U. S. Environmental Protection Agency

May 3, 1999

Document Released for Stakeholder Review and Comment

"Fleet Characterization Data for MOBILE6:Development and Use of
Age Distributions,Average Annual Mileage Accumulation Rates, and
Projected Vehicle Counts for Use in MOBILE6" 


Report Number EPA420-P-99-011
 
The Office of Mobile Sources, Assessment and Modeling Division,
announces the release of"Fleet Characterization Data for
MOBILE6:Development and Use of Age Distributions, Average Annual
Mileage Accumulation Rates, and Projected Vehicle Counts for Use
in MOBILE6" for stakeholder review and comment.  This document
EPA420-P99-011 also known as document M6.FLT.007.is available at
the MOBILE6 section of the OMS Web Site
(http://www.epa.gov/oms/m6.htm).

The MOBILE model requires estimates of a distribution of
registered vehicles by age, average annual mileage accumulation
rates by age and vehicle category, and estimates of the projected
size of the fleet in future years.  While this type of
information exists in the current version of the model, MOBILE5,
the data contained in that model is outdated.  Therefore it was
necessary to develop new estimates for use in the new version of
the model MOBILE6.  The new estimates are largely based on work
done by Arcadis, Geraghty & Miller in a report entitled  "Update
of Fleet Characterization Data for Use in MOBILE6."  The Arcadis
report describes the number of vehicles registered by age and
class and the average mileage accumulation rates on July 1, 1996. 
The following report describes the methodology EPA used to
convert the July 1, 1996 registration profile into a
generally-applicable registration distribution by age, the use of
the average annual mileage accumulation rates, and the
methodology for projecting the size of future vehicle fleets by
vehicle category.  The report also describes how the results of
this analysis will be applied in the model.

Comments on this report and its proposed use in MOBILE6 should be
sent to the attention of Tracie Jackson.  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 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 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