United States Air and Radiation EPA420-R-03-012
Environmental Protection September 2003
Agency M6.EXH.013
v>EPA Update to the Accounting for
the Tier 2 and Heavy-Duty
2005/2007 Requirements in
MOBILES
> Printed on Recycled Paper
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EPA420-R-03-012
September 2003
Update to the Accounting for the Tier 2 and Heavy-Duty
2005/2007 Requirements in MOBILE6
M6.EXH.013
John Koupal
David Brzezinski
Assessment and Modeling Division
Office of Transportation and Air Quality
U.S. Environmental Protection Agency
NOTICE
This technical report does not necessarily represent final EPA decisions or positions.
It is intended to present technical analysis of issues using data that are currently available.
The purpose in the release of such reports is to facilitate the exchange of
technical information and to inform the public of technical developments which
may form the basis for a final EPA decision, position, or regulatory action.
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Introduction
This document (M6.EXH.013) updates the CO emission factors originally described in
the document M6.EXH.004 (November 2001) for light duty Tier 2 vehicles. The update is
necessary to account for the changes made in MOBILE6 to account for the effects of Tier 2 HC
and NOx standards on CO emission rates. This document completely supercedes the previous
document (M6.EXH.004) and contains all of the descriptions contained in that document, but the
descriptions have been updated to reflect the subsequent changes in CO emission rates for
MOBILE6.
The purpose of this report is to describe how MOBILE6 accounts for the effects of the
Tier 2 vehicle and fuel program for light-duty vehicles,1 and new standards for heavy-duty
vehicles beginning as required under two recently finalized regulations known as the "Heavy-
Duty 2005 rule" and the "Heavy-Duty 2007 rule".2'3 The focus of this report is to present the
methodology for implementing these requirements in MOBILE6, and contains only a brief
overview of each requirement. The requirements themselves should be consulted for an in-depth
treatment of the rule provisions, and for background on the terminology applied in the rules.
Tier 2
Vehicle exhaust standards
The Tier 2 vehicle program, finalized in December 1999, represents significantly more
stringent tailpipe standards for HC and NOx across all light-duty vehicles and trucks.
Ultimately, all light-duty vehicles and trucks will be held to the same fleet average emission
standard. However, the Tier 2 program allows significant flexibility in meeting these fleet
average emission requirements, including the use of interim standards and the use of multiple
certification "bins" which manufacturers can use to comply with the overall Tier 2 requirement
(see Appendix B). This flexibility allows innumerable approaches which manufacturers can take
to comply with Tier 2, which in turn introduces considerable complexity in addressing Tier 2 in
MOBILE6. The approach for Tier 2 compliance contained in MOBILE6 (Appendix A) reflects
one set of assumptions about how manufacturers will comply with the requirement, but it is not
the sole approach available.
federal Register Volume 65, Number 28, February 10 2000, Page 6698 "Control of Air Pollution from
New Motor Vehicles: Tier 2 Motor Vehicle Emissions Standards and Gasoline Sulfur Control Requirements"
Federal Register Volume 65, Number 195, October 6, 2000, Page 59897 "Emissions Control, Air Pollution
from 2004 and Later Model Year Heavy-Duty Highway Engines and Vehicles"
Federal Register Volume 66, Number 12, January 18, 2001, Page 5002 "Control of Air Pollution from
New Motor Vehicles: Heavy-Duty Engine and Vehicle Standards and Highway Diesel Fuel Sulfur Control
Requirements"
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The overall Tier 2 requirement is implemented from model years 2004 through 2009.
Ultimately, all light-duty vehicles (LDVs) and trucks (LDTs) are required to meet, on average, a
full-useful life NOx standard of 0.07 grams/mile by 2009. Prior to this, LDVs and trucks under
6,000 pounds (LDTls and LDT2s) are subject to one set of fleet average NOx requirements, and
trucks over 6,000 pounds (LDT3s and LDT4s) another. The fleet average NOx emission
standards and phase-in schedules proposed for the vehicle component of the Tier 2/Sulfur
program are shown in Table 1. In 2004, LDT2s would meet the same emission standards
required under the National Low-Emitting Vehicle (NLEV) program for LDVs and LDTls (i.e.
"LDV LEV" standards). LDVs, LDTls and LDT2s as a group would then phase in to a 0.07 full
useful life (120,000 mile) gram/mile NOx standard from 2004 to 2007. LDT3s and LDT4s are
treated as a separate group; in 2004, these vehicles would meet standards for MDV2s under
California's Low-Emitting Vehicle (LEV I) program; as a group, LDT3s and LDT4s would then
phase in to a 0.20 gram/mile NOx standard (and 0.156 gram/mile NMOG standard) from 2004 to
2007. Finally, LDT3s and LDT4s would phase in to the 0.07 gram/mile NOx and 0.09
gram/mile NMOG standards over 2008 and 2009.
Table 1 - Fleet Average Tier 2 NOx Standards and Required Phase-In Schedules
Model Year
2004 (Interim)
2004
2005
2006
2007
2008
2009 and later
LDV/T1/T2
Full Useful Life NOx
Fleet Average Standard
(g/mi)
0.30
0.07
0.07
0.07
0.07
0.07
Required
Phase-In
100%
25%
50%
75%
100%
100%
LDT3/4
Full Useful Life NOx
Fleet Average Standard
(g/mi)
0.60
0.20
0.20
0.20
0.20
0.07
Required
Phase-In
100%
25%
50%
75%
100%
50%
Fleet Average Across All Classes = 0.07 gram/mile
Under the Tier 2 program, manufacturers may certify their vehicles in any combination
of 10 certification emission standard "bins" (Appendix B) which result in the NOx fleet average
and phase-in requirements contained in Table 1 (for a complete description of the Tier 2 bin
structure and individual bin emission standards, consult the Tier 2 final rule). Many of these
certification bins overlap with the emission certification categories in California's LEV II
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September 2003
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program: LEV, ULEV, SULEV, and ZEV.4
We have developed one possible phase-in schedule for inclusion in MOBILE6, based on
several assumptions about how manufacturers will comply with the requirement. This phase-in
schedule is shown in Appendix A. This phase-in schedule is based on the premise that
manufacturers will take full advantage of the opportunity to trade off higher emissions on
heavier trucks with lower emissions on LDVs and lighter trucks. Specifically, we are assuming
that the bin structure will provide incentives for manufacturers to build LDV/LDT1 SULEVs
under the Tier 2 program because of this ability to trade off with the heavier trucks. It is also
likely that manufacturers who produce partial ZEVs (PZEVs) to comply with the ZEV
requirement in California will certify these vehicles as SULEVs federally.
The default Tier 2 phase-in schedule included in MOBILE6 was developed using four
basic principles:
1) Only LDV/LDTls will certify in Bin 2 (SULEV) and Bin 3.
2) During phase-in years, manufacturers will comply with the lightest classes first (i.e.,
100 percent of LDV/T1 will meet the 0.07 g/mi NOx requirement before any LDT2s are
brought in, and the 50 percent LDT3/4 0.07 g/mi NOx requirement in 2008 will be met
with LDT3s only).
3) Manufacturers will trade off LDT2 vs. LDV/T1 in 2007, resulting in a 120,000 mile
NMOG average of 0.077 g/mi for LDV/LDT1/LDT in 2007 and 2008.
4) Manufacturers will trade off LDT3/4 vs. LDV/T1/T2 in 2009, so that all LDT3/4
(except the LDT3s required to be at 0.07 to meet the LDT3/4 requirement) are in Bin 8;
this results in a 120,000 mile NMOG average of 0.07 g/mi across all vehicles for 2009
and later.
The Tier 2 program does not contain a specific NMOG fleet average requirement, but
NMOG emissions will be reduced under Tier 2 through the implementation of the certification
"bin" structure. The fleet-average NMOG emission values under Tier 2 are driven solely by the
distribution of vehicles across the certification bins. Table 2 shows the NOx and NMOG fleet
averages which result when the default MOBILE6 phase-in assumptions are employed in
California Air Resources Board, "LEV II and CAP 2000 Amendments to the California Exhaust and
Evaporative Emission Standards and Test Procedures for Passenger Cars, Light-Duty Trucks and Medium-Duty
Vehicles, and to the Evaporative Emission Requirements for Heavy-Duty Vehicles: Final Statement of Reasons",
September 1999
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conjunction with the projected sales splits assumed implicitly within MOBILE6.5
Table 2: 120K Light-Duty NOx/NMOG Fleet Averages (g/mi)
Model
Year
2004
2005
2006
2007
2008
2009
2010
NOx
0.277
0.214
0.152
0.088
0.079
0.070
0.070
NMOG
0.108
0.106
0.104
0.088
0.081
0.070
0.070
For MOBILE6, basic emission rates for each Tier 2 certification bin were estimated
based on the basic emission rates for Tier 1 vehicles adjusted by the ratio of the Tier 2 standards
to the Tier 1 standards. The method is similar to the methodology presented in MOBILE6 report
M6.EXH.007, "Determination of NOx and HC Basic Emission Rates, OBD and I/M Effects for
Tier 1 and later LDVs and LDTs" and report M6.EXH. 12, "Update to the Determination of CO
Basic Emission Rates, OBD and I/M Effects for Tier 1 and Later LDVs and LDTs". This is
done by weighting the Tier 2 emission standard rates (in Appendix B) by the phase in fractions
(in Appendix A) to give a composite emission standard rate. This rate is divided by the
corresponding Tier 1 emission standard and the ratio is multiplied by the emission rate
determined for Tier 1 vehicles by MOBILE6 to give the Tier 2 emission rate.
The exception to this method is the determination of CO emission rates. As described in
M6.EXH. 12, the LEV CO emission rates are adjusted by the ratio of LEV certification test
results to Tier 1 certification test results to reflect the effect of enhanced emission control
systems on LEVs necessary to meet the more stringent HC and NOx LEV emission standards.
This allows the CO emissions for LEVs to be reduced even though the CO emission standard for
LEVs is identical to the CO emission standard for Tier 1 vehicles. The same adjustment (0.505)
used for LEVs is used when determining the composite emission standard rates for Tier 2 bins 5
through 10. The Tier 2 CO emission standard rate for these bins (as shown in Appendix B) is
not used. The adjustment is applied to the corresponding Tier 1 CO emission standard rate and
MOBILE6 assumes that the share of truck sales relative to vehicles would grow to 60 percent in 2008, then
level off. Within the truck classes, the splits were held constant: LDT1 = 18%, LDT2 = 57%, LDTS = 17%, LDT4 =
8%, as derived from projected sales data for the 1999 model year.
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September 2003
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that adjusted rate is used instead. This reduces the effective composite CO emission standard
rate used to determine the CO emission rates for Tier 2 vehicles. The effective Tier 2 CO
standards are shown in Appendix C.
Vehicle Evaporative Standards
The Tier 2 requirement includes more stringent standards for the 2 and 3-day evaporative
test procedure. California's LEV II requirement also includes evaporative emission standards.
The standards for both the Tier 2 and LEV II programs are shown in Table
Table 3: Evaporative HC Standards Under Tier 2 and LEV II
(grams/test over 3-day diurnal + hot soak)
Vehicle Class
LDV
LDT1
LDT2
LDT3/LD4
Current
2.0
Tier 2
0.95
0.95
0.95
1.2
LEV II
0.5
0.65
0.65
0.95
California's program requires the phase-in to the LEV II standards at 40 percent in 2004,
80 percent in 2005, and 100 percent in 2006. The Tier 2 standards are phased-in according to the
same schedule required for the final NOx exhaust standards, presented in Table 1.
For MOBILE6 we are assuming that the LEV II evaporative standards will drive benefits
under the Tier 2 program as well. This approach is based on our analysis of the relative
stringency of the California and EPA standards as well as input from auto manufacturers, who
have indicated to EPA their plans to build a single evaporative emission control system to
comply with both the Federal and California evaporative requirements. The primary driver of
this is that the Tier 2 evaporative program, while having slightly less stringent certification
standards, includes a provision which requires manufacturers to certify the durability of their
systems using the maximum allowable alcohol fuel levels; California does not require this
provision. To compensate for the increased vulnerability of system components to alcohol fuel,
manufacturers will need to build a more durable system than the standard would imply using the
same low permeability hoses and low loss connections planned for LEV II vehicles.
Manufacturers have provided written assurances to EPA that the alcohol fuels provision
of the federal standards, and relative difficulty in "finessing" evaporative emissions between the
LEV II and Tier 2 standards, will necessitate the development of a single federal system
complying with the California standards. We will revisit this assumption when certification data
is available on evaporative Tier 2 vehicles to determine whether this approach is still warranted.
September 2003
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MOBILE6 estimates evaporative emissions under the new standards by applying a
percent reduction to the basic emission rates for diurnals and hot soak according to the percent
reduction between the current standards and the LEV II standards. Thus, the percent reduction
for LDVs is 75 percent, for LDTls and LDT2s 67.5 percent, and for LDT3s and LDT4s 52.5
percent.
Fuel standards
Under the Tier 2 rule, gasoline producers are required to reduce fuel sulfur levels to 120
ppm in 2004, 90 ppm in 2005 and 30 ppm in 2006, on average. However, there are provisions
which allow small refiners and gasoline producers in western states to achieve the 30 ppm
average on a longer timetable. In addition, Averaging, Banking and Trading (ABT) provisions
allow refiners who achieve early reductions in gasoline fuel sulfur levels to apply these
reductions against the requirement in later years.
MOBILE6 accounts for the small refiner (termed "SBREFA"), geographic phase-in
(termed "GPI") and ABT provisions contained in the Tier 2 fuel program through the
development of composite by-calendar year fuel sulfur levels which estimate the effects of these
provisions on a volume basis. The MOBILE6 modeling approach is based directly on the
modeling assumptions developed in support of the Tier 2 rule, which developed composite fuel
sulfur levels by calendar year for several fuel "categories" accounting all fuel sold in the U.S.6
Based on the definition of Eastern U.S and Western U.S. defined by API and NPRA in their
sulfur program proposed to EPA,7 the Tier 2 modeling methodology divided the fuel produced in
the 47-state region into five fuel categories, as shown in Table 4. The primary modification
between the approach used in the Tier 2 rule modeling and MOBILE6 is the definition of these
fuel categories; MOBILE6 developed three categories based on aggregating the five categories
defined for the Tier 2 modeling. As shown in Table 4, the three MOBILE6 categories are East
Conventional, RFG, and West.
Table 4 - MOBILE6 Fuel Categories
"Development of Light-Duty Emission Inventory Estimates in the Final Rulemaking for Tier 2 and Sulfur
Standards", Memorandum from John Koupal to Docket A-97-10, December 15, 1999.
7Underthe API/NPRA proposal, Eastern U.S. consists of eastern Texas, Oklahoma, Mississippi, Tennessee,
Missouri, Illionois, Wisconsin, and all those states (including the District of Columbia) east of these states. A
detailed accounting of the API proposal is contained in the Tier 2 regulatory docket, A-97-10
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Tier 2 Fuel Category
East Convential Gasoline (CG)
East SBREFA
Reformulated Gasoline (RFG)
West SBREFA
West GPI
Description
Conventional gasoline areas in the east
Fuel produced by SBREFA refiners in the east
Reformulated Gasoline areas (all in the east)
Fuel produced by SBREFA refiners in the west
Fuel produced by western refiners under the
geographic phase-in
MOBILE6
Category
East CG
RFG
West
The default sulfur levels contained in MOBILE6 were developed by first estimating
sulfur levels for each of the five Tier 2 categories shown in Table 4, then aggregating into the
three MOBILE6 categories according to weightings of fuel production across each of the
categories. The first step in this analysis was to define the sulfur levels (average and cap) for
each fuel category by calendar year for the baseline and control scenarios. Focusing on the
projection of the average sulfur levels first, the sulfur levels in 2000 were determined from an
assessment of refiner's certification records from 1998. Outside of California, gasoline sulfur
levels averaged 268 ppm in 1998. EPA projects that RFG will average roughly 150 ppm
beginning in 2000 in order to meet the Phase 2 RFG NOx performance specification.8
Comments from a number of oil refiners and NPRA indicated that refiners would not reduce the
sulfur of their total gasoline pool in order to meet the Phase 2 RFG NOx performance
specification in 2000, but would shift sulfur from RFG to CG in the summer and vice versa in
the winter. The average sulfur level of RFG in 1998 was 207 ppm. Because this level is fairly
close to the 150 ppm RFG target, it is quite conceivable that refiners could perform the sulfur
shift outlined in the comments to the proposed rule. Assuming that the sulfur level of summer
RFG was reduced from 207 to 150 ppm, we determined that the sulfur level of CG and winter
RFG would increase from its 1998 level of 295 ppm to 300 ppm. For the baseline case, sulfur
levels are assumed to stay constant from calendar year 2000 onward; the baseline levels for years
2000 and later are shown in Table 5. Because the SBREFA and GPI provisions are not
applicable in the baseline case, the fuel categories developed for the Tier 2 modeling
methodology are directly applicable in MOBILE6.
Table 5 - Default MOBILE6 Sulfur Levels Without Tier 2 (ppm)
"Draft Regulatory Impact Analysis - Control of Air Pollution from New Motor Vehicles: Tier 2 Motor
Vehicle Emissions Standards and Gasoline Sulfur Control Requirements", EPA Report EPA420-D-99-001, April
1999
September 2003
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Calendar Year
2000 & later
East Conventional
Average
300
Cap
1000
RFC
Average
150
Cap
500
West Conventional
Average
300
Cap
1000
For the "with Tier 2" case, sulfur levels in 2001-2003 were estimated from 2000 sulfur
levels using the sulfur reductions which would occur from desulfurization units projected to be
built and operating prior to 2004. These projections are described in Section IV.B.8. of the Final
Tier 2 Regulatory Impact Analysis (RIA).9 Based on the operation of these new units, we project
that pool sulfur levels will decrease by 1, 21 and 37 ppm in 2001, 2002, and 2003. These
reductions were applied uniformly to each fuel category with one exception. In 2003, a
reduction of 37 ppm would have reduced RFG sulfur levels to less than 120 ppm, the corporate
average standard in 2004. To avoid this, the RFG sulfur level was assumed to decrease to only
120 ppm in 2003 and the sulfur level of the remainder category of CG and RFG was decreased
by 41 ppm instead of only 37 ppm. This results in a 37 ppm reduction in the non-California pool
average sulfur level.
In 2004 and 2005, fuel subject to the corporate average standards, RFG and the
remainder category of RFG and CG, was assumed to average at the corporate average standards,
120 and 90 ppm, respectively. The average sulfur levels of fuel certified to these standards may
be below these levels due to refiners desire to maintain a safety margin between their actual
sulfur levels and enforcement levels. However, the degree of this potential margin is not known
and is not guaranteed by the applicable standards.
In 2004-2007, small refiners under the SBREF A program are governed by average
standards which are a function of their current sulfur level. We estimated these standards for the
16 small refiners based on their sulfur certification data in 1998. In the east, the volume-
weighted average of these standards was 191 ppm and in the west was 208 ppm. We assumed
that these refiners would produce fuel at these sulfur levels until 2008, when the 30 ppm refinery
average standard applies.
In 2004-2006, refineries covered by the geographic phase-in must meet a 150 ppm
refinery average standard. We assumed that these refineries would produce fuel at this level.
For all categories of fuel, once the 30 ppm refinery average standard began to apply, we
assumed that commercial gasoline in these categories would average at the standard, 30 ppm.
With respect to the maximum sulfur level possible in any fuel category, we based these
levels on the maximum allowable sulfur level from any individual refinery in the category. The
"Regulatory Impact Analysis - Control of Air Pollution from New Motor Vehicles: Tier 2 Motor Vehicle
Emissions Standards and Gasoline Sulfur Control Requirements", EPA Report EPA420-R-99-023, December 1999
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September 2003
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Complex Model places a limit of 500 ppm sulfur on RFG and 1000 ppm for CG; therefore these
levels were applied to RFG and CG fuel categories, respectively, from 2000-2003. Beginning in
2004, the maximum sulfur level of each fuel category was assumed to be the cap applicable to
that category of fuel. Thus, these levels are simply a function of the final caps for these fuel
categories. Maximum sulfur levels are used only for the calculation of sulfur "irreversibility"
effects, discussed in detail in the MOBILE6 report M6.FUL.001, "Fuel Sulfur Effects on
Exhaust Emissions".
Table 6 shows the sulfur levels with Tier 2 as derived by the process described above, for
the disaggregated categories from Table 4. These disaggregate categories were then weighted by
the fuel production weightings in Table 7, resulting in the MOBILE6 sulfur levels with Tier 2
across the three MOBILE6 fuel categories.
Table 6 - Sulfur Levels With Tier 2: Disaggregate Categories (ppm)
Year
2000
2001
2002
2003
2004
2005
2006
2007
2008 & later
East
Conventional
Avg
300
299
279
259
120
90
30
30
30
Cap
1000
1000
1000
1000
300
300
80
80
80
East SBREFA
Avg
300
299
279
263
191
191
191
191
30
Cap
1000
1000
1000
1000
450
450
450
450
80
RFG
Avg
150
149
129
120
120
90
30
30
30
Cap
500
500
500
500
300
300
80
80
80
West SBREFA
Avg
300
299
279
263
208
208
208
208
30
Cap
1000
1000
1000
1000
450
450
450
450
80
West GPI
Avg
300
299
279
263
150
150
150
30
30
Cap
1000
1000
1000
1000
300
300
300
80
80
Table 7 - Non-RFG Category Weightings (by fuel consumption)
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September 2003
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Tier 2 (Disaggregate) Fuel
Category
East CG
East SBREFA
West SBREFA
West GPI
Weightings
0.98
0.02
0.16
0.84
MOBILE6
Category
East CG
West
Table 8 - Sulfur Levels With Tier 2: MOBILE6 Categories (ppm)
Year
2000
2001
2002
2003
2004
2005
2006
2007
2008 & later
East Conventional
Average
300
299
279
259
121
92
33
33
30
Cap
1000
1000
1000
1000
303
303
87
87
80
RFC
Average
150
149
129
120
120
90
30
30
30
Cap
500
500
500
500
300
300
80
80
80
West Conventional
Average
300
299
279
263
160
160
160
60
30
Cap
1000
1000
1000
1000
325
325
325
142
80
New Standards for Heavy-Duty Gasoline Vehicles
Methodology for Developing Basic Exhaust Emission Rates
Heavy-Duty Gas Vehicles (HDGVs) will be subject to new standards under three
separate requirements. A first phase of exhaust and evaporative standards affecting all HDGVs
will begin implementation in 2005, and hence are referred to as the "2005 rule"; the Tier 2
"Medium Duty Passenger Vehicle" (MDPV) standards will reduce emissions further for a subset
of HDGV2bs beginning in 2008. The recently finalized Heavy-Duty 2007 rule ("2007 rule") for
diesel engines also will require emission reductions for the remainder of HDGVs beginning in
2008. These standards are shown in Table 9.
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September 2003
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Table 9: HC/NOx 120,000 Mile Standards for HDGV (g/mi unless otherwise noted)
Class
Pre-2005
(all g/bhp-hr)
2005 Rule
Tier 2
2007 Rule
2b
MDPV
Other
Complete
Incomplete
(g/bhp-hr)
3
Complete
Incomplete
(g/bhp-hr)
0.9/4.00
0.28/0.9
0.075/0.07
0.075/0.07
0.28/0.9
0.28/0.9
0.195/0.2
0.2/0.8
0.2/0.8
0.14/0.2
0.33/1.0
0.33/1.0
0.23/0.4
0.2/0.8
0.2/0.8
0.14/0.2
4-8
(g/bhp-hr)
1.7/4.0
0.2/0.8
0.2/0.8
0.14/0.2
2005 Standards
The methodology for deriving HC and NOx BERs for HDGVs under the 2005
requirements is contained in the Chapter 7 of the Regulatory Impact Analysis (RIA) for the
Heavy-Duty Gas rulemaking.10 As outlined in this document, BERs were derived by assuming a
similar margin of compliance with the certification standards as for the pre-control BERs. In
the RIA, separate BERs were derived for three sets of HDG classes: 2b Completes, 3 Completes,
and Incomplete for all classes. Because MOBILE6 will not differentiate between Complete and
Incomplete certification classes, an additional step was required for this analysis to generate a
combined BER for the 2b and 3 classes. The was performed by weighting together the
Complete/Incomplete emission rates according to sales figures for the 1996 model year provided
by manufacturers in the Heavy-Duty Gas 2005 rule, which indicated that Completes would
comprise 96 percent of HDGV2b (458,447 out of 485,046) and 15 percent of HDGV3 (38,733
out of 124,265). For the MOBILE6 analysis, the BERs for Completes/Incompletes presented in
the HDG rule where therefore weighted according to 96/4 and 15/85 splits for 2bs and 3s,
respectively. The resulting BERs are shown in Tables 2 and 3. Because the 2005 HDG
standards for HC are expressed as NMOG, the BERs also reflect NMOG and should be handled
accordingly in the model. CO standards are not reduced in 2005, so updated BERs are not
required to reflect the heavy-duty rule.
Tier 2 MDPV Standards
The Tier 2 Medium-Duty Passenger Vehicle provisions require that a subset of HDG2bs
used primarily as passenger vehicles (i.e. large sport utility vehicles such as the GM Suburban)
meet the final Tier 2 standards (NMOG, NOx and CO) for light-duty trucks over 6,000 pounds
by 2009. The specific requirement for these trucks is a full useful life standard of 0.09 g/mi
"Regulatory Impact Analysis: Control of Emissions of Air Pollution from Highway Heavy-Duty
Engines", EPA Report EPA420-R-00-010, July 2000
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September 2003
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NMOG and 0.07 g/mi NOx, phasing-in beginning in 2008 at 50 percent and 100 percent in 2009.
In developing MOBILE6 BERs it was assumed that the subset of HDGV2bs required to meet
these standards will follow this phase-in schedule.
The effect of these standards was estimated through the 2009 and later BERs for
HDG2bs. BERs for MDPVs were calculated by reducing the 2005 BERs (ZML and DR) by the
ratio of the MDPV standards to the 2005 standards. The fraction of HDGV2b sales attributed to
MDPVs was derived by dividing an estimate of annual sales for MDPVs of 75,000 from the Tier
2 RIA (Chapter 6)11 by the number of HDGV2bs estimated in the heavy-duty rule (485,046),
resulting in a fraction of 0.155. The overall 2009 HDGV2b BERs was then calculated by
weighting together the 2005 (pre-Tier 2 BER) and the MDPV BER by a weighting split of
0.845/0.155. To model the 50 percent phase-in in 2008, the 2009 and 2005 BERs were
averaged.
2007 Rule Standards
Basic emission rates corresponding to the standards under the 2007 rule were developed
using the same methodology applied for the 2005 rule. Specifically, the same level of
compliance was assumed in relation to the certification standard between the baseline (pre-
2005), 2005 rule standards and 2007 rule standards. The emission rates were thus derived by
applying the ratio of the 2005 and 2007 standards to the model year 2005 emission rates for all
of the vehicles affected by the 2007 standards (including Class 2b vehicles not falling under the
Tier 2 MDPV requirement).
The resulting emission rates reflecting the 2005, Tier 2 MPDV and 2007 rules are shown
in Tables 10 through 13, by HDGV class 2b through 8b, and buses.
Table 10: Low Altitude NMOG Basic Emission Rates for MOBILE6 (g/mi)
NMOG ZML
Class:
2005-07
2008
2009+
2b
0.118
0.098
0.078
3
0.104
0.088
0.073
4
0.096
0.082
0.067
5
0.113
0.096
0.079
6
0.111
0.095
0.078
7
0.123
0.105
0.086
8a
0.131
0.112
0.092
81)
0.131
0.112
0.092
Bus
0.153
0.130
0.107
"Regulatory Impact Analysis - Control of Air Pollution from New Motor Vehicles: Tier 2 Motor Vehicle
Emissions Standards and Gasoline Sulfur Control Requirements", EPA Report EPA420-R-99-023, December 1999
-13-
September 2003
-------
NMOG DR (per 10K miles)
Class:
2005-07
2008
2009+
2b
0.008
0.007
0.005
3
0.006
0.005
0.004
4
0.006
0.005
0.004
5
0.007
0.006
0.005
6
0.007
0.006
0.005
7
0.007
0.006
0.005
8a
0.008
0.007
0.006
81)
0.008
0.007
0.006
Bus
0.009
0.008
0.006
Table 11: Low Altitude NOx Basic Emission Rates for MOBILE6 (g/mi)
NOx ZML
Class:
2005-07
2008
2009+
2b
0.573
0.347
0.121
3
0.594
0.379
0.163
4
0.578
0.361
0.145
5
0.675
0.422
0.169
6
0.669
0.418
0.167
7
0.737
0.461
0.184
8a
0.785
0.491
0.196
81)
0.785
0.491
0.196
Bus
0.916
0.573
0.229
NOx DR (per 10K miles)
Class:
2005-07
2008
2009+
2b
0.008
0.005
0.002
3
0.008
0.005
0.002
4
0.008
0.005
0.002
5
0.009
0.006
0.002
6
0.009
0.006
0.002
7
0.010
0.006
0.003
8a
0.011
0.007
0.003
8b
0.011
0.007
0.003
Bus
0.013
0.008
0.003
Table 12: High Altitude NMOG Basic Emission Rates for MOBILE6 (g/mi)
NMOG ZML
Class:
2005-07
2008
2009+
2b
0.219
0.182
0.145
3
0.193
0.163
0.136
4
0.179
0.152
0.125
5
0.209
0.178
0.146
6
0.207
0.176
0.145
7
0.228
0.194
0.160
8a
0.243
0.207
0.170
8b
0.243
0.207
0.170
Bus
0.283
0.241
0.198
-14-
September 2003
-------
NMOGDR
Class:
2005-07
2008
2009+
2b
0.015
0.013
0.009
3
0.012
0.009
0.007
4
0.011
0.009
0.008
5
0.012
0.010
0.008
6
0.012
0.010
0.008
7
0.013
0.011
0.009
8a
0.014
0.012
0.010
81)
0.014
0.012
0.010
Bus
0.017
0.014
0.012
Table 13: High Altitude NOx Basic Emission Rates for MOBILE6 (g/mi)
NOx ZML
Class:
2005-07
2008
2009+
2b
0.469
0.284
0.098
3
0.486
0.310
0.134
4
0.473
0.296
0.118
5
0.552
0.345
0.138
6
0.547
0.342
0.137
7
0.603
0.377
0.151
8a
0.642
0.401
0.161
8b
0.642
0.401
0.161
Bus
0.749
0.468
0.187
NOXDR
Class:
2005-07
2008
2009+
2b
0.007
0.004
0.002
3
0.007
0.004
0.002
4
0.006
0.004
0.002
5
0.008
0.005
0.002
6
0.008
0.005
0.002
7
0.008
0.005
0.002
8a
0.009
0.006
0.002
81)
0.009
0.006
0.002
Bus
0.010
0.006
0.003
Evaporative Emission Rates for HDGV 2005/2007 Requirements
The 2005 and 2007 rules contain evaporative emission standards as well as exhaust
standards. The methodology and emission rates for these requirements are contained in
MOBILE6 report M6.EVP.001, "Evaluating Resting Loss and Diurnal Evaporative Emissions
Using RTD Tests", April 2001.
Heavv-Dutv Diesel 2007 Rule
The heavy-duty 2007 rule requires significant reductions in PM, HC and NOx for all
heavy-duty diesel engines beginning in 2007. Standards of 0.20 g/bhp-hr for NOx and 0.14
g/bhp-hr for NMHC are required on 50 percent of engines in 2007, and 100 percent in 2010.
However, a 0.01 g/bhp-hr PM standard applies to 100 percent of engines in 2007, and the
exhaust aftertreatment required to comply with this standard is expected to drive 100 percent
compliance with the HC standard in 2007, and provide residual benefits in CO as well. These
-15-
September 2003
-------
effects are modeled through the basic emission rates developed in MOBILE6.
The basic emission rates for MOBILE6 have been developed directly from those used in
the emission inventory work in support of the final rule, detailed in the Regulatory Impact
Analysis of the final rule.12 The primary modifications required for inclusion in MOBILE6 were
a) the conversion of g/bhp-hour emission rates to grams/mile, using conversion factors
developed for late-model heavy-duty engines and discussed in separate MOBILE6
documentation;13 and b) the disaggregation of weight classes from those used in the regulatory
support work to the MOBILE6 weight class definitions. The weight classes used in the
regulatory work were simply an aggregation of the MOBILE6 classes, and the disaggregation
process consisted of applying the aggregate emission rates (e.g. for the regulatory modeling class
"light-heavy duty diesels") across each of the sub-classes (e.g. the MOBILE6 weight classes 2b
and 3). This was therefore a trivial step but resulted in duplicate emission rates across multiple
MOBILE6 classes. The basic emission rates, in g/bhp-hr and gram/mile, are shown in Tables
14-16.
Table 14: 2007+ HDDV CO Basic Emission Rates for MOBILE6
Class
2b
o
J
4
5
6
7
8a
8b
School Bus
Transit Bus
Start MY
2007
2007
2007
2007
2007
2007
2007
2007
2007
2007
g/bhp-hr
ZML
0.120
0.120
0.120
0.120
0.100
0.100
0.120
0.120
0.100
0.110
DR
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
Correction
Factor
1.09
1.25
1.458
1.573
1.942
2.409
2.763
3.031
2.989
4.679
g/mile
ZML
0.131
0.150
0.175
0.189
0.194
0.241
0.332
0.364
0.299
0.515
DR
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
"Regulatory Impact Analysis - Control of Air Pollution from New Motor Vehicles: Heavy-Duty Engine
and Vehicle Standards and Highway Diesel Fuel Sulfur Control Requirements", EPA Report EPA420-R-00-026,
December 2000
13"Updated Heavy-Duty Engine Emission Conversion Factors for MOBILE6: Analysis of BSFCs and
Calculation of Heavy-Duty Engine Emission Conversion Factors", EPA Report EPA420-P-98-015, May 1998
-16-
September 2003
-------
Table 15: 2007+ HDDV NMHC Basic Emission Rates for MOBILE6
Class
2b
3
4
5
6
7
8a
8b
School Bus
Transit Bus
Start MY
2007
2007
2007
2007
2007
2007
2007
2007
2007
2007
g/bh
ZML
0.129
0.129
0.129
0.129
0.129
0.129
0.129
0.129
0.129
0.080
p-hr
DR
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
Correction
Factor
1.09
1.25
1.458
1.573
1.942
2.409
2.763
3.031
2.989
4.679
g/mile
ZML
0.141
0.161
0.188
0.203
0.251
0.311
0.356
0.391
0.386
0.374
DR
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
Table 16: 2007+ HDDV NOx Basic Emission Rates for MOBILE6
Class
2b
2b
3
o
J
4
4
5
5
6
6
7
7
8a
8a
8b
8b
School Bus
School Bus
Transit Bus
Transit Bus
Start MY
2007
2010
2007
2010
2007
2010
2007
2010
2007
2010
2007
2010
2007
2010
2007
2010
2007
2010
2007
2010
g/bh
ZML
1.139
0.180
1.139
0.180
1.139
0.180
1.139
0.180
1.131
0.180
1.131
0.180
1.063
0.180
1.063
0.180
1.131
0.180
1.200
0.180
p-hr
DR
0.001
0.000
0.001
0.000
0.001
0.000
0.001
0.000
0.001
0.000
0.001
0.000
0.002
0.000
0.002
0.000
0.001
0.000
0.002
0.000
Correction
Factor
1.09
1.09
1.25
1.25
1.458
1.458
1.573
1.573
1.942
1.942
2.409
2.409
2.763
2.763
3.031
3.031
2.989
2.989
4.679
4.679
g/mile
ZML
1.242
0.196
1.424
0.225
1.661
0.262
1.792
0.283
2.196
0.350
2.725
0.434
2.937
0.497
3.222
0.546
3.381
0.538
5.615
0.842
DR
0.001
0.000
0.001
0.000
0.001
0.000
0.002
0.000
0.002
0.000
0.002
0.000
0.006
0.000
0.006
0.000
0.003
0.000
0.009
0.000
-17-
September 2003
-------
Appendix A
Tier 2 Phase-In Schedule
Model Year
LDV/LDT1
2004
2005
2006
2007
2008
2009
2010
LDT2
2004
2005
2006
2007
2008
2009
2010
LDT3
2004
2005
2006
2007
2008
2009
2010
LDT4
2004
2005
2006
2007
2008
2009
2010
Emission Certification Bin
1
0.000
0.000
0.000
0.000
0.000
0.000
0.000
1
0.000
0.000
0.000
0.000
0.000
0.000
0.000
1
0.000
0.000
0.000
0.000
0.000
0.000
0.000
1
0.000
0.000
0.000
0.000
0.000
0.000
0.000
2
0.000
0.000
0.000
0.100
0.100
0.250
0.250
2
0.000
0.000
0.000
0.000
0.000
0.000
0.000
2
0.000
0.000
0.000
0.000
0.000
0.000
0.000
2
0.000
0.000
0.000
0.000
0.000
0.000
0.000
3
0.000
0.000
0.000
0.300
0.300
0.550
0.550
3
0.000
0.000
0.000
0.000
0.000
0.000
0.000
3
0.000
0.000
0.000
0.000
0.000
0.000
0.000
3
0.000
0.000
0.000
0.000
0.000
0.000
0.000
4
0.000
0.000
0.000
0.200
0.200
0.100
0.100
4
0.000
0.000
0.000
0.000
0.000
0.200
0.200
4
0.000
0.000
0.000
0.000
0.000
0.000
0.000
4
0.000
0.000
0.000
0.000
0.000
0.000
0.000
5
0.386
0.787
1.000
0.400
0.400
0.100
0.100
5
0.000
0.000
0.337
0.400
0.400
0.200
0.200
5
0.000
0.000
0.000
0.000
0.740
0.740
0.740
5
0.000
0.000
0.000
0.000
0.000
0.000
0.000
6
0.000
0.000
0.000
0.000
0.000
0.000
0.000
6
0.000
0.000
0.000
0.300
0.300
0.300
0.300
6
0.000
0.000
0.000
0.000
0.000
0.000
0.000
6
0.000
0.000
0.000
0.000
0.000
0.000
0.000
7
0.000
0.000
0.000
0.000
0.000
0.000
0.000
7
0.000
0.000
0.000
0.300
0.300
0.300
0.300
7
0.000
0.000
0.000
0.000
0.000
0.000
0.000
7
0.000
0.000
0.000
0.000
0.000
0.000
0.000
8
0.000
0.000
0.000
0.000
0.000
0.000
0.000
8
0.000
0.000
0.000
0.000
0.000
0.000
0.000
8
0.370
0.740
1.000
1.000
0.260
0.000
0.000
8
0.000
0.000
0.220
1.000
1.000
0.000
0.000
9
0.614
0.213
0.000
0.000
0.000
0.000
0.000
9
1.000
1.000
0.663
0.000
0.000
0.000
0.000
9
0.000
0.000
0.000
0.000
0.000
0.000
0.000
9
0.000
0.000
0.000
0.000
0.000
0.000
0.000
10
0.000
0.000
0.000
0.000
0.000
0.000
0.000
10
0.000
0.000
0.000
0.000
0.000
0.000
0.000
10
0.630
0.260
0.000
0.000
0.000
0.000
0.000
10
1.000
1.000
0.780
0.000
0.000
0.000
0.000
11
0.000
0.000
0.000
0.000
0.000
0.000
0.000
11
0.000
0.000
0.000
0.000
0.000
0.000
0.000
11
0.000
0.000
0.000
0.000
0.000
0.260
0.260
11
0.000
0.000
0.000
0.000
0.000
1.000
1.000
-18-
September 2003
-------
Appendix B
Tier 2 Standards at 50,000 Miles
As Used in MOBILE6
Bin
1
2
3
4
5
6
7
8
9
10
11
Bin
1
2
3
4
5
6
7
8
9
10
11
Bin
1
2
3
4
5
6
7
8
9
10
11
Non-Methane Organic Gases (grams per mile)
LDV
0.000
0.007
0.040
0.051
0.075
0.075
0.075
0.100
0.075
0.125
0.000
LDT1
0.000
0.007
0.040
0.051
0.075
0.075
0.075
0.100
0.075
0.125
0.000
LDT2
0.000
0.007
0.040
0.051
0.075
0.075
0.075
0.100
0.100
0.125
0.000
LDT3
0.000
0.007
0.040
0.051
0.075
0.075
0.075
0.125
0.140
0.160
0.100
LDT4
0.000
0.007
0.040
0.051
0.075
0.075
0.075
0.125
0.140
0.195
0.100
Carbon Monoxide (grams per mile)
LDV
0.0
1.7
1.7
1.7
3.4
3.4
3.4
3.4
3.4
3.4
0.0
LDT1
0.0
1.7
1.7
1.7
3.4
3.4
3.4
3.4
3.4
3.4
0.0
LDT2
0.0
1.7
1.7
1.7
3.4
3.4
3.4
3.4
3.4
3.4
0.0
LDT3
0.0
1.7
1.7
1.7
3.4
3.4
3.4
3.4
3.4
4.4
0.0
LDT4
0.0
1.7
1.7
1.7
3.4
3.4
3.4
3.4
3.4
4.4
0.0
Oxides of Nitrogen (grams per mile)
LDV
0.000
0.014
0.021
0.029
0.050
0.080
0.110
0.140
0.200
0.400
0.000
LDT1
0.000
0.014
0.021
0.029
0.050
0.080
0.110
0.140
0.200
0.400
0.000
LDT2
0.000
0.014
0.021
0.029
0.050
0.080
0.110
0.140
0.200
0.400
0.000
LDT3
0.000
0.014
0.021
0.029
0.050
0.080
0.110
0.140
0.200
0.400
0.000
LDT4
0.000
0.014
0.021
0.029
0.050
0.080
0.110
0.140
0.200
0.400
0.000
-19-
September 2003
-------
Appendix C
Effective Tier 2 Standards at 50,000 Miles
As Used in MOBILE6 For CO Emissions
Bin
1
2
3
4
5
6
7
8
9
10
11
Tierl
Carbon Monoxide (grams per mile)
LDV
0.0
1.7
1.7
1.7
.717
.717
.717
.717
.717
.717
0.0
3.4
LDT1
0.0
1.7
1.7
1.7
.717
.717
.717
.717
.717
.717
0.0
3.4
LDT2
0.0
1.7
1.7
1.7
2.222
2.222
2.222
2.222
2.222
2.222
0.0
4.4
LDT3
0.0
1.7
1.7
1.7
2.222
2.222
2.222
2.222
2.222
2.222
0.0
4.4
LDT4
0.0
1.7
1.7
1.7
2.525
2.525
2.525
2.525
2.525
2.525
0.0
5.0
-20-
September 2003
------- |