[Federal Register Volume 69, Number 97 (Wednesday, May 19, 2004)]
[Rules and Regulations]
[Pages 28830-28832]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 04-11340]
[[Page 28830]]
=======================================================================
-----------------------------------------------------------------------
ENVIRONMENTAL PROTECTION AGENCY
40 CFR Part 51
[FRL-7663-6]
Official Release of the MOBILE6.2 Motor Vehicle Emissions Factor
Model and the December 2003 AP-42 Methods for Re-Entrained Road Dust
AGENCY: Environmental Protection Agency (EPA).
ACTION: Notice of availability.
-----------------------------------------------------------------------
SUMMARY: EPA is approving and announcing the availability of the
MOBILE6.2 motor vehicle emissions factor model for official use in
particulate matter (PM10 and PM2.5) SIPs and
transportation conformity determinations outside of California.
MOBILE6.2 is an update to MOBILE6 which adds the capability to estimate
direct exhaust and brake and tire wear particulate matter emission
factors for PM10 and PM2.5, and exhaust emission
factors for particulate precursors to the MOBILE6 model. MOBILE6.2 is a
substantial improvement over previous methods for estimating PM
emissions and incorporates EPA's most current estimates of PM emissions
for use by state and local governments to meet Clean Air Act
requirements.
EPA is also approving and announcing the availability of new
methods for the estimation of re-entrained road dust emissions from
cars, trucks, buses, and motorcycles on paved and unpaved roads for
PM10 and PM2.5 state implementation plans (SIPs)
and transportation conformity analyses. These new methods are
incorporated in the December 2003 edition of Chapter 13 of Compilation
of Air Pollutant Emission Factors, AP-42, Fifth Edition, Volume I:
Stationary Point and Area Sources.
Today's action also starts time periods after which MOBILE6.2 and
the December 2003 AP-42 methods are required to be used in new
transportation conformity analyses for PM10 emissions.
EPA strongly encourages areas to use the interagency consultation
process to examine how MOBILE6.2 and the December 2003 AP-42 methods
will affect future transportation conformity analyses, so, if
necessary, PM10 SIPs and motor vehicle emissions budgets can
be revised with MOBILE6.2 and AP-42 or transportation plans and
programs can be revised as appropriate prior to the end of the
conformity grace period.
DATES: EPA's approval of the MOBILE6.2 emissions factor model and
December 2003 AP-42 methods for re-entrained road dust is effective May
19, 2004. See below for further information regarding how today's
approval starts time periods after which MOBILE6.2 and the December
2003 AP-42 methods are required in new transportation conformity
analyses and certain SIP and motor vehicle emissions budget revisions.
FOR FURTHER INFORMATION CONTACT: If you have questions on this notice,
please send an e-mail to EPA at [email protected] or contact EPA at (734)
214-4636 for technical model questions about MOBILE6.2. Please send an
e-mail to EPA at [email protected] or contact EPA at (919) 541-1000
for technical questions about the December 2003 AP-42 methods.
SUPPLEMENTARY INFORMATION:
Availability of Models and Support Materials
Copies of the official version of the MOBILE6.2 model are available
on EPA's MOBILE Web site, http://www.epa.gov/otaq/m6.htm. The MOBILE
Web site also contains the following support materials for implementing
the new model: a detailed MOBILE6.2 User's Guide; EPA's ``Policy
Guidance on the Use of MOBILE6.2 and the December 2003 AP-42 Method for
Re-Entrained Road Dust for SIP Development and Transportation
Conformity''; EPA's ``Technical Guidance on the Use of MOBILE6.2 for
Emission Inventory Preparation''; and a list of Frequently Asked
Questions about MOBILE6.2. EPA will continue to update this Web site in
the future as other MOBILE6.2 support materials are developed.
Individuals who wish to receive EPA announcements related to the
MOBILE model should subscribe to the EPA-MOBILENEWS e-mail listserver.
To subscribe to the EPA-MOBILENEWS listserver, write the following in
the body of the e-mail message:
subscribe EPA-MOBILENEWS FIRSTNAME LASTNAME where FIRSTNAME and
LASTNAME is your name (for example: John Smith) and send the e-mail to
the EPA Listserver at [email protected].
Your e-mail address will then be added to the list of subscribers
and a confirmation message will be sent to your e-mail address.
Whenever a message is posted to the EPA-MOBILENEWS listserver by the
listserver owner (the Assessment and Standards Division of the EPA
Office of Transportation and Air Quality), a copy of that message will
be sent to every person who has subscribed.
You can remove yourself from the list by sending another message to
the listserver address. This message must be sent from the same e-mail
address that you used to subscribe, and should contain the message:
unsubscribe EPA-MOBILENEWS.
Copies of the official version of the December 2003 edition of
Sections 13.2.1 and 13.2.2 of AP-42 can be found at www.epa.gov/ttn/chief/ap42/ch13/index.html. In the rest of this document, unless
otherwise indicated, ``AP-42'' refers to the December 2003 edition of
Sections 13.2.1 and 13.2.2 of AP-42.
I. What Is MOBILE6.2 and How Is It Different From MOBILE6?
MOBILE is an EPA emissions factor model for estimating pollution
from on-road motor vehicles in states outside of California. The model
accounts for the emission impacts of factors such as changes in vehicle
emission standards, changes in vehicle populations and activity, and
variation in local conditions such as temperature, humidity, fuel
quality, and air quality programs.
MOBILE is used to calculate current and future inventories of motor
vehicle emissions at the national and local level. These inventories
are used to make decisions about air pollution policies and programs at
the local, state and national level. Inventories based on MOBILE are
also used to meet the federal Clean Air Act's state implementation plan
(SIP) and transportation conformity requirements.
The previous version of MOBILE, known as MOBILE6, calculated
emissions of volatile organic compounds (VOCs), nitrogen oxides
(NOX) and carbon monoxide (CO) from passenger cars,
motorcycles, buses, and light-duty and heavy-duty trucks. MOBILE6.2 is
an update to MOBILE6 which adds the capability to estimate direct
particulate matter (PM) emission factors for PM10 and
PM2.5, and emission factors for particulate precursors, to
the original MOBILE6 model. In other words, MOBILE6.2 allows the
estimation of emission factors for HC (and air toxics), NOX,
CO, gaseous SO2, ammonia, and direct PM from vehicle exhaust
and brake and tire wear. MOBILE6.2 also corrects some minor coding
errors in the portion of the model code that estimates HC,
NOX, and CO emission factors, and it adds the capability of
entering hourly relative humidity values. MOBILE6.2 also incorporates
some revisions to CO emission factors for cars and light-duty trucks
that meet national low emission vehicle (NLEV), low emission vehicle
(LEV), and Tier 2 vehicle standards.
[[Page 28831]]
Functionally, MOBILE6.2 now replaces MOBILE6 as the highway vehicle
emission factor model that EPA will maintain and support.
II. What Is the Impact of MOBILE6.2 on Ozone and CO SIPs and Conformity
Determinations?
Although MOBILE6.2 includes some corrections and enhancements to
parts of the model that estimate emissions of HC, NOX, and
CO, the impact of these changes is generally small. Even though
MOBILE6.2 is very similar to MOBILE6 for these pollutants, states and
local agencies outside of California should use MOBILE6.2 for future
HC, NOX, and CO SIPs and conformity analyses in order to
take full advantage of the improvements incorporated in this version.
SIPs and conformity analyses already in progress with MOBILE6 can be
completed using MOBILE6 as determined through the interagency
consultation process. Because the changes in HC, NOX, and CO
emissions in MOBILE6.2 are generally very small, the release of
MOBILE6.2 does not start a new grace period before MOBILE6.2 is
required to be used for all new transportation conformity analyses in
ozone or CO nonattainment or maintenance areas and it does not trigger
the need for any new ozone or CO SIP revisions.
III. What Are the December 2003 AP-42 Methods?
Motor vehicle emissions inventories for PM are comprised of four
components: exhaust emissions, emissions from brake wear, emissions
from tire wear, and re-entrained road dust. MOBILE6.2 does not include
the capability of estimating the emissions of re-entrained road dust as
the result of motor vehicle activity. EPA has developed separate
revised AP-42 methodologies for estimating re-entrained road dust from
paved and unpaved roads. These new methods for estimating road dust
emission factors for paved and unpaved roads are being incorporated in
EPA's document AP-42. These new AP-42 methodologies (AP-42, Sections
13.2.1, Paved Roads and 13.2.2, Unpaved Roads, each dated December
2003) replace previous methods for estimating re-entrained road dust
emissions for these categories with some limitations. AP-42 is the
approved method only for situations for which silt loading, mean
vehicle weight, and mean vehicle speed fall within ranges given in AP-
42 section 13.2.1.3 and with reasonably free-flowing traffic. For other
conditions, areas may use an appropriate method approved by EPA on a
case-by-case basis. In some areas, alternate methods may be more
appropriate than AP-42 given specific local conditions even within the
parameters given in AP-42 section 13.2.1.3. State and local agencies
should consult with EPA for approval of alternative approaches. This
policy is described in more detail in the document ``Policy Guidance on
the Use of MOBILE6.2 and the December 2003 AP-42 Method for Re-
Entrained Road Dust for SIP Development and Transportation Conformity''
(available at http://www.epa.gov/otaq/models/mobile6/mobil6.2_letter.pdf). The following discussion of the use of AP-42 in SIPs and
conformity determinations also applies to approved alternatives to AP-
42.
IV. PM10 SIP Policy for MOBILE6.2 and AP-42
EPA has articulated its policy regarding the use of MOBILE6.2 and
AP-42 in PM10 SIP development in its ``Policy Guidance on
the Use of MOBILE6.2 and the December 2003 AP-42 Method for Re-
Entrained Road Dust for SIP Development and Transportation
Conformity.'' Today's action highlights certain aspects of the
guidance, but state and local governments should refer to the guidance
for more detailed information on how and when to use MOBILE6.2 and AP-
42 in attainment and maintenance PM10 SIPs, inventory
updates, and other PM10 SIP submission requirements. See
Availability of Related SIP Policies to obtain the MOBILE6.2 and AP-42
policy guidance.
PM10 SIPs that EPA has already approved are not
typically required to be revised now that EPA has approved MOBILE6.2
and AP-42. Although MOBILE6.2 and AP-42 should be used in new
PM10 SIP development as expeditiously as possible, EPA also
recognizes the time and level of effort that States have already
undertaken in PM10 SIP development with previous models or
methods. States that have already submitted PM10 SIPs or
will submit PM10 SIPs shortly after EPA's approval of
MOBILE6.2 and AP-42 are not required to revise these SIPs simply
because a new motor vehicle emissions model is now available. States
can choose to use MOBILE6.2 in these SIPs, for example, if it is
determined that future conformity determinations would be ensured
through such a SIP revision. However, EPA does not believe that a
State's use of an earlier model such as PART5 should be an obstacle to
EPA approval for SIPs that have been or will soon be submitted,
assuming that such SIPs are otherwise approvable and significant SIP
work has already occurred (e.g., attainment modeling for an attainment
SIP has already been completed with an earlier model). It would be
unreasonable to require States to revise these SIPs with MOBILE6.2 and
AP-42 since significant work has already occurred, and EPA intends to
act on these SIPs in a timely manner.
States should use MOBILE6.2 and AP-42 where PM10 SIP
development is in its initial stages or hasn't progressed far enough
along that switching to MOBILE6.2 and AP-42 would create a
significantly adverse impact on State resources. For example,
PM10 SIPs that will be submitted late in 2004 should be
based on MOBILE6.2 and AP-42 since there is adequate time to
incorporate the new model's results. MOBILE6.2 and AP-42 should be
incorporated into these SIPs since emissions estimates in these models
are based on the best information currently available, as required by
Clean Air Act section 172(c)(3) and 40 CFR 51.112(a)(1).
V. PM10 Transportation Conformity Policy for MOBILE6.2 and
AP-42
Transportation conformity is a Clean Air Act requirement to ensure
that federally supported highway and transit activities are consistent
with (``conform to'') the SIP. Conformity to a SIP means that a
transportation activity will not cause or contribute to new air
pollution violations; worsen existing violations; or delay timely
attainment of federal air quality standards.
The transportation conformity rule (40 CFR part 93) requires that
conformity analyses be based on the latest motor vehicle emissions
model approved by EPA. Section 176(c)(1) of the Clean Air Act states
that ``. * * * [t]he determination of conformity shall be based on the
most recent estimates of emissions, and such estimates shall be
determined from the most recent population, employment, travel, and
congestion estimates * * *.'' When we approve new emissions models such
as MOBILE6.2 and AP-42, a grace period is established before the models
are required for conformity analyses. The conformity rule provides for
a grace period for new emissions models of between 3-24 months.
EPA articulated its intentions for establishing the length of a
conformity grace period in the preamble to the 1993 transportation
conformity rule (58 FR 62211):
``EPA and [the Department of Transportation (DOT)] will consider
extending the grace period if the effects of the new emissions model
are so significant that previous SIP demonstrations of what emission
levels are consistent with attainment would be substantially
affected. In such cases, States should have an
[[Page 28832]]
opportunity to revise their SIPs before MPOs must use the model's
new emissions factors.''
In consultation with the DOT, EPA considers many factors in
establishing the length of the grace period, including the degree of
change in emissions models and the effects of the new model on the
transportation planning process (40 CFR 93.111).
Upon consideration of all of these factors, EPA is establishing a
2-year grace period, which begins today and ends on May 19, 2006,
before MOBILE6.2 and AP-42 are required for new PM10
conformity analyses in most cases. During this grace period, areas
should use the interagency consultation process to examine how
MOBILE6.2 and AP-42 will affect their future conformity determinations.
However, the grace period will be shorter than 2 years for
PM10 if an area revises its SIP and budgets with MOBILE6.2
and AP-42 and such budgets become applicable for conformity purposes
prior to the end of the 2-year grace period. For example, if an area
revises a previously submitted (but not approved) PART5-based
PM10 SIP with MOBILE6.2 and AP-42 and EPA finds the revised
budgets adequate for conformity, such budgets would apply for
conformity on the effective date of the Federal Register notice
announcing EPA's adequacy finding.
During the grace period, areas can use earlier models such as PART5
for PM10 conformity determinations or choose to use
MOBILE6.2 and AP-42 on a faster time frame. When the grace period ends
on May 19, 2006, MOBILE6.2 will become the only approved motor vehicle
emissions model for new PM10 transportation conformity
analyses outside of California and AP-42 will become the approved
method for estimating re-entrained road dust unless an alternate method
is approved as described in section III above. In general, this means
that all new PM10 conformity analyses started after the end
of the 2-year grace period must be based on MOBILE6.2 and AP-42, even
if the SIP is based on PART5. As discussed above, the grace period for
new conformity analyses would be shorter for PM10 if an area
revised its SIP and budgets with MOBILE6.2 and AP-42 and such budgets
became applicable for conformity purposes prior to the end of the 2-
year grace period. EPA strongly encourages areas to use the
consultation process to examine how MOBILE6.2 and AP-42 will affect
future conformity determinations, so, if necessary, PM10
SIPs and budgets can be revised with MOBILE6.2 and AP-42 or
transportation plans and programs can be revised as appropriate prior
to the end of the grace period.
Finally, the conformity rule provides some flexibility for analyses
that are started before or during the grace period. Regional conformity
analyses that began before the end of the grace period may continue to
rely on earlier models such as PART5. Conformity determinations for
transportation projects may also be based on an earlier model if the
regional analysis was begun before the end of the grace period, and if
the final environmental document for the project is issued no more than
three years after the issuance of the draft environmental document (see
40 CFR 93.111(c)). The interagency consultation process should be used
if it is unclear whether an analysis based on an earlier model was
begun before the end of the grace period.
The release of MOBILE6.2 and AP-42 does not trigger the need for
quantitative conformity hot-spot modeling to estimate concentrations of
PM10 at this time. However, qualitative hot spot analyses
are still required in PM10 nonattainment and maintenance
areas.
VI. PM2.5 SIP and Transportation Conformity Policy for
MOBILE6.2 and AP-42
EPA has not yet finalized implementation policy for the
PM2.5 National Ambient Air Quality Standards (NAAQS).
However, when that policy is finalized and PM2.5
nonattainment areas have been designated, MOBILE6.2 (except in
California) and AP-42 (except in areas where another dust methodology
has been approved) will be the approved models for estimating motor
vehicle exhaust, brake and tire wear, and re-entrained road dust
emissions in PM2.5 SIPs and conformity determinations, until
they are replaced by newer models or methods. No PM2.5 SIPs
have previously been done using other models and therefore, the release
of MOBILE6.2 and AP-42 does not constitute a change in models which
might result in inconsistencies between the SIP and transportation
analyses. As a result, there is no need for a PM2.5
conformity grace period for MOBILE6.2 and AP-42. MOBILE6.2 (except in
California) and AP-42 (except in areas where another dust methodology
has been approved) must be used in all PM2.5 conformity
analyses, until they are replaced by newer approved methods or models.
Dated: May 11, 2004.
Margo Tsirigotis Oge,
Director, Office of Transportation and Air Quality.
[FR Doc. 04-11340 Filed 5-18-04; 8:45 am]
BILLING CODE 6560-50-P