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Modeling and Inventories
The following information covers OTAQ modeling and inventories. Modeling is EPA's method for estimating emissions from on-road vehicles, nonroad sources, and fuels. Inventories are calculations of total emissions of a pollutant for a given area at a defined time and set of conditions.
MOVES (MOtor Vehicle Emission Simulator) is EPA’s current official model for estimating air pollution emissions from cars, trucks and motorcycles. In the future the model will also cover nonroad emissions.
NONROAD Model links to information on the NONROAD emission inventory model, which is a software tool for predicting emissions of hydrocarbons, carbon monoxide, oxides of nitrogen, particulate matter, and sulfur dioxides from small and large nonroad vehicles, equipment, and engines.
NMIM, or National Mobile Inventory Model, is a free, desktop computer application developed by EPA to help you develop estimates of current and future emission inventories for on-road motor vehicles and nonroad equipment. NMIM uses current versions of MOBILE6 and NONROAD to calculate emission inventories, based on multiple input scenarios that you enter into the system. You can use NMIM to calculate national, individual state, or county inventories.
MOBILE Model links to information on the MOBILE vehicle emission factor model, which was EPA’s official model for estimating air pollution emissions from cars, trucks, and motorcycles until it was replaced by MOVES.
Fuels Models links to information on EPA's heavy-duty diesel fuel analysis program, which seeks to quantify the air pollution emission effects of diesel fuel parameters on various nonroad and highway heavy-duty diesel engines. It also links to the Complex Model and the Simple Model used for the Reformulated Gasoline Program.
OMEGA, the Optimization Model for Reducing Emissions of Greenhouse Gases from Automobiles, which estimates the technology cost for automobile manufacturers to achieve variable fleet-wide levels of vehicle greenhouse gas emissions.
GEM, the Greenhouse gas Emissions Model, estimates the greenhouse gas emissions and fuel efficiency performance of specific aspects of heavy-duty vehicles. This model is a means for determining compliance with EPA’s GHG emissions standards and NHTSA’s fuel consumption standards, for Class 7 and 8 combination tractors and Class 2b-8 vocational vehicles.
Related Information:
Special Modeling in Support of the Heavy Duty Engine/Vehicle and Highway Diesel Fuel Final Rule
This web page provides support documentation and modeling procedures for the Heavy Duty Engine/Vehicle and Highway Diesel Fuel Final Rule. This page includes, but is not limited to, a modeled estimate for one-hour concentrations of fine particulate matter, ground-level ozone levels in extended time periods, PM emissions as they impact national scale toxics, and diesel fuel requirement.
Special Modeling in Support of the Tier 2/Gasoline Sulfur Final Rule
This web page provides information about special vehicle and engine emission modeling completed in support of the Tier 2/Gasoline Sulfur Final Rulemaking. The modeling analyzed on-highway, light-duty vehicles and trucks (all pollutants), heavy-duty gasoline vehicles (NOx and VOC), heavy-duty vehicles (PM and SOx), nonroad stationary, and other sources. Also, photochemical ozone modeling and toxics modeling are provided.
Emission Inventories
This web site contains the document, "Procedure for Emission Inventory Preparation - Volume IV: Mobile Sources" and several EPA papers that describe the effects of raising speed limits on vehicle emissions.
Mobile Source Observation Database (MSOD)
- MSOD Description and Ordering Information
- MSOD User Guide and Reference (PDF) (2.4MB, EPA420-B-08-017, November 2008, About PDF)
CALINE Models (e.g., CALINE3 & CALINE4)
Vehicle Clean Screening
This web page provides information on vehicle clean screening, vehicle profiling, and remote sensing device issues. Clean Screening is the term used to describe methods that states can use to excuse cars from a scheduled Inspection and Maintenance emissions test. Remote sensing is a way to measure pollutant levels in a vehicle's exhaust while the vehicle is traveling down the road.
Links to Related EPA Information:
Clearinghouse for Inventories and Emissions Factors (CHIEF)
Emission Factor and Inventory Group, Office of Air Quality Planning and Standards Latest emission factor and inventory information, including AP-42 emission factor documents, inventory training tools, emission estimation software, and emissions modeling tools.
Air Pollution Emissions Overview
Office of Air Quality Planning and Standards Information on what emissions are and where they come from, and on measuring, reporting, and using emissions data.
Links to Related Non-EPA web Sites:
Mobile Source Emission Inventory Program 
California Environmental Protection Agency, California Air Resources Board
This web site contains information on California's on-road and nonroad mobile source emission factors for California and the motor vehicle activity components such as vehicle-miles-traveled, starts and vehicle population. It includes recent publications, the on-road model software and associated system documentation and commonly requested outputs from this model, known as "model runs."
Travel Model Improvement Program
U.S. Department of Transportation
The Travel Model Improvement Program (TMIP) is a multi-year, multi-agency program to develop new travel demand modeling procedures that accurately and reliably forecast travel for a broad range of modes, policy actions and operational conditions. This web site has been established to assure that practitioners have access to the best transportation planning methods available.