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Official Release of EMFAC2002 Motor Vehicle Emission Factor Model for Use in the State of California

 [Federal Register: April 1, 2003 (Volume 68, Number 62)]
[Notices]
[Page 15720-15723]
From the Federal Register Online via GPO Access [wais.access.gpo.gov]
[DOCID:fr01ap03-58]

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ENVIRONMENTAL PROTECTION AGENCY
[CA090-NOA; FRL-7475-6]
 
Official Release of EMFAC2002 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. EMFAC2002 is the latest update to 
the EMFAC model for use by California state and local governments to 
meet Clean Air Act (CAA) requirements. EMFAC2002 calculates air 
pollution emission factors for passenger cars, trucks and buses. The 
new model is based on new and improved data and is also a more user-
friendly version of the model, allowing agencies to update assumptions 
and run multiple scenarios for emissions analyses. Today's notice also 
starts a time period before EMFAC2002 is required to be used statewide 
in all new transportation conformity analyses in California. Since the 
EMFAC model is only used in California, EPA's approval of the model 
does not affect MOBILE model users in other states.

DATES: This determination is effective April 1, 2003. See below for 
further information regarding how today's approval starts a time period 
after which EMFAC2002 is required in new transportation conformity 
analyses.

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.

SUPPLEMENTARY INFORMATION: Copies of the official version of the 
EMFAC2002 model are available on the California Air Resources Board 
(CARB) Web site: http://www.arb.ca.gov/planning/emfac2002/emfac2002.htm 
Exit Disclaimer (transmittal and links to support documents) and 
http://www.arb.ca.gov/msei/on-road/latest_version.htm Exit Disclaimer 
(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 motor vehicles for calendar years 
from 1970 to 2040 operating in California. Pollutant emissions for 
hydrocarbons, carbon monoxide, nitrogen oxides, particulate matter, 
lead, sulfur oxides, and carbon dioxide are output from the model. 
Emissions are calculated for passenger cars, eight different classes of 
trucks, motorcycles, urban diesel and school busses and motor homes. 
The EMFAC2002 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, county, air district, air basin, or air 
basin within 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 
day, 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 
state

[[Page 15721]]

implementation plan (SIP) and transportation conformity requirements.

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

    Most SIPs in California were developed using the vehicle emission 
models EMFAC7F (released by CARB September 1993) or EMFAC7G (released 
by CARB July 1997). EPA approved use of EMFAC7F in May 1994 and then 
EMFAC7G in April 1998. EMFAC7G was considered a minor update to EMFAC 
(similar to MOBILE5b as a minor update to MOBILE5a), thus areas with 
SIP motor vehicle emissions budgets developed using EMFAC7F were 
allowed to continue to use EMFAC7F for conformity. EMFAC7G included 
updated data on control measures (e.g. inspection and maintenance and 
truck standards), updated vehicle information (e.g. vehicle population 
and starts/vehicle/day) and vehicle activity data (e.g. vehicle miles 
per day and vehicle miles per speed distribution). Areas with SIP 
budgets developed using EMFAC7G were required to use EMFAC7G for 
regional conformity analyses.
    Since the release of EMFAC7G, CARB has made several interim updates 
to EMFAC, EMFAC2000 and EMFAC2001. Of these models, only EMFAC2000 was 
submitted to EPA for approval and used in development of a SIP. Like 
EMFAC7G, EMFAC2000 included updated data on control measures (e.g., 
cleaner fuels, new vehicle standards for motorcycles, buses, and heavy-
duty trucks), updated vehicle information (e.g., vehicle population, 
starts/vehicle/day) and updated vehicle activity data (e.g., vehicle 
miles per day, vehicle miles per speed distribution, and mileage 
accrual rates). In January 2002, EPA approved EMFAC2000 (67 FR 1464, 
January 11, 2002) for use only in the San Francisco Bay Area (Bay 
Area), for estimation of ozone precursor emission factors. EPA's 
approval of EMFAC2000 was limited because: (1) EMFAC2000 was an 
improvement on existing available models despite certain technical 
limitations; and (2) CARB has committed to revise the Bay Area ozone 
attainment SIP's motor vehicle emissions budgets with EMFAC2001 or a 
successor model as part of its mid-course review SIP revision in April 
2004.

C. Why Have Transportation Agencies Stopped Using EMFAC7F and EMFAC7G 
for Regional Conformity Emissions Analyses?

    On May 2, 2002, the Federal Highway Administration (FHWA) and the 
Federal Transit Administration (FTA) sent a letter to CARB indicating 
that, after December 31, 2002, they would not continue to make 
conformity determinations that require a new regional emissions 
analysis, unless the analysis incorporates more recent vehicle data. 
The letter indicated that vehicle data embedded in the EMFAC7F and 
EMFAC7G versions of the EMFAC emission factor model were about ten 
years old. Consistent with the U.S. DOT/EPA January 18, 2001, guidance 
on latest planning assumptions, new vehicle registration data must be 
used when it is available for conformity purposes. Since newer vehicle 
data was available but was not included in the older versions of EMFAC, 
EMFAC7F and EMFAC7G have not been used in any new regional emissions 
analyses since December 31, 2002.

D. 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 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 conformity analyses. In a 
December 20, 2002 letter, CARB requested that EPA approve EMFAC2002 for 
use in developing SIPs and in determining conformity of transportation 
plans in California. EMFAC2002 is a significant change from previous 
EMFAC models and is capable of calculating motor vehicle emissions for 
all California areas. EMFAC2002 is being approved as the latest 
emissions model for statewide use in SIP development (rather than as an 
interim update to the EMFAC model as EMFAC7G was an interim update to 
EMFAC7F). 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.

II. EPA Action

A. What Version of EMFAC Is EPA Approving?

    In this notice, EPA is approving and announcing that EMFAC2002 is 
available to use in statewide California SIP development. EMFAC2002 was 
developed by CARB and transmitted for approval to EPA on December 20, 
2002.
    On January 28, 2003, CARB also transmitted a methodology to adjust 
vehicle activity data used by EMFAC2002 when updated data is available. 
Since the transportation conformity rule (40 CFR 93.110) requires areas 
to use the latest information for estimating vehicle activity, we are 
also approving the CARB methodology for updating vehicle activity data 
in EMFAC2002.
    CARB's methodology, ``Recommended Methods for Use of EMFAC2002 to 
Develop Motor Vehicle Emission Budgets and Assess Conformity,'' 
explains how vehicle activity data should be updated. The methodology 
explains how each parameter associated with vehicle activity was 
originally developed in EMFAC, how each parameter is related, and how 
each can be updated when new data becomes available. These 
relationships are important when adjusting vehicle trips or VMT. For 
example, VMT in EMFAC2002 is directly related to vehicle population \1\ 
and mileage accrual rate. Similarly, start and evaporative vehicle 
emissions are also related to vehicle population levels. If new VMT 
data is available, CARB suggests modifying the input vehicle population 
levels, instead of directly inputting new VMT data so that start and 
evaporative emissions are revised appropriately. Updated vehicle 
activity data (vehicle miles traveled) can also be input to EMFAC using 
the WIS interface. As CARB states, local circumstances may 
alternatively support adjustment of mileage accrual rates, subject to 
the interagency consultation process. In addition, CARB intends to 
periodically update vehicle population information, including vehicle 
classes by model year, in EMFAC2002.
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    \1\ Vehicle population includes vehicle type (class) and age 
distribution.
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B. What Pollutants Can EMFAC2002 Estimate?

    EPA is approving the model to estimate regional emissions of 
hydrocarbons (HC), carbon monoxide (CO), nitrogen oxides 
(NOX), particulate matter (PM), lead, sulfur oxides and 
carbon dioxide. However, EMFAC2002 will only be used in transportation 
conformity for pollutants and precursors that affect transportation 
emissions and are identified in air quality plans as significant. 
Transportation-related pollutants and precursors that are currently 
covered by the conformity rule are HC, NOX, CO, and PM-10. 
EPA is also approving EMFAC2002 to estimate hotspot emissions for 
carbon monoxide.

[[Page 15722]]

C. Why Does EPA Consider EMFAC2002 as a Major Update to EMFAC?

    EMFAC2002 includes significant changes to its model interface, new 
data and methodologies regarding calculation of vehicle emissions, 
revisions to implementation data for control measures, and corrections 
to technical errors mentioned in our prior approval of EMFAC2000. The 
new WIS interface makes EMFAC2002 both more user friendly and allows 
users to change input data updated for factors that had previously been 
embedded within the model (e.g. fleet vehicle data). EMFAC2002 includes 
updated data estimating idle emissions from heavy duty trucks and 
school buses. Base emission rates for light-duty vehicles are now drawn 
from the real-world unified drive cycle. EMFAC2002 accounts for gross 
evaporative emissions (i.e., ``liquid leakers'') and updates 
particulate emissions to account for smoking vehicles. The model also 
accounts for recent amendments to California's low emissions vehicle 
and fuels regulations, as well as updated heavy-duty truck standards. 
Full chassis dynamometer tests, rather than engine dynamometer tests, 
are now the source of heavy-duty truck emissions factors. CARB's web 
site describes these and other model changes at http://www.arb.ca.gov/
planning/sip/emfac2002/encl_a.pdf. Exit Disclaimer

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

    Since 1999, CARB has held a series of public workshops to discuss 
proposed model updates and receive comments on interim versions of the 
new model. In the most recent workshops, held June 11 and 13, 2002, 
CARB described the latest EMFAC changes under consideration and sought 
public input. Those changes are reflected in the final EMFAC2002 model 
released in October 2002. Two additional public information briefings 
were held on November 6 and 7, 2002, to share the emissions estimates 
resulting from use of the final model with updated travel activity, as 
well as plans for transmittal of EMFAC2002 to U.S. EPA. CARB has also 
discussed both the model and the activity update methodology with 
affected transportation and air agencies as part of the interagency 
consultation process.
    CARB also released a series of technical memos, that describe each 
update to the model, and a public information document that summarizes 
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/on-road/
latest_revisions.htm. Exit Disclaimer Each memo describes the model update, 
the reason for the change, how the change was incorporated into the EMFAC 
model, and the resulting emissions impact. The public information 
document is also available on the CARB Web site at: http://www.arb.ca.gov/
msei/on-road/briefs/2002.pdf. Exit Disclaimer This document summarizes the 
major changes to the EMFAC model and contains tables showing the impacts 
of the changes both statewide and by county for VOC, CO, NOX and PM. The 
detailed description of all major model updates since EMFAC7F is an 
enclosure to the transmittal package and available on the CARB Web site 
at: http://www.arb.ca.gov/planning/sip/emfac2002/encl_a.pdf. Exit Disclaimer

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

    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 we approve a 
new emissions model such as EMFAC2002, 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 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 
3-month grace period before EMFAC2002 is required for new conformity 
analyses. The grace period begins today and ends on June 30, 2003. As 
discussed earlier in the notice, several prior versions of EMFAC 
(EMFAC7F, EMFAC7G) are no longer used in California for new regional 
emissions analyses for transportation plan and transportation 
improvement program (TIP) conformity determinations. Therefore it is 
appropriate to set a short grace period since all areas in California 
will need to use EMFAC2002 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.
    When the grace period ends on June 30, 2003, EMFAC2002 will become 
the only approved motor vehicle emissions model for new regional and 
hot-spot transportation conformity analyses across California. In 
general, this means that all new VOC, NOX, PM-10, and CO 
regional conformity analyses and CO hot-spot analyses started after the 
end of the 3-month grace period must be based on EMFAC2002, even if the 
SIP is based on an earlier version of the EMFAC model.

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

    Yes, in limited cases. The only area in California with motor 
vehicle emission budgets developed with EMFAC2000 and approved to use 
EMFAC2000 is the Bay Area. During the grace period, the Bay Area can 
continue to use EMFAC2000 for regional analyses for ozone precursors or 
choose to use EMFAC2002 on a shorter time frame. DOT's May 2, 2002 memo 
did not preclude the continuing use of EMFAC2000 for use in new 
regional conformity determinations. In addition, the Bay Area could 
proceed with transportation plan and TIP conformity analyses for ozone 
precursors based on EMFAC2000 if the analysis was begun before or 
during the grace period. (40 CFR 93.111(c))
    Conformity determinations for transportation projects can also be 
based on EMFAC7F 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)). The interagency 
consultation process should be used if it is unclear whether an EMFAC7F 
or EMFAC7G based analysis was begun before the end of the grace period.

G. Related SIP Development Actions

    The Bay Area 2001 ozone SIP included a commitment from CARB to 
revise the SIP with the latest technical information as part of its 
mid-course review in April 2004. This commitment was referenced in 
EPA's approval of EMFAC2000 (67 FR 1464, January 11, 2002), with the 
understanding that CARB would submit revisions to the EMFAC model 
(e.g., EMFAC2002) in early 2003, so that the Bay Area SIP revision 
would occur within one year of EPA's approval of EMFAC2002. This is

[[Page 15723]]

consistent with EPA's past practice where an older version of the 
MOBILE model has been used prior to the release of a newer version that 
includes technical corrections in emission estimates. We understand 
that the Bay Area has begun work on the plan revision, that the 
EMFAC2002 model will be used in development of the motor vehicle 
emission inventories in the plan and that the SIP should be submitted 
to EPA by the April 2004 deadline.
    In addition, on June 14, 2002, CARB submitted a letter indicating 
the State's intention to submit comprehensive revisions to the 
progress, attainment, and maintenance SIPs and the budgets for most 
areas in California. These SIP revisions, would reflect, among other 
new information, the State's revised motor vehicle emissions factors 
using EMFAC2002 and updated information on vehicle fleet, age 
distribution, and activity levels (letter from Michael P. Kenny, CARB, 
to Wayne Nastri, EPA). In this letter, CARB acknowledged that the 
previously approved budgets had become outdated and made clear its 
intention to update these budgets as part of a comprehensive update to 
the plans. CARB also requested that EPA limit the duration of its prior 
approvals of the emission budgets.
    In response, on July 16, 2002 (67 FR 46618), EPA proposed to limit 
our approvals of the existing SIP budgets to last only until the 
effective date of our adequacy finding for new budgets that replace the 
existing approved budgets for the same pollutant, CAA requirement, and 
year. That proposal was finalized on November 15, 2002 (67 FR 69139), 
limiting our prior approvals of the emission budgets. Normally, new 
budgets that replace existing budgets in approved plans cannot be used 
until the corresponding plans have been fully approved as part of the 
SIP (see 40 CFR 93.118(e)). However, since approval of the existing 
budgets now expires when we determine that the new budgets are 
adequate, the updated budgets can be employed in transportation 
conformity determinations within a few months of their submission, 
rather than only when the SIP is finally approved, which could take as 
long as 18 months.
    Consistent with the June 2002 letter, CARB has already begun 
submitting revised SIPs. Ozone maintenance plans, new and revised, have 
already been submitted for San Diego and Santa Barbara. A revised 
statewide CO maintenance plan and revised regional air quality plans 
for San Joaquin Valley, South Coast, Coachella Valley, and Ventura 
County are also expected within the next year. Motor vehicle emission 
budgets from all of these plans would go into effect upon determination 
of a positive adequacy finding, rather than after a full plan approval 
and be available for conformity analyses using EMFAC2002.

H. Summary of EPA Actions

    EPA is approving EMFAC2002 as submitted by CARB on December 20, 
2002 with the following limitations and conditions.
    (1) The approval is limited to California.
    (2) The approval is Statewide and applies to estimation of 
hydrocarbon, carbon monoxide, nitrogen oxides, and particulate matter 
emissions, lead, sulfur oxides and carbon dioxide. However, EMFAC2002 
will only be used in transportation conformity for pollutants and 
precursors that affect transportation emissions and are identified in 
air quality plans as significant. EPA is also approving EMFAC2002 to 
estimate hotspot emissions for carbon monoxide.
    (3) A 3-month statewide conformity grace period will be established 
beginning April 1, 2003 and ends June 30, 2003.

    Dated: March 20, 2003.
Wayne Nastri,
Regional Administrator, EPA Region IX.
[FR Doc. 03-7815 Filed 3-31-03; 8:45 am]
BILLING CODE 6560-50-P

 
 

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