U.S. Environmental Protection Agency

                        May 3, 1999
                                
      Document Released for Stakeholder Review and Comment
                                
 MOBILE6 Inspection / Maintenance Benefits Methodology for 1981
             through 1993 Model Year Light Vehicles
                                
                 Report Number EPA420-P-99-007

The Office of Mobile Sources, Assessment and Modeling Division,
announces the release of "MOBILE6 Inspection / Maintenance
Benefits Methodology for 1981 through 1993 Model Year Light
Vehicles" for stakeholder review and comment. This document, also
known as M6.IM.001, is available at the MOBILE6 section of the
OMS Web Site (http://www.epa.gov/oms/m6.htm).

This document describes EPA's new methodology for estimating
exhaust emission Inspection / Maintenance (I/M) credits.  This
includes the methodology for various tests such as the IM240, the
Idle test, the 2500 RPM/Idle test, and the ASM test.  It includes
the methodology used for all cars and light trucks for model
years 1981 through 1993, and for non-Tier1 cars and trucks for
model years 1994 and 1995.  The I/M credit methodology for the
pre-1996 model year will also be used for 1996 and later model
years which receive only exhaust I/M tests.   This document also
describes how credits and debits for the remote sensing device
(RSD) testing will be incorporated into MOBILE6.  The I/M credits
for the pre-1981 model years are not being revised for MOBILE6. 
The I/M credits for post-1995 model years with OBD systems, and
the evaporative emission I/M test credits will be discussed in
separate documents "Determination of Emissions, OBD, and I/M
Effects for Tier1, TLEV, LEV, and ULEV Vehicles" - EPA document
M6.EXH.007, and "Inspection / Maintenance Credits for Evaporative
Control System Tests" -  EPA document M6.IM.003.  The derivation
of repair effects for start emissions will be described in detail
in the report "Determining Repair Effects on IM240 Cold Start
Emissions for 1981 and later Light Duty Vehicles," M6.IM.002.

Comments on this report and its proposed use in MOBILE6 should be
sent to the attention of Ed Glover. 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. Data sets for this document will be provided in
electronic format if requested.

This document is being released and posted on May 3, 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 followup 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