U.S. Environmental Protection Agency

April 2001

Document Released for Public Information

"MOBILE6 Emission Factors for Natural Gas Vehicles" 

Report Number   EPA420-R-01-033     (M6.FUL.004)
 
	The Office of Transportation and Air Quality, Assessment and 
Standards Division announces the release of "MOBILE6 Emission Factors for Natural Gas 
Vehicles" for public information.  This document EPA420-R-01-033, also 
known as M6.FUL.004, is available at the MOBILE6 section of the OTAQ Web Site 
(http://www.epa.gov/otaq/m6.htm).

	This document is structured into two primary sections. The first section 
shows the basic NGV emission factors which were incorporated into MOBILE6, and 
provides some rationale as to why these values were selected.  The second section 
is an Appendix which describes the data and analysis performed by EPA to develop the 
preliminary NGV emission factor estimates.  In some cases these values were retained
 in the final model, and in other cases alternative emission factors provided by 
the natural gas industry based on actual vehicle testing were incorporated into 
the final model.

	This report was originally released (as a draft) in May, 1999 under the title,
"Modeling Emission Factors for Compressed Natural Gas Vehicles".  It was subsequently
revised in March, 2001.  This current version is the final revision of the
March, 2001 draft (of M6.EXH.009).  This final revision incorporates suggestions 
and comments received from stakeholders during the 60-day review period and from peer 
reviewers.