EMFAC (Emission Factors Model) is a motor vehicle emissions modeling system developed by the California Air Resources Board (CARB) to estimate pollutant emissions from on-road vehicles operating in California. EMFAC produces emissions inventories for criteria pollutants, air toxics, greenhouse gases (GHGs), and particulate matter across a wide range of vehicle types, model years, and operating conditions. [1]
The United States Environmental Protection Agency (EPA) has formally approved the use of EMFAC for State Implementation Plans (SIPs) and transportation conformity analyses in California regions. [2]
EMFAC is primarily used for:
Government agencies use EMFAC to calculate emissions of:
Metropolitan planning organizations (MPOs) use EMFAC outputs to determine whether future transportation plans meet federal Clean Air Act requirements.
EMFAC estimates inform:
Universities, consultants, and transportation agencies use EMFAC for evaluating:
EMFAC produces emissions based on vehicle population, activity, and emission rates, using three core components:
Determines:
Emission factors (grams per mile, gram per start, etc.) are developed through:
EMFAC integrates activity and emissions across the vehicle fleet, outputting total emissions for:
Earlier versions used for SIP development and conformity through the mid-2010s.
Approved by EPA for federal conformity in 2019. [2]
The most recent model, incorporating: [1]
29+ vehicle classes, including:
Includes modeling for:
Frequently used to evaluate:
EMFAC and MOVES share similar goals but differ in methodology and geographic focus.
| Feature | EMFAC | MOVES |
|---|---|---|
| Primary Use | California SIP & conformity | National emissions modeling |
| Developer | CARB | U.S. EPA |
| Vehicle Activity | California-specific data | National multi-state datasets |
| ZEV Modeling | ZEV Modeling | Broader national assumptions |