EPA GEM User Guide

About this manual

The EPA Greenhouse Gas Emissions Model (GEM) is a free desktop application used to assess compliance with proposed GHG emissions and fuel‑consumption standards for heavy‑duty vehicles. The guide explains how to download, install, and operate the MATLAB/Simulink version of GEM.

GEM models six vehicle systems—Ambient, Driver, Electric, Engine, Transmission, and Vehicle—using predefined input parameters for Class 7/8 combination tractors and Class 2b‑8 vocational vehicles. The guide also details output calculations and provides example input files.

What's inside

• Vehicle Model Architecture
• Predefined Input Parameters for Class 7/8 Combination Tractors
• Predefined Input Parameters for Class 2b‑8 Vocational Vehicles
• Output Processes
• Installation and Usage

Specifications

Frequently asked questions

Which vehicle classes does GEM model?

GEM models Class 7 and 8 combination tractors and Class 2b‑8 vocational vehicles.