March 9, 1999
   
   
   Document Released for Stakeholder Review and
   Comment
   
   Soak Length Activity Factors for Diurnal
   Emissions
   
   EPA Publication Number EPA420-P-98-019
   
   MOBILE6 Report Number M6.FLT.006
   
        The Office of Mobile Sources, Assessment
   and Modeling Division, announces the release of
   "Soak Length Activity Factors for Diurnal
   Emissions" for stakeholder review and comment. 
   This document M6FLT006.PDF/M6FLT006.WPD is
   available at the MOBILE6 section of the OMS Web
   Site (http://www.epa.gov/omswww/models.htm). 
   It is supplemented by two Excel files: 
   Di_rule.xls and Evpdiu2a.xls.
   
        Diurnal activity estimates have been
   derived for use in MOBILE6.  They were derived
   primarily from instrumented vehicle study data
   collected in Spokane, Atlanta and Baltimore. 
   These activity estimates will be used to
   properly distribute the diurnal evaporative
   emissions in MOBILE6 between the hours of the
   day, and within a given hour.  The report also
   discusses the various types of diurnals.  These
   include interrupted diurnals, full diurnals and
   multi-day diurnals.   The rules which are used
   to determine which type of diurnal is present
   as a function of time of day and the length of
   the diurnal soak period are also discussed.  An
   attached spreadsheet is available which
   illustrates the application of the diurnal
   activity factors with early draft diurnal
   emission estimates.
   
        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, or 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
   March 9, 1999.  Comments will be accepted for
   sixty (60) days, ending May10, 1999  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