U.S. Environmental Protection Agency

April 2001

Document Released for Public Information

"Estimating Weighting Factors for Evaporative Emissions in MOBILE6"

Report Number   EPA420-R-01-022     (M6.EVP.006)
 
	The Office of Transportation and Air Quality, Assessment and 
Standards Division announces the release of "Estimating Weighting 
Factors for Evaporative Emissions in MOBILE6" for public information.  
This document EPA420-R-01-022, also known as M6.EVP.006, is available 
at the MOBILE6 section of the OTAQ Web Site 
(http://www.epa.gov/otaq/m6.htm).

	In three parallel documents (M6.EVP.001, M6.EVP.002, and 
M6.EVP.005), EPA identified the methods used in MOBILE6 for estimating 
resting loss and diurnal emissions based (in part) on the performance 
of the vehicles (i.e., pass or fail) on the purge and pressure tests.  
EPA computes model-year and age specific average resting loss and 
diurnal emissions by weighting together the emissions of passing and 
failing vehicles according to their frequency in the in-use fleet.  
This document describes this approach and EPA's predictions of pass 
and fail rates (i.e., weighting factors) as functions of vehicle age.

	This report was originally released (as a draft) in June 1999.  
This current version is the final revision of that draft.  This final 
revision incorporates suggestions and comments received from 
stakeholders during the 60-day review period and from peer reviewers.