U.S. Environmental Protection Agency

May 17, 1999

Document Released for Stakeholder Review and Comment
	
"Modeling Emission Factors for Compressed Natural Gas Vehicles"


Report Number EPA420-P-99-012
 
The office of Mobile Sources, Assessment and Modeling Division 
announces the release of "Modeling Emission Factors for 
Compressed Natural Gas Vehicles" for stakeholder review and 
comment.  This document EPA420-P99-012, also known as document 
M6.FUL.004, is available at the MOBILE6 section of the OMS Web 
Site (http://www.epa.gov/oms/m6.htm). 

Under the Clean Air Act (CAA) Amendments of 1990, states which 
have serious, severe, or extreme ozone non-attainment areas, and 
areas with carbon monoxide design values greater than 16 ppm must 
establish a Clean Fuel Fleet (CFF) Program.  Under the CFF 
program, a certain percentage of light-duty vehicles, light-duty 
trucks, and heavy-duty vehicles acquired by certain fleet owners 
located in covered areas will be required to meet clean-fuel 
emissions standards.  Clean Fuel Fleet emissions standards are 
lower than those set by the CAA.  Many states have incorporated 
compressed natural gas vehicles (CNGVs) into their CFF programs, 
and need to model the emission factors and benefits obtained 
through the addition of CNGVs to the in-use vehicle fleets in 
their states.


This document examines the emissions benefits of CNGVs and how 
these benefits will be modeled in MOBILE6.  It also describes the 
data the methodology used to determine these benefits.

Comments on this report and its proposed use in MOBILE6 should be 
sent to the attention of Janet Kremer.  Comments may be submitted 
electronically to mobile@epa.gov, by fax to (734) 214-4939, or by 
mail to MOBILE6 Review Comments, US EPA Assessment and Modeling 
Division, 2000 Traverwood Drive, Ann Arbor, MI 48105.  Electronic 
submission of comments is preferred.  In your comments please 
note clearly the document that you are commenting on including 
the report title and the code number listed.  Please be sure to 
include your name, address, affiliation and any other pertinent 
information.

This document is being released and posted on May 17, 1999. 
Comments will be accepted for sixty (60) days.  EPA will then 
review and consider all comments received and will provide a 
summary of those comments and how we are responding to them in the
form of a follow-up document.

Thank you for your continuing interest in the development of 
MOBILE6.

Sincerely,

Emission Inventory Group, 
Assessment and Modeling Division, 
US EPA, Office of Mobile Sources