Official Release of EMFAC2007 Motor Vehicle Emission Factor Model for Use in the State of California, 3464-3467 [E8-876]

Agencies

• ENVIRONMENTAL PROTECTION AGENCY

[Federal Register Volume 73, Number 13 (Friday, January 18, 2008)]
[Notices]
[Pages 3464-3467]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: E8-876]


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ENVIRONMENTAL PROTECTION AGENCY

[CAXXX-NOA; FRL-8517-9]


Official Release of EMFAC2007 Motor Vehicle Emission Factor Model 
for Use in the State of California

AGENCY: Environmental Protection Agency (EPA).

ACTION: Notice of Availability.

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SUMMARY: EPA is approving and announcing the availability of the latest 
version of the California EMFAC model for use in state implementation 
plan (SIP) development in California. EMFAC2007 is the latest update to 
the EMFAC model for use by California state and local governments to 
meet Clean Air Act (CAA) requirements. The new model, which is based on 
new and improved data, calculates air pollution emission factors for 
passenger cars, trucks, motorcycles, motor homes and buses. Today's 
notice also sets the date after which EMFAC2007 is required to be used 
statewide in all new regional emissions analyses and carbon monoxide 
(CO) hot-spot analyses for transportation conformity determinations in 
California. EPA also intends to approve EMFAC2007 in the future for 
particulate matter (PM10 and PM2.5) hot-spot 
analyses in California, once EPA issues quantitative hot-spot modeling 
guidance for such analyses. Since the EMFAC model is used only in 
California, EPA's approval of the model does not affect MOBILE model 
users in other states.

DATES: This determination is effective January 18, 2008. EMFAC2007 must 
be used for all new regional emissions

[[Page 3465]]

analyses and CO hot-spot analyses that are started on or after April 
18, 2008.

FOR FURTHER INFORMATION CONTACT: Karina O'Connor, 
oconnor.karina@epa.gov, (775) 833-1276, Air Planning Office (AIR-2), 
Air Division, U.S. EPA, Region 9, 75 Hawthorne Street, San Francisco, 
California, 94105-3901. For questions regarding the future development 
of quantitative PM10 and PM2.5 hot-spot modeling 
guidance, contact Meg Patulski, patulski.meg@epa.gov, (734) 214-4842, 
Transportation and Regional Programs Division, U.S. EPA's Office of 
Transportation and Air Quality, 2000 Traverwood Road, Ann Arbor, MI 
48105.

SUPPLEMENTARY INFORMATION: Copies of the official version of the 
EMFAC2007 model are available on the California Air Resources Board 
(CARB) Web site: https://www.arb.ca.gov/msei/onroad/latest_version.htm 
(model, technical support documents, etc).

I. Background

A. What Is the EMFAC Model?

    The EMFAC model (short for EMission FACtor) is a computer model 
that can estimate emission rates for on-road mobile sources (``motor 
vehicles'') for calendar years from 1970 to 2040 operating in 
California. Pollutant emissions for hydrocarbons (HC), CO, nitrogen 
oxides (NOX), PM10, PM2.5, lead, and 
sulfur oxides are output from the model. Emissions are calculated for 
thirteen different vehicles classes comprised of passenger cars, 
various types of trucks and buses, motorcycles, and motor homes. The 
EMFAC2007 model is operated with a user-friendly graphical user 
interface (GUI) which facilitates data input and allows the development 
of alternative emissions scenarios through a What If Scenarios (WIS) 
generator. The WIS interface can be used to incorporate updated vehicle 
data, adjust ambient conditions or make changes to potential emission 
control programs in a specific area.
    EMFAC is used to calculate current and future inventories of motor 
vehicle emissions at the state, air district, air basin, or county 
level. EMFAC contains default vehicle activity data, and the option of 
modifying that data, so it can be used to estimate a motor vehicle 
emission inventory in tons/day for a specific year, month, or season, 
and as a function of ambient temperature, relative humidity, vehicle 
population, mileage accrual, miles of travel and speeds. Thus the model 
can be used to make decisions about air pollution policies and programs 
at the local or state level. Inventories based on EMFAC are also used 
to meet the federal CAA's SIP and transportation conformity 
requirements. Transportation conformity is required under CAA section 
176(c) to ensure that federally supported transportation plans, 
transportation improvement programs (TIPs), and highway and transit 
projects are consistent with (``conform to'') the purpose of the SIP.

B. What Versions of EMFAC Are Currently in Use in California?

    Most SIPs in California were developed using EMFAC2002 (released by 
CARB in October 2002) or EMFAC2000 (released by CARB in May 2000). EPA 
approved use of EMFAC2000 in January 2002 only for the San Francisco 
Bay Area (67 FR 1464). EPA approved EMFAC2002 in April 2003 (68 FR 
15720) for all areas in California.
    EMFAC2002 was considered a major update to previous versions of 
EMFAC and most SIPs in California were updated with EMFAC2002 in the 
2003-2006 timeframe. EMFAC2002 included significant changes to its 
model interface, new data and methodologies regarding calculation of 
motor vehicle emissions, revision to implementation data for control 
measures, and corrections to technical errors mentioned in our prior 
approval of EMFAC2000. Areas with SIP motor vehicle emissions budgets 
developed using earlier versions of EMFAC were required to use 
EMFAC2002 for regional conformity analyses at the end of the grace 
period provided by 40 CFR 93.111(b).

C. Why Is EPA Announcing Its Approval of the EMFAC Model?

    CAA section 172(c)(3) and 40 CFR 51.112(a)(1) require that SIP 
inventories be based on the most current, accurate, and applicable 
models that are available at the time the SIP is developed. CAA section 
176(c)(1) requires that the latest emissions estimates be used in 
conformity analyses. EPA approves models that fulfill these 
requirements.
    Under 40 CFR 93.111(a), EPA must approve new versions of EMFAC for 
SIP purposes before they can be used in transportation conformity 
analyses. In an April 18, 2007 letter, CARB requested that EPA approve 
EMFAC2007 for use in developing SIPs and in determining conformity in 
California. EMFAC2007 is a significant change from previous EMFAC 
models and is capable of calculating motor vehicle emissions for all 
California areas. EMFAC2007 is being approved as the latest emissions 
model for statewide use in SIP development. Since the EMFAC model is 
only used in California, EPA's statewide approval of the model does not 
affect MOBILE emissions factor model users in other states.

D. Why Have Transportation Agencies Stopped Using EMFAC2002 for 
Regional Conformity Emissions Analyses?

    On February 1, 2007, the Federal Highway Administration (FHWA) sent 
a letter to all of the Metropolitan Planning Organizations in 
California and Caltrans Districts indicating that, after August 1, 
2007, they would not be able to start any new transportation conformity 
determinations that require a new regional emissions analysis, unless 
the analysis incorporates more recent vehicle data consistent with the 
latest planning assumptions requirements in the conformity rule (40 CFR 
93.110). The letter indicated that updated vehicle data was available 
in EMFAC2007, which was released to the public in November 2006. The 
letter indicated that FHWA, the Federal Transit Administration (FTA), 
and EPA were providing agencies with a 6-month transition period, 
beginning on February 1, 2007 before the new vehicle fleet data was 
required in conformity determinations. Consistent with the EPA/USDOT 
January 18, 2001, guidance on latest planning assumptions and EPA's 
July 1, 2004 final rule (69 FR 40052-40056), new vehicle registration 
data must be used when it is available at the start of new conformity 
analyses. Since newer vehicle data was available but was not included 
in the older version of EMFAC, EMFAC2002 has not been used in any new 
regional emissions analyses that were started since August 1, 2007.

II. EPA Action

A. What Version of EMFAC Is EPA Approving?

    In this notice, EPA is approving and announcing that EMFAC2007 is 
available to use in statewide California SIP development and for 
regional emissions analyses and carbon monoxide (CO) hot-spot analyses 
for transportation conformity analyses. EMFAC2007 was developed by CARB 
and transmitted for approval to EPA on April 18, 2007.
    On January 28, 2003, CARB also transmitted a methodology 
(``Recommended Methods for Use of EMFAC2002 to Develop Motor Vehicle 
Emission Budgets and Assess Conformity'') to adjust vehicle activity 
data used by EMFAC2007 when updated data is available. EPA previously 
approved this CARB

[[Page 3466]]

methodology on April 1, 2003 (68 FR 15720, at 15721) for use with 
EMFAC2002, since the transportation conformity rule (40 CFR 93.110) 
requires areas to use the latest information for estimating vehicle 
activity. With EMFAC2007, CARB has not made any changes to the 
methodology to adjust vehicle activity data, and therefore the existing 
approved methodology will continue to be approved with no change. 
However, the methodology has been included in the updates to Chapter 8 
of the EMFAC user's guide. Therefore, CARB's methodology should 
continue to be used to update vehicle activity data in EMFAC2007, as 
described in the EMFAC user's guide.

B. What Analyses Can EMFAC2007 Be Used For?

    EPA is approving the model to estimate regional emissions of HC, 
CO, NOX, PM10, PM2.5, lead, and sulfur 
oxides. However, EMFAC2007 will only be used in transportation 
conformity for pollutants and precursors that affect transportation 
emissions, e.g., HC, NOX, CO, PM10 and 
PM2.5.
    EPA is also approving EMFAC2007 to estimate CO emissions for hot-
spot analyses involving individual transportation projects. A hot-spot 
analysis is defined in 40 CFR 93.101 as an estimation of likely future 
localized pollutant concentrations resulting from a new transportation 
project and a comparison of those concentrations to the relevant air 
quality standard. This analysis is conducted on a smaller scale, e.g., 
for a congested roadway intersection.
    EPA also notes that today's approval action does not impact what 
methodology is required for calculating re-entrained road dust or 
ammonia emissions for regional PM10 and PM2.5 SIP 
and transportation conformity analyses. EMFAC2007's PM10 and 
PM2.5 estimates do not include such emissions. When 
applicable, PM10 and PM2.5 nonattainment and 
maintenance areas are required to use EPA's AP-42 road dust method for 
calculating road dust emissions, unless a local method is approved by 
EPA.\1\ EMFAC2007 does not estimate ammonia emissions; air quality and 
transportation agencies should contact the regional office if ammonia 
emission estimates are needed.
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    \1\ For further information, see EPA's August 2, 2007 memorandum 
entitled, ``Policy Guidance on the Use of the November 1, 2006, 
Update to AP-42 for Re-entrained Road Dust for SIP Development and 
Transportation Conformity.''
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C. Is EMFAC2007 Being Approved for PM10 and PM2.5 Hot-spot Analyses At 
This Time?

    On March 10, 2006, EPA published a final rule that established the 
transportation conformity procedures for analyzing PM10 and 
PM2.5 hot-spot impacts of new projects involving significant 
levels of on-road diesel traffic (71 FR 12468). Quantitative 
PM10 and PM2.5 hot-spot analyses have not yet 
been required for the projects of local air quality concern described 
in 40 CFR 93.123(b)(1) due to the need to develop EPA modeling guidance 
and appropriate methods (71 FR at 12498-12502). Section 93.123(b)(4) of 
the conformity rule states that the requirements for quantitative 
PM10 and PM2.5 hot-spot analyses will not take 
effect until EPA releases modeling guidance and announces in the 
Federal Register that these requirements are in effect. At present, 
project sponsors are currently following EPA and FHWA's qualitative 
hot-spot modeling guidance for conformity determinations involving 
projects of local air quality concern.\2\ EMFAC2007 is capable of 
assessing project-level emissions for PM10 and 
PM2.5 hot-spot analyses, but as described in the March 2006 
final rule and 40 CFR 93.123(b)(4), EPA believes that quantitative PM 
hot-spot modeling guidance is also necessary before quantitative PM 
hot-spot analyses can be required. Therefore, since such guidance is 
currently not available, EPA is not approving EMFAC2007 for 
PM10 and PM2.5 hot-spot conformity analyses at 
this time.
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    \2\ ``Transportation Conformity Guidance for Qualitative Hot-
Spot Analyses in PM2.5 and PM10 Nonattainment 
and Maintenance Areas'' jointly published by EPA and FHWA in March 
2006.
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    Over the next year, EPA intends to develop quantitative 
PM10 and PM2.5 hot-spot modeling guidance, which 
will contain information on how to use EMFAC2007 and how to apply the 
appropriate dispersion models for such analyses in California. EPA will 
announce the availability of the guidance and approval of EMFAC2007 for 
quantitative PM hot-spot analyses when the guidance is completed for 
California. EPA will consult with FHWA, FTA, CARB, the California state 
department of transportation (Caltrans), other stakeholders, and the 
public in the development of this guidance, as described in the March 
2006 final rule. Please see the FOR FURTHER INFORMATION CONTACT section 
if you have questions regarding the development of conformity guidance 
for quantitative PM10 and PM2.5 hot-spot analyses 
in California.

D. Why Does EPA Consider EMFAC2007 as a Major Update to EMFAC?

    EMFAC2007 includes new data and methodologies regarding calculation 
of motor vehicle emissions and revisions to implementation data for 
control measures. EMFAC2007 includes updated data supporting new 
emission factors and speed correction factors for estimating emissions 
from heavy-heavy duty diesel trucks. The model includes modifications 
to the algorithms for inspection and maintenance as well as corrections 
for heavy-duty truck gas cap benefits from the inspection and 
maintenance program. Impacts of ethanol permeation and updates to fuel 
correction factors are included as well as revisions to particulate 
brake wear emissions. EMFAC2007 incorporates new temperature and 
humidity profiles. In addition to these changes, which impact emission 
factors for each area in California, EMFAC incorporates new mileage 
accrual rates and speed distributions, a redistribution of heavy-duty 
diesel truck vehicle miles traveled (VMT) and updated VMT for all 
vehicle classes. CARB's web site describes these and other model 
changes at: https://www.arb.ca.gov/msei/workshops.htm#work20061115.

E. How Were Stakeholders and the Public Involved in the EMFAC 
Development Process?

    Since 2005, CARB has held a series of public workshops to discuss 
proposed model updates and receive comments on interim versions of the 
new model. Three workshops were held to solicit input from stakeholders 
and the public in March of 2005. Then, in workshops held on September 
11 and November 15 and 16, 2006, CARB described the latest EMFAC 
changes under consideration and sought public input. Those changes are 
reflected in the final EMFAC2007 model submitted to EPA in April 2007. 
One additional public information briefing was held on December 15, 
2006, to share the emissions estimates resulting from use of the final 
model with updated travel activity, as well as plans for transmittal of 
EMFAC2007 to U.S. EPA. CARB has also discussed both the model and the 
impact of the changes to emission totals for the state at the 
workshops.
    CARB also released a series of technical memos that describe each 
update to the model, and public presentations that summarize the 
changes from earlier versions of the model. The technical memos are 
available on CARB's Web site at: https://www.arb.ca.gov/msei/
supportdocs.htm. Each memo describes the model update,

[[Page 3467]]

the reason for the change, how the change was incorporated into the 
EMFAC model, and the resulting emissions impact. All presentations from 
the public workshops are available on the CARB Web site at: https://
www.arb.ca.gov/msei/workshops.htm#work200612. These presentations 
summarize the major changes to the EMFAC model and contain tables 
showing the impacts of the changes both statewide and by county for HC, 
CO, NOX, PM10, and PM2.5.

F. Will a Transportation Conformity Grace Period Be Set by This 
Approval?

    Yes. The transportation conformity rule (40 CFR part 93.111) 
requires that conformity analyses be based on the latest motor vehicle 
emissions model approved by EPA for SIP purposes for a state or area. 
Section 176(c)(1) of the CAA 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 EPA approves 
a new emissions model such as EMFAC2007, a grace period is established 
before the model is required for conformity analyses. However, areas 
have the option of using the new model prior to the end of the grace 
period. The conformity rule provides for a grace period for new 
emissions models of between 3 to 24 months. In consultation with FHWA 
and FTA, 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 
3-month grace period before EMFAC2007 is required for the following 
conformity analyses:
     All new HC, NOX, PM10, 
PM2.5 and CO regional emissions analyses (e.g., supporting 
transportation plan and TIP conformity determinations); and
     All new CO hot-spot analyses supporting project-level 
conformity determinations.
    The grace period begins today and ends on April 18, 2008. As 
discussed earlier in the notice, the last version of EMFAC (EMFAC2002) 
is no longer used in California for new regional emissions analyses for 
transportation plan and TIP conformity determinations. Therefore it is 
appropriate to set a short grace period since all areas in California 
will need to use EMFAC2007 to begin any new regional conformity 
analyses. A longer grace period would provide no practical benefit for 
transportation plan and TIP conformity determinations, since older 
EMFAC models cannot be used in new regional analyses due to the latest 
planning assumptions requirements in the conformity rule (40 CFR 
93.110).
    When the grace period ends on April 18, 2008, EMFAC2007 will become 
the only approved motor vehicle emissions model for all new regional 
and CO hot-spot transportation conformity analyses across California. 
In general, this means that all new HC, NOX, 
PM10, PM2.5, and CO regional conformity analyses 
and CO hot-spot analyses started after the end of the 3-month grace 
period must be based on EMFAC2007, even if the SIP is based on an 
earlier version of the EMFAC model.

G. Can Areas Use Any Other Models During the Grace Period?

    Yes, in limited cases. CO hot-spot analyses for project-level 
conformity determinations can be based on EMFAC2002 if the analysis was 
begun before the end of the grace period, started before August 1, 2007 
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 EMFAC2002 based analysis is 
covered by the circumstances described above.

H. Future Updates to EMFAC

    On January 31, 2006, CARB submitted a letter to EPA and to the 
California Division of the FHWA indicating the State's intention to 
update future revisions to EMFAC. These EMFAC updates would reflect, 
among other new information, updated vehicle fleet data every three 
years. In California, Metropolitan Planning Organizations and Air 
Districts have not been able to update vehicle fleet data embedded into 
EMFAC. The EPA/USDOT January 18, 2001, guidance on latest planning 
assumptions and EPA's July 2004 final rule, indicate that new vehicle 
registration data must be used when it is available prior to the start 
of new conformity analyses and that states should update the data at 
least every five years. The State reaffirmed their commitment to 
keeping the latest planning assumptions included in EMFAC updated on a 
three year cycle in the April 18, 2007 EMFAC submittal letter. The next 
update to the planning assumptions in EMFAC is expected in 2010, which 
would most likely also include updates to the emissions factors of the 
model as well.

III. Summary of EPA Actions

    EPA is approving EMFAC2007 as submitted by CARB on April 18, 2007 
with the following limitations and conditions:
    (1) The approval is limited to California.
    (2) The approval is Statewide and applies to estimation of 
emissions of hydrocarbon, carbon monoxide, nitrogen oxides, particulate 
matter (PM10 and PM2.5), lead, and sulfur oxides. 
However, EMFAC2007 will only be used in transportation conformity 
analyses for pollutants and precursors that affect regional on-road 
mobile emissions and are applicable in a given nonattainment or 
maintenance area. EPA is also approving EMFAC2007 to estimate hot-spot 
emissions for carbon monoxide conformity analyses.
    (3) A 3-month statewide transportation conformity grace period will 
be established beginning January 18, 2008 and ending April 18, 2008 for 
the transportation conformity uses described in (2) above.

    Dated: January 10, 2008.
Jane Diamond,
Acting Regional Administrator, Region IX.
[FR Doc. E8-876 Filed 1-17-08; 8:45 am]
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