U.S. Environmental Protection Agency

                        May 3,1999
                                
      Document Re-Released for Stakeholder Review and Comment
                                
          The Determination of Hot Running Emissions 
                     from FTP Bag Emissions
                                
                 Report Number EPA420-P-99-014

The Office of Mobile Sources, Assessment and Modeling Division,
announces the re-release of "The Determination of Hot Running
Emissions from FTP Bag Emissions" for stakeholder review and
comment. This document, also known as M6.STE.002, is available at
the MOBILE6 section of the OMS Web Site
(http://www.epa.gov/oms/m6.htm).

It is one of four documents (M6.STE.002, M6.STE.003, M6.EXH.001,
and M6.EXH.002) that collectively describe the methodology and
proposed findings on the in-use exhaust deterioration of
1981-1993 model year cars and trucks. This document (M6.STE.002)
describes a methodology to separate FTP data into start and
running emissions. This methodology is then applied in the other
documents to estimate start and running emissions deterioration
as a function of mileage. All four documents are being released
concurrently for review. This document is being re-released since
it is related to the other three.

This document describes our efforts to develop a simple model for
estimating hot running 505 (HR505) emissions from FTP data. The
HR505 is an extra exhaust emissions "bag" performed immediately
following the third "bag" of the standard FTP. This new "bag" is
a duplicate in terms of speed/time to the first and third "bags".
The only difference between the "bags" is the HR505 does not
contain an engine start. The HR505 was developed to allow the
separation of the emission effects of vehicle start with the
effects of hot running operation.

Comments on this report and its proposed use in MOBILE6 should be
sent to the attention of David Brzezinski or 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.

This document is being re-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