s input files, algorithms, and output files. The pdf file also contains the input files that were used to determine the stringency of the proposed Greenhouse Gas Emissions Standards and Fuel Efficiency Standards for Medium- and Heavy-Duty Vehicles. The downloadable installation zip file below contains the application executable files. Lastly, the MATLAB/Simulink version of GEM is included to allow individuals to review the model architecture in detail.
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Software & Documentation
- Read the guide for model architecture, how to use the model, and inputs used to determine the proposed standards (PDF) (15 pp, 755K, EPA-420-B-10-039, October 2010)
- Download the MATLAB/Simulink version of GEM v1.0 to review the model architecture (ZIP) (154K)
- Start the MATLAB and change the current directory to the location where the tool is unzipped and saved.
- Run the MATLAB script "Run_GEM_sim.m" to launch the GUI window to start using the tool.
- Select one radial button on the left-hand side of the window to choose an appropriate truck subcategory.
- Enter proper values for "Coefficient of Aerodynamic Drag," "Steer Tire Rolling Resistance," and "Drive Tire Rolling Resistance" on the right-hand side of the window.
- Click the "RUN" button. Then, the tool will simulate the three different driving cycles and display the final results in the MATLAB Command Window.