U.S. Environmental Protection Agency

November 17, 1999

Document Released for Stakeholder Review and Comment

Estimating Benefits of Inspection/Maintenance Programs for
Evaporative Control Systems

Report Number EPA420-P-99-031

The Office of Mobile Sources, Assessment and Modeling Division 
announces the release of "Estimating Benefits of 
Inspection/Maintenance Programs for Evaporative Control
Systems" for stakeholder review and comment.  This document 
EPA420-P-99-031 (also known as M6.IM.003)is available at the
MOBILE6 section of the OMS Web Site
(http://www.epa.gov/oms/m6.htm)

This draft report outlines our proposal for how MOBILE6 will
adjust evaporative (non-exhaust) emission estimates to
account for Inspection/Maintenance (I/M) programs that include
tests of automotive evaporative control systems. Evaporative
emissions include the evaporation of hydrocarbons (HC) as
diurnals, resting loss, hot soak and running loss.

For MOBILE6 evaporative emissions are calculated as a
weighted average of emissions by test-status sub-groups.
There are four original test-status groups:  pass/pass, pass
pressure/fail purge, fail pressure/pass purge and fail/fail. To
calculate the benefits of evaporative I/M, we assume that the
effect of I/M is to shift vehicles from higher-emitting sub-
groups to lower-emitting groups.


Comments on this report and its proposed use in MOBILE6 should be
sent to the attention of Megan Beardsley. 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 November 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