[Federal Register Volume 62, Number 168 (Friday, August 29, 1997)]
[Notices]
[Pages 45802-45803]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 97-23034]


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ENVIRONMENTAL PROTECTION AGENCY

[FRL-5885-5]


Air Pollution Control; Motor Vehicle Emission Factors

AGENCY: Environmental Protection Agency (EPA).

ACTION: Notice of public workshop.

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SUMMARY: The Environmental Protection Agency is now in the process of 
developing revisions and improvements to the highway vehicle emission 
factor model (the MOBILE model). The current version of the model, 
MOBILE5a, was released for use March 26, 1993. The next version of the 
model, MOBILE6, is tentatively planned for completion early in 1998 and 
release for use in the summer of 1998. This notice announces the second 
public workshop for the purpose of discussing issues raised by the 
pending revisions to the model. At this workshop, EPA will present 
results of analyses that have been completed to date, raise new issues 
for discussion and comment, and generally provide an update as to the 
progress that has been made since the first MOBILE6 workshop held in 
March, 1997. There is likely to be one additional MOBILE6 workshop, 
probably in the spring of 1998. As at the March 1997 workshop, this 
workshop will also include a presentation on EPA's progress in the 
development of a nonroad mobile source emissions inventory model.

DATES: The workshop will be held Wednesday, October 1 and Thursday, 
October 2, 1997. The times are from 8:30 am to 4:30 pm October 1, and 
8:30 am to 5 pm October 2. All times are Eastern Daylight Time (EDT).

ADDRESSES: The workshop will be held in Powsley Auditorium of the 
Morris Lawrence Building, Washtenaw Community College, 400 East Huron 
River Drive, Ann Arbor, MI 48106. Directions to the workshop can be 
requested from the contact person listed below, or through accessing 
the OMS World Wide Web (WWW) site (www.epa.gov/omswww/). Information on 
how to electronically access this and other workshop-related 
information appears below.

FOR FURTHER INFORMATION CONTACT: Ms. Betty Measley, U. S. EPA Office of 
Mobile Sources, Assessment and Modeling Division, Emission Inventory 
Group, 2565 Plymouth Road, Ann Arbor MI 48105. Telephone: (313) 741-
7902; fax (313) 741-7939.
    This notice, as well as related information concerning the 
workshop, may be found in the OMS section of the EPA Web site. To 
access this information using the WWW:

http://www.epa.gov/OMSWWW/models.htm
gopher: gopher.epa.gov  menus->Offices: Air: OMS
ftp: ftp.epa.gov  Chg Dir->pub/gopher/OMS

    Workshop-related files, including a copy of this notice, a map 
showing the location of WCC and the Morris Lawrence Building, and later 
additional information as described in the body of this announcement, 
will be found at the OMS Section, Models & Utilities Subsection.

SUPPLEMENTARY INFORMATION: Under section 130 of the Clean Air Act 
Amendments of 1990, EPA is required to review, and to revise as 
necessary, the emission factors used to estimate emissions of volatile 
organic compounds (VOC), carbon monoxide (CO), and oxides of nitrogen 
(NO X) from area and mobile sources. In the case of highway 
vehicles, emission factors for these pollutants as a function of 
various parameters are estimated using the highway vehicle emission 
factor model, commonly referred to as MOBILE. This model, first 
developed in the late 1970s, has been revised, updated, and improved 
periodically since that time to account for increasing data and 
analyses concerning in-use emissions performance of highway vehicles, 
changes in vehicle and emission control technology, changes in fuel 
composition, strengthening of applicable emission standards, 
refinements to applicable test procedures, and other items that affect 
in-use emission levels.
    Section 130 of the Act requires that this emission factor review, 
and revision as needed, be performed at least every three years. As 
noted above, the current official version of the model, MOBILE5a, was 
released in March 1993. Since that time, two interim updates to the 
model have been developed, MOBILE5a__H (released in November 1995) and 
MOBILE5b (released in October 1996). While not involving revision and 
update to the entire model, these versions were developed to address 
specific needs on the part of emission factor users. MOBILE5a__H 
incorporated a number of changes intended to improve the ability of 
modelers, particularly States and local/regional governments, in 
estimating the benefits of various innovative inspection and 
maintenance (I/M) programs and to improve the accuracy of modeling 
situations in which such programs change over time or different 
programs are applied to different subsets of the covered fleet. 
MOBILE5b greatly simplified the use of the features first provided in 
MOBILE5a__H, and included a number of other minor changes, corrections, 
and improvements.
    The time elapsed since the last complete revision to the model and 
the additional test data and analyses available since that time warrant 
another thorough update and revision to the model. OMS plans 
significant changes not only to the underlying emission factor 
estimates, but to how emission factors are modeled to account for 
things such as separation of start and running exhaust emissions, 
roadway facility type, average traffic speeds, and a number of other 
important changes that will affect the input information required to 
use the model as well as the type of information produced by the

[[Page 45803]]

model. The first MOBILE6 workshop last March presented an overview of 
the more important model revisions being planned. Since then, 
considerable analyses have been performed, and the model revisions 
proposed in March have been modified to some extent in response 
comments received since then. At this workshop, results will be 
presented in a number of topical areas that were discussed only in 
terms of proposals at the first workshop.
    The tentative agenda for this workshop is discussed below. Other 
aspects of the modeling of highway vehicle emissions that are not 
specifically included within the following discussion may also be 
briefly addressed in this workshop; however, the agenda discussed below 
is intended to illustrate the major areas of discussion for the 
workshop.
    The workshop being announced by today's notice will span two days. 
In an effort to facilitate travel plans on the part of attendees, a 
preliminary agenda for the two days is presented below. Note that, as 
was done for the March 1997 workshop, the first day (October 1) is 
largely devoted to ``technical'' issues involved in updating and 
revising the model, including revisions to emission factors and 
calculation methodologies, while the second day (October 2) is focused 
more on ``user changes,'' meaning those revisions planned that will 
affect the input data requirements and file structure and output 
changes. The update on the progress of EPA's development of a nonroad 
emission inventory model will also be presented on the second day. Many 
attendees will likely want to be present for both sessions, however, 
some may find that they can limit their attendance to one or the other 
days based on their specific interests and needs.
    Topics to be discussed on October 1. The first day of the workshop 
is planned to include discussion of the stakeholder review process; 
start-related emissions, separation of start from running (driving) 
exhaust emissions, and revisions to the basic emission rate equations; 
the use of facility-specific driving cycles and means for weighting 
such emission factors by vehicle miles traveled (VMT) to develop area-
wide emission factor estimates; the impacts of air conditioning use on 
exhaust emissions; the effects of fuel sulfur content on emissions, and 
of fuel oxygenate content on carbon monoxide (CO) emissions; the 
modeling of heavy-duty vehicle emissions; and revisions and 
improvements to evaporative emissions estimates (including real-time 
diurnals, resting losses, liquid leaks, and hot soak emissions). Each 
presentation will be followed by a short discussion/question and answer 
period, and there should be some time left at the end of the day for 
more general open discussion of the material that has been presented.
    These are the main areas in which presentations are planned for the 
first day of the workshop. Results of test programs and data analyses 
will be presented where available, and in all subject areas plans for 
additional work and proposed revisions to the model's treatment of each 
area will be discussed.
    Topics to be discussed on October 2. On the second day, EPA will 
present its proposal for modeling the benefits of second-generation 
onboard diagnostic systems (OBD-II) in MOBILE6. This will be followed 
by discussions of the changes to input files/structure/content and 
proposed changes to the output files produced by the model. A 
significant amount of time will be spent on these ``input/output'' 
issues on the second day, as EPA is hoping to engage workshop attendees 
in active discussions concerning these changes.
    The last presentation on October 2 will be an update on the 
development of the proposed nonroad emission inventory model for mobile 
sources. The workshop will conclude with reminders to the audience on 
how to keep abreast of progress, stakeholder review and comment of 
products to be used in MOBILE6 and the nonroad emission inventory 
model, and discussion of the schedule for development of MOBILE6 and 
the nonroad emission inventory model over the coming months.
    Additional Information. To the extent possible, EPA will post 
material at the OMS Web site described under FOR FURTHER INFORMATION 
CONTACT, above, in advance of the workshop. Those planning to attend, 
and those interested in following the progress of workshop planning 
more closely, should periodically visit the workshop information site. 
For example, some of the presentation materials that will be used at 
the workshop will be posted in advance to facilitate discussion and 
comment at the workshop.

    Dated: August 22, 1997.
Richard D. Wilson,
Acting Assistant Administrator, Office of Air and Radiation.
[FR Doc. 97-23034 Filed 8-28-97; 8:45 am]
BILLING CODE 6560-50-P