[Federal Register Volume 78, Number 44 (Wednesday, March 6, 2013)]
[Pages 14533-14536]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2013-05245]

[[Page 14533]]



[EPA-R09-OAR-2013-0126; FRL-9788-3]

Official Release of EMFAC2011 Motor Vehicle Emission Factor Model 
for Use in the State of California

AGENCY: Environmental Protection Agency (EPA).

ACTION: Notice of Availability.


SUMMARY: EPA is approving and announcing the availability of the latest 
version of the California EMFAC model (short for EMission FACtor) for 
use in state implementation plan (SIP) development and transportation 
conformity in California. EMFAC2011 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 emissions factors for passenger 
cars, trucks, motorcycles, motor homes and buses. Today's notice also 
sets the date after which EMFAC2011 is required to be used statewide in 
all new regional emissions analyses and carbon monoxide (CO), 
particulate matter of ten microns or less (PM10) and fine 
particulate matter (PM2.5) hot-spot analyses for 
transportation conformity determinations in California. Since the EMFAC 
model is used only in California, EPA's approval of the model does not 
affect MOVES model users in other states.

DATES: EPA's approval of the EMFAC2011 emissions model for SIP and 
conformity purposes is effective March 6, 2013. EMFAC2011 must be used 
for all new regional emissions analyses and CO, PM10 and 
PM2.5 hot-spot analyses that are started on or after 
September 6, 2013.

[email protected], (775) 433-8176, Air Planning Office (AIR-2), 
Air Division, U.S. EPA, Region 9, 75 Hawthorne Street, San Francisco, 
California, 94105-3901.

SUPPLEMENTARY INFORMATION: Copies of the official version of the 
EMFAC2011 model are available on the California Air Resources Board 
(CARB) Web site: http://www.arb.ca.gov/msei/modeling.htm (model, 
technical support documents, etc.).

I. Background

A. What is the EMFAC model?

    The EMFAC model is a computer model that can estimate emission 
rates for on-road mobile sources (``motor vehicles'') for calendar 
years from 1990 to 2035 operating in California. Pollutant emissions 
for hydrocarbons (HC), CO, nitrogen oxides (NOX), 
PM10, PM2.5, lead, carbon dioxide 
(CO2), and sulfur oxides are output from the model. 
Emissions are calculated for forty-two different vehicle classes 
composed of passenger cars, various types of trucks and buses, 
motorcycles, and motor homes.
    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 
emissions 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. 
Conformity to a SIP means that a transportation activity will not cause 
or contribute to new air quality violations, worsen existing 
violations, or delay timely attainment of the national ambient air 
quality standards (NAAQS) or interim milestones. EPA's transportation 
conformity regulations (40 CFR Parts 51.390 and 93) describe how 
federally funded and approved highway and transit projects meet these 
statutory requirements.

B. What versions of EMFAC are currently in use in California?

    Most SIPs in California were developed using EMFAC2007 (released by 
CARB in October 2007) or EMFAC2002 (released by CARB in October 2002). 
EPA approved EMFAC2007 on January 18, 2008 (73 FR 3464) and approved 
EMFAC2002 on April 1, 2003 (68 FR 15720) for all areas in California.
    EMFAC2007 was considered a major update to previous versions of 
EMFAC and most SIPs in California were updated with EMFAC2007 in the 
2007-2008 timeframe. EMFAC2007 included new data and methodologies 
regarding calculation of motor vehicle emissions, and revisions to 
implementation data for control measures.

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 
    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 6, 2012 letter, CARB requested that EPA approve 
EMFAC2011 for use in developing SIPs and in determining conformity in 
California.\1\ EMFAC2011 is a significant change from previous EMFAC 
models with a new model user interface and is capable of calculating 
motor vehicle emissions for all California areas. EMFAC2011 is being 
approved as the latest emissions model for statewide use in SIP 
development and emissions analyses for conformity purposes. Since the 
EMFAC model is only used in California, EPA's statewide approval of the 
model does not affect MOVES emissions factor model users in other 

    \1\ The EMFAC2011 model and supporting information is available 
for downloading at http://www.arb.ca.gov/msei/modeling.htm. 
Technical documentation explaining the changes to the model and the 
technical foundations for the model is available at http://www.arb.ca.gov/msei/emfac2011-documentation-final.pdf.

II. EPA Action

A. What version of EMFAC is EPA approving?

    In this notice, EPA is approving and announcing that EMFAC2011 is 
available to use in statewide California SIP development and for 
regional emissions analyses and CO, PM10 and 
PM2.5 hot-spot analyses for transportation conformity. 
EMFAC2011 was developed by CARB and transmitted for approval to EPA on 
April 6, 2012.
    The EMFAC2011 model is composed of a new modular structure that 
will facilitate future model updates and allow CARB to incorporate 
updated information about truck and bus activity and emissions data 
into the model. The three major modules of EMFAC include EMFAC-LDV, 
EMFAC-HD and EMFAC-SG. EMFAC-LDV can be used to estimate emissions for 
gasoline powered on-road vehicles and smaller on-road diesel vehicles 
and urban transit buses. EMFAC-HD provides

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emissions factors for heavy-duty diesel trucks and buses. EMFAC-SG 
allows users to run one tool for SIP inventories and regional emissions 
analyses to combine the emissions factors from both EMFAC-LDV and 
EMFAC-HD with user defined vehicle miles of travel and speeds, combine 
emissions from multiple model-defined subareas and incorporate 
reductions associated with CARB's Pavley and Low Carbon Fuel standard 
    CARB developed the EMFAC-SG module to provide users, including 
transportation planners, with a simplified method to generate emissions 
with different future growth scenarios for specific geographic areas 
needed for transportation conformity and SIP development. CARB also 
developed the EMFAC-PL tool for use for doing multiple model runs to 
extract emissions factors for project-level analyses needed for hot-
spot analyses.\2\ Due to the modular structure of the EMFAC2011 model, 
to obtain emissions factors for project-level analyses, an EMFAC2011 
user would have to run multiple modules to generate emission factors. 
Therefore ARB has developed the EMFAC-PL tool to produce emissions 
factors for projects that are consistent with the default assumptions 
in EMFAC2011. For projects that have site-specific ambient temperature 
and relative humidity profiles, project-specific vehicle age 
distributions and/or project-specific rest and soak time data, the user 
will have to use a more detailed approach other than EMFAC-PL that 
requires getting emissions factors from EMFAC-LDV and EMFAC-HD. As 
discussed later in this notice, EPA is consulting with CARB to provide 
updated EMFAC guidance for how to apply the EMFAC2011 emissions model 
through either the EMFAC-PL tool or the more detailed approach that 
would not use EMFAC-PL.

    \2\ The EMFAC-PL tool is available at: http://www.arb.ca.gov/msei/modeling.htm. In an email to EPA dated 2/08/2013, CARB 
clarified that the EMFAC-PL tool is available for use in project-
level assessments.

B. What analyses can EMFAC2011 be used for?

    EPA is approving the model to estimate regional emissions of HC, 
CO, NOX, PM10, PM2.5, lead, and sulfur 
oxides.\3\ However, EMFAC2011 will only be used in transportation 
conformity for pollutants and precursors that affect transportation-
related emissions, e.g., HC, NOX, CO, PM10 and 

    \3\ EPA notes that EMFAC2011 can be used for CO2 
emissions analyses as well, but there are no SIP or transportation 
conformity requirements for greenhouse gases (GHGs).

    EPA is also approving EMFAC2011 to estimate CO, PM10 and 
PM2.5 emissions for conformity 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 and a comparison of those concentrations to the relevant 
NAAQS. This analysis is conducted on a smaller scale than a 
nonattainment or maintenance area, e.g., for a congested roadway 
    EPA also notes that today's approval action does not impact what 
methodology is required for calculating re-entrained road dust for 
regional PM10 and PM2.5 SIPs and transportation 
conformity analyses. EMFAC2011'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 in advance by 
EPA.\4\ In addition, EMFAC2011 does not estimate ammonia emissions; air 
quality and transportation agencies should contact the EPA Regional 
Office if ammonia emissions estimates are needed for SIPs or regional 
conformity emissions analyses.

    \4\ For further information, see EPA's February 4, 2011 Notice 
of Availability for the January 2011 AP-42 Method for Estimating Re-
entrained Road Dust from Paved Roads (76 FR 6328). Also, for using 
AP-42 for unpaved roads, see EPA's August 2, 2007 memorandum, 
``Policy Guidance on the Use of the November 1, 2006, Update to AP-
42 for Re-entrained Road Dust for SIP Development and Transportation 

C. Why is EMFAC2011 being approved for PM10 and PM2.5 hot-spot analyses 
at this time?

    On December 20, 2010, EPA published a notice which announced the 
availability of EPA guidance documents for completing quantitative hot-
spot analyses and approved the use of the MOVES and the EMFAC2007 
models for use in quantitative PM10 and PM2.5 
hot-spot analyses (75 FR 79370). That notice started a two-year grace 
period requiring project sponsors to use EMFAC2007 for new quantitative 
PM10 and PM2.5 hot-spot analyses in California, 
for conformity determinations involving projects of local air quality 
    As with EMFAC2007, EMFAC2011 is capable of assessing project-level 
emissions for PM10 and PM2.5 hot-spot analyses, 
therefore EPA is approving EMFAC2011 for use in quantitative PM hot-
spot analyses for transportation conformity purposes within California. 
As mentioned earlier, CARB has developed the EMFAC-PL tool, as a 
simplified method to extract the appropriate emissions factors for 
alternative vehicle data and speeds from EMFAC2011 for appropriate 
projects. In today's notice, EPA recognizes the importance of this tool 
for ensuring that project-level conformity analyses are done in a 
consistent and accurate matter. To that end, we are also approving the 
EMFAC-PL tool for project-level conformity analyses, and allowing other 
tools to be approved by EPA, if such alternate project-level tools 
provide for similar performance in applying EMFAC2011 emissions factors 
for appropriate projects.\5\ EPA is updating Section 5 and related 
appendices of our PM hot-spot quantitative guidance to describe how to 
use the EMFAC2011 model for PM hot-spot analyses.\6\ EPA's revised 
guidance will include details on what PM hot-spot analyses can rely on 
the EMFAC-PL tool and which projects will require a different approach 
to obtain the appropriate project-level EMFAC2011 emission factors. EPA 
intends to complete its PM hot-spot guidance revision in the near 
future. When completed, the updated guidance will be made available on 
EPA's Web site: www.epa.gov/otaq/stateresources/transconf/projectlevel-hotspot.htm.

    \5\ EPA would approve any alternate project-level tool through a 
letter, after completion of its review of model documentation 
showing consistency with the EMFAC-PL approach.
    \6\ ``Transportation Conformity Guidance for Quantitative Hot-
Spot Analyses in PM2.5 and PM10 Nonattainment 
and Maintenance Areas'' [EPA-420-B-10-040]. See www.epa.gov/otaq/stateresources/transconf/projectlevel-hotspot.htm.

D. Why does EPA consider EMFAC2011 as a major update to EMFAC?

    EMFAC2011 includes significant changes to its model interface, new 
data and methodologies regarding calculation of motor vehicle emissions 
and revisions to implementation data for control measures. EMFAC2011 
includes updated data on truck activity, and emissions reductions 
associated with the 2010 Truck and Bus rule, supporting new estimates 
of emissions from heavy-heavy duty diesel trucks and buses. Motor 
vehicle fleet age, vehicle types and vehicle population have also been 
updated based on 2009 California Department of Motor Vehicle (DMV) 
data. EMFAC2011 incorporates new temperature and humidity profiles. 
Each of these changes impact emission factors for each area in 
California. In addition to changes to truck activity, EMFAC 
incorporates updated vehicle

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miles traveled (VMT) for all vehicle classes. The new model interface 
EMFAC-SG module will allow users to update the default VMT data and 
speed profiles by vehicle class for different future scenarios. CARB's 
web site describes these and other model changes at: http://www.arb.ca.gov/msei/emfac2011-documentation-final.pdf.

E. How were stakeholders and the public involved in the EMFAC 
development process?

    Since 2010, CARB has held a series of public workshops to discuss 
emissions inventory updates related to California's In-Use Heavy-Duty 
Diesel Fueled Truck and Bus regulation (``Truck and Bus Regulation''), 
and to receive comments on the regulations and the resulting changes in 
the emissions inventory. Since the major changes to the EMFAC model are 
associated with incorporation of the Truck and Bus Regulation into the 
model, the technical foundations of these changes were presented to the 
public in these workshops. CARB also conducted extensive beta testing 
of interim versions of the model with air districts and Metropolitan 
Planning Organizations (MPOs). These stakeholders had the opportunity 
to request briefings with CARB staff and provide them with comments and 
suggestions to improve the model. EPA was included in those discussions 
and our suggestions were incorporated into the material available on 
the CARB EMFAC2011 public web site. CARB also developed and posted 
training modules for EMFAC2011 and supports a mobile source emissions 
inventory email listserv to announce updates and changes to the EMFAC 
supporting material.\7\

    \7\ To subscribe to CARB's listserv for Mobile Source Emission 
Inventory development, see ``Join our MSEI listserv'' at 

    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: http://www.arb.ca.gov/msei/supportdocs.htm and 
at http://www.arb.ca.gov/msei/categories.htm#onroad_motor_vehicles 
Specific changes incorporated into the EMFAC2011 model are also 
discussed in http://www.arb.ca.gov/msei/emfac2011-documentation-final.pdf. All presentations from the public workshops are available on 
the CARB Web site at: http://www.arb.ca.gov/msprog/onrdiesel/workshops.htm.

F. Will a transportation conformity grace period be set by this 

    Yes. The transportation conformity rule (40 CFR 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 EMFAC2011, EPA will 
consult with the U.S. Department of Transportation (DOT) to establish a 
grace period before the model is required for conformity analyses (40 
CFR 93.111(b)). 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 the Federal Highway Administration (FHWA) and the 
Federal Transit Administration (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 
transportation planning in order to assure conformity (40 CFR 93.111).
    Upon consideration of all of these factors, EPA is establishing a 
6-month grace period before EMFAC2011 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, PM10 and PM2.5 hot-spot 
analyses supporting project-level conformity determinations.
    The grace period begins on March 6, 2013 and ends on September 6, 
2013. As discussed earlier in the notice, EMFAC2011 incorporates 
significant changes to the model interface and procedures used to 
estimate both emissions for regional emissions analysis and emissions 
factors for hot-spot analyses for CO and PM. While these changes are 
significant, the model has been available for review by air quality and 
transportation agencies, consultants and the public since September 
    For application of EMFAC2011 at the project level, CARB's EMFAC-PL 
tool for appropriate projects has just recently been released, 
therefore project sponsors developing project-level analysis may need 
some time to familiarize themselves with this tool. EPA is also 
updating our PM hot-spot quantitative guidance to include the new 
EMFAC2011 procedures.
    Therefore, it is appropriate to set a 6-month grace period to allow 
all areas in California to incorporate these new procedures in 
conformity hot-spot analysis \8\ and apply the changes to the model 
structure and updated planning assumptions incorporated in EMFAC2011 in 
a timely manner. In the interim, new quantitative PM hot-spot analyses 
that are started prior to the end of the EMFAC2011 grace period can be 
based on EMFAC2007 and EPA's existing PM hot-spot guidance and 
subsequently completed.

    \8\ EMFAC-PL or an alternative method or tool must be used for 
new EMFAC2011 analyses of appropriate projects after the 6-month 
grace period. If EPA approves alternative tools to the EMFAC-PL 
tool, EPA does not intend to establish a new 6-month grace period.

    When the grace period ends on September 6, 2013, EMFAC2011 will 
become the only approved motor vehicle emissions model for all new 
regional and CO, PM10 and PM2.5 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, 
PM10 and PM2.5 hot-spot analyses started after 
the end of the 6-month grace period must be based on EMFAC2011, 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, the conformity rule provides some flexibility for regional 
emissions analyses that are started before the end of the grace period. 
Analyses that begin before or during the grace period may continue to 
rely on EMFAC2007. The interagency consultation process should be used 
if it is unclear if an EMFAC2007-based analysis was begun before the 
end of the grace period. When the grace period ends on September 6, 
2013, EMFAC2011 will become the only approved motor vehicle emissions 
model for regional emissions analyses for transportation conformity in 
    CO, PM10 and PM2.5 hot-spot analyses for 
project-level conformity determinations can be based on EMFAC2007 if 
the 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)). Therefore new quantitative and qualitative analysis 
already underway that were started before the

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end of the grace period using EMFAC2007 can be completed as long as 
93.111(c) is satisfied. The interagency consultation process should be 
used if it is unclear whether an EMFAC2007-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 
make future revisions to update EMFAC. These EMFAC updates would 
reflect, among other new information, updated vehicle fleet data every 
three years. In California, MPOs and Air Districts have not been able 
to update vehicle fleet data embedded into EMFAC. The EPA/USDOT 
December 2008 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 and MPOs are strongly encouraged to update the data at 
least every five years. CARB 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 2014 or 2015 which 
would most likely also include updates to the emissions factors of the 
model as well.

III. Summary of EPA Actions

    As described in this notice, EPA is approving EMFAC2011 as 
submitted by CARB on April 6, 2012 with the following limitations and 
    (1) The approval is limited to California.
    (2) The approval is Statewide and applies to estimation of 
emissions of HC, CO, NOX, PM10, PM2.5, 
lead, and sulfur oxides. However, EMFAC2011 will be used in 
transportation conformity regional emissions analyses for pollutants 
and precursors that are applicable in a given nonattainment or 
maintenance area. EPA is approving all components of EMFAC2011, 
specifically EMFAC-SG, EMFAC-LDV and EMFAC-HD. EPA is also approving 
EMFAC2011 and the EMFAC-PL tool to estimate project-level emissions for 
CO, PM10 and PM2.5 conformity hot-spot analyses.
    (3) A 6-month statewide transportation conformity grace period will 
be established beginning March 6, 2013 and ending September 6, 2013 for 
the transportation conformity uses described in (2) above.

    Dated: February 22, 2013.
Jared Blumenfeld,
Regional Administrator, Region IX.
[FR Doc. 2013-05245 Filed 3-5-13; 8:45 am]