when the battery has energy available. Engine operation during these
scenarios may be required because of such design aspects as blended
operation when both the electric power and the engine are being
utilized, or during conditions such as when heat or air conditioning
is needed for the cabin and can only be obtained with engine
operation.
    \479\ Because most CD operation occurs without engine operation,
the CO2 value for CD operation is often 0 or near 0 g/mi.
This means that a high utility factor results in a CO2
compliance value that is heavily-weighted with 0 or near 0 g/mi.
---------------------------------------------------------------------------

    Because the tailpipe CO2 produced from PHEVs varies
significantly between CD and CS operation, both the charge depleting
range and the utility factor curves play an important role in
determining the magnitude of CO2 that is calculated for
compliance. In charge depleting mode, EPA is proposing to maintain a
zero gram per mile contribution when the internal combustion engine is
not running. The significant difference is between, potentially, zero
grams per mile in CD mode versus CO2 grams per mile that are
likely to be similar to a hybrid (non-plug-in) vehicle in CS mode.
Charge depleting range for a PHEV is determined by performing single
cycle city and highway charge depleting tests according to SAE Standard
J1711,\480\ Recommended Practice for Measuring the Exhaust Emissions
and Fuel Economy of Hybrid-Electric Vehicles,

Including Plug-In Hybrid Vehicles. The charge depleting range is
determined by arithmetically averaging the city and highway range
values weighted 55 percent/45 percent, respectively as noted in 40 CFR
600.311-12(j)(4)(i).
---------------------------------------------------------------------------

    \480\ SAE J1711. 2023. ``Recommended Practice for Measuring the
Exhaust Emissions and Fuel Economy of Hybrid-Electric Vehicles,
Including Plug-in Hybrid Vehicles.'' Issued 1999-03, Revised 2010-
06, Revised 2023-02, February.
---------------------------------------------------------------------------

i. FUF Comparisons With Real World Data
    Recent literature and data have identified that the current utility
factor curves may overestimate the fraction of driving that occurs in
charge depleting operation.481 482 This literature also
concludes that vehicles with lower charge depleting ranges have even
greater discrepancy in CO2 emissions.
---------------------------------------------------------------------------

    \481\ Pl[ouml]tz, P. and J[ouml]hrens, J. (2021): Realistic Test
Cycle Utility Factors for Plug-in Hybrid Electric Vehicles in
Europe. Karlsruhe: Fraunhofer Institute for Systems and Innovation
Research ISI. Retrieved from. https://www.isi.fraunhofer.de/content/dam/isi/dokumente/cce/2021/BMU_Kurzpapier_UF_final.pdf.
    \482\ https://www.transportenvironment.org/wp-content/uploads/2022/06/TE-Anlaysis_-Update-of-PHEV-utility-factors-1.pdf.
---------------------------------------------------------------------------

    EPA and ICCT \483\ have also evaluated recently available OBD data
\484\ that has been collected through the California Bureau of
Automotive Repair (BAR) and found that the data shows that, on average,
there is more charge sustaining operation and more gasoline operation
than is predicted by the current fleet utility factor curves. The BAR
OBD data enable the evaluation of real-world PHEV distances travelled
in various operational modes; these include charge-depleting engine-off
distance, charge-sustaining engine-on distance, total distance
traveled, odometer readings, total fuel consumed, and total grid energy
inputs and outputs of the battery pack. These fields of data allow us
to use the BAR OBD data to filter the data and calculate 5-cycle
comparable real-world driving ratios of charge depleting distance to
total distance and to then compare to the existing FUFs, using the 5-
cycle range from the fuel economy and environment label.\485\
---------------------------------------------------------------------------

    \483\ ``Real world usage of plug-in hybrid vehicles in the
United States.'' Aaron Isenstadt, Zifei Yang, Stephanie Searle, John
German, ICCT Report, December 2022.
    \484\ California Air Resource Board [OBD data records dated
October 2022], https://www.bar.ca.gov/records-requests.
    \485\ Because the data collected is real-world data, we used the
combined city and highway 5-cycle label range as an input to the FUF
curve described in SAE J2841, to create an apples-to-apples
comparison. The existing regulatory FUFs are separate city and
highway curves, and the charge depleting ranges that are used with
the city and highway FUF curves are 2-cycle range.
---------------------------------------------------------------------------

    In addition to the BAR OBD data, ICCT also evaluated a dataset from
Fuelly.com. Fuelly.com is a website and smartphone application that
allows users to self-report fuel consumption data. The curve that is
fitted from the Fuelly.com data also yields lower utility factors than
the SAE J2841 FUF curve, for the same charge depleting distance;
however, the Fuelly curve is not as low as the BAR OBD curve.
    A comparison of the results of EPA's data analysis as well as the
ICCT analyses is shown in Figure 13. The FUF applied in the current
regulations is labeled as ``SAE J2841 FUF''. EPA's data analysis of the
BAR OBD data is labeled as ``Linear Regression Fit'' and the two ICCT
curves are labeled as ``ICCT-BAR'' and ``ICCT-FUELLY''. ICCT created
the ICCT-BAR and ICCT-Fuelly curves by adjusting the normalized
distances in the UF equation for both the BAR OBD data and the Fuelly
user-reported data, using sample-size weighted nonlinear least squares
regression.\486\ As shown in Figure 13, the EPA ``Linear Regression
Fit'', where about 78 percent of the total data points are between 12-
to 32-miles for the CD range, lies on top of the ``ICCT-BAR'' curve.
---------------------------------------------------------------------------

    \486\ Supra footnote 483.
---------------------------------------------------------------------------

    The BAR OBD data is a recent and relatively large dataset that
includes the charge depleting distance (or electric operating distance)
and total distance, which makes it a reasonable source for evaluating
the real-world utility factors for recent PHEV usage. However, we
recognize that the curve developed from this data is a departure from
the SAE J2841 FUF curves, that the BAR OBD data has some limitations
(see DRIA Chapter 3), and that the original SAE J2841 FUF methodology
was also a reasonable approach at the time it was adopted. Therefore,
we created the proposed curve by averaging the SAE J2841 FUF curve and
the ICCT-BAR curve. The resulting proposed FUF curve lies almost on top
of the ICCT-FUELLY curve. Some of the data suggest that a lower curve
might more appropriately reflect current real-world usage, however, EPA
recognizes that PHEV technology has the potential to provide
significant GHG reductions and an overly low FUF curve could
disincentivize manufacturers to apply this technology. In addition,
anticipated longer all-electric range and greater all-electric
performance, partially driven by CARB's ACC II program, as well as
increased consumer technology familiarity and available infrastructure
should result in performance more closely matching our proposed curve.
EPA will continue to monitor real-world data as it becomes available.

[GRAPHIC] [TIFF OMITTED] TP05MY23.016

    We believe that it is important for PHEV compliance utility factors
to accurately reflect the apportionment of charge depleting operation,
for weighting the 2-cycle CO2 test results; therefore, we
are proposing to update the city and highway fleet utility factor
curves with a new, single curve that is shown in Figure 12. We are
proposing a single curve to better reflect real world performance where
the underlying real-world data is not parsed into city and highway
data. Since the fleet average calculations are based on a combined city
and highway CO2 value, a single FUF curve can be used for
these calculations. EPA is requesting comment on whether the ICCT-BAR
curve shown in Figure 13 is a more appropriate fleet utility factor
curve instead of the FUF proposed curve, as shown in the same figure.
    EPA has chosen the proposed FUF curve based on the best data
available. Commentors may have other data sets from PHEV vehicles; EPA
would welcome additional data on real-world PHEV operation, which we
would consider and may use to update the utility factor in a future
rulemaking. The type of data that would be most useful would have
measured mileage in charge depleting range and measured total mileage
for a large number of PHEV vehicles that are nationally representative
and cover a broad range of PHEV models.
ii. Impact on Compliance
    The proposed revisions to the PHEV FUF curve will increase
CO2 compliance values for PHEVs because the charge depleting
test values will be weighted less heavily than they are currently in
compliance calculations. Based on EPA's review of real-world utility
factor data it appears the assumptions in SAE J2841 tend to
overestimate the charge depleting operation of PHEVs. As such, the
Agency is proposing to use the FUF determined from real world data.
This change will result in a reduction to the FUF used to determine
PHEV CO2 compliance values. PHEVs that are designed with a
large charge depleting range would still have a significantly lower
compliance value than their hybrid counterparts would have.
iii. Consideration of CARB ACC II PHEV Provisions
    CARB recently set minimum performance requirements for PHEVs in
their ACC II program. These requirements include performance over the
US06 test cycle and a minimum range and are meant to set qualifications
for PHEV's to be included in a manufacturer's ZEV compliance. EPA is
not proposing to adopt the range and US06 performance requirements or
fleet penetration limits that are included in the CARB ACC II ZEV
provisions. EPA agrees that the performance provisions required by CARB
in ACC II are important real-world performance attributes and have the
ability to provide greater environmental benefits as compared to PHEVs
that are less capable. However, unlike the ACC II program, the GHG
program in this proposal is performance-based and not a ZEV mandate. In
that regard, EPA believes that it is appropriate to have a robust GHG
compliance program for PHEVs that properly accounts for their GHG
emissions independent of a PHEV's range or capability over the US06
test cycle.
9. Small Volume Manufacturer GHG Standards
i. Background
    EPA's light-duty vehicle greenhouse gas (GHG) program for model
years (MYs) 2012-2016 provided a conditional exemption for small volume
manufacturers (SVMs) with annual U.S. sales of less than 5,000 vehicles
due to unique feasibility issues faced by these SVMs.\487\ The
exemption was conditioned on the manufacturer making a good faith
effort to obtain credits from larger volume manufacturers. For the MY
2017-2025 light-duty vehicle GHG program (i.e., the 2012 rule), EPA
adopted specific

regulations allowing SVMs to petition EPA for alternative standards,
again recognizing that the primary program standards may not be
feasible for SVMs and could drive these manufacturers from the U.S.
market.\488\
---------------------------------------------------------------------------

    \487\ 75 FR 25419-25421, May 7, 2010. Note that SVMs are
generally not small businesses that qualify for EPA's small business
provisions discussed in Section III.B.10.
    \488\ 77 FR 62789-62795, October 15, 2012.
---------------------------------------------------------------------------

    EPA acknowledged in the 2012 final rule that SVMs may face a
greater challenge in meeting CO2 standards compared to large
manufacturers because they only produce a few vehicle models, mostly
focused on high performance sports cars and luxury vehicles. SVMs have
limited product lines across which to average emissions, and the few
vehicles they produce often have very high vehicle CO2 g/
mile levels. EPA also noted that the total U.S. annual vehicle sales of
SVMs are much less than 1 percent of total sales of all manufacturers
and contribute minimally to total vehicular GHG emissions, and foregone
GHG reductions from SVMs likewise are a small percentage of total
industry-wide reductions. EPA adopted a regulatory pathway for SVMs to
apply for alternative GHG emissions standards for MYs 2017 and later,
based on information provided by each SVM on factors such as technical
feasibility, cost, and lead time.\489\
---------------------------------------------------------------------------

    \489\ 40 CFR 86.1818-12(g).
---------------------------------------------------------------------------

    The regulations established in the 2012 rule outline eligibility
criteria and a framework for establishing SVM alternative standards.
Manufacturer average annual U.S. sales must remain below 5,000 vehicles
to be eligible for SVM alternative standards.\490\ The regulations
specify the requirements for supporting technical data and information
that a manufacturer must submit to EPA as part of its application.\491\
SVMs may apply for alternative standards for up to five model years at
a time. SVMs may use the averaging, banking, and trading provisions to
meet the alternative standards, but may not trade credits to another
manufacturer.\492\
---------------------------------------------------------------------------

    \490\ 40 CFR 86.1818-12(g)(1).
    \491\ 40 CFR 86.1818-12(g)(4).
    \492\ 40 CFR 86.1818-12(g)(6).
---------------------------------------------------------------------------

    EPA received applications for SVM alternative standards for MYs
2017-2021 from four manufacturers: Aston Martin, Ferrari, Lotus and
McLaren.\493\ The regulations require SVMs to submit information,
including cost information, to EPA as part of their applications. Each
SVM provided its technical basis for the requested standards including
a discussion of technologies that could and could not be feasibly
applied to their vehicles in the time frame of the standards. In 2019,
EPA issued proposed determinations of SVM alternative standards,
including background information and EPA's assessment of the proposed
standards, and requested public comment.\494\ In 2020, EPA finalized
the SVM alternative standard determinations as proposed, shown in Table
37.\495\
---------------------------------------------------------------------------

    \493\ Ferrari was previously owned by Fiat Chrysler Automobiles
(FCA) and petitioned EPA for operationally independent status under
40 CFR 86.1838-01(d). In a separate decision EPA granted this status
to Ferrari starting with the 2012 model year, allowing Ferrari to be
treated as an SVM under EPA's GHG program. Ferrari has since become
an independent company and is no longer owned by FCA.
    \494\ 84 FR 37277.
    \495\ 85 FR 39561 (July 1, 2020). See also docket EPA-HQ-OAR-
2019-0210 for additional information on the SVM alternative
standards setting proceedings.

                             Table 37--Summary of Current SVM Alternative Standards
                                                    [g/mile]
----------------------------------------------------------------------------------------------------------------
                                                   Aston Martin       Ferrari          Lotus          McLaren
----------------------------------------------------------------------------------------------------------------
MY 2017.........................................             431             421             361             372
MY 2018.........................................             396             408             361             372
MY 2019.........................................             380             395             344             368
MY 2020.........................................             374             386             341             360
MY 2021.........................................             376             373             308             329
----------------------------------------------------------------------------------------------------------------

ii. Proposed SVM Standards for MY 2022 and Later
    EPA established the SVM alternative standards option in the 2012
rule when ICE technologies were the primary CO2 control
technologies and vehicle electrification technologies were in their
relative infancy. The landscape has fundamentally changed with
electrification technologies maturing to become significant control
technologies in this proposal. Vehicle electrification technologies are
currently being implemented across many vehicle types including both
luxury and high-performance vehicles by larger manufacturers and EPA
expects this trend to continue. EPA believes that meeting the
CO2 standards is becoming less a feasibility issue and more
a lead time issue for SVMs. Also, the credit trading market has become
more robust since we initially established the SVM unique standards
provisions. Now that it has, we would expect SVMs to be able to seek
credit purchases as a compliance strategy.\496\ As electrification
technologies become more widespread and commonly used, EPA believes
there is no reason SVMs cannot adopt similar technological approaches
with enough lead time (or purchase credits from other OEMs).
---------------------------------------------------------------------------

    \496\ ``The 2022 EPA Automotive Trends Report, Greenhouse Gas
Emissions, Fuel Economy, and Technology since 1975,'' EPA-420-R-22-
029, December 2022.
---------------------------------------------------------------------------

    Given this changed landscape for SVMs, EPA believes it is
appropriate to transition away from unique SVM standards and bring SVMs
into the primary program. As a reasonable way to transition SVMs into
the primary program, EPA is proposing to phase in primary standards
gradually over MYs 2025-2032 resulting in SVMs being ``caught up'' to
the proposed primary program standards by MY 2032.\497\ Specifically,
EPA proposes that SVM alternative standards established for MY 2021
would apply through MY 2024 to provide stability for SVMs so that SVMs
have an opportunity to reduce their GHG emissions in future years. EPA
proposes that starting in MY 2025, SVMs would meet primary program
standards albeit with additional lead-time. As shown in Table 38, EPA
proposes that SVMs would meet the primary program standards for MY 2023
in MY 2025, providing two years of additional lead time. EPA is also
proposing a period of stability rather than year-over-year incremental
reductions in the standards levels for SVMs. SVMs have fewer vehicle
models over which to average, and EPA believes a staggered phase down
in standards with a period of stability between the steps is
reasonable. As shown in Table 38, EPA proposes that the two-year offset
would then continue with a period of stability between step changes

in the standards until SVMs are required to meet the proposed MY 2032
standards in MY 2032. EPA is not reopening the eligibility requirements
for the proposed SVM standards currently in the regulations for SVM
alternative standards and SVMs would need to remain eligible to use
these proposed provisions.\498\
---------------------------------------------------------------------------

    \497\ See 40 CFR 86.1818-12(c) for the primary program standards
through MY 2026.
    \498\ See 40 CFR 86.1818-12(g).

   Table 38--Proposed Additional Lead Time for SVM Standards Under the
                             Primary Program
------------------------------------------------------------------------
                                              Primary
                                              program        Years of
               Model year                 standards that    additional
                                               apply         lead time
------------------------------------------------------------------------
2025....................................            2023               2
2026....................................            2023               3
2027....................................            2025               2
2028....................................            2025               3
2029....................................            2027               2
2030....................................            2028               2
2031....................................            2030               1
2032 and later..........................            2032               0
------------------------------------------------------------------------

    This additional lead time approach is similar to the approach EPA
used in the 2012 rule to provide additional lead time to intermediate
volume manufacturers.\499\ As with the intermediate volume manufacturer
temporary lead time flexibility, EPA believes that the proposed
additional lead time for SVMs will be sufficient to ease the transition
to more stringent standards in the early years of the proposed program
that could otherwise present a difficult hurdle for them to overcome.
The proposed alternative phase-in would provide necessary lead time for
SVMs to better plan and implement the incorporation of CO2
reducing technologies and/or provide time needed to seek and secure
credits from other manufacturers to bring them into compliance with the
primary standards.
---------------------------------------------------------------------------

    \499\ 77 FR 62623 (October 15, 2023) at 62795.
---------------------------------------------------------------------------

    Importantly, SVMs would continue to remain eligible to use the ABT
5-year credit carry-forward provisions, allowing SVMs to bank credits
in these intermediate years to further help smooth the transition from
one step change in the standards to the next. EPA is, however,
proposing to prohibit any SVM opting to use the additional lead time
allowance from trading credits generated under the additional lead time
standards to another manufacturer. These proposed credit provisions are
also currently in place as part of the current SVM alternative
standards. EPA believes that credit banking along with the staggered
phase down of the standards would help SVMs meet the standards,
recognizing that they have limited product lines. As with the SVM
alternative standards, SVMs would have the option of following the
additional lead time pathway with credit trading restrictions or opt
into the primary program with no such restrictions. Once opted into the
primary program, however, manufacturers would no longer be eligible for
the alternative standards.
    EPA requests comment on the proposal to apply the primary program
standards, including the proposed standards, to SVMs with the specified
additional lead time through MY 2032 EPA requests comment on whether
the phase-in appropriately provides additional lead time for SVMs,
including whether SVMs should be brought into the primary program
sooner than proposed.

C. Proposed Criteria and Toxic Pollutant Emissions Standards for Model
Years 2027-2032

    EPA is proposing changes to criteria pollutant emissions standards
for both light-duty vehicles and medium duty vehicles (MDV). Light-duty
vehicles include LDV, LDT, and MDPV. NMOG+NOX changes for
light-duty vehicles include a fleet average that declines from 2027-
2032 in the early compliance program (or steps down in 2030 for GVWR
>6,000 pounds in the default program), the elimination of higher
certification bins, a requirement for the same fleet average emissions
standard to be met across four test cycles (25 [deg]C FTP, HFET, US06,
SC03), a change from fleet average NMHC standards to one fleet average
NMOG+NOX standard in the -7 [deg]C FTP test, and three
NMOG+NOX provisions similar to requirements defined by the
CARB Advanced Clean Cars II program. NMOG+NOX changes for
MDV include a fleet average that declines from 2027-2032 in the early
compliance program (or steps down in 2030 in the default program), the
elimination of higher certification bins, a requirement for the same
fleet average emissions standard to be met across four test cycles (25
[deg]C FTP, HFET, US06, SC03), and a new fleet average
NMOG+NOX standard in the -7 [deg]C FTP. EPA is proposing a
requirement for spark ignition and compression ignition MDV with GCWR
above 22,000 pounds to comply with engine-dynamometer-based criteria
pollutant emissions standards under the heavy-duty engine program \500\
instead of the chassis-dynamometer-based criteria pollutant emissions
standards.
---------------------------------------------------------------------------

    \500\ https://www.epa.gov/regulations-emissions-vehicles-and-engines/final-rule-and-related-materials-control-air-pollution.
---------------------------------------------------------------------------

    EPA is proposing to continue light-duty vehicle and MDV fleet
average FTP NMOG+NOX standards that include both ICE-based
and zero emission vehicles in a manufacturer's compliance calculation.
Performance-based standards that include both ICE and zero emission
vehicles are consistent with the existing NMOG+NOX program
as well as the GHG program. EPA has considered the availability of
battery electric vehicles as a compliance strategy in determining the
appropriate fleet average standards. Given the cost-effectiveness of
BEVs for compliance with both criteria pollutant and GHG standards, EPA
anticipates that most (if not all) automakers will include BEVs in
their compliance strategies. However, the standards continue to be a
performance-based fleet average standard with multiple paths to
compliance, depending on choices manufacturers make about deployment of
a variety of emissions control technologies for ICE as well as
electrification and credit trading.
    EPA is proposing a PM standard of 0.5 mg/mi for light-duty vehicles
and MDV

that must be met across three test cycles (-7 [deg]C FTP, 25 [deg]C
FTP, US06), a requirement for PM certification tests at the test group
level, and a requirement that every in-use vehicle program (IUVP) test
vehicle is tested for PM. The 0.5 mg/mi standard is a per-vehicle cap,
not a fleet average.
    EPA is proposing CO and formaldehyde (HCHO) emissions requirement
changes for light-duty vehicles and MDVs including transitioning to
emissions caps (as opposed to bin-specific standards) for all emissions
standards, a requirement that CO emissions caps be met across four test
cycles (25 [deg]C FTP, HFET, US06, SC03), and a CO emissions cap for
the -7 [deg]C FTP that is the same for all light-duty vehicles and
MDVs.
    EPA is proposing a refueling standards change to require incomplete
MDVs to have the same on-board refueling vapor recovery standards as
complete MDVs. EPA is also proposing eliminating commanded enrichment
as an AECD for power and component protection.
    The proposal allows light-duty vehicle 25 [deg]C FTP
NMOG+NOX credits and -7 [deg]C FTP NMHC credits (converting
to NMOG+NOX credits) to be carried into the new program. It
only allows MDV 25 [deg]C FTP NMOG+NOX credits to be carried
into the new program if a manufacturer selects the early compliance
pathway. New credits may be generated, banked and traded within the new
program to provide manufacturers with flexibilities in developing
compliance strategies.
1. Phase-in of Criteria Pollutant Standards
    The proposed phase-in for criteria pollutant standards, including
NMOG+NOX, PM, CO, HCHO, CARB ACC II NMOG+NOX
provisions, and elimination of enrichment, is described in this
section. Proposed refueling standards for incomplete vehicles begin
with model year 2030 and are not part of the early phase-in scenario
for the other pollutant standards. Table 39 shows eight phase-in
scenarios that manufacturers may choose from. Manufacturers may comply
with phase-in scenarios based on model year (MY) sales or MY U.S.
directed production volume.
    Under the default compliance scenario shown in the bottom matrix in
Table 39, 40 percent of vehicles with gross vehicle weight rating
(GVWR) at or below 6,000 pounds must comply in MY 2027, 80 percent in
MY 2028, and 100 percent in MY 2029 and after. For the heavier vehicle
classes, 100 percent of vehicles must comply starting in MY 2030 in a
single step under the default compliance pathway, which provides a full
four years of lead time as required by CAA section 202(a)(3)(C). Under
this default compliance scenario, chassis cert vehicles between 8501
and 14,000 pounds GVWR may not carry forward Tier 3 NMOG+NOX
credits (as allowed by the early phase-in schedule), and engine cert
vehicles between 8501 and 14,000 pounds GVWR may not use HD phase 2
work factor based GHG standards after 2027 (as allowed by the early
phase-in schedule). Details are provided in Sections III.B.3, III.C.5,
and III.C.9.
    The top matrix in Table 39 describes the phase-in scenario where a
manufacturer chooses an early phase-in schedule for all vehicle
classes. In this scenario 40 percent of the vehicles of each class
(each column) comply in MY 2027, 80 percent comply in MY 2028, and 100
percent comply starting in MY 2029 and after. If a manufacturer chooses
this phase-in scenario, phase-in percentages for vehicles at or below
8500 pounds GVWR are calculated as one group. Chassis cert vehicles
between 8501 and 14,000 pounds GVWR may carry forward Tier 3
NMOG+NOX credits, and engine cert vehicles between 8501 and
14,000 pounds GVWR may use the HD phase 2 work factor based GHG
standards from MY 2026 without a capped GCWR input from MY 2027 to MY
2029. Then in MY 2030 chassis cert vehicles between 8501 and 14,000
pounds GVWR must switch to new work factor based GHG standards with the
capped work factor equation.
    The six phase-in scenarios between default and early show other
options that manufacturers may select from. Any scenario that follows
an early phase-in schedule for vehicles at or below 8500 pounds GVWR,
results in phase-in percentages being calculated as one group. Any
scenario that follows an early phase-in schedule for chassis cert
vehicles between 8501 and 14,000 pounds GVWR may carry forward Tier 3
NMOG+NOX credits. And any scenario that follows an early
phase-in schedule for engine cert vehicles between 8501 and 14,000
pounds GVWR may use the HD phase 2 work factor based GHG standards from
MY 2026 without a capped GCWR input from MY 2027 to MY 2029.
    Vehicles that are not part of the phase-in percentages are
considered interim vehicles, which must continue to demonstrate
compliance with all Tier 3 regulations with the exception that all
vehicles (interim and those that are part of the phase-in percentages)
contribute to the NMOG+NOX fleet average standards shown in
Table 40 and Table 41.
    EPA requests comment on increasing or decreasing the proposed
phase-in percentages shown in Table 39.

               Table 39--Proposed Criteria Pollutant Phase-In Scenarios Available to Manufacturers
----------------------------------------------------------------------------------------------------------------
                                                                              8,501-14,000 lb.  8,501-14,000 lb.
                         Model year                             <=8,500 lb.     GVWR Chassis    GVWR Engine cert
                                                                 GVWR (%)         cert (%)             (%)
----------------------------------------------------------------------------------------------------------------
                          Early phase-in schedule for all vehicle classes (Scenario A)
----------------------------------------------------------------------------------------------------------------
2027........................................................              40                40                40
2028........................................................              80                80                80
2029........................................................             100               100               100
2030+.......................................................             100               100               100
----------------------------------------------------------------------------------------------------------------
                                       Intermediate scenario (Scenario B)
----------------------------------------------------------------------------------------------------------------
2027........................................................              40                 0                40
2028........................................................              80                 0                80
2029........................................................             100                 0               100
2030+.......................................................             100               100               100
----------------------------------------------------------------------------------------------------------------

                                       Intermediate scenario (Scenario C)
----------------------------------------------------------------------------------------------------------------
2027........................................................              40                40                 0
2028........................................................              80                80                 0
2029........................................................             100               100                 0
2030+.......................................................             100               100               100
----------------------------------------------------------------------------------------------------------------
                                       Intermediate scenario (Scenario D)
----------------------------------------------------------------------------------------------------------------
2027........................................................              40                 0                 0
2028........................................................              80                 0                 0
2029........................................................             100                 0                 0
2030+.......................................................             100               100               100
----------------------------------------------------------------------------------------------------------------

                                                                              8,501-14,000 lb.  8,501-14,000 lb.
                 Model year                     <=6,000 lb.   6,001-8500 lb.    GVWR Chassis    GVWR Engine cert
                                                   GVWR          GVWR (%)         cert (%)             (%)
----------------------------------------------------------------------------------------------------------------
                                       Intermediate scenario (Scenario E)
----------------------------------------------------------------------------------------------------------------
2027........................................              40               0                40                40
2028........................................              80               0                80                80
2029........................................             100               0               100               100
2030+.......................................             100             100               100               100
----------------------------------------------------------------------------------------------------------------
                                       Intermediate scenario (Scenario F)
----------------------------------------------------------------------------------------------------------------
2027........................................              40               0                 0                40
2028........................................              80               0                 0                80
2029........................................             100               0                 0               100
2030+.......................................             100             100               100               100
----------------------------------------------------------------------------------------------------------------
                                       Intermediate scenario (Scenario G)
----------------------------------------------------------------------------------------------------------------
2027........................................              40               0                40                 0
2028........................................              80               0                80                 0
2029........................................             100               0               100                 0
2030+.......................................             100             100               100               100
----------------------------------------------------------------------------------------------------------------
                                    Default compliance scenario (Scenario H)
----------------------------------------------------------------------------------------------------------------
2027........................................              40               0                 0                 0
2028........................................              80               0                 0                 0
2029........................................             100               0                 0                 0
2030+.......................................             100             100               100               100
----------------------------------------------------------------------------------------------------------------

2. Proposed NMOG+NOX Standards
    EPA is proposing new NMOG+NOX standards for MY 2027 and
later. The standards are structured to take into account the increased
electrification of new light-duty vehicles and MDVs that is projected
to occur over the next decade.
    The current Tier 3 fleet average NMOG+NOX emissions
standards were fully phased-in for Class 2b and Class 3 (MDV within
this proposal) in MY 2022 at 178 and 247 mg/mi, respectively. Tier 3
standards for light-duty vehicles, including LDT3 and LDT4 above 6,000
pounds GVWR and medium-duty passenger vehicles (MDPVs), will be fully
phased into the Tier 3 30 mg/mi fleet average NMOG+NOX
standard in MY 2025. Tier 3 standards include a Bin 0 which allows
PEV's to be averaged with conventional ICE-based vehicles. In the
absence of our proposed NMOG+NOX standards, as sales of PEVs
continue to increase, there would be an opportunity for the ICE portion
of light-duty vehicles and MDVs to reduce emission control system
content (i.e., system costs) and comply with less stringent
NMOG+NOX standard bins under Tier 3. If this were to occur,
it would have the effect of increasing NMOG+NOX emissions
from the ICE portion of the light-duty vehicle and MDV fleet and delay
the overall fleet emission reductions of NMOG+NOX that would
have occurred from increased penetration of PEVs into the light-duty
vehicle and MDV fleets.
    The structure of the proposed NMOG+NOX standards has
been designed to cap the NMOG+NOX contribution of ICE
vehicles at approximately Tier 3 levels for light-duty vehicles and at
approximately 100 mg/mi NMOG+NOX for MDV. The feasibility of
ICE MDV meeting 100 mg/mi NMOG+NOX by 2027 is discussed in
further detail within Chapter <IP_ADDRESS> of the DRIA. EPA projects the
year-over-year reductions in MY 2027 and later light-duty vehicle and
MDV NMOG+NOX standards from an average of 30 mg/mi and 100
mg/mi,

respectively, thus would occur primarily from increased year-over-year
electrification of new vehicle sales and the resulting averaging of
zero emission vehicles with ICE vehicles within the fleet average
light-duty vehicle and MDV NMOG+NOX standards.
    The CAA requires 4 years of lead time and 3 years of standards
stability for heavy-duty vehicles. There are three categories of
vehicles that are currently regulated as light-duty vehicles but are
defined within the CAA as heavy-duty vehicles for purposes of lead time
and standards stability: The heavy-light-duty truck categories (LDT3
and LDT4) and MDPV.\501\ Furthermore, MDVs are also defined as heavy-
duty vehicles under the CAA. EPA is proposing several alternative
pathways for these three categories of vehicles for compliance with the
proposed NMOG+NOX standards. The Agency's early compliance
NMOG+NOX program would apply to all LDV, LDT, MDPV, and MDV
vehicles beginning in 2027 in order to coincide with the timing of
increased electrification of these vehicles. However, mandatory
regulations beginning in 2027 would not provide 4 years of lead time as
required for vehicles defined as heavy-duty under the CAA. To address
this issue, we are proposing two schedules for compliance with
NMOG+NOX standards for LDT3, LDT4, MDPV, and MDV. The eight
alternatives describe the breadth of compliance scenarios. The two
schedules referenced here include one for early compliance and one for
later compliance for each reg class.
---------------------------------------------------------------------------

    \501\ Light-duty truck 3 (LDT3) is defined as any truck with
more than 6,000 pounds GVWR and with an ALVW of 5,750 pounds or
less. Light-duty truck 4 (LDT4) is defined as any truck is defined
as any truck with more than 6,000 pounds GVWR and with an ALVW of
more than 5,750 pounds. See 40 CFR 86.1803-01--Definitions. For
current and proposed MDPV definitions, see Section III.D.
---------------------------------------------------------------------------

    The early compliance pathway shown in Table 40 has LDT3, LDT4 and
MDPV meeting identical and gradually declining fleet average
NMOG+NOX emissions standards to those for LDV, LDT1 and LDT2
as described in Section III.C.2.iii; and includes separate gradually
declining fleet average NMOG+NOX emissions standards for MDV
at or below 22,000 pounds GCWR as described in Section III.C.2.iv. This
pathway for earlier compliance with NMOG+NOX emissions
standards for LDT3, LDT4, MDPV, and MDV includes additional
flexibilities. We request comment on the addition of a temporary ``bin
200'' (200 mg/mi NMOG+ NOX) that would apply solely to MY
2027 and MY 2028 Class 3 MDV for manufacturers opting into early
compliance for MDV.
    The second, and default, schedule to NMOG+NOX compliance
shown in Table 41 has LDV, LDT1, and LDT2 meeting a gradually declining
fleet average NMOG+NOX standards from 2027 through 2032.
Vehicles in the LDT3, LDT4, and MDPV categories would continue to meet
Tier 3 standards through the end of MY 2029 and then would proceed to
meeting a 12 mg/mi NMOG+NOX standard in a single step in MY
2030 in order to comply with CAA provisions for 4 years of lead time
and 3 years of standards stability. Similarly, MDVs would continue to
meet Tier 3 standards through the end of MY 2029 and then MDVs at or
below 22,000 pounds GCWR would proceed to meeting a 60 mg/mi
NMOG+NOX standard in a single step in 2030 in order to
comply with CAA provisions for 4 years of lead time and 3 years of
standards stability.
    We are also proposing a similar choice between early compliance and
default compliance pathways for MDVs with high GCWR, which are defined
as being above 22,000 pounds. Under the early compliance pathway, high
GCWR MDVs would comply with MY 2027 and later heavy-duty engine
criteria pollutant emissions standards beginning with MY 2027 (Section
III.C.5). Manufacturers with high GCWR MDVs choosing the early
compliance pathway would have additional flexibilities with respect to
GHG compliance. They could delay entry into the MDV GHG work factor-
based fleet average standards until the beginning of MY 2030 (see
Section III.B.3).
    Under the default compliance path, high GCWR MDVs would continue to
comply with Tier 3 standards until the end of MY 2029 and then would
comply with MY 2027 and later heavy-duty engine criteria pollutant
emissions standards beginning with MY 2030 in order to comply with CAA
provisions for 4 years of lead time. Under this default compliance
path, high GCWR MDVs would comply with fleet average MDV GHG emissions
beginning with MY 2027 (see Section III.B.3).

      Table 40--LDV, LDT, MDPV, and MDV Fleet Average NMOG+NOX Standards Under the Early Compliance Pathway
----------------------------------------------------------------------------------------------------------------
                                                             LDV, LDT1, LDT2,      MDV[dagger] NMOG+NOX (mg/mi)
                                                              LDT3[dagger],
                       Model year                             LDT4[dagger] &     -------------------------------
                                                          MDPV[dagger] NMOG+NOX
                                                                 (mg/mi)             Class 2b         Class 3
----------------------------------------------------------------------------------------------------------------
2026...................................................                     * 30           * 178           * 247
2027...................................................                       22             160
2028...................................................                       20             140
2029...................................................                       18             120
2030...................................................                       16             100
2031...................................................                       14              80
2032 and later.........................................                       12              60
----------------------------------------------------------------------------------------------------------------
* Tier 3 standards provided for reference.
[dagger] NMOG+NOX credit generated under Tier 3 can be carried forward for 5 years after it is generated. MDV
  standards only apply for vehicles at or below 22,000 lb. GCWR.

     Table 41--LDV, LDT, MDPV and MDV Fleet Average NMOG+NOX Standards under the Default Compliance Pathway
----------------------------------------------------------------------------------------------------------------
                                                                                MDV[dagger] NMOG+NOX (mg/mi)
                                    LDV, LDT1 & LDT2        LDT3, LDT4 & MDPV
          Model year                NMOG+NOX (mg/mi)         NMOG+NOX (mg/mi)    -------------------------------
                                                                                Class 2b         Class 3
----------------------------------------------------------------------------------------------------------------
2026..........................                     * 30                     * 30           * 178           * 247
2027..........................                       22                     * 30           * 178           * 247
2028..........................                       20                     * 30           * 178           * 247
2029..........................                       18                     * 30           * 178           * 247
2030..........................                       16                       12              60
2031..........................                       14                       12              60
2032 and later................                       12                       12              60
----------------------------------------------------------------------------------------------------------------
* Tier 3 standards provided for reference.
[dagger] MDV standards only apply for vehicles at or below 22,000 lb GCWR.

i. NMOG+NOX Bin Structure for Light-Duty Vehicles and MDVs
    The bin structure being proposed for light-duty vehicles and MDVs
is shown in Table 42. The upper two bins (Bin 160 and Bin 125) are only
available to MDV at or below 22,000 pounds GCWR.\502\
---------------------------------------------------------------------------

    \502\ MDV at or above 22,000 pounds GCWR must comply with 2027
and later heavy-duty engine emissions standards.
---------------------------------------------------------------------------

    For light-duty vehicles, the proposed bin structure removes the two
highest Tier 3 bins (Bin 160 and Bin 125) and adds several new bins
(Bin 60, Bin 40, Bin 10). For MDV, the proposed bin structure moves
away from separate bins for Class 2b and Class 3 vehicles, adopting
light-duty vehicle bins with higher bins only available to MDV.

       Table 42--Light-Duty Vehicle and MDV NMOG+NOX Bin Structure
------------------------------------------------------------------------
                                                           NMOG+NOX (mg/
                         LDV bin                                mi)
------------------------------------------------------------------------
Bin 160 *...............................................             160
Bin 125 *...............................................             125
Bin 70..................................................              70
Bin 60..................................................              60
Bin 50..................................................              50
Bin 40..................................................              40
Bin 30..................................................              30
Bin 20..................................................              20
Bin 10..................................................              10
Bin 0...................................................               0
------------------------------------------------------------------------
* MDV only.

ii. Smog Scores for the Fuel Economy and Environment Label
    This proposed rule includes new Tier 4 bins that do not directly
align with the existing smog scores used on the Fuel Economy and
Environment Label (see 40 CFR 600.311-12(g)). We are therefore seeking
comment on fitting the new Tier 4 bins into the existing MY 2025 Tier 3
smog score structure for the Tier 4 phase-in period (MY 2027-2029), and
we are also seeking comment on a new Tier 4 smog score structure for MY
2030 and later. For both ratings structures, it is important to avoid
having any bin assigned to a higher score in a newer model year than it
was assigned in an older model year (no ``backsliding'' for smog score
ratings).
    For MY 2027-2029, EPA is seeking comment on how the new Tier 4 bins
and California LEV IV categories should fit into the existing Tier 3
bin structure for smog scores. For example, EPA seeks comment on what
smog score should apply to the new Tier 4, bin 10 and new California
LEV IV category of SULEV 15. The current MY 2025 Tier 3 rating system
in Table 1 of 40 CFR 600.311-12(g) has a smog score of 10 for bin 0 and
a score of 7 for bin 20, suggesting that a smog score of 8 might be
appropriate for SULEV 15 and a smog score of 9 might be appropriate for
bin 10; however we may also consider assigning bin 10 and SULEV 15 to
the same rating, either 8 or 9. In addition, EPA is seeking comment on
the smog scores that should apply to Tier 4 bin 60/LEV IV ULEV 60, Tier
4 bin 40/LEV 40, and SULEV 25. We seek comment on assigning bin 60/ULEV
60 a score of 4, sharing a rating with bin 70 ULEV 70; assigning bin
40/ULEV 40 a rating of 5, sharing a rating with bin 50; and assigning
SULEV 25 a rating of 6, sharing a rating with bin 30. These assignments
would allow the MY 2025 Tier 3 ratings to remain in place, while
placing the new Tier 4 bins and LEV IV categories in logical locations.
    For MY 2030 and later, we seek comment on maintaining the smog
rating bin assignments from MY 2027-2029 for bin 40/ULEV 40 and lower
bins. Since there is no longer a need for Tier 3 bin 160 or bin 125
after MY 2029, we seek comment on assigning a smog score of 2 to bin
70/ULEV 70, a score of 3 to bin 60/ULEV 60, and a score of 4 to bin 50/
ULEV 50. This approach allows bin 40 through bin 70 to each correspond
to a single smog score.
    We welcome comment on this approach and after consideration of
comment may adopt final smog scores that are higher or lower.
iii. NMOG+NOX Standards and Test Cycles for Light-Duty
Vehicles
    EPA is proposing increasingly stringent light-duty vehicle
NMOG+NOX standards (Table 43) for the sales weighted average
inclusive of all LDV, LDT and MDPV (e.g. ICE vehicles, BEVs, PHEVs,
fuel cell, vehicles, etc.). The proposed phase-in of the standards by
vehicle category is described in Section III.C.1.
    EPA recognizes that vehicles will differ with respect to their
levels of NMOG+NOX emissions control depending on degree of
electrification, choice of fuel, ICE technology, and other differences.
The proposed fleet average standards are feasible in light of
anticipated technology penetration rates commensurate with the GHG
technology implementation during this same time period and increasing
electrification of light-duty vehicles.

  Table 43--NMOG+NOX Fleet Average Standards Over the FTP [dagger] for
                          Light-Duty Vehicles *
------------------------------------------------------------------------
                                                           NMOG+NOX (mg/
                       Model year                               mi)
------------------------------------------------------------------------
2027....................................................              22
2028....................................................              20
2029....................................................              18
2030....................................................              16
2031....................................................              14
2032 and later..........................................              12
------------------------------------------------------------------------
[dagger] As defined in 40 CFR 1066.801(c)(1)(i) and 1066.815.
* For a complete description of fleet average NMOG+NOX standards for
  LDT3, LDT4, and MDPV under both the early compliance and default
  programs, see Section III.C.1.

    The declining fleet average standards over the FTP cycle ensure
that NMOG+NOX continues to decrease over time for the light-
duty fleet. The

elimination of the two highest bins (Table 42) caps the maximum
NMOG+NOX emissions from an individual new vehicle model. EPA
anticipates that electrified technology, including BEVs, will play a
significant role within the compliance strategies for meeting the fleet
average NMOG+NOX standards for each manufacturer. However,
EPA anticipates that manufacturers may use multiple technology
solutions to comply with fleet average NMOG+NOX standards.
For example, a manufacturer may choose to offset any ICE increases with
increased BEV sales, or could alternatively improve engine and exhaust
aftertreatment designs to reduce emissions for ICE vehicles while
planning for a more conservative percentage of BEV sales as part of
their compliance with the declining fleet average NMOG+NOX
standards reflected in Table 43.
    Since technologies are available to further reduce
NMOG+NOX emissions relative to the current fleet, and since
more than 20 percent of MY 2021 Bin 30 vehicle certifications already
show an FTP certification value under 15 mg/mi NMOG+NOX,
achieving reduced NMOG+NOX emissions through improved ICE
technologies is feasible and reasonable. Regardless of the compliance
strategy chosen, overall, the fleet will become significantly cleaner.
    EPA is proposing that the same bin-specific numerical standards be
applied across four test cycles: 25 [deg]C FTP,\503\ HFET,\504\ US06
\505\ and SC03.\506\ This means that a manufacturer certifying a
vehicle to comply with Bin 30 NMOG+NOX standards would be
required to meet the Bin 30 emissions standards for all four test
cycles. Meeting the same NMOG+NOX standards across four
cycles is an increase in stringency from Tier 3, which had one standard
for the higher of FTP and HFET, and a less stringent composite based
standard for the SFTP (weighted average of 0.35*FTP + 0.28*US06 +
0.37*SC03).
---------------------------------------------------------------------------

    \503\ 40 CFR 1066.801(c)(1)(i) and 1066.815.
    \504\ 40 CFR 1066.840.
    \505\ 40 CFR 1066.831.
    \506\ 40 CFR 1066.835.
---------------------------------------------------------------------------

    Present-day engine, transmission, and exhaust aftertreatment
control technologies allow closed-loop air-to-fuel (A/F) ratio control
and good exhaust catalyst performance throughout the US06 and SC03
cycles. As a result, higher emissions standards over these cycles are
no longer necessary. Approximately 60 percent of the test group/vehicle
model certifications from MY 2021 have higher NMOG+NOX
emissions over the FTP cycle as compared to the US06 cycle, supporting
the conclusion that a single standard is feasible and appropriate.
    EPA is proposing to replace the existing -7 [deg]C FTP NMHC fleet
average standard of 300 mg/mi for passenger cars and LDT1, and 500 mg/
mi fleet average standard for LDT2 through LDT4 and MDPV, with a single
NMOG+NOX fleet average standard of 300 mg/mi for LDV, LDT1
through 4 and MDPVs to harmonize with the combined NMOG+NOX
approach adopted in Tier 3 for all other cycles (i.e., 25 [deg]C FTP,
HFET, US06, and SC03 cycles). EPA emissions testing at -7 [deg]C FTP
showed that a 300 mg/mi standard is feasible with a large compliance
margin for NMOG+NOX. See DRIA for additional certification
data to support the proposed fleet average NMOG+NOX standard
of 300 mg/mi. EPA did not include EVs in the assessment of the proposed
fleet average standard and therefore EVs and other zero emission
vehicles are not included and not averaged into the fleet average -7
[deg]C FTP NMOG+NOX standards.
    Since -7 [deg]C FTP and 25 [deg]C FTP are both cold soak tests that
include TWC operation during light-off and at operating temperature, it
is appropriate to apply the same Tier 3 useful life to both standards.
    EPA requests comment on whether a 400 mg/mi cap should replace the
proposed 300 mg/mi fleet average for the -7 [deg]C FTP
NMOG+NOX standard. Additional discussion on the feasibility
of the proposed standards can be found in DRIA Chapter 3.2.
    The proposed standards apply equally at high altitude, rather than
including compliance relief provisions from Tier 3 for certification at
high altitude. Modern engine management systems can use idle speed,
engine spark timing, valve timing, and other controls to offset the
effect of lower air density on exhaust catalyst performance at high
altitudes.
iv. NMOG+NOX Standards and Test Cycles for MDV at or Below
22,000 lb GCWR
    The proposed MDV (medium duty vehicles, 8,501 to 14,000 pounds
GVWR) NMOG+NOX standards for vehicles at or below 22,000
pounds GCWR are shown in Table 44. Certification data show that for MY
2022-2023, 75 percent of sales-weighted Class 2b/3 gasoline vehicle
certifications were below 120 mg/mi in FTP and US06 tests. Diesel-
powered MDVs designed for high towing capability (i.e., GCWR above
22,000 pounds) were higher (75 percent were below 180 mg/mi) but they
are not being used to inform the proposed MDV standard because the
Agency is proposing the requirement that MDVs (diesel and gasoline)
with GCWR (gross combined weight rating) above 22,000 pounds comply
with criteria pollutant emissions standards under the HD engine
program, as described in Section I.A.1, MDVs at or below 22,000 pounds
GCWR have comparable emissions performance to LDVs and LDTs. The year-
over-year fleet average FTP standards for MDV at or below 22,000 pounds
GCWR and the rationale for the manufacturer's choice of early
compliance and default compliance pathways is described in Section
III.C.1. For further discussion of MDV NMOG+NOX feasibility,
please refer to Chapter 3.2 of the DRIA.
    The proposed MDV NMOG+NOX standards are based on
applying existing light-duty vehicle technologies, including
electrification, to MDV. As with the light-duty vehicle categories, EPA
anticipates that there will be multiple compliance pathways, such as
increased electrification of vans together with achieving 100 mg/mile
NMOG+NOX for ICE-power MDV. Present-day MDV engine and
aftertreatment technology allows fast catalyst light-off after cold-
start followed by closed-loop A/F control and excellent exhaust
catalyst emission control on MDV, even at the adjusted loaded vehicle
weight, ALVW [(curb + GVWR)/2] test weight, which is higher than loaded
vehicle weight, LVW (curb + 300 pounds) used for testing light-duty
vehicles. The proposed MDV standards begin to take effect in 2030,
consistent with the CAA section 202(a)(3)(C) lead time requirement for
these vehicles.

     Table 44--MDV Fleet Average NMOG+NOX Standards Under the Early
                       Compliance Pathway [dagger]
------------------------------------------------------------------------
                                                 NMOG+NOX (mg/mi)
               Model year                -------------------------------
                                             Class 2b         Class 3
------------------------------------------------------------------------
2026....................................           * 178           * 247
2027....................................             160
2028....................................             140
2029....................................             120
2030....................................             100
2031....................................              80
2032 and later..........................              60
------------------------------------------------------------------------
[dagger] Please refer to Section III.C.1 for further discussion of the
  early compliance and default compliance pathways.
* Tier 3 standards provided for reference.

 Table 45--MDV Fleet Average Chassis Dynamometer FTP NMOG+NOX Standards
                  Under the Default Compliance Pathway
------------------------------------------------------------------------
                                           MDV [dagger] NMOG+NOX (mg/mi)

               Model year                -------------------------------
                                             Class 2b         Class 3
------------------------------------------------------------------------
2026....................................           * 178           * 247
2027....................................           * 178          * 247;
2028....................................           * 178           * 247
2029....................................           * 178           * 247
2030....................................              60
2031....................................              60
2032 and later..........................              60
------------------------------------------------------------------------
* Tier 3 standards provided for reference.
[dagger] MDV chassis dynamometer NMOG+NOX standards only apply for
  vehicles at or below 22,000 lb GCWR.

    If a manufacturer has a fleet mix with relatively high sales of MDV
BEV, that would ease compliance with MDV NMOG+NOX fleet
average standards for MDV ICE-powered vehicles. If the manufacturer has
a fleet mix with relatively low BEV sales, then improvements in
NMOG+NOX emissions control for ICE-powered vehicles would be
required to meet the fleet average standards. Improvements to
NMOG+NOX emissions from ICE-powered vehicles are feasible
with available engine, aftertreatment, and sensor technology, and has
been shown within an analysis of MY 2022-2023 MDV certification data
(see DRIA Chapter 3.2). Fleet average NMOG+NOX will continue
to decline to well below the final Tier 3 NMOG+NOX standards
of 178 mg/mi and 247 mg/mi for Class 2b and 3 vehicles, respectively.
    The proposed standards require the same MDV numerical standards be
met across all four test cycles, the 25 [deg]C FTP, HFET, US06 and
SC03, consistent with the proposed approach for light-duty vehicles
described in Section III.C.1.ii. This would mean that a manufacturer
certifying a vehicle to bin 60 would be required to meet the bin 60
emissions standards for all four cycles.
    Meeting the same NMOG+NOX standard across four cycles is
an increase in stringency from Tier 3, which had one standard over the
FTP and less stringent bin standards for the HD-SFTP (weighted average
of 0.35xFTP + 0.28xHDSIM + 0.37xSC03, where HDSIM is the driving
schedule specified in 40 CFR 86.1816-18(b)(1)(ii)). Current MDV control
technologies allow closed-loop A/F control and high exhaust catalyst
emissions conversion throughout the US06 and SC03 cycles, so compliance
with higher numerical emissions standards over these cycles is no
longer needed. Manufacturer submitted certification data and EPA
testing show that Tier 3 MDV typically have similar NMOG+NOX
emissions in US06 and 25 [deg]C FTP cycles, and NMOG+NOX
from the SC03 is typically much lower. Testing of a 2022 F250 7.3L at
EPA showed average NMOG+NOX emissions of 56 mg/mi in the 25
[deg]C FTP and 48 mg/mi in the US06. Manufacturer-submitted
certifications show that MY 2021+2022 gasoline 2b/3 trucks achieved, on
average, 69/87 mg/mi in the FTP, and 75/NA \507\ mg/mi in the US06, and
18/25 mg/mi in the SC03.
---------------------------------------------------------------------------

    \507\ Tier 3 US06 certification data are not available for class
3 trucks because Tier 3 requires them to certify using the LA92
instead of the US06.
---------------------------------------------------------------------------

    Several Tier 3 provisions would end with the elimination of the HD-
SFTP and the combining of bins for Class 2b and class 3 vehicles.
First, Class 2b vehicles with power-to-weight ratios at or below 0.024
hp/pound could no longer replace the full US06 component of the SFTP
with the second of three sampling bags from the US06. Second, class 3
vehicles would no longer use the LA-92 cycle in the HD-SFTP calculation
but would rather have to meet the NMOG+NOX standard in each
of four test cycles (25 [deg]C FTP, HFET, US06 and SC03). Third, the
SC03 could no longer be replaced with the FTP in the SFTP calculation.
    The proposed standards do not include relief provisions for MDV
certification at high altitude. Modern engine systems can use idle
speed, engine spark timing, valve timing, and other controls to offset
the effect of lower air density on catalyst light-off at high
altitudes.
    EPA is also proposing a new -7 [deg]C FTP NMOG+NOX fleet
average standard of 300 mg/mi for gasoline and diesel MDV. EPA testing
has demonstrated the feasibility of a single fleet average -7 [deg]C
FTP NMOG+NOX standard of 300 mg/mi across light-duty
vehicles and MDV. EPA did not include EV's in the assessment of the
proposed fleet average standard and therefore EVs and other zero
emission vehicles are not included and not averaged into the fleet
average -7 [deg]C FTP NMOG+NOX standards.

    Since -7 [deg]C FTP and 25 [deg]C FTP are both cold soak tests that
include TWC operation during light-off and at operating temperature, it
is appropriate to apply the same Tier 3 useful life to both standards.
    EPA requests comment on whether a 400 mg/mi cap should replace the
proposed 300 mg/mi fleet average for the -7 [deg]C FTP
NMOG+NOX standard. Additional discussion on the feasibility
of the proposed standards can be found in DRIA 3.2.
3. Revised PM Standard
i. PM Standard and Test Cycles for Light-Duty Vehicles and MDV
    EPA is proposing several changes to the current Tier 3 p.m.
requirements. These changes include a more stringent standard for the
25 [deg]C FTP and US06 test cycles, and addition of a cold PM standard
for the existing Cold Test (-7 [deg]C FTP). The same numerical standard
of 0.5 mg/mi and the same certification test cycles are being proposed
for both light-duty vehicles (LDV, LDT, and MDPV) and MDV (Class 2b and
3 vehicles) at or below 22,000 pounds GCWR, as shown in Table 46 for
light-duty vehicles and Table 47 for MDV. Comparisons to current Tier 3
p.m. standards are provided for reference. The same Tier 3 defined
useful life standard applies to all three test cycles.

           Table 46--Proposed Light-Duty Vehicle PM Standards
------------------------------------------------------------------------
                                                            Proposed PM
           Test cycle              Tier 3 standards (mg/   standard (mg/
                                            mi)                 mi)
------------------------------------------------------------------------
25 [deg]C FTP...................  3.....................             0.5
US06............................  6.....................             0.5
-7 [deg]C FTP...................  Not applicable........             0.5
------------------------------------------------------------------------

                 Table 47--Proposed MDV (Class 2b and 3) at or Below 22,000 lb GCWR PM Standards
----------------------------------------------------------------------------------------------------------------
                                                                                Proposed PM
                Test cycle                                Tier 3 standards (mg/mi)                 standard (mg/
                                                                                mi)
----------------------------------------------------------------------------------------------------------------
25 [deg]C FTP.............................  8/10 for 2b/3 vehicles..............................             0.5
US06......................................  10/7 for 2b/3 vehicle on SFTP.......................             0.5
-7 [deg]C FTP.............................  Not applicable......................................             0.5
----------------------------------------------------------------------------------------------------------------

    EPA believes that these standards are appropriate and feasible to
reduce PM emissions over the broadest range of vehicle operating and
environmental conditions. The current Tier 3 p.m. standards capture
only a portion of vehicle operation. EPA has observed that PM emissions
increase dramatically during cold cold-starts and during high engine
power driving not captured by on-cycle tests. While several vehicles in
the current fleet demonstrate emissions performance that could comply
with the proposed standards at 25 [deg]C, the -7 [deg]C PM standard
will most likely lead to the adoption of Gasoline Particulate Filters
(GPF) as the most practical and cost-effective means to control PM
emissions. GPF is a mature and cost-effective technology that operates
under all vehicle operating conditions. Current GPF technology (e.g.,
MY 2022 GPFs) has high filtration efficiency, even during and
immediately after GPF regenerations, when the GPF cannot rely on soot
loading to improve filtration. GPFs are being widely used in Europe and
China and vehicle manufacturers are already building GPF-equipped
vehicles in the United States for sale in other countries.
    In support of the proposed PM standards, EPA has conducted robust
and detailed GPF testing to characterize GPF performance. During this
testing EPA not only measured the change in PM and polyaromatic
hydrocarbon (PAH) emissions, with and without the GPF installed, but
also assessed impacts on GHG emissions and vehicle performance. In
summary, EPA noted that with a properly sized GPF, no measurable impact
on GHG emissions and only slight impact on vehicle performance should
occur, while PM emissions are typically reduced by over 95 percent and
filter-collected PAH emissions are typically reduced by over 99
percent. A review of GPF technology, analyses of its benefits,
challenges and costs, and demonstration of the feasibility of the
proposed PM standard are discussed in Chapter 3.2 of the DRIA.
ii. Phase-In for Light-Duty Vehicles and MDV at or Below 22,000 lb GCWR
    The proposed phase-in for the PM standard is the same as for other
criteria emissions, as described in Section III.C.1. EPA requests
comment on accelerating the phase-in for PM relative to other criteria
emissions requirements of this rule (NMOG+NOX, CO, HCHO,
NMOG+NOX previsions aligned with the CARB ACC II program,
certifying high GCWR MDV under the HD engine program for criteria
pollutants, evaporative emissions, and elimination of enrichment)
because GPFs are a mature technology that has been in mass production
since 2017 in Europe, since 2020 in China, and since 2023 in India, and
because several manufacturers assemble vehicles equipped with GPF in
the U.S. for export to other markets. An accelerated phase-in could
also be supported by increased availability of BEVs. EPA requests
comment on accelerating PM phase-in to 50% or 80% in MY 2027 and 100%
in MY 2028 for vehicles with GVWR<=14,000 pounds under the early
compliance pathway, and for vehicles with GVWR<=6000 pounds under the
default compliance pathway.
iii. Feasibility of the PM Standard and Selection of Test Cycles
    The PM standards that EPA is proposing would require vehicle
manufacturers to produce vehicles that emit PM at GPF-equipped levels
(GPF-level PM). The proposed rule does not require that GPF hardware be
used on vehicles, but rather reflects EPA's judgement that it is
feasible and appropriate to achieve the proposed PM standards
considering the availability of this technology. It is expected that
GPF technology will be the most practical and cost-effective pathway
for meeting the standard, especially in -7 [deg]C FTP and US06 test
cycles.

    To establish what level of PM standards are appropriate for this
proposal, EPA conducted a test program that considered multiple vehicle
types and powertrain technologies as well as GPF technology. Much like
many other aspects of aftertreatment technology and emissions controls,
GPFs have gone through considerable development since their initial
introduction and as a result have provided significantly improved
effectiveness with each successive iteration. EPA evaluated available
technology with respect to the emissions benefits observed over the
regulated cycles, including two generations of GPF technology.
    The PM test program included five chassis dynamometer test cells at
EPA, Environment and Climate Change Canada (ECCC), and FEV North
America Inc., and five test vehicles (2011 F150, 2019 F150, 2021 F150
HEV, 2021 Corolla, 2022 F250) tested in stock and GPF configurations.
These test vehicles include a passenger car, three Class 2a trucks, and
one Class 2b truck. The two generations of GPFs include series
production MY 2019 and series production MY 2022 models, catalyzed and
bare substrates, and close-coupled and underfloor GPF installations.
Results from the test program are summarized in Figure 14. The study
demonstrates that Tier 3 light-duty vehicles and MDV equipped with GPFs
that are currently in series production in Europe and China (i.e., MY
2022 GPF) can easily meet the proposed standard of 0.5 mg/mi in all
three test cycles with a large compliance margin.
    In Figure 14, tests without GPFs are shown in black, tests with MY
2019 GPFs are shown in gray, and tests performed with MY 2022 GPFs are
shown in stripes. The top of each bar represents the highest
measurement set mean of one vehicle in one laboratory and the bottom of
each bar represents the lowest measurement set mean. The tops of the
black bars are off scale in this figure, but their values are indicated
with numbers above the bars.
    The striped bars include PM measurements from two vehicles: A 2021
F150 HEV (Class 2a vehicle) retrofit with a MY 2022 bare GPF in the
underfloor location, and a 2022 F250 7.3L (Class 2b vehicle) retrofit
with two MY 2022 bare GPFs, one for each engine bank, in the underfloor
location.
    Results show that only the GPF-equipped vehicles could meet the 0.5
mg/mi proposed standard in the -7 [deg]C FTP test. The MY 2019 GPFs
failed to meet the proposed standard in the US06 because passive GPF
regeneration occurred as a result of high exhaust gas temperatures (GPF
inlet gas temperature greater than 600 [deg]C). GPF regeneration
oxidizes stored soot and reduces GPF filtration efficiency during and
immediately after the regeneration. Vehicles equipped with MY 2022 GPFs
met the 0.5 mg/mi standard in all three test cycles with a compliance
margin of 100 percent or more. The MY 2022 GPFs showed high filtration
efficiencies generally over 95 percent, even in the US06 cycle because
they did not rely on stored soot for high filtration efficiency. The
mean of test sets with MY 2022 GPF are over 95 percent lower than the
mean of non-GPF test sets in each of the three test cycles.
    The data show that MY 2022 GPFs are capable of emissions
performance commensurate with EPA's goal of requiring GPF-level
emissions over the broadest range of vehicle operating and
environmental conditions. The results support the conclusion that a 0.5
mg/mi PM standard over the -7 [deg]C FTP, 25 [deg]C FTP, and US06 test
cycles is feasible and appropriate.
    The -7 [deg]C FTP test cycle is crucial to the proposed PM standard
because it differentiates vehicles with GPF-level PM from vehicles with
Tier 3 levels of PM, and because -7 [deg]C is an important real-world
temperature that addresses uncontrolled cold PM emissions in Tier 3.
    The US06 cycle is similarly crucial to the proposed PM standard
because it induces passive GPF regeneration across vehicle-GPF
combinations (i.e., light-duty vehicles and MDV, naturally aspirated
and turbocharged engines, close-coupled and underfloor GPF
installations, bare and catalyzed GPFs), and GPF regeneration is an
important mode of operation with respect to emissions. GPF regeneration
does not occur in the -7 [deg]C FTP, 25 [deg]C FTP, and LA-92 across
vehicle and exhaust system combinations. Including a certification test
in which passive GPF regeneration occurs is important because it
ensures low tailpipe PM during and immediately after GPF regenerations,
which occur during high load operation, including road grades, towing,
and driving at higher speeds.
    Older GPF technology does not exhibit high PM filtration during and
immediately after GPF regeneration. Older GPF technology can have
filtration efficiency as low as 50 percent, as opposed to generally
more than 95 percent demonstrated by the MY 2022 GPFs shown in Figure
14. Without the US06 test cycle, manufacturers could employ old GPF
technology that has poor PM control during high load operation. Average
US06 p.m. from the MY 2019 GPFs is 15 times higher than average US06
p.m. from the MY 2022 GPFs from the data shown in Figure 14.
BILLING CODE 6560-50-P

[GRAPHIC] [TIFF OMITTED] TP05MY23.017

BILLING CODE 6560-50-C
    MDVs are certified at higher test weights and road load
coefficients than light-duty vehicles, but measurements show that
series production MY 2022 GPF technology enables meeting the proposed
0.5 mg/mi standard equally well on MDV as light-duty vehicles, with
compliance margins of over 100 percent. Measurements comparing PM from
a Class 2b vehicle with a current technology GPF (MDV MY 2022 F250 with
a MY 2022 GPF), to a Class 2a vehicle with a current technology GPF
(LDV MY 2021 F150 HEV with a MY 2022 GPF) are shown in Figure 15.
Additional testing supports the same conclusion for Class 3 vehicles.

[GRAPHIC] [TIFF OMITTED] TP05MY23.018

    As was the case for light-duty vehicles, the -7 [deg]C FTP cycle is
crucial because it differentiates Tier 3 levels of PM from GPF-level PM
and because -7 [deg]C is an important real-world temperature that
addresses uncontrolled cold PM emissions in Tier 3. Furthermore, as was
the case for light-duty vehicles, the US06 cycle is crucial to the
proposed PM standard for MDV because the US06 induces passive GPF
regeneration across different vehicle-GPF combinations and GPF
regeneration is an important mode of operation with respect to
emissions. The LA-92, which was used instead of the US06 cycle on Class
3 vehicles in Tier 3, does not induce GPF regeneration, and for this
reason the US06 cycle is required for all light-duty vehicles and MDV
in the proposed standard.
    GPF inlet gas temperatures measured on the MY 2022 F250 7.3L during
sampled US06, sampled hot LA-92, and -7 [deg]C FTP operation, are shown
in Figure 16. Fast soot oxidation begins in a GPF around 600
[deg]C.\508\ The US06 is the only cycle where GPF inlet gas temperature
of the MY 2022 F250 exceeded 600 [deg]C and it exceeded it for a
significant amount of time (265 seconds), resulting in passive GPF
regeneration. Peak inlet gas temperature was 674 [deg]C in the US06. In
contrast, GPF inlet gas temperature never exceeded 600 [deg]C in the
LA-92 and only exceeded 500 [deg]C for a limited period of time. Peak
GPF inlet gas temperature in the LA-92 (566 [deg]C) was closer to the -
7 [deg]C FTP (493 [deg]C) than the US06 (674 [deg]C).
---------------------------------------------------------------------------

    \508\ Achleitner, E., Frenzel, H., Grimm, J., Maiwald, O.,
R[ouml]sel, G., Senft, P., Zhang, H., ``System approach for a
vehicle with gasoline direct injection and particulate filter for
RDE,'' 39th International Vienna Motor Symposium, Vienna, April 26-
27, 2018.
---------------------------------------------------------------------------

    In this vehicle configuration, GPF regeneration does not occur in
LA-92, 25 [deg]C FTP, or -7 [deg]C FTP cycles to a significant degree,
which makes those cycles unable to force PM emissions control
commensurate with MY 2022 GPF technology. Additional tests performed
with the MY 2022 F250 with MY 2022 GPFs using test weight and road load
coefficients from a MY 2022 F350 Class 3 vehicle show that even with
the higher test weight and road load, the GPFs did not undergo
substantial regeneration in the LA-92 cycle. Without requiring the US06
as a certification cycle for MDV, the GPF may not undergo GPF
regeneration and high PM filtration, which new GPF technology offers,
would not be ensured during high load operation, including trailer
towing, road grades, or high speeds, for which these vehicles are
designed.

[GRAPHIC] [TIFF OMITTED] TP05MY23.019

    Under the proposed standards, Class 2b vehicles with power-to-
weight ratios at or below 0.024 hp/pound could no longer replace the
full US06 component of the SFTP with the second of three phases of the
US06 for their PM certification. If a test vehicle is unable to follow
the trace, it must perform maximum effort to follow the trace, and that
would not result in a voided test. This procedure mimics how vehicles
with low power-to-weight tend to be driven in the real world.
    Also, Class 3 vehicles would not use the LA-92 for PM
certification, as they did in Tier 3. Instead, Class 3 vehicles would
have to meet the 0.5 mg/mi PM standard across the same three test
cycles as light-duty vehicles and other MDV: -7 [deg]C FTP, 25 [deg]C
FTP, and US06.
    GPF technology is both mature and cost effective. It has been used
in series production on all new pure gasoline direct injection (GDI)
vehicle models in Europe since 2017 (WLTC and RDE test cycles) and on
all pure GDI vehicles in Europe since first registration of 2019 (WLTC
and RDE test cycles) to meet Europe's emissions standards. All gasoline
vehicles in China have had to meet similar standards in the WLTC since
2020, and in the WLTC and RDE starting in 2023. All pure GDI vehicles
in India also have to meet similar GPF-forcing standards starting in
2023. GPFs like the MY 2022 GPFs described by Figure 14 and Figure 15
are being used in series production by U.S., European, and Asian
manufacturers, and several manufacturers currently assemble vehicles
equipped with GPF in the U.S. for export to other markets.
    Further details and discussion of test vehicles, GPFs, test
procedures, and results are provided in the DRIA 3.2.
iv. PM Measurement Considerations
    Current test procedures, as outlined in 40 CFR part 1066, allow
robust gravimetric PM measurements well below the proposed PM standard
of 0.5 mg/mi. Repeat measurements in EPA laboratories, at different
levels of PM below 0.5 mg/mi, are shown in Figure 17. The size of the
error bars relative to the measurement averages at and below 0.5 mg/mi
demonstrates that the measurement methodology is sufficiently precise
to support a 0.5 mg/mi standard. Other than selecting test settings
appropriate for quantifying low PM, no test procedure changes are
needed. Good engineering judgment should be used with respect to
dilution factor, filter media selection, filter flow rate, using a
single filter for all phases of a test cycle, filter static charge
removal, robotic weighing, and minimizing contamination during filter
handling. EPA is not reopening the test procedures, nor does the agency
believe that test procedure changes are required, to measure PM for the
proposed PM standards. Further discussion of selecting test settings is
discussed in the DRIA.

[GRAPHIC] [TIFF OMITTED] TP05MY23.020

v. Pre-Production Certification
    EPA is proposing that PM emissions be certified over -7 [deg]C FTP,
25 [deg]C FTP, and US06 cycles with at least one Emissions Data Vehicle
(EDV) per test group in model years 2027, 2028, and 2029+ for light-
duty vehicles and MDV compliant with the new 0.5 mg/mi standard in the
early compliance program. In the default program, PM emissions would be
certified with at least one EDV per test group in model years 2027,
2028, and 2029+ for light-duty vehicles compliant with the new
standard, and with at least one EDV per test group in 2030+ for MDV
compliant with the new standard. See 40 CFR 86.1829-15. This level of
certification testing matches the requirement to certify gaseous
criteria emissions at the test group level and ensures that the
significantly lower PM emissions standard of 0.5 mg/mi is being met
across a wide range of ICE technologies. The requirement to certify PM
emissions at the test group level is an increase in testing
requirements relative to Tier 3, where PM emissions could be certified
at the durability group level. The increase in testing requirement is
tempered by the phase-in of the PM standard described in Table 39, and
since BEVs do not require testing.
    EPA solicits comment on whether pre-production PM certification
should go back to testing at the durability group level in 2030 for
light-duty vehicles and in 2031 for MDV after PM control technologies
have been demonstrated across a range of ICE technologies. If PM
certification were to go back to testing at the durability level in
2030/2031, manufacturers would still have to attest that the 0.5 mg/mi
standard is being met by all test groups.
    EPA is proposing to update the instructions to select a worst-case
test vehicle from each test group by considering -7 [deg]C FTP testing
with all the other criteria standards. This contrasts with the current
approach, in which manufacturers select worst-case test vehicles
separate from -7 [deg]C FTP testing and then select a test vehicle for
-7 [deg]C FTP testing from those test vehicles included in the same
durability group. The current approach is appropriate for measuring CO
and NMHC for -7 [deg]C FTP testing. However, the concern for PM
emissions with -7 [deg]C FTP testing are on par with concern for the
other standards already considered for selecting a worst-case test
vehicle to represent the test group. EPA requests comments on different
approaches for selecting test vehicles to most effectively apply test
resources to ensure compliance with the range of emission standards.
vi. In-Use Compliance Testing
    In addition to pre-production certification, the proposed PM
standard requires in-use compliance testing as part of the in-use
vehicle program (IUVP). The proposed PM standard requires that PM from
each in-use test vehicle be tested using 25 [deg]C FTP and US06 cycles
and meet the 0.5 mg/mi PM standard. In-use vehicles are also required
to comply with the -7 [deg]C FTP standard, but manufacturers are not
required to test using this cycle to reduce testing burden. EPA may
test in-use vehicles using -7 [deg]C FTP, 25 [deg]C FTP, and US06
cycles to ensure compliance. Given the certification test demonstration
for meeting the -7 [deg]C FTP PM standard, along with expected IUVP
testing over 25 [deg]C FTP and US06 cycles and the potential for EPA
testing, we find that there is not enough justification to require the
additional test burden associated with IUVP testing for PM emissions
over the -7 [deg]C FTP cycle.
vii. OBD Monitoring
    Since GPF technology is expected to be an important enabler for
meeting the proposed PM standard, OBD monitoring of the GPF system is
necessary. If a vehicle uses a GPF, the OBD system must detect GPF-
related malfunctions, store trouble codes related to detected
malfunctions, and alert operators appropriately.
    It is expected that the OBD system detect system tampering and
major malfunctions using, for example, using a pressure sensor. The
same pressure

sensor that senses GPF soot overloading may be used to detect system
tampering and major malfunctions. It is expected that if a pressure
sensor is used for OBD functions, it should detect a GPF pressure drop
greater than zero and less than an expected maximum as a function of
engine operating point. Further OBD discussion is provided in Section
III.G.
viii. GPF Cost
    A GPF cost model is described in DRIA Chapter 3.2 and GPF cost is
included in the OMEGA model. The model anticipates the direct
manufacturing cost (DMC) for a bare downstream GPF ranges from $51
dollars for a 1.0-liter engine using a relatively low GPF volume to
engine displacement ratio, up to $166 dollars for a 7.0 liter engine
using a relatively high GPF volume to engine displacement ratio.
4. Revised CO and Formaldehyde (HCHO) Standards
i. CO and HCHO Standards for Light-Duty Vehicles
    EPA is proposing CO and formaldehyde (HCHO) emissions caps for
light-duty vehicles shown in Table 48. The proposed value of the CO
emissions cap for the 25 [deg]C FTP, HFET, US06, SC03 test cycles, 1.7
g/mi, is the same as the Tier 3 bin-specific standards for Bin 50 and
Bin 70, but it must be met across four cycles instead of the Tier 3
cycles of 25 [deg]C FTP and a separate standard for the SFTP.
    The proposed value of the HCHO emissions cap, 4 mg/mi, is the same
as the Tier 3 bin-specific standards for Bin 20 through Bin 160. The
HCHO cap only applies to the 25 [deg]C FTP, as in Tier 3.
    The proposed CO emissions cap for the -7 [deg]C FTP is 10.0 g/mi.
This differs from the current standards in that the same cap applies to
all light-duty vehicles. The current CO cap is 10.0 g/mi for LDV and
LDT1, and 12.5 g/mi for LDT2, LDT3, LDT4, and MDPV.

         Table 48--Light-Duty Vehicle CO and HCHO Emissions Caps
------------------------------------------------------------------------

------------------------------------------------------------------------
CO cap for 25 [deg]C FTP, HFET, US06, SC03 (g/mi).......             1.7
HCHO cap for 25 [deg]C FTP (mg/mi)......................               4
CO cap for -7 [deg]C FTP (g/mi).........................            10.0
------------------------------------------------------------------------

ii. CO and HCHO Standards for MDV at or Below 22,000 lb GCWR
    EPA is proposing CO and formaldehyde (HCHO) emissions caps for MDV
at or below 22,000 pounds GCWR shown in Table 49. The proposed value of
the CO emissions cap for the 25 [deg]C FTP, HFET, US06, SC03 test
cycles, 3.2 g/mi, is the same as the Tier 3 bin-specific standard for
Bin 20 through Bin 160, but it must be met across four cycles instead
of the Tier 3 cycles of 25 [deg]C FTP and a separate standard for the
SFTP.
    The proposed value of the HCHO emissions cap, 6 mg/mi, is the same
as the Tier 3 bin-specific standards for Bin 20 through Bin 160. The
HCHO cap only applies to the 25 [deg]C FTP, as in Tier 3.
    The proposed CO emissions cap for the -7 [deg]C FTP is 10.0 g/mi.

   Table 49--MDV at or Below 22,000 lb GCWR CO and HCHO Emissions Caps
------------------------------------------------------------------------

------------------------------------------------------------------------
CO cap for 25 [deg]C FTP, HFET, US06, SC03 (g/mi)..............      3.2
HCHO cap for 25 [deg]C FTP (mg/mi).............................        6
CO cap for -7 [deg]C FTP (g/mi)................................     10.0
------------------------------------------------------------------------

    Present-day MDV gasoline engine aftertreatment technology allows
fast catalyst light-off followed by closed-loop A/F control and
excellent emissions conversion on Class 2b and 3 vehicles, even at the
ALVW [(curb + GVW)/2] test weight, which is higher than light-duty
vehicle test weight of LVW (curb + 300 pounds). Testing of a 2022 F250
7.3L in the -7 [deg]C FTP at EPA showed average CO emissions of 2.7 g/
mi CO, demonstrating that a 10.0 g/mi standard is feasible for MDV.
5. Requirements To Certify MDV With High GCWR Under the HD Engine
Program for Criteria Emissions
    The Agency is proposing mandatory engine certification for
compliance with criteria pollutant emissions standards for MDVs above
22,000 pounds GCWR. The proposed standards would include both spark
ignition and compression ignition (diesel) engines, complete and
incomplete vehicles, and require compliance with all of the same engine
certification criteria pollutant requirements and standards as for 2027
and later engines installed in Class 4 and higher HD vehicles,
including NMHC, CO, NOX and PM standards, useful life,
warranty and in-use requirements that were finalized in December
2022.\509\ Complete MDVs would still require chassis dynamometer
testing for demonstrating compliance with GHG standards as described in
Section III.B.3 and would be included within the fleet average MDV GHG
emissions standards along with the other MDVs at or below 22,000 GCWR.
Manufacturers could certify incomplete MDVs to GHG standards under 40
CFR 86.1819 or 40 CFR part 1037. Note that existing regulations (40 CFR
1037.150(l)) allow a comparable dual testing methodology, which
utilizes engine dynamometer certification for demonstration of
compliance with criteria pollutant emissions standards while
maintaining chassis dynamometer certification for demonstration of
compliance with GHG emissions standards under 40 CFR 86.1819. One
manufacturer has been using this provision to certify all gasoline
vehicles over 14,000-pound GVWR and the corresponding engines since MY
2016. Proposed requirements are summarized in Table 50.
---------------------------------------------------------------------------

    \509\ See https://www.epa.gov/regulations-emissions-vehicles-and-engines/final-rule-and-related-materials-control-air-pollution.
---------------------------------------------------------------------------

    The purpose of this proposed change is to ensure that criteria
pollutant emissions are controlled under the sustained high load
conditions that many of these vehicles encounter, particularly during
heavy towing operation. Some Class 2b and Class 3 trucks have towing
capability exceeding that of Class 4 and Class 5 trucks. Some diesel
Class 3 emissions families have GCWR in excess of 40,000 pounds. The
agency considers trucks above 22,000 pounds GCWR to be predominantly
work vehicles that will reasonably encounter significant towing and/or
other highly loaded use during normal operation. Many of these vehicles
currently do not have exhaust aftertreatment sized for effective
emissions control under sustained high loads. Current chassis
dynamometer test cycles used for demonstrating compliance do not
include such sustained high load operation. Manufacturers have also
indicated to the agency that there is a trade-off between sustained
high load exhaust aftertreatment performance and cold-start light off
performance over the FTP cycle. It is more appropriate that trucks
above 22,000 pounds GCWR be tested as heavy-duty engines due
capabilities and predominant use that are much more closely aligned
with Class 4 and above heavy-duty applications than with light-duty
vehicles and light-duty trucks.
    Based on an analysis of the MY 2022 and MY 2023 emissions
certification data, most MDV complete and incomplete diesel pickup
trucks would be required to switch to engine dynamometer certification;
MY 2022 vans would not be required to use engine dynamometer
certification; and only a small number of gasoline pickup trucks would
be required to switch to engine certification.

    As described in Section III.C.1, under the CAA trucks over 6,000
pounds GVWR are allowed 4 years of lead time before they are required
to begin implementation of new criteria pollutant emission standards.
The agency is providing an earlier implementation pathway beginning in
2027 in order for manufacturers to better plan for program changes over
a larger time window and to encourage earlier emissions reductions.
Because of this earlier opportunity for manufacturers and the potential
for the agency to realize earlier emission reductions, we are providing
additional flexibilities.
    Manufacturers who choose to optionally implement this engine
certification requirement for all their trucks above 22,000 pounds GCWR
beginning in 2027 model year will be allowed an additional GHG
compliance flexibility. If manufacturers choose to certify their
vehicles to these proposed standards in 2027 MY, they will be allowed
to continue to use the HD GHG Phase 2 based final 2026 work factor-
based target GHG standards, without a capped GCWR input for the work
factor-based target standard. This allowance would continue through
2029 MY, after which vehicle manufacturers would be required to switch
to the new work factor standards and the capped GCWR work factor
equation input proposed in Section III.B.3 in 2030. This will provide
an opportunity for manufacturers to balance the implementation of new
GHG program plans for these much higher GCWR vehicles while also
achieving important criteria pollutant emission reductions earlier in
the program. The agency seeks comments on additional flexibilities that
achieve the same or similar emission reductions.
    The default compliance pathway for MDV would be compliance with
2027 and later HD engine emissions standards beginning in 2030. Under
the default compliance pathway, GHG compliance flexibilities to extend
compliance with the heavy-duty Phase 2 GHG standards beyond the 2026
model year do not apply and manufacturers would need to meet the
proposed MDV GHG standards described in Section III.B.3 beginning with
the 2027 model year.
    The Agency seeks comment on several alternatives for high GCWR MDV
criteria pollutant emissions standards: (1) MDV above 22,000 pounds
GCWR would comply with the MDV chassis dynamometer standards proposed
in Section III.C with the introduction of additional engine-
dynamometer-based standards over the Supplemental Emissions Test as
finalized within the Heavy-duty 2027 and later standards; (2) MDV above
22,000 pounds GCWR would comply with the MDV chassis dynamometer
standards proposed in Section III.C with additional in-use testing and
standards comparable to those used within the California ACC II; (3)
Introduction of other test procedures for demonstration of effective
criteria pollutant emissions control under the sustained high-load
conditions encountered during operation above 22,000 pounds GCWR.

                           Table 50--Certification Requirements of High GCWR Vehicles
----------------------------------------------------------------------------------------------------------------
                                                                   Criteria
           Vehicle                GVWR (lb)       GCWR (lb)       pollutant      GHG standards     Compared to
                                                                  standards                           tier 3
----------------------------------------------------------------------------------------------------------------
Complete.....................     8500-14,000        <=22,000  Part 86........  Part 86........  Same.
                                              ------------------------------------------------------------------
Incomplete...................     8500-14,000        <=22,000               Part 86              Same.
                                                                             -OR-
                                                                  Part 1036 Part 1036 & 1037
                                              ------------------------------------------------------------------
Complete.....................     8500-14,000         >22,000  Part 1036......  Part 86........  New for
                                                                                criteria.
Incomplete...................     8500-14,000         >22,000  Part 1036......  Part 86 or 1037  New for
                                                                                criteria.
----------------------------------------------------------------------------------------------------------------

6. Refueling Standards for Incomplete Spark-Ignition Vehicles
    The agency is proposing to require that incomplete medium duty
vehicles meet the same on-board refueling vapor recovery (ORVR)
standards as complete vehicles. Incomplete vehicles have not been
required to comply with the ORVR requirements to date because of the
potential complexity of their fuel systems, primarily the filler neck
and fuel tank. Unlike complete vehicles, which have permanent fuel
system designs that are fully integrated into the vehicle structure at
time of original construction by manufacturers, it was previously
believed that incomplete vehicles may need to change or modify some of
fuel system components during their finishing assembly. For this
reason, it was previously determined that ORVR might introduce
complexity for the upfitters that is unnecessarily burdensome.
    Since then, the agency has newly assessed both current ORVR
equipped vehicles and their incomplete versions. Based on our updated
assessment, the agency believes that the fuel system designs are almost
identical with only the ORVR components removed for the incomplete
version. The complete and incomplete vehicles appear to share the same
fuel tanks, lines, and filler tubes. The original thought that
extensive differences between the original manufacturer's designs and
the upfitter modifications to the fuel system would be required have
not been observed. Therefore, the agency believes that all incomplete
vehicles can comply with the same ORVR standards as complete vehicles
with the addition of the same ORVR components on the incomplete
vehicles as the complete version of the vehicle possesses.
    The current practice of manufacturers of the original incomplete
vehicles is to specify to the upfitter that modifications of the fuel
system are not allowed by the upfitter. This is because the incomplete
vehicle manufacturers are responsible for all current evaporative
requirements (2-day, 3-day, running loss, spitback, etc.) and almost
any modification could compromise compliance with those program
standards. There is also an aspect of compliance with crash and safety
requirements that prevent upfitters from making changes to the fuel
system components. For these reasons, with rare exception, the fuel
system design and installation is completed by the original vehicle
manufacturer. The exception that the agency observed is that some
incomplete vehicles do not have the filler tube permanently mounted to
a body structure until the upfitter adds the finishing body hardware
(i.e., flatbed, box). In these cases, the upfitter is limited to only
attaching the filler tube to their added structure but must maintain
the original manufacturer designs that are certified to meet

existing EPA evaporative emission standards.
    Net emission impacts are expected to be small in the context of the
entire inventory and were not estimated for the NPRM, but the VOC and
air toxics reductions will be important in locations where these
vehicles are commonly refueled.
i. Summary of Medium Duty Vehicle Refueling Emission Standards and Test
Procedures
    Compliance with evaporative and refueling emission standards is
demonstrated at the vehicle level. The vehicle manufacturers produce MD
spark-ignition (SI) complete vehicles and, in some instances, sell
incomplete vehicles to secondary manufacturers. As noted in the
following sections, we are proposing refueling emission standards for
incomplete vehicles 8501 to 14,000 pounds GVWR. These proposed
standards would apply over a useful life of 15 years or 150,000 miles,
whichever occurs first, consistent with existing evaporative emission
standards for these vehicles and for complete versions. No changes to
evaporative and refueling emission standards for complete vehicles are
being proposed by this rulemaking.
ii. Current Refueling Emission Standard and Test Procedures
    Spark-ignition medium duty vehicles generally operate with volatile
liquid fuel (such as gasoline or ethanol) or gaseous fuel (such as
natural gas or LPG) that have the potential to release high levels of
evaporative and refueling HC emissions. As a result, EPA has issued
evaporative emission standards that apply to vehicles operated on these
fuels.\510\ Refueling emissions are evaporative emissions that result
when the pumped liquid fuel displaces the vapor in the vehicle tank.
Without refueling emission controls, most of those vapors are released
into the ambient air. The HC emissions emitted are a function of
temperature and the Reid Vapor Pressure (RVP).\511\ The emissions
control technology which collects and stores the vapor generated during
refueling events is the Onboard Refueling Vapor Recovery (ORVR) system.
---------------------------------------------------------------------------

    \510\ 40 CFR 86.1813-17.
    \511\ E.M. Liston, American Petroleum Institute, and Stanford
Research Institute. A Study of Variables that Effect the Amount of
Vapor Emitted During the Refueling of Automobiles. Available online:
http://books.google.com/books?id=KW2IGwAACAAJ, 1975.
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    Light-duty vehicles and chassis-certified complete medium-duty
vehicles that are 14,000 pounds GVWR and under have been meeting
evaporative and refueling requirements for many years. ORVR
requirements for light-duty vehicles started phasing in as part of
EPA's National Low Emission Vehicle (NLEV) and Clean Fuel Vehicle (CFV)
programs in 1998.\512\ In EPA's Tier 2 vehicle program, all complete
vehicles with a GVWR of 8,501 to 14,000 pounds were required to phase-
in ORVR requirements between 2004 and 2006 model years.\513\ In the
Tier 3 rulemaking, all complete vehicles were required to meet a more-
stringent standard of 0.20 grams of HC per gallon of gasoline dispensed
by MY 2022 (see 40 CFR 86.1813-17(b)).\514\ The recent 2027 heavy duty
final rule added refueling standards for incomplete heavy-duty vehicles
over 14,000 pounds GVWR. This left incomplete medium duty SI engine
powered vehicles 8,501 to 14,000 pounds GVWR as the only SI vehicles
not required to meet refueling standards.
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    \512\ 62 FR 31192 (June 6, 1997) and 63 FR 926 (January 7,
1998).
    \513\ 65 FR 6698 (February 10, 2000).
    \514\ 79 FR 23414 (April 28, 2014) and 80 FR 0978 (February 19,
2015).
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    While the agency does not believe manufacturers of the very limited
volumes of incomplete LD vehicles (i.e., mainly some LD pick-ups for
commercial customers who upfit application specific boxes and flatbeds)
are currently ``removing'' any ORVR related hardware already required
for the complete vehicle version like what has been observed in the MDV
applications, and this proposal focuses on the known incomplete
vehicles without ORVR in MDVs, the agency seeks comment on whether to
extend this ORVR requirement to all incomplete LDVs and MDVs to prevent
any future removal of ORVR from LDVs.
iii. Proposed ORVR HC Standard
    We are proposing a refueling emission standard of 0.20 grams HC per
gallon of dispensed fuel for incomplete vehicles 8,501 to 14,000 pounds
GVWR (0.15 grams for gaseous-fueled vehicles), which is the same as the
existing refueling standards for complete vehicles.\515\ We note that
these proposed refueling emission standards would apply to all liquid-
fueled and gaseous-fueled spark-ignition medium-duty vehicles,
including gasoline and ethanol blends.\516\ We believe it is feasible
for manufacturers to achieve these standards by adopting the technology
in use on complete vehicles.
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    \515\ 40 CFR 86.1813-17.
    \516\ Refueling requirements for incomplete medium duty vehicles
that are fueled by CNG or LNG would be the same as the current
complete gaseous-fueled Spark-ignition medium-duty vehicle
requirements.
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    We are proposing to apply the refueling standards for new
incomplete vehicles starting with model year 2030. This meets the
statutory obligation to allow four years of lead time for new emissions
standards for criteria pollutants for heavy-duty vehicles. This
schedule also complements the alternative phase-in provisions adopted
in our final rule setting these same standards for vehicles above
14,000 pounds GVWR (88 FR 4296, January 24, 2023). Those alternative
phase-in provisions allowed for manufacturers to phase in certification
of all their incomplete medium-duty and heavy-duty vehicles to the new
standards from 2027 through 2030. This proposed rule provides a
complete set of options for manufacturers. Specifically, manufacturers
may certify incomplete heavy-duty vehicles above 14,000 pounds GVWR to
the refueling standards in 2027 and incomplete medium-duty vehicles to
the refueling standards in 2030. The second option is to meet the
phase-in for the combined set of vehicles for 2027 through 2030.
    We request comment on our proposed standards.
iv. Impact on Secondary Manufacturers
    For incomplete vehicles 8,501 to 14,000 pounds GVWR, the chassis
manufacturer performs the evaporative emissions testing and obtains the
vehicle certificate from EPA. When the chassis manufacturer sells the
incomplete vehicle to a secondary vehicle manufacturer, the chassis
manufacturer provides specific instructions to the secondary
manufacturer indicating what they must do to maintain the certified
configuration, how to properly install components, and what, if any,
modifications may be performed. For the evaporative emission system, a
chassis manufacturer may require specific tube lengths and locations of
certain hardware, and modifications to the fuel tank, fuel lines,
evaporative canister, filler tube, gas cap and any other certified
hardware would likely be limited.
    We anticipate that the addition of any ORVR hardware and all ORVR-
related aspects of the certified configuration would continue to be
managed and controlled by the chassis manufacturer that holds the
vehicle certificate. The engineering associated with all aspects of the
fuel system design, which would include the ORVR system, is closely
tied to the engine design, and the chassis manufacturer is the most
qualified party to ensure its performance and

compliance with applicable standards. Example fuel system changes the
OEM may implement include larger canisters bracketed to the chassis
frame close to the fuel tanks. Additional valves may be necessary to
route the vapors to the canister(s) during refueling. Most other
evaporative and fuel lines would remain in the same locations to meet
existing evaporative requirements. There may be slightly different
filler neck tube designs (smaller fuel transfer tube) as well as some
additional tubes and valves to allow proper fuel nozzle turn-off (click
off) at the pump, but this is not expected to include relocating the
filler neck. Based on the comments received during the 2027 HD rule
making that established refueling requirements for incomplete vehicles
over 14,000 GVWR, we believe these changes would not adversely impact
the secondary manufacturers finishing the vehicles.\517\
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    \517\ See comments from the Manufacturers of Emission Controls
Association (EPA-HQ-OAR-2019-0055-0365) and Ingevity Corporation
(EPA-HQ-OAR-2019-0055-0271).
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    The instructions provided by the chassis manufacturer to the
secondary manufacturer to meet our proposed refueling standards should
include new guidelines to maintain the certified ORVR configuration. We
do not expect the new ORVR system to require significant changes to the
vehicle build process, since chassis manufacturers would have a
business incentive to ensure that the ORVR system integrates smoothly
in a wide range of commercial vehicle bodies. Accordingly, we do not
expect that addition of the ORVR hardware would result in any
appreciable change in the secondary manufacturer's obligations or
require secondary builders to perform significant modifications to
their products.
v. Feasibility Analysis for the Proposed Refueling Emission Standards
    This section describes the effectiveness and projected costs of the
emissions technologies that we analyzed for our proposed refueling
standards. Feasibility of the proposed refueling standard of 0.20 grams
of HC per gallon is based on the widespread adoption of ORVR systems
used in the light-duty and complete medium-duty vehicle sectors. As
described in this section, we believe manufacturers can effectively use
the same technologies already implemented in the complete medium-duty
versions of the same vehicles to meet the proposed standard.
vi. Summary of Refueling Emission Technologies Considered
    This section summarizes the specific technologies we considered as
the basis for our analysis of the proposed refueling emission
standards. The technologies presented in this section are described in
greater detail in the DRIA.
    Instead of releasing HC vapors into the ambient air, ORVR systems
capture HC emissions during refueling events when liquid fuel displaces
HC vapors present in the vehicle fuel tank as the tank is filled. These
systems recover the HC vapors and store them for later purging from the
system and use as fuel to operate the engine. An ORVR system consists
of four main components that are incorporated into the existing fuel
system: Filler pipe and seal, flow control valve, carbon canister, and
purge system.
    The filler pipe is the section of line from the fuel tank to where
fuel enters the fuel system from the fuel nozzle. The filler pipe is
typically sized to handle the maximum fill rate of liquid fuel allowed
by law and integrates either a mechanical or liquid seal to prevent
fuel vapors from exiting through the filler pipe to the atmosphere. The
flow control valve senses that the fuel tank is getting filled and
triggers a unique low-restriction flow path to the canister. The carbon
canister is a container of activated charcoal designed to effectively
capture and store fuel vapors. Carbon canisters are already a part of
MD SI fuel systems to control evaporative emissions. Fuel systems with
ORVR would require additional capacity, by increasing either the
canister volume or the effectiveness of the carbon material. The purge
system is an electro-mechanical valve used to redirect fuel vapors from
the fuel tank and canister to the running engine where they are burned
in the combustion chamber.\518\
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    \518\ This process displaces some amount of the liquid fuel that
would otherwise be used from the fuel tank and results in a small
fuel savings.
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    The fuel systems on 8,501 to 14,000 pounds GVWR incomplete heavy-
duty vehicles are similar, if not identical to those on complete
medium-duty vehicles that are currently subject to refueling standards.
These incomplete vehicles may have slightly larger fuel tanks than most
certified (complete) medium-duty vehicles and in some applications may
have dual fuel tanks. These differences may necessitate greater ORVR
system storage capacity and possibly some unique accommodations for
dual tanks (e.g., separate fuel filler locations), as commented by ORVR
suppliers in response to the similar program in the HD 2027 ANPR.\519\
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    \519\ See comments from the Manufacturers of Emission Controls
Association (EPA-HQ-OAR-2019-0055-0365) and Ingevity Corporation
(EPA-HQ-OAR-2019-0055-0271).
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vii. Projected Refueling Emission Technology Packages
    The ORVR emission controls we projected in our feasibility analysis
build upon four components currently installed on complete medium-duty
vehicles 8,501 to 14,000 pounds GVWR to meet the Tier 3 evaporative
emission standards: The carbon canister, flow control valves, filler
pipe and seal, and the purge system. For our feasibility analysis, we
assumed a 35-gallon fuel tank to represent an average tank size \520\
of medium-duty gasoline fueled vehicles 8,501 to 14,000 pounds GVWR. A
summary of the projected technology updates and costs are presented in
this section. See the DRIA for additional details.
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    \520\ Advertised MY 2022 fuel tank sizes ranged from 31 to 43
gallons.
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    In order to capture the vapor volume of fuel tanks during
refueling, we project manufacturers would increase canister vapor or
``working'' capacity of their liquid-sealed canisters by 15 to 40
percent depending on the individual vehicle systems. If a manufacturer
chooses to increase the canister volume using conventional carbon, we
project a canister meeting Tier 3 evaporative emission requirements
with approximately 2.5 liters of conventional carbon would need up to
an additional 1 liters of carbon to capture refueling emissions from a
35-gallon fuel tank. A change in canister volume to accommodate
additional carbon would result in increased costs for retooling and
additional canister plastic, as well as design considerations to fit
the larger canister on the vehicle. Alternatively, a manufacturer could
choose to use the same size fuel tank and canister currently used to
meet refueling requirements for complete medium duty vehicles to avoid
the re-tooling costs. Another approach, based on discussions with
canister and carbon manufacturers, could be for manufacturers to use a
higher adsorption carbon and modify compartmentalization within the
existing shell to increase the canister working capacity. We do not
have data to estimate the performance or cost of higher adsorption
carbon and so did not include this additional approach in our analysis.
    The projected increase in canister volumes assumes manufacturers
would use a liquid seal in the filler pipe, which

is less effective than a mechanical seal. For a manufacturer that
replaces their liquid seal with a mechanical seal, we assumed an
approximate 20 percent reduction in the necessary canister volume.
Despite the greater effectiveness of a mechanical seal, manufacturers
in the past have not preferred this approach because it introduces
another wearable part that can deteriorate, introduces safety concerns,
and may require replacement during the useful life of the vehicle. To
meet the proposed ORVR standards, manufacturers may choose the
mechanical seal design to avoid retooling charges. We included this
potential compliance approach in our cost analysis. We assumed a cost
of $10.00 per seal for a manufacturer to convert from a liquid seal to
a mechanical seal. We also analyzed costs based on the use of liquid
seals, and we assumed zero cost in our analysis for manufacturers to
maintain their current liquid seal approach for filler pipes already
used in the complete medium-duty applications.
    In order to manage the large volume of vapors during refueling,
manufacturers' ORVR updates would include flow control valves
integrated into the roll-over/vapor lines. We assumed manufacturers
would, on average, install one flow control valve per vehicle that
would cost $6.50 per valve. And lastly, we project manufacturers may
need to update their purge strategy to account for the additional fuel
vapors from refueling. Manufacturers may add hardware and optimize
calibrations to ensure adequate purge in the time allotted over the
preconditioning drive cycle of the demonstration test.
    Table 51 presents the ORVR system specifications and assumptions
used in our cost analysis, including key characteristics of the
baseline incomplete vehicle's evaporative emission control system.
Currently manufacturers may size the canisters of their Tier 3
evaporative emission control systems based on the diurnal 3-day test
and the Bleed Emission Test Procedure (BETP).\521\ During the diurnal
test, the canister is loaded with hydrocarbons over two or three days,
allowing the hydrocarbons to load a conventional carbon canister (1,500
GWC, gasoline working capacity) at a 70 g/L effectiveness. In contrast,
a refueling event takes place over a few minutes, and the ORVR directs
the vapor from the gas tank onto the carbon in the canister at a
canister loading effectiveness of 50 g/L. For our analysis, we added a
design safety margin of 10 percent extra carbon to our ORVR systems.
While less overall vapor mass may be vented into the canister from the
fuel tank during a refueling event compared to the three-day diurnal
test period, a higher amount of carbon is needed to contain the faster
rate of vapor loaded at a lower efficiency during a refueling event.
These factors were used to calculate the canister volumes for the two
filler neck options in our cost analysis.
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    \521\ 40 CFR 86.1813-17(a).

   Table 51--ORVR Specifications and Assumptions Used in the Cost Analysis for HD SI Incomplete Vehicles Above
                                                 14,000 lbs GVWR
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                                                                              ORVR filler neck options
                                            Tier 3 baseline       ----------------------------------------------
                                                                          Mechanical seal           Liquid seal
----------------------------------------------------------------------------------------------------------------
                                      Diurnal....................  ORVR
----------------------------------------------------------------------------------------------------------------
Diurnal Heat Build..................  72-96 [deg]F...............  80 [deg]F
                                     ---------------------------------------------------------------------------
RVP.................................  9 psi
                                     ---------------------------------------------------------------------------
Nominal Tank Volume.................  35 gallons
                                     ---------------------------------------------------------------------------
Fill Volume.........................  40%........................  10% to 100%
                                     ---------------------------------------------------------------------------
Air Ingestion Rate..................  ...........................  0%...........................          13.50%
                                     ---------------------------------------------------------------------------
Mass Vented per heat build, g/d.....  60.........................  .............................  ..............
Mass Vented per refueling event.....  ...........................  128..........................             158
Hot Soak Vapor Load.................  2.5........................  .............................  ..............
Mass vented over 48-hour test.......  114........................  .............................  ..............
Mass vented over 72-hour test.......  162........................  .............................  ..............
1,500 GWC, g/L \a\..................  70.........................  50...........................              50
Excess Capacity.....................  10%........................  10%..........................             10%
----------------------------------------------------------------------------------------------------------------
Estimated Canister Volume
 Requirement, liters \b\