Modeling Alternative NLEV Implementation and
Adoption of California Standards in MOBILE6
February 2,2005
This document supplements and revises the guidance given in Section 7.4.1 of the document
entitled: "Technical Guidance on the Use of MOBILE6 for Emission Inventory Preparation"
located on EPA/OTAQ's website f http://w ww.epa.gov/otao/models/mobile6/m6techgd.i]df), and
supercedes draft supplemental guidance on this subject dated December 21, 2001. This revision
updates the treatment of the 2003 model year under the LEV II program, and the modeling of
evaporative emissions for Partial Zero Emission Vehicles (PZEVs) based on consultation with
California's Air Resources Board (ARB).
The default case in MOBDLE6 for post-Tier 1 emission control programs assumes that the
National Low Emission Vehicle (NLEV) program applicable to the non-Northeastern states is
implemented in model year 2001, and that the Federal Tier 2 program begins implementation in
model year 2004. Users who wish to use MOBILE6 with alternate control program scenarios
will need to invoke additional input features as described in this guidance.
An earlier phase-in of these NLEVs would be modeled using an alternate input file in
conjunction with the "94+ LDG IMP" command, detailed in the MOBILE6 User's Guide
(Section 2.8.11.4). An alternate data file (NLEVNE.D), developed by EPA and provided with
the final model release, reflects the appropriate phase-in of NLEV standards in the 1999 and
2000 models years. Northeastern states subject to the earlier phase-in provisions on NLEV
should use the NLEVNE.D file instead of the MOBILE6 default for accurate representation of
the NLEV program in their area.
Under Section 177 of the Clean Air Act, states have the option to adopt California emission
control programs instead of the federal program if the California programs would help achieve
the air quality goals of that state. The focus of this option has been the evaluation of programs
which are alternatives to the Federal Tier 1 and Tier 2 programs. California's emission control
program for light-duty vehicles consists of the LEV I and LEV II programs, which are considered
separable for states outside of California and in MOBILE6's modeling approach.
California's LEV I program affects light-duty vehicles beginning with the 1994 model year and
continuing until the start of the LEV II program. Some northeastern states adopted California's
LEV I program as an alternative to the Federal Tier 1 and NLEV programs. Because the specific
implementation schedules of the LEV I program vary from state to state, users wishing to model
the LEV I program in a specific non-California state will need to develop a custom input file to
be used in conjunction with the "94+ LDG IMP" command. This custom file should be based
on the default file P941MP.D provided with the final model release, modified as appropriate to
reflect the appropriate phase-in schedule of vehicles under the LEV I program (i.e. TLEV, LEV,
ULEV and ZEV) for that state. The modified phase-in schedule should only affect model years
1994 through 2003; beginning in model year 2004, the model assumes implementation of the
Tier 2 program.

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Beginning in 2004, the MOBILE6 default case is the federal Tier 2 program under the phase-in
presented in the MOBILE6 report M6.EXH.004, "Accounting for the Tier 2 and Heavy-Duty
2005/2007 requirements in MOBILE6". States have the option of adopting California's LEV II
program m place of the Federal Tier 2 program. The ARB's phase-in of the LEV II program (as
of July 17, 2001) is given by vehicle type in the three tables in the appendix of this guidance. For
all pollutants, analysis of the LEV II option in MOBILE6 will be performed using alternative
input files (listed in parentheses) in conjunction with these four commands:
 T2 EXH PHASE-IN, which provides phase-in percentages by exhaust certification
bin, vehicle class and pollutant (corresponding input file LEVIIPH.D) (for model
years 2004 through 2015),
	T2 CERT, which defines the 50,000 mile standard levels by exhaust certification bin,
vehicle class and pollutant (corresponding input file LEVIIST.D)), and
	T2 EVAP PHASE-IN, which provides phase-in percentages for evaporative standards
(similar to the phase-in of the exhaust standards) by vehicle class for model years
beginning with 2004 (corresponding input file LEVIIEVP.D).
	94+ LDG IMP (corresponding input file LEVII94.D) has two uses:
 for model years 1994 through 2003 is used to establish the fraction of
certification standard classes, from Tier 0 through ZEV. The provided file
reflects the NLEV program for states not affected by the early NLEV phase-in
provisions for Northeastern states.
 for model years 2004 through 2025 is used ONLY to establish the fraction of
zero-emitting exhaust vehicles (ZEVs). The remainder of vehicles (for each of
those model years) are categorized simply as "Tier 2" and allocated according to
the bin phase-in fractions provided with the preceding "T2 EXH PHASE-IN"
and "T2 EVAP PHASE-IN" commands.
Users who would like to model the LEV I or northeastern NLEV and LEV II programs
in conjunction can create a single input file (94+ LDG IMP) for this command (for
both exhaust and evaporative emissions) which reflects the phase-in tor the appropriate
programs from 1994 onward.
These four commands and the corresponding input files are described in the User's Guide to
MOBELE6 (Sections 2.8.11.3 and 2.8.11.4).
The four input files listed above were developed for MOBILE6 directly from LEV II phase-in
assumptions developed for EMFAC2001 by the California ARB. Thus, these files reflect the
California LEV II program as projected to be implemented in California. The analysis of LEV II-
based programs which differ from California's implementation will require modification to the
above files. It is important to note that MOBILE6 only checks to make sure that phase-in

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perccntages for a given vehicle class and model year add to 1. MOBILE6 does not check to
ensure the phase-in schedule or standards entered in the model arc in compliance with the
provisions of either the Tier 2 Rile or LEV n rule; it is, therefore, up to the user to ensure that
alternate Tier 2 or LEV II phase-in schedules and standards are accurate and meet the
requirements of these rules. Users should contact EPA to ensure the correct modifications are
made to the default input files.
Two aspects of the LEV IT rule cannot be modeled directly in MOBILE6, requiring
approximations to be applied. The first applies to PZEVs in model year 2003. California's
current requirement is that 0.4 percent of LDV/LDTls be certified as ZEVs and 9.3 percent of
LDV/LDTls be certified as PZEVs in 2003. The 2003 ZEV requirement is in the ZEV column
of the T F.VTTQ4.D input file. However, MOBILE6 does not provide the flexibility to model
PZEVs in 2003, hence EPA is accounting for PZEVs as ULEVs in model year 2003 only.
The second aspect of the LEV II rule requiring approximation is the treatment of PZEV
evaporative emissions in all model years. MOBILE6 does not provide the flexibility to model
PZEVs as a separate evaporative category; the two candidate categories to account for PZEV
evaporative emissions are the standard LEV II standards, or ZEV levels (i.e. zero emissions).
Recent consultation with the ARB indicates that the EMFAC model does assign emissions and
deterioration to PZEVs. EPA, therefore, believes that it is more appropriate to treat PZEVs no
different than standard LEV II vehicles in terms of evaporative emissions, rather than ZEVs.
This approximation is reflected by using the LEVII94.D file for both exhaust and evaporative
emission phase-in.

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APPENDIX
Table A-1
ARB's LEV II Phase-In (as of July 17, 2001) of
Passenger Cars (PC) and Light-Duty Truck 1's (LDT1)
Mdl Yr
2003
LEV I
ULEV 1
LEV 11
ULEV 11
Tier2-4
Tler2-3
PZEV
ATPZEV
ZEV
70.3%
20.0%
0.0%
0.0%
0.0%
0.0%
8.4%
0.9%
0.4%
2004
61.0%
0.0%
20.1%
0.0%
0.0%
0.0%
16.6%
1.9%
0.4%
2005
12.0%
9.0%
51.3%
0.0%
0.0%
0.0%
25.1%
2.2%
0.4%
2006
0.0%
0.0%
40.5%
23.0%
0.0%
0.0%
33.0%
3.0%
0.5%
2007
0.0%
0.0%
25.0%
15.0%
19.1%
0.0%
36.9%
3.4%
0.6%
2008
0.0%
0.0%
15.0%
25.0%
14.6%
0.0%
41.0%
3.8%
0.6%
2009
0.0%
0.0%
4.0%
6.0%
10.0%
29.0%
44.9%
5.2%
0.9%
2010
0.0%
0.0%
4.0%
6.0%
10.0%
24.4%
49.0%
5.6%
1.0%
2011
0.0%
0.0%
4.0%
6.0%
10.0%
19.8%
53.1%
6.1%
1.0%
2012
0.0%
0.0%
4.0%
6.0%
10.0%
14.2%
56.6%
7.8%
1.4%
2013
0.0%
0.0%
4.0%
6.0%
10.0%
14.2%
56.6%
7.8%
1.4%
2014
0.0%
0.0%
4.0%
6.0%
10.0%
14.2%
56.6%
7.8%
1.4%
2015
0.0%
0.0%
4.0%
6.0%
10.0%
11.1%
56.7%
10.3%
1.9%
2016
0.0%
0.0%
4.0%
6.0%
10.0%
11.1%
56.7%
10.3%
1.9%
2017
0.0%
0.0%
4.0%
6.0%
10.0%
11.1%
56.7%
10.3%
1.9%
2018
0.0%
0.0%
4.0%
6.0%
10.0%
8.0%
56.7%
12.9%
2.4%
2019
0.0%
0.0%
4.0%
6.0%
10.0%
8.0%
56.7%
12.9%
2.4%
2020
0.0%
0.0%
4.0%
6.0%
10.0%
8.0%
56.7%
12.9%
2.4%

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Table A-2
ARB's LEV II Phase-In (as of July 17, 2001) of
Light-Duty Truck 2's (LDT2)
Mdl Yr
LEV I
ULEVI
Tier2-9
LEV II
ULEVII
Tier2-4
2003
85.0%
15.0%
0.0%
0.0%
0.0%
0.0%
2004
0.0%
0.0%
75.0%
25.0%
0.0%
0.0%
2005
0.0%
0.0%
50.0%
50.0%
0.0%
0.0%
2006
0.0%
0,0%
25.0%
75.0%
0.0%
0.0%
2007
0.0%
0.0%
0.0%
50.0%
50.0%
0.0%
2008
0.0%
0.0%
0.0%
40.0%
60.0%
0.0%
2009
0.0%
0.0%
0.0%
40.0%
40.0%
20.0%
2010
0.0%
0.0%
0.0%
35.0%
45.0%
20.0%
2011
0.0%
0.0%
0.0%
35.0%
45.0%
20.0%
2012
0.0%
0.0%
0.0%
35.0%
45.0%
20.0%
2013
0.0%
0.0%
0.0%
35.0%
45.0%
20.0%
2014
0.0%
0.0%
0.0%
35.0%
45.0%
20.0%
2015
0.0%
0.0%
0.0%
35.0%
45.0%
20.0%
2016
0.0%
0.0%
0.0%
35.0%
45.0%
20.0%
2017
0.0%
0.0%
0.0%
35.0%
45.0%
20.0%
2018
0.0%
0.0%
0.0%
35.0%
45.0%
20.0%
2019
0.0%
0.0%
0.0%
35.0%
45.0%
20.0%
2020
0.0%
0.0%
0.0%
35.0%
45.0%
20.0%

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Table A-3
ARB's LEV II Phase-In (as of July 17, 2001) of
Medium-Duty Trucks
Mdl Yr
LEVI
ULEV I
Tier2-10
Tier2-8
LEV II
2003
60.00%
40.00%
0.00%
0.00%

2004
0.00%
0
81.50%
18.50%

2005
0.00%
0
63.00%
37.00%

2006
0.00%
0
39.00%
61.00%

2007

--
0.00%
0.00%
100%
2008


0.00%
0.00%
100%
2009


0.00%
0.00%
100%
2010

--
0.00%
0.00%
100%
2011


0,00%
0.00%
100%
2012


0.00%
0.00%
100%
2013
"

0.00%
0.00%
100%
2014


0.00%
0.00%
100%
2015


0.00%
0.00%
100%
2016


0.00%
0.00%
100%
2017


0.00%
0.00%
100%
2018
"

0.00%
0.00%
100%
2019


0.00%
0.00%
100%
2020
"
--
0.00%
0.00%
100%

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