presents the regulatory changes we are adopting after consideration of
comments received. Additional details on comments received on these
provisions and our responses are available in Chapter 2.4 of our
Response to Comments.
    In the existing regulations at 40 CFR 1036.150(p), EPA provided
special flexibility for engine manufacturers that certify all their
model year 2020 engines within an averaging set to the model year 2021
FTP and SET standards and requirements. Where 40 CFR 1036.150(p)
applies, paragraph (p)(1) specifies that GHG emission credits that
manufacturers generate with model year 2018 through 2024 engines may be
used through model year 2030, instead of being limited to a five-year
credit life as specified in 40 CFR 1036.740(d). Note that under the
Phase 2 final rule this provision in effect only applies to
manufacturers of tractor engines, as under 40 CFR 1036.701(j) EPA did
not allow the carryover of Phase 1 vocational engine credits into the
Phase 2 program (81 FR 73499, October 25, 2016). Where 40 CFR
1036.150(p) applies, paragraph (p)(2) specifies that manufacturers are
also allowed to certify model year 2024 through 2026 tractor engines to
alternative standards that are slightly higher than the otherwise
applicable standards. Note that in the table of alternative standards
in the Phase 2 final rule EPA included values for medium and heavy
heavy-duty vocational engines, but these values are identical to the
Phase 2 standards and not slightly higher due to our concerns about
windfall credits if carryover of Phase 1 credits were allowed.
    The applicability of 40 CFR 1036.150(p) is based on the choices
manufacturers made when certifying their MY 2020 engines. Instead of
certifying engines to the final year of the Phase 1 engine standards,
manufacturers electing the alternative instead certified to the MY 2021
Phase 2 engine standards. Because these engine manufacturers reduced
emissions of engines that would otherwise have been subject to the more
lenient MY 2020 Phase 1 engine standards, there can be a net benefit to
the environment. These engines do not generate credits relative to the
Phase 1 standards but instead generate credits relative to the pulled
ahead MY 2021 Phase 2 engine standards. Because the vehicle standards
themselves are unaffected, the alternative MY 2024-2026 engine
standards will not dilute or diminish the overall GHG reductions or
fuel savings of the program. Vehicle manufacturers using engines
subject to the alternative MY 2024-2026 standards would need to adopt
additional vehicle technology (i.e., technology beyond that projected
to be needed to meet the engine standards) to meet the applicable
vehicle GHG standards. The result is that the vehicles would still
achieve the same GHG emissions in use.
    The proposed rule included an amendment to address the concern
regarding Phase 1 windfall credits and requested comment on the
possibility of a similar set of alternative standards for vocational
engines. CARB and Volvo commented that they support these changes and
flexibilities. Cummins commented opposing both the alternative MY 2024
through 2026 vocational engine standards and extending the life of
credits generated from early compliance with Phase 2 vocational
standards. The American Council for an Energy-Efficient Economy
commented opposing extending the life of vocational engine credits
generated in Phase 1, stating that doing so does not result in emission
reductions but would increase emissions and reduce the rule's overall
stringency. Cummins also commented that manufacturers had already
developed and certified MY 2020 products without consideration of these
changes, and even if post hoc recertification was possible, allowing
them now would potentially be an advantage or disadvantage to
individual manufacturers.
    As discussed in section II.B.1, we are finalizing provisions on
calculating credits relative to a baseline that addresses these
windfall credit concerns, which also results in the extended credit
life flexibility under 40 CFR 1036.150(p)(1) now being available to
vocational vehicles that qualify under 40 CFR 1036.150(p). We are also
finalizing a set of alternative standards for vocational engines, as
shown in Table II-4.

        Table II-4--Alternative Standards for Vocational Engines
------------------------------------------------------------------------
                                                 Medium     Heavy  heavy-
                                               heavy-duty       duty
                 Model years                   vocational    vocational
                                                (g/hp-hr)     (g/hp-hr)
------------------------------------------------------------------------
2024-2026...................................          542           510
------------------------------------------------------------------------

    The Phase 2 standards are implemented in three MY steps: 2021,
2024, and 2027. The largest step change in stringency occurs in MY
2024, where approximately two-thirds of the total numeric reduction in
the MY 2021 through MY 2027 standards is achieved, with the remaining
one-third occurring in MY 2027. For the alternative tractor engine
standards, EPA reversed the magnitude of the MY 2024 and MY 2027 step
changes, where the MY 2024 alternative standard represents one-third of
the total numeric reduction and is slightly higher than the Phase 2
standard. The standards at the beginning (MY 2021) and ending (MY 2027)
steps of the Phase 2 program remain the same in either case, and only
the level of decrease in standard for MY 2024 changes with the
alternative standards. EPA determined the alternative standards for
vocational engines by adjusting the magnitude of the MY 2024 standard
in the same manner as used to determine the alternative tractor engine
standards in the Phase 2. The Phase 2 vocational engine standards
decrease by 10 g/hp-hr between MY 2021 and MY 2027, with a 7 g/hp-hr
step change in the MY 2024 standard (approximately two-thirds of the
total numeric reduction) and a 3 g/hp-hr step change in MY 2027. For
the alternative vocational engine standards in MY 2024-2026, we are
adopting a 3 g/hp-hr reduction from the MY 2021 standard (from 545 to
542 g/hp-hr for

medium heavy-duty (MHD) and 513 to 510 g/hp-hr for heavy heavy-duty)
instead of 7 g/hp-hr. EPA believes that allowing these slightly higher
(approximately 0.7 to 0.8% compared to the Phase 2 final rule) engine
standards for vocational vehicles is justified, as the overall vehicle
standards will still be met. Engine development and vehicle technology
choices are pathways to meeting overall vehicle standards, as is the
use of credits generated by early compliance. EPA's alternative engine
standards provisions for vocational vehicles for MYs 2024-2026 allows
manufacturers flexibility to choose the mix of engine and vehicle
technologies that will comply with the standards. As noted in the Phase
2 final rule and this rule's proposal, EPA views this type of
alternative as being positive from the environmental and energy
conservation perspectives, as vehicle-level emission standards remain
the same, but manufacturers are provided with significant flexibility
on engine emission standards and credit life provisions that may reduce
their compliance costs.
    Regarding the adverse comments received, including whether or not
manufacturers had the opportunity to consider these changes prior to MY
2020, these changes correspond to the corrected approach to Phase 1
credit calculations explained in Section II.B.1 above. At the time of
the Phase 2 final rule, we believed that allowing Phase 1 vocational
engine credits, without adjustment, to be carried over to the Phase 2
program would result in ``windfall'' credits, or dilution of the
benefits of the Phase 2 program, and we adopted restrictions to limit
their use. However, after the Phase 2 final rule we recognized that an
alternative to restricting Phase 1 vocational engine credits because of
windfall concerns would be to adjust credits earned in Phase 1
downward, relative to a baseline of the lower Phase 2 emissions
standards, and in doing so, we would be extending to vocational engine
manufactures the same flexibilities that were provided to tractor
engine manufacturers. In this final rule we are allowing the vocational
engine credits generated in Phase 1 to be adjusted downward and used in
Phase 2 program through MY 2030, just as they were for tractors. In
setting lower baseline emission values for Phase 1 vocational engine
credits and providing the corresponding program flexibilities, EPA does
not intend to advantage or disadvantage any manufacturer. Rather, we
are removing restrictions that were applied only to vocational engines
but no longer should be applied now that we are finalizing provisions
that provide a proper accounting of the emission improvements realized
by manufacturers who chose to certify their MY 2020 engines to the MY
2021 Phase 2 standards, so vocational and tractor engines are treated
the same. In addition, the revised MY 2024-2026 alternative standards
for vocational engines, while slightly higher than those in the Phase 2
final rule by 0.7 to 0.8%, do not reduce the overall stringency of the
Phase 2 program, but instead reflect the alternative standards we would
have adopted in the Phase 2 final rule alongside the similar tractor
provisions, and for the same reasons we finalized those tractor
provisions, had we considered adjusting baseline emission rates used
for calculating Phase 1 credits. Manufacturers that qualify to use the
alternative MYs 2024-2026 engine standards accelerated their compliance
with the more stringent MY 2021 Phase 2 standards by one model year. As
we explained in the Phase 2 final rule, because the vehicle standards
themselves are unaffected, these alternative engine standards will not
dilute or diminish the overall GHG reductions or fuel savings of the
program. Vehicle manufacturers using engines subject to the alternative
MYs 2024-2026 standards will need to adopt additional vehicle
technology (i.e., technology beyond that projected to be needed to meet
the engine standard) to meet the applicable vehicle GHG standards. The
result is that the vehicles using engines that comply with the
alternative standards will still achieve the same overall GHG emissions
in use. EPA believes that these alternative standards are appropriate,
and allowing alternative engine standards for vocational vehicles that
qualify is justified, for these reasons, and that vocational engine
manufacturers who met the Phase 2 engine standards one year in advance
of the MY 2021 implementation date should have the same flexibility as
tractors to earn and use those credits through MY 2030.
3. Confirmatory Testing of Engines and Measurement Variability
    EPA proposed updates to the procedure for confirmatory testing of
the fuel mapping test procedure related to providing an interim 2%
allowance during confirmatory testing of the fuel mapping test
procedure finalized in the Phase 2 final rule and requested comment on
``. . . whether it appropriately balances the impacts of testing
variability for fuel maps'' (see 85 FR 28146, May 12, 2020). This
section presents the changes we are adopting to the confirmatory
testing portion of the fuel mapping test procedure after consideration
of comments received. Additional details on these comments and our
responses are available in Chapter 2 of our Response to Comments.
    During the Phase 2 rulemaking, manufacturers raised concern about
measurement variability impacting the stringency of the engine GHG
standards and fuel map requirements. As noted in the Phase 2 final
rule, the final standards were developed to account for this. (81 FR
73571, October 25, 2016). Manufacturers raised particular concern about
variability of fuel map measurements because neither they nor EPA had
sufficient experience measuring fuel maps (in a regulatory context) to
fully understand the potential impacts of measurement variability. We
estimated the fuel map uncertainty to be equivalent to the uncertainty
associated with measuring CO2 emissions and fuel consumption
over the FTP and SET cycles, which we estimated to be about one
percent. However, the Phase 2 final rule noted that we were
incorporating test procedure improvements that would further reduce
test result uncertainty. We also noted that ``[i]f we determine in the
future . . . that the +1.0 percent we factored into our stringency
analysis was inappropriately low or high, we will promulgate technical
amendments to the regulations to address any inappropriate impact this
+1.0 percent had on the stringency of the engine and vehicle
standards.'' (81 FR 73571, October 25, 2016)
    In conjunction with this intention, EPA has worked with engine
manufacturers to better understand the variability of measuring fuel
maps using the test procedures and cycles specified by EPA in the Phase
2 final rule. Through that work, we identified several sources of
variability that can be reduced by making small changes to the test
procedures. EPA is adopting these changes, as explained in Sections
II.A.1 through II.A.3 of this final rule.
    SwRI performed emission measurements in multiple test cells and
identified distributions of error for other test inputs such as
measured fuel properties and calibration gas concentrations. SwRI then
used a Monte Carlo simulation to estimate a distribution of errors in
measured fuel maps.\17\ After reviewing the results, EPA had several
significant observations which we discussed in the proposal for

this final rule and which EPA confirms in this final action:
---------------------------------------------------------------------------

    \17\ Sharp, Christopher A., et al., ``Measurement Variability
Assessment of the GHG Phase 2 Fuel Mapping Procedure'', Southwest
Research Institute, Final Report, December 2019.
---------------------------------------------------------------------------

    1. The variability of measuring CO2 and fuel consumption
during fuel mapping is greater than the one percent assumed in the
Phase 2 final rule. Variability from vehicles without idle test cycles
is <1.8% (1.68 to 1.8%), while variability from vehicles with idle test
cycles is <2.8% (2.0 to 2.79%).
    2. The variability of measuring CO2 and fuel consumption
during the fuel mapping procedure is roughly the same as that of the
FTP and SET cycles, 3.34% for the FTP and 1.99% for the SET.
    3. Measuring CO2 and fuel consumption at idle is
particularly challenging.
    4. The data obtained during the test program at SwRI did not
include all the test procedure changes being adopted in 40 CFR parts
1036 and 1037 that will further reduce fuel mapping test variability
and therefore the variability is likely to be lower than reported by
the SwRI.
    Manufacturers have indicated they are concerned about the
possibility of EPA changing an official fuel map result as a
consequence of EPA confirmatory testing where the measured maps were
within an expected range of variability. In the context of the SwRI
test program, EPA observed similarity between the range of variability
of measuring fuel maps and the range of variability of measuring
CO2 and fuel consumption over the FTP and SET cycles
(measurements for which EPA has already determined in both Phase 1 and
Phase 2 that no such allowances are needed). These results indicate
that there is no additional source of increased variability associated
with the fuel mapping test procedure and suggest that manufacturers
should be able to comply without any special provisions. Additionally,
the data we have available indicates that the manufacturers may
potentially over time be able to take advantage of the 2% allowance,
resulting in a reduction in stringency of the standards. We anticipate
that this would not happen over the next few model years, as
manufacturers will need time to implement the revised test procedures
adopted in this rule that will reduce the variability of the fuel map
test procedure to levels at or below the variability of the FTP and SET
test procedures.
    After considering the comments received, we are adopting the
limited transitional approach aimed at addressing the manufacturers'
variability concerns. As manufacturers implement this rule's revised
test procedures to reduce variability, we will analyze and compare a
manufacturer's declared and measured fuel maps to those that result
from our confirmatory testing, with the goal of ensuring the long-term
integrity of the Phase 2 program. We are codifying the interim
provision for model years 2021 and later in 40 CFR 1036.150, under
which EPA will not replace a manufacturer's fuel maps during
confirmatory testing if the difference between the EPA-measured fuel
maps and the manufacturer's declared maps is less than or equal to 2.0
percent. We may revisit the interim 2% allowance in a future
rulemaking.
    EPA also intends to further review data and developments in this
area. We intend to review this provision as we learn more about the
impact of measurement variability on measured and declared fuel maps
submitted during the certification process for future model years
(including the full impact of the test procedure improvements that are
intended to reduce measurement variability), which may inform whether
we determine additional action is warranted in the future with respect
to fuel mapping variability. We also intend to enter into a round robin
study of criteria and GHG pollutant engine testing variability with
interested engine manufacturers, with the involvement of the Truck and
Engine Manufacturer's Emission Measurement and Testing Committee. This
data will add to the existing knowledge regarding the variability of
the FTP, SET and fuel mapping test procedures and may help inform if
future action is needed to further improve the test procedures.
    We are also finalizing an algorithm for comparing fuel maps.
Because fuel maps are multi-point surfaces instead of single values, it
would be a common occurrence that some of EPA's points would be higher
than the manufacturer's while others would be lower. This algorithm was
inadvertently proposed as an interim provision in 40 CFR 1036.150(q)
along with the 2.0 percent variability allowance. The algorithm and
fuel map comparison process during a confirmatory test is needed for
confirmatory testing regardless of an allowance. Therefore, in this
final rule the algorithm and all supporting text are located at 40 CFR
1036.235(c)(5). The limited interim 2.0 percent variability allowance
is located at 40 CFR 1036.150(q).
    EPA's measured fuel maps will be used with GEM according to 40 CFR
1036.540 to generate emission duty cycles which simulate several
different vehicle configurations, generating emission results for each
of the vehicles for each of the duty cycles. Each individual duty cycle
result will be weighted using the appropriate vehicle category
weighting factors in Table 1 of 40 CFR 1037.510 to determine a
composite CO2 emission value for that vehicle configuration.
Note that the equation is being finalized to use values before rounding
as this is consistent with the provisions in 40 CFR 1065.20 to not
round intermediate values. When the process is repeated for the
manufacturer's fuel maps, the average percent difference between fuel
maps will be calculated as:
[GRAPHIC] [TIFF OMITTED] TR29JN21.008

Where:

i = an indexing variable that represents one individual weighted
duty cycle result for a vehicle configuration.
N = total number of vehicle configurations.
eCO2compEPAi = unrounded composite mass of CO2
emissions in g/ton-mile for the EPA confirmatory test.
eCO2compManu = unrounded composite mass of CO2
emissions in g/ton-mile for the manufacturer declared map.
4. Other Minor Heavy-Duty Engine Amendments
    EPA proposed three additional updates to the testing and
measurement provisions of 40 CFR part 1036, related to measuring
emissions from heavy-duty

engines and requested comment on general improvements to the engine
test procedures and compliance provisions (see 85 FR 28147). This
section presents these three additional changes we are adopting to
engine test procedures. Additional details on these and other engine
testing and measurement amendments or clarifications requested by
commenters and our responses are available in Chapter 2 of the Response
to Comments.
     Correcting the assigned N2O deterioration factor in Sec.
1036.150(g). In the Phase 2 proposed rule, EPA proposed to lower the
N2O standard from 0.10 g/hp-hr to 0.05 g/hp-hr for model
year 2021 and later diesel engines. In that context, we also proposed
to lower the assigned deterioration factor (DF) from 0.020 g/hp-hr to
0.010 g/hp-hr for model year 2021 and later diesel engines. EPA
explained in the preamble to the Phase 2 final rule that we were not
finalizing the change to the standard (81 FR 73530, October 25, 2016),
but inadvertently finalized the proposed DF change in the regulations.
We proposed in this rulemaking to correct this error, consistent with
EPA's clear statement in the Phase 2 final rule that we were not
finalizing the change to the standard. However, given that finalizing
the assigned DF of 0.01 g/hp-hr for N2O in the regulations
was an oversight on EPA's part in the Phase 2 final rule and that the
Phase 2 final rule was inadvertently internally inconsistent, and after
consideration of EMA's comment that manufacturers will not have time to
correct or account for a change in the assigned DF in time for their MY
2021 certifications, we are deferring changing the assigned DF to 0.02
g/hp-hr until MY 2022 within the revisions finalized in this
rulemaking.
     Clarifying a reference to non-gasoline engine families in
Sec.  1036.705(b)(5). The second sentence of Sec.  1036.705(b)(5) is
intended to refer to non-gasoline engine families. However, the
existing text is not clear. As written, it can be read to mean that
gasoline engine families may not generate emission credits. EPA is
adding ``non-gasoline'' to clarify the intended meaning.
     Engine families. We are revising Sec.  1036.230 to allow
engine families to be divided into subfamilies with respect to
CO2. This allowance simplifies the certification process
without changing the overall requirements.
     Adding a summary of previously applicable emission
standards as appendix A of part 1036. The new appendix is being
provided for reference purposes only regarding previously applicable
emission standards and will cover regulatory text being deleted from 40
CFR part 86.
    Except as noted above, we received no adverse comments on these
proposed amendments and are adopting them without modification.

C. Heavy-Duty Vehicle GHG Emission Standards and Flexibility

1. Aerodynamic Compliance Provisions
    In addition to the aerodynamic test procedure amendments described
in Section II.A.6, we proposed several updates to Sec.  1037.150(s) as
it relates to EPA's confirmatory testing of aerodynamic parameters and
Sec.  1037.305 as it relates to our selective enforcement audit (SEA)
procedures. We also requested comment on general improvements to the
aerodynamic compliance provisions (see 85 FR 28147). This section
presents the changes we are adopting to our confirmatory testing and
SEA procedures after consideration of comments received. Additional
details on these and other aerodynamic amendments or clarifications
requested by commenters and our responses are available in Chapter 2 of
our Response to Comments.
a. Confirmatory Testing for Falt-aero
    As described in 40 CFR 1037.235(c), EPA may perform confirmatory
testing on a manufacturer's vehicles, including a vehicle tested to
establish the Falt-aero value. The regulations also include
an interim provision in Sec.  1037.150(s) that outlines how EPA may and
when EPA will not replace a manufacturer's Falt-aero value
based on confirmatory test results. This interim provision connects
EPA's confirmatory testing to the audit procedures of Sec.  1037.305.
In keeping with the principle that good engineering judgment \18\ would
generally call for more data rather than selecting a single value, and
after consideration of comment, EPA is finalizing our proposed
provision to require EPA to perform a minimum of 100 valid runs before
replacing a manufacturer's Falt-aero value in confirmatory
testing with some additional clarifications in Sec.  1037.150(s).
---------------------------------------------------------------------------

    \18\ Good engineering judgment is defined in 40 CFR 1068.30 as
judgments made consistent with generally accepted scientific and
engineering principles and all available relevant information. See
40 CFR 1068.5 for requirements regarding applying good engineering
judgment.
---------------------------------------------------------------------------

    CARB commented in support of increasing the number of runs from SEA
to 100 to limit false failures, but requested in comment to know the
origin of the proposed minimum 100 valid runs for confirmatory testing.
Our intent with the finalized requirement for 100 valid confirmatory
runs is to maintain consistency with the existing regulatory language
adopted in the Phase 2 final rulemaking for SEA testing. The existing
Sec.  1037.305(a)(7)(iii) states: ``The vehicle passes if you perform
100 coastdown runs and CdAwa-upper is greater
than and CdAwa-lower is lower than the upper
limit of the bin to which you certified the vehicle.'' Similarly, as
noted below in Section II.C.1.b, we are also finalizing our
corresponding proposed language in the audit procedures of Sec.
1037.305(a)(5) clarifying that manufacturers must perform a minimum of
24 runs to pass and a minimum of 100 runs to fail.
    EMA requested additional modifications to Sec.  1037.150(s)
regarding EPA's approach to calculating a new Falt-aero
value in confirmatory testing. EMA suggested that the regulation more
explicitly connect to the SEA procedures for pass/fail criteria and the
coastdown procedures for calculating Falt-aero. They also
suggested we directly outline how EPA will replace a manufacturer's
Falt-aero. EMA suggested that EPA calculate two
Falt-aero values and apply the average of those values to
replace a manufacturer's value. We agree with EMA's suggestions to
clarify the connections to the SEA procedures of Sec.  1037.305 and the
coastdown test procedures of Sec.  1037.528 and we updated Sec.
1037.150(s) accordingly. While we generally agree that additional data
is preferable, we are not committing to calculating multiple
Falt-aero values, as requested by EMA, due to consideration
of potential resource constraints; however, we have revised the
regulatory language to allow for it. We also are not finalizing an
approach to calculate the final Falt-aero when there are
multiple values. Our revised Sec.  1037.150(s) states that EPA will
``will generate a replacement value of Falt-aero based on at
least one CdA value and corresponding effective yaw angle''.
    Additionally, as noted in the proposal regarding Sec.  1037.150(s),
we recognize that test conditions for coastdown testing are an
important consideration. For our confirmatory testing, EPA intends to
minimize the differences between our test conditions and those of the
manufacturer and we proposed a note in Sec.  1037.150(s) stating our
intent to test at similar times of the year. EMA requested additional
regulatory language regarding our intent to test at the same location
as well as time of year. We are expanding our proposed note in Sec.
1037.150(s) to include our intent to test at both the same time of year
and the same location, subject to

certain considerations. More specifically, we emphasize that the note
in Sec.  1037.150(s) is not a commitment by the agency due to the
limited number of coastdown test facilities, the challenges of
scheduling time for testing, and our prerogative to choose an
alternative facility if we have concerns about the original test
location. Our revised language in Sec.  1037.150(s) states that we
intend to test ``at similar times of the year where possible and at the
same location where possible and when appropriate.''
b. Selective Enforcement Audits for Tractors
    We proposed and received no adverse comments to three typographical
edits to our aerodynamic testing audit procedures for tractors in Sec.
1037.305. We are finalizing those three edits as proposed and
additional editorial edits as follows:
     Section 1037.305--Replaced reference to 40 CFR 1068.420
with the range ``40 CFR 1068.415 through 1068.425'' as proposed.
     Section 1037.305(a)--Rephrased ``whether or not a tractor
fails to meet'' to the more concise ``whether a tractor meets''.
     Section 1037.305(a)(2)--Corrected ``coastdown effective''
to ``coastdown effective yaw angle'' as proposed.
     Section 1037.305(a)(7)--Added a missing ``m2'' following
the bin value of 5.95 in the example as proposed. Editorial revisions
to remove passive voice.
    In comment, EMA suggested additional revisions to Sec.  1037.305(a)
allowing manufacturers to apply good engineering judgment in their
selective enforcement audit (SEA) testing if a production vehicle could
not be configured to meet the trailer height specified in Sec.
1037.501(g)(1)(i). We accept that a future production vehicle may be
designed such that it cannot be configured to match a trailer that
meets our current definition of standard trailer. We are finalizing a
broader revision to address all such scenarios where a production
vehicle cannot be configured to match a trailer that meets our current
definition of standard trailer, including but not limited to height,
that will address EMA's specific concern with meeting the standard
trailer's height requirements. We are adding language to clarify that a
manufacturer may seek EPA approval to use an alternate or modified
vehicle configuration, consistent with good engineering judgment, if
EPA chooses to audit a production vehicle configuration that cannot
meet any of the standard trailer requirements specified in Sec.
1037.501(g)(1).
    As noted in Section II.C.1.a, we proposed and are finalizing a
provision in Sec.  1037.150(s) to require EPA to perform a minimum of
100 valid runs before replacing a manufacturer's Falt-aero
value in confirmatory testing. Similarly, we are finalizing our
corresponding proposed language in the audit procedures of Sec.
1037.305(a)(5) clarifying that manufacturers must perform a minimum of
24 runs to pass and a minimum of 100 runs to fail. Finally, we received
no adverse comments and are finalizing the proposed regulatory language
in Sec.  1037.305(a)(7)(v) allowing manufacturers to continue testing
and to generate additional data that EPA may consider in our pass/fail
determinations.
2. Idle Reduction Technologies
    EPA proposed several provisions related to idle reduction
technologies. This section presents the changes we are adopting after
consideration of the comments received. See Chapter 2 of our Response
to Comments for further details, including additional idle reduction
amendments or clarifications requested by commenters and our responses.
a. Extended-Idle Reduction for Tractors
    The Phase 1 version of GEM gives credit for extended idle emission
reduction technologies that include a tamper-proof automatic engine
shutoff system (AESS), with few override provisions. Phase 2 GEM gives
credit for a wider variety of idle reduction strategies, recognizing
technologies that are available on the market today, such as auxiliary
power units (APUs), diesel fired heaters, and battery powered units.
For example, a tamper-proof AESS with a diesel APU would be credited
with a 4 percent reduction in emissions, while an adjustable AESS with
a diesel fired heater would be credited with a 2 percent reduction in
emissions (81 FR 73601, October 25, 2016).
    Our proposal to revise Sec.  1037.520(j)(4) to include GEM input
values for combinations of these technologies received support from
CARB, EMA, and Volvo and we are finalizing our proposed combinations of
idle reduction technologies as shown in Table II-5. Adding these values
to GEM reduces the compliance burden for manufacturers who would
otherwise need to apply for off-cycle credits for these technology
combinations. The values of these technology benefits were determined
using the same methodology used in the Phase 2 final rule.

              Table II-5--GEM Input Values for AES Systems
------------------------------------------------------------------------
                                                     GEM input values
                                                ------------------------
                   Technology                                   Tamper-
                                                  Adjustable   resistant
------------------------------------------------------------------------
Standard AES system............................            1           4
With diesel APU................................            3           4
With battery APU...............................            5           6
With automatic stop-start......................            3           3
With fuel-operated heater (FOH)................            2           3
With diesel APU and FOH........................            4           5
With battery APU and FOH.......................            5           6
With stop-start and FOH........................            4           5
------------------------------------------------------------------------

b. Idle Reduction Overrides
    In 40 CFR 1037.660, we identify three idle reduction technologies
(i.e., automatic engine shutdown, neutral idle, and stop-start) and
specify how these systems must operate to qualify for GEM credit.
Included among those provisions are allowances for overriding these
systems where it may damage the engine or create a safety issue for the
vehicle occupants or service personnel. This section highlights the
some of the idle reduction override provisions we are adopting, either
as proposed or further revisions after consideration of comments
received.
i. Automatic Engine Shutdown (AES) Overrides
    While we did not specifically propose or request comment on AES
overrides, New Flyer (a bus manufacturer) commented that the override
condition for AES systems during servicing in Sec.  1037.660(b)(1)(ii)
(cross-referenced under the existing regulations for vocational
vehicles in Sec.  1037.660(b)(2)(i)) could pose a safety risk to
maintenance personnel. They stated that maintenance personnel may not
have a diagnostic scan tool required to deactivate the system and some
maintenance may require longer than the current 60-minute limit before
reactivation. New Flyer suggested an ``open engine compartment'' would
be a more appropriate override condition.
    After consideration of New Flyer's safety concern for vocational
vehicles, we are revising Sec.  1037.660(b)(2) to allow a vocational
vehicle's AES system to delay shutdown if necessary while servicing the
vehicle without the scan tool requirement and time limit. Our final
revision removes the cross-reference in Sec.  1037.660(b)(2)(i) to that
particular provision in Sec.  1037.660(b)(1) and replaces it with a new
provision in Sec.  1037.660(b)(2)(ii). Our new provision allows a delay
in shutdown for vocational vehicles if the engine compartment is open
and replaces the

regulatory text regarding unsafe cab temperatures in the current Sec.
1037.660(b)(2)(ii), which is redundant with the existing cross-
reference to paragraph (b)(1) in paragraph (b)(2)(i). For vocational
vehicles, we believe an open engine compartment sufficiently indicates
that a vocational vehicle is being serviced and automatic engine
shutdown would provide limited environmental benefit. We are not taking
final action to revise the tractor-specific provision of Sec.
1037.660(b)(1)(ii) to allow an open engine compartment as a condition
for AES override, since the environmental benefits of AES on tractors
occurs when these vehicles are parked for extended durations where an
open engine compartment may not be a sufficient deterrent for the
operator to circumvent the AES.\19\
---------------------------------------------------------------------------

    \19\ Tractor manufacturers have the option to request and we may
approve additional override criteria as needed to protect the engine
and vehicle from damage and to ensure safe vehicle operation, as
stated in Sec.  1037.660(b).
---------------------------------------------------------------------------

    We are finalizing editorial revisions to Sec.  1037.660(b) so the
paragraphs consistently begin with ``When''. Additionally, we reordered
the paragraphs of Sec.  1037.660(b)(1) to move the servicing provision
previously located at paragraph (b)(1)(ii) to paragraph (b)(1)(vi) such
that the vocational vehicle AES provisions can continue to reference
the range of relevant (b)(1) paragraphs in paragraph (b)(2)(i).
ii. Neutral Idle Overrides
    EPA proposed and is finalizing a provision in Sec.
1037.660(b)(3)(ii) that would allow the neutral idle system to delay
shifting the transmission into neutral if the transmission is in
reverse gear (85 FR 28271, May 12, 2020). New Flyer requested an
additional override when the vehicles is on a road grade of 6.0 percent
or more to prevent the safety concern of vehicle rollback. EPA agrees
with this safety concern and is finalizing a provision in Sec.
1037.660(b)(3)(iii) to allow a delay in neutral idle when the vehicle
is on a grade greater than or equal to 6.0 percent. EMA requested
additional overrides for ``safety; thermal protection of the emissions
aftertreatment; and maintenance of aftertreatment temperature within a
range for adequate emissions control''. EPA is not adopting EMA's
suggested override conditions as we do not think that they would likely
be appropriate without more specific criteria. Manufacturers continue
to have the option to justify the need for additional overrides for
their individual systems and seek EPA approval through Sec.
1037.660(b).
iii. Stop-Start Overrides
    We requested comment on a specific list of override conditions for
stop-start systems (85 FR 28151, May 12, 2020). CARB expressed concern
that additional overrides may compromise emissions and requested a
requirement that manufacturers bring their proposed overrides to EPA
for approval. We are not requiring a ``case-by-case'' approval process
for these overrides, as suggested by CARB, but we note that, in the
certification application provisions of Sec.  1037.205(b)(5),
manufacturers are required to include a description of their idle
reduction technology, including the override conditions of Sec.
1037.660. We believe this continues to be an appropriate level of
oversight for these idle technologies and their associated override
conditions.
    EMA and New Flyer supported the inclusion of all override
conditions listed in the proposed rule for comment, but their comments
did not expand on the need for any of the individual conditions to be
adopted. Each commenter requested additional override conditions and
included the rationale for those requests. Our final revisions to Sec.
1037.660(b)(4) cross-reference the provisions for vocational vehicle
AES (paragraph (b)(2)) and neutral idle (paragraphs (b)(3)(ii) and
(iii)) such that the new open engine compartment, reverse gear, and
road grade provisions for those systems also apply for stop-start
systems. EPA considered the original list and the commenters'
additional suggested override conditions and we are adopting the
following additional override criteria specific to stop-start systems
to ensure safety and/or effective system operation as noted in Sec.
1037.660(b)(4):
     When the steering angle is at or near the limit of travel
to avoid steering wheel kickback during engine start.
     When a wheel speed sensor failure may prevent the anti-
lock braking system from detecting vehicle speed.
     When an automatic transmission is in ``park'' or in
``neutral'' with the parking brake engaged because the feature is
intended to be used during driving operation.
     When a component failure protection mode is active, such
as starter motor overheating, which may prevent the engine from
restarting.
     When a fault is active on a system component needed to
start the engine, which may prevent the engine from restarting.
     When the flow of diesel exhaust fluid is limited due to
freezing, because an engine-off condition may further delay thawing and
SCR operation.
    It was not clear that the remaining override conditions suggested
by commenters or presented for comment in the proposed rule pose a
widespread concern for safety, vehicle operation, or serviceability, or
could not be easily overridden by the driver, and we are not adopting
those overrides in our final revisions. However, manufacturers continue
to have the option to seek EPA approval for these or additional
criteria they believe are needed to protect the engine and vehicle from
damage and to ensure safe vehicle operation (see Sec.  1037.660(b)).
3. Weight Reduction
    EPA proposed minor revisions to the weight reduction provisions
(see 85 FR 28150). This section presents the changes we are adopting
after consideration of comments received. See Chapter 2 of our Response
to Comments for additional details on some of these amendments,
including other amendments or clarifications requested by commenters
and our responses.
    The regulations in 40 CFR 1037.520 include tables to calculate
weight reduction values for using certain lightweight components. The
sum of the weight reductions is used as an input to GEM. As noted in
Section II.A.2, EPA proposed two changes to Table 8 of that section
allowing manufacturers to use the heavy heavy-duty (HHD) values for
medium heavy-duty (MHD) vehicles with three axles (i.e., 6x4 and 6x2
configurations) and adding a footnote to the table to clarify that the
weight reduction values apply per vehicle (instead of per component)
unless otherwise noted. We received no adverse comments to the proposed
updates to Table 8 and we are finalizing the two changes.
    We received comment from EMA requesting ``a process for adding in
other weight-savings technologies''. As described in Sec.
1037.520(e)(5), this process is available in the existing off-cycle
provisions of Sec.  1037.610 and no further action is needed or being
finalized in this rule. EMA also requested clarification on the origin
of certain weight reduction values for tires and recommended use of a
``base'' value for comparison. We note that all the values in Table 6
through Table 8 of Sec.  1037.520 were developed through notice and
comment in the HD Greenhouse Gas Emissions Phase 1 and Phase 2
rulemakings based on information as described in the Regulatory Impact
Analysis for the rules. We did not propose changes to the weight
reduction tables and are not taking any final action at this time to

update values to refer to a base weight, but manufacturers continue to
have the ability to apply through our off-cycle process.
4. Self-Contained Air Conditioning Units
    We proposed a revision to Sec.  1037.115(e) to clarify that it is
``intended to address air conditioning systems for which the primary
purpose is to cool the driver compartment (85 FR 28151). This would
generally include all complete pickups and vans, but not self-contained
air conditioning or refrigeration units on vocational vehicles.'' CARB
and New Flyer requested additional clarification on the phrase ``self-
contained''. After consideration of submitted comments, we are
finalizing a modified version of the proposed changes to Sec.
1037.115(e)(1) that incorporates some of the feedback from commenters.
We are maintaining the proposed statement that this provision is
intended for A/C systems that cool the driver compartment. We're
clarifying that it generally applies to ``cab-complete'' pickups and
vans (see definition at Sec.  86.1803-01) which is more appropriate for
heavy-duty than ``complete pickups and vans'' as proposed. We are
expanding the existing statement that the paragraph does not apply for
self-contained A/C or refrigeration units by adding the phrases ``used
to cool passengers'' and ``used to cool cargo''. Finally, we further
clarify that a self-contained system for purposes of this provision is
an ``enclosed unit with its own evaporator and condenser even if it
draws power from the engine.''
5. Manufacturer Testing of Production Vehicles
    The regulations require tractor manufacturers to annually chassis
test five production vehicles over the GEM cycles to verify that
relative reductions simulated in GEM are being achieved in actual
production. See 40 CFR 1037.665. We do not expect absolute correlation
between GEM results and chassis testing. GEM makes many simplifying
assumptions that do not compromise its usefulness for certification but
do cause it to produce emission rates different from what would be
measured during a chassis dynamometer test. Given the limits of
correlation possible between GEM and chassis testing, we would not
expect such testing to accurately reflect whether a vehicle was
compliant with the GEM standards. Therefore, Sec.  1037.665 does not
apply compliance liability to such testing.
    The regulation also allows manufacturers to request approval of
alternative testing ``that will provide equivalent or better
information.'' Manufacturers have asked us to clarify this allowance
and we proposed to revise Sec.  1037.665 to provide an example that the
EPA may allow manufacturers to provide CO2 data from in-use
operation, and CO2 data from manufacturer-run on-road
testing, as long as the data allows for reasonable year-to-year
comparisons and includes testing from non-prototype vehicles (85 FR
28148). We didn't receive any comments on the proposed changes to Sec.
1037.665, and we are finalizing changes to the regulation as proposed.
To qualify, the vehicles would need to be actual production vehicles
rather than custom-built prototype vehicles. Such vehicles could be
covered by testing or manufacturer owned exemptions but would need to
be produced on an assembly line or other normal production practices.
Manufacturers would also need to ensure test methods are sufficiently
similar from year to year to allow for a meaningful analysis of trends.
6. Vehicle Model Year Definition
    For Phase 2 tractors and vocational vehicles, the vehicle's
regulatory model year is usually the calendar year corresponding to the
vehicle's date of manufacture. However, the Phase 2 regulations allow
the vehicle's model year to be designated as the year before the
calendar year corresponding to the vehicle's date of manufacture if the
engine's model year is from an earlier year. We are amending as
proposed the definition of model year in Sec.  1037.801 to allow
vehicle manufacturers to extend the period during which a vehicle's
certification is valid to account for this flexibility. This
clarification more explicitly explains how vehicle manufacturers
utilize this existing flexibility.
    After promulgation of the Phase 2 final rule, it became apparent
that the Phase 2 vehicle model year definition does not allow starting
vehicle production before the start of the named year if the engine
model year also begins in the earlier year. For example, if a
manufacturer would start its 2024 engine model year in December 2023,
the definition would not allow vehicles produced in 2023 to be model
year 2024.
    To address this issue, EPA is allowing the option for the vehicle's
model year to be designated as the year after the calendar year
corresponding to the vehicle's date of manufacture. This has the effect
of allowing manufacturers to meet standards earlier with aligned engine
and vehicle model years. Model years would still be constrained to
reflect annual (rather than multi-year) production periods and include
January 1 of the named year.
    We did not receive comments on these proposed change to the
definition of model year for vehicles. We are accordingly adopting the
revised definition for model year in 40 CFR 1037.801 for tractors and
vocational vehicles with a date of manufacture on or after January 1,
2021, as proposed, except that the final rule includes additional text
to make explicit the requirement for the model year to be based on the
manufacturer's annual production period for new models. This is
consistent with the definition of model year for vehicles subject to
Phase 1 standards in the same section.
7. Compliance Margins for GEM Inputs
    The regulations at 40 CFR 1037.620(d) allow component manufacturers
to conduct testing for vehicle manufacturers, but they do not specify
restrictions for the format of the data. Vehicle manufacturers have
raised concerns about component manufacturers including compliance
margins in GEM inputs--in other words, inputting a value that is
significantly worse than the tested result. They state that many
component suppliers are providing GEM inputs with compliance margins,
rather than raw test results. However, when stacked together, the
compliance margins would result in inappropriately high GEM results
that would not represent the vehicles being produced.
    We proposed to note in 40 CFR 1037.501(i) that declared GEM inputs
for fuel maps and aerodynamic drag area will typically include
compliance margins to account for testing variability and that, for
other measured GEM inputs, the declared values will typically be the
measured values, and received comment requesting additional
clarification and providing additional suggested revisions as described
in Chapter 2 of the Response to Comments document. One commenter
suggested that EPA finalize default allowance values at this time,
however we lack adequate data to make a thorough determination on what
these values should be. In addressing manufacturers' concern, it is
important to distinguish between engine fuel maps (which are certified
separately) and other GEM inputs that are not certified. As is
discussed in Section II.B.3, certified engine fuel maps are expected to
include compliance margins to account for manufacturing and test
variability. However, EPA did not expect each of the other GEM input to
have a

significant compliance margin of its own. (Note that the aerodynamic
bin structure serves to provide an inherent compliance margin for most
vehicles.) Rather, we expected the certifying original equipment
manufacturer (OEM) to include compliance margins in their Family
Emission Limits (FELs) relative to the GEM outputs.
    For vehicle GHG standards, the primary role for FEL compliance
margins is to protect against SEA failures. Without a compliance margin
under the Phase 2 regulations, normal production variability would
cause some vehicles to fail, which would require the testing of
additional vehicles. Even if the family ultimately passed the SEA, it
would probably require the manufacturer to test a large number of
vehicles. However, because SEAs and confirmatory tests for particular
components would not target GEM inputs for other components, a modest
vehicle FEL compliance margin determined by the vehicle manufacturer,
that accounts for the component input with the highest uncertainty used
to determine the vehicle FEL, would be sufficient to cover the full
range of uncertainty for all components.
    While we are not adopting explicit changes with respect to
compliance margins that were requested in comments, we are finalizing
the revision in Sec.  1037.501(i) as with clarifying edits that, for
other measured GEM inputs, the declared values are typically the
measured values without adjustment, and finalizing a related provision
after consideration of comments on this proposed revision and on
conducting a confirmatory test and SEA for an axle or transmission
apart from a specific vehicle. Specifically, the additional change
clarifies this intent for confirmatory testing in 40 CFR 1037.235(c)(2)
by stating that the results will only affect your vehicle FEL if the
results of our confirmatory testing result in a GEM vehicle emission
value that is higher than the vehicle FEL declared by the manufacturer.
    These revisions further obviate a need for component-specific
compliance margins and should thus further clarify that component-
specific suppliers should be providing GEM inputs with raw test
results, rather than values that include an associated compliance
margin. While we do not believe that suppliers should normally include
compliance margins when providing test data to OEMs for GEM inputs, we
do believe they should provide to OEMs some characterization of the
statistical confidence they have in their data. This allows the OEM to
apply an appropriate overall compliance margin for their vehicle FEL.
During a confirmatory test, EPA would compare the GEM results using our
measured inputs with the declared FEL for the vehicles, which means
that the compliance margin for measurement variability should be built
into the FEL of the vehicle. Again, EPA notes that the certified engine
fuel maps are expected to include small compliance margins to account
for manufacturing and test variability.
    Finally, none of this is intended to discourage suppliers and OEMs
from entering into commercial agreements related to the accuracy of
test results or SEA performance.
8. SEAs for Axles and Transmissions
    Under 40 CFR 1037.320, a selective enforcement audit (SEA) for
axles or transmissions would consist of performing measurements with a
production axle or transmission to determine mean power loss values as
declared for GEM simulations, and running GEM over one or more
applicable duty cycles based on those measured values. The axle or
transmission is considered passing for a given configuration if the new
modeled emission result for every applicable duty cycle is at or below
the modeled emission result corresponding to the declared GEM inputs.
As described below, EPA is revising the provision regarding where an
axle or transmission does not pass.
    We believe special provisions are needed for axles and
transmissions given their importance as compliance technologies and a
market structure in which a single axle or transmission could be used
by multiple certifying OEMs. Under the existing SEA regulations, if an
axle or transmission family from an independent supplier fails a SEA,
vehicle production could be disrupted for multiple OEMs and have
serious economic impacts on them. We are finalizing a revision that
will minimize the disruption to vehicle production.
    Under the revised provision, if the initial axle or transmission
passes, then the family would pass, and no further testing would be
required. This is the same as under the existing regulations. However,
if the initial axle or transmission does not pass, two additional
production axles or transmissions, as applicable, would need to be
tested. We are finalizing this revision as proposed, except we are
finalizing additional changes to Sec.  1037.320(c) after consideration
of comments received to the proposal in a couple respects. We further
clarified that these additional production axels or transmissions to be
tested could be different axle and transmission configurations within
the family to cover the range of product included in the family. We
also are finalizing an additional clarification in 40 CFR 1037.320(c)
that further address how the results from the SEA will be used to
determine if the manufacturer declared map should be replaced, by
stating that if you fail the audit test for any of the axles or
transmissions tested, the audit result becomes the declared map, also
requiring revision of any analytically derived maps if applicable, and
that these would become official test results for the family. In other
words, this approach would correct the data used by the OEM for their
end-of-year report.
    After consideration of comments, we are also finalizing changes to
40 CFR 1037.320(b) to clarify that the test transmission's gear ratios
and not the default ratios in 40 CFR 1036.540 should be used in GEM.
After consideration of comment regarding the lack of an engine defined
for use as a GEM input when a component-level SEA is being performed,
we have specified the use of the default engine map in 40 CFR part
1036, appendix C, and a default torque curve that we have added as
Table 1 to 40 CFR 1037.520. The axle and transmission GEM inputs can
now be determined based on the default map and torque curve. See
Chapter 2 of the Response to Comments for further details on comments
received and our responses.
9. Electric and Hybrid Vehicles in Vocational Applications
    Prior to the proposal, manufacturers expressed concern that the
Phase 2 regulations are not specific enough regarding how to classify
hybrid vocational vehicles (see Sec.  1037.140). This is not an issue
for tractors, which are classified based on gross vehicle weight rating
(GVWR). However, vocational vehicles are generally classified by the
class of the engines. Obviously, this approach does not work for
electric vehicle without engines. This approach could also misrepresent
a hybrid vehicle that is able to use an undersized engine. To address
these problems, we proposed changes to Sec.  1037.140(g)(1) to clarify
that the classification for tractors where provisions are the same as
vocational vehicles applies for hybrid and non-hybrid vehicles, and
paragraph (g)(4) to clarify that Class 8 hybrid and electric vehicles
are Heavy HDVs and all other vehicles are classified by GVWR classes.
CARB and Tesla supported the regulation changes proposed in Sec.
1037.140(g). We did not receive any

adverse comments on these proposed revisions and we are finalizing the
proposed revisions with the addition of ``electric'' to paragraph
(g)(1) for consistency with the rest of the section and an expanded
clarification in paragraph (g)(4)(iii) that Class 8 hybrid and electric
vehicles are considered Heavy HDV, regardless of the engine's primary
intended service class.
    CARB suggested tying certification provisions such as warranty and
useful life to the vehicle GVWR to avoid allowing a downsized hybrid
powertrain installed in a heavier vehicle weight class to have shorter
useful life and emission warranty obligations. We note that useful life
(Sec.  1037.105(e)) and warranty (Sec.  1037.120(b)) for vocational
vehicles are defined by vehicle service class (i.e., Light HDV, Medium
HDV, and Heavy HDV) and our final revision to Sec.  1037.140(g)(4)
ensures all Class 8 hybrid and electric vehicles are classified in our
heaviest weight class with the longest useful life and warranty
periods. Consequently, any powertrain in a Class 8 vehicle, including a
downsized hybrid, would be a Heavy HDV and subject to all corresponding
certification provisions for Heavy HDVs.
    We also requested comment on alternative approaches, such as
specifying the useful life in hours rather than miles for these
vocational vehicles or allowing electric vehicles to step down one
weight class, with justification from the manufacturer. With respect to
the potential alternative approaches we requested comment on, Ford
supported specifying useful life in hours rather than miles for
vocational vehicles. However, CARB raised questions on how the useful
life in miles correlates to engine hours. Tesla encouraged EPA to
continue to use a single, miles-based criteria for useful life. In
addition, Ford expressed support for allowing electric vehicles to step
down one weight class. We are not taking final action on any of the
potential alternative approaches at this time. Regarding adopting
useful life criteria based on engine hours, we currently lack the data
required to link engine hours to miles for the range of vocational
vehicles. Regarding potentially allowing electric vehicles to step down
one weight class, we currently have concerns that this may allow for
inappropriate useful life and warranty requirements.
    Section 1037.140(g)(5) references Sec.  1037.106(f) in specifying
that, in certain circumstances, you may certify vehicles to standards
that apply for a different vehicle service class. We received comments
from EMA and Volvo and agree with the commenters' suggestion to clarify
how our revision to Sec.  1037.140(g)(1) regarding hybrid and electric
tractors interacts with the cross-referenced Sec.  1037.106(f).
Consistent with our explanation at proposal that the current
requirements in Sec.  1037.140(g) applied to all tractors, we are also
finalizing a corresponding clarification in Sec.  1037.106(f)(2)
regarding Class 7 hybrid and electric tractor's ability to certify to
the Class 8 standards, by adding a sentence that ``[t]his applies
equally for hybrid and electric vehicles.'' See Chapter 2 of the
Response to Comments for further details on comments received and our
responses.
10. Vocational Vehicle Segmentation
    The Phase 2 regulatory structure applies the primary vocational
standards by subcategory. Manufacturers are generally allowed to
certify vocational vehicles in the particular duty-cycle subcategory
they believe to be most appropriate, consistent with good engineering
judgment.\20\ This process for selecting the correct subcategory is
often called ``segmentation.'' Under this structure, EPA expects
manufacturers to choose a subcategory for each vehicle configuration
that best represents the type of operation that vehicle will actually
experience in use. This is important because several technologies
provide very different emission reductions depending on the actual in-
use drive cycle. For example, stop-start would provide the biggest
emission reductions for urban vehicles and much less reduction for
vehicles that operate primary on long intercity drives.
---------------------------------------------------------------------------

    \20\ See 40 CFR 1068.5 for specifications on applying good
engineering judgment.
---------------------------------------------------------------------------

    Vocational vehicles are classified based upon the gross vehicle
weight rating (GVWR) as defined in Sec.  1037.140(g). Once classified,
manufacturers identify the intended regulatory subcategory duty cycles
(i.e., Urban, Multi-purpose, or Regional) for each vocational vehicle
configuration as indicated in Sec.  1037.140(h). There are constraints
for vocational duty cycle and regulatory subcategory, specified in
Sec.  1037.150(z).
    Prior to the proposal, manufacturers raised concerns about the
impact of this structure on their ability to plan for and monitor
compliance. They suggested that more objective and quantitative ``good
engineering judgment'' criteria would be helpful. In response to these
concerns, EPA proposed an interim ``safe harbor'' provision in Sec.
1037.150(bb) for vocational vehicle segmentation. Under the proposal,
manufacturers meeting the safe harbor criteria would be presumed to
have applied good engineering judgment, and we explained that we
thought the criteria were consistent with the intent of the Phase 2
program and would not allow manufacturers to reduce the effective
stringency the standards.
    The first principle of the proposed safe harbor was that any
vehicle could be classified as Multi-purpose. The Multi-purpose duty
cycle weighting factors include significant weightings for highway
operation, lower speed transient operation, and idle. Thus, it would
not generally overvalue an individual technology. The second principle
of the proposed safe harbor was that vehicles not classified as Multi-
purpose should not be exclusively Regional or Urban. We proposed a
quantitative measure that evaluates the ratio of Regional vehicles to
Urban vehicles within an averaging set. Specifically, we proposed that
the ratio of Regional vehicles to Urban vehicles must be between 1:5
and 5:1. EPA requested comment on the proposed approach overall and the
range of acceptable ratios.
    CARB supported the proposed provision of allowing any vocational
vehicle to be classified as Multi-purpose. However, both EMA and CARB
questioned the ratios for vocational vehicle categories in the proposed
provisions of Sec.  1037.150(bb). EMA commented that the proposed
ratios were ``arbitrary'' and may not be represent a manufacturer's
model mix during any specific year. Instead, EMA suggested that more
appropriate ``good engineering judgment'' would be to base the vehicle
category on ``the duty cycle weighting under which it performs most
efficiently in GEM.'' CARB commented that the ratio could inadvertently
drive manufacturers to certify the vehicles with an inappropriate duty
cycle and recommended all vehicles be certified as Multi-purpose unless
the manufacturer could provide ``good justification'' for a Regional or
Urban categorization.
    We are finalizing a revision in Sec.  1037.140(h) and throughout
Sec.  1037.150(z) to replace ``duty cycle'' with the term ``regulatory
subcategory'' that more appropriately reflects the intent of
classifying a vehicle and its connection to a standard. Additionally,
after considering the comments, EPA is finalizing one principle of the
safe harbor provision proposed as Sec.  1037.150(bb); specifically, the
paragraph that allows manufacturers to select the Multi-purpose
subcategory for any vocational vehicle, unless otherwise

specified in Sec.  1037.150(z).\21\ As noted previously, selecting this
subcategory and associated duty cycle would require technologies that
reduce emissions across all operation (i.e., high speed, lower speed
transient, and idle) and we believe it is an appropriate default duty
cycle if a manufacturer is unsure of the final vehicle application when
applying the good engineering judgment provision of Sec.  1037.140(h).
We agree with the concerns expressed by CARB and EMA and are not
finalizing the ratios of Regional to Urban vehicles in paragraph Sec.
1037.150(bb)(2) of the proposed safe harbor provision. Instead, as
discussed further below, we continue to rely on the constraints listed
in Sec.  1037.150(z) to guide manufacturers in identifying an
appropriate duty cycle, with the addition of a Multi-purpose safe
harbor.
---------------------------------------------------------------------------

    \21\ This portion of the proposed safe harbor provision was
proposed as Sec.  1037.150(bb)(1).
---------------------------------------------------------------------------

    Section 1037.150(z) outlines the constraints manufacturers apply
when determining the appropriate vocational subcategory for their
vehicles as described in Sec.  1037.140. Instead of adding a new
paragraph (bb) as proposed, we are reordering Sec.  1037.150(z) and
incorporating a new paragraph to allow the Multi-purpose
classification. The modified Sec.  1037.150(z)(1) through (3) now
include the current provisions that identify the vehicle configurations
(designed for higher-speed cruise operation) for which manufacturers
must select the Regional subcategory, specifically if certified based
solely on testing with the high-speed Supplemental Emission Test, if
certified as a coach bus or motor home, or if equipped with a manual
transmission after MY 2024. Except where one of those existing three
criteria for the Regional subcategory apply, a new paragraph (z)(4)
allows manufacturers to select the Multi-purpose subcategory for any
vocational vehicle. The remaining renumbered paragraphs (z)(5) through
(7) describe the current regulation's existing allowances for and
limitations on selecting the Urban subcategory that are based on the
most appropriate transmission configurations for lower speed, stop-and-
go driving.
    We continue to believe market forces will induce manufacturers to
design their vocational vehicles such that their GHG emission
performance (and fuel efficiency) is optimized for their customers'
specific applications and, in most cases, it will be clear which
subcategory and associated duty cycle is appropriate for a given
vocational vehicle configuration. Consequently, the vehicles and their
associated technology packages will also be relatively optimized for
one of the vocational duty cycles available for compliance using GEM,
as shown in Table 1 of Sec.  1037.510. Where it is unclear, we would
evaluate whether a manufacturer has applied the good engineering
judgment required under Sec.  1037.140(h) taking into consideration
whether the subcategory selected is best suited for the vehicle as
indicated by the totality of its powertrain options, vehicle features,
and duty cycle performance under which it demonstrates the most
favorable emissions result relative to the emission standard. We note
that in our review of a manufacturer's good engineering judgment
request, we reserve the right to require the use of a more appropriate
duty cycle and subcategory. We will continue to monitor use of the good
engineering judgment provision of Sec.  1037.140(h) and the constraints
listed in Sec.  1037.150(z) and may re-evaluate our approach in the
future if we determine it is necessary.
    Thus, the final regulations include consideration of both EMA and
CARB's suggestions. As noted previously, we would consider the duty
cycle weighting under which the vehicle performs most efficiently in
GEM in considering whether good engineering judgment was used, and have
provided manufacturers of vehicles not subject to the constraints
listed in Sec.  1037.150(z) with a clear pathway to certify those
vehicles as Multi-purpose if they are otherwise unable to justify
Regional or Urban duty cycle when exercising good engineering judgment.
    In the proposed rule, we also requested comment on the need for the
subcategory on the label. EMA commented that it is unnecessary and a
complication and burden for manufacturers to identify whether the
vehicle is in the Urban, Multi-Purpose or Regional subcategory on the
label and requested that we ``remove the requirements in Sec.
1037.135(c)(3) and (4)''. CARB commented and encouraged EPA to require
the subcategory be on the label because it would help consumers choose
the appropriate certified vehicles for their intended vehicle operation
cycles. After consideration of EMA's and CARB's comments, we are
removing the requirement to explicitly state the regulatory subcategory
on the emission label as specified in Sec.  1037.135(c)(4). In the
Phase 2 final rulemaking, we concluded that it was unnecessary for the
emission label to contain a comprehensive list of all emission
components and that it is important to balance the manufacturers'
``need to limit label content with the [the agencies'] interest in
providing the most useful information for inspectors'' (81 FR 73636,
October 25, 2016). Since stating the regulatory subcategory on the
label provides limited additional information inspectors could use to
quickly determine if the vehicle is in its certified condition and the
subcategory can be identified from the vehicle family name required by
paragraph (c)(3), we believe it is appropriate to remove it as a
requirement on the emission label. We are not revising the current
requirement to print the standardized designation for the vehicle
family name as required by Sec.  1037.135(c)(3), which ensures
consistency between the label and other compliance provisions that
require the vehicle family name. As such, the regulatory subfamily can
continue to be identified from the family name, which should help
address CARB's concern if a consumer chooses to use the emissions label
when deciding to purchase a vehicle.
11. Early Certification for Small Manufacturers
    Vehicle manufacturers that qualify as small businesses are exempt
from the Phase 1 standards, but must meet the Phase 2 standards
beginning January 1, 2022.\22\ However, some vehicle families have been
certified voluntarily to Phase 1 standards by small manufacturers. In
an effort to encourage more voluntary early certification to Phase 1
standards, we proposed a new interim provision in Sec.  1037.150(y)(4)
for small manufacturers that certify their entire U.S.-directed
production volume to the Phase 1 standards for calendar year 2021 (85
FR 28150). Small manufacturers may delay complying with the Phase 2
standards by one year, and instead comply with the Phase 1 standards
for that year, if they voluntarily comply with the Phase 1 standards
for one full prior year. Specifically, small manufacturers may certify
their model year 2022 vehicles to the Phase 1 greenhouse gas standards
of Sec. Sec.  1037.105 and 1037.106 if they certify all the vehicles
from their annual U.S.-directed production volume to the Phase 1
standards starting on or before January 1, 2021. If the small
manufacturers do so, the provision allows these manufacturers to
certify to the Phase 1 standards for model year 2022 (instead of the
otherwise applicable Phase 2 standards). Early compliance with the
Phase 1 standards should more than offset any reduction in benefits
that would otherwise be

achieved from meeting Phase 2 standards starting January 1, 2022.\23\
---------------------------------------------------------------------------

    \22\ See 40 CFR 1037.150(c).
    \23\ The magnitude of any impact on air quality would be small
because of the low production volumes from these small business
manufacturers.
---------------------------------------------------------------------------

    The provision we proposed also allows the Phase 1 vehicle credits
that small manufacturers generate from model year 2018 through 2022
vocational vehicles to be used through model year 2027. Under the
existing regulations, all manufacturers that generate credits under the
Phase 1 program are allowed to use such Phase 1 vehicle credits in the
Phase 2 vehicle averaging, banking, and trading program, but the
credits are subject to the five-year credit life. As noted in the
proposed rule, we believe the limit on credit life can be problematic
for small manufacturers with limited product lines which allow them
less flexibility in averaging, and the longer credit life will provide
them additional flexibility to ensure all their products are fully
compliant by the time the Phase 2 standards are fully phased in for
model year 2027. We note that these Phase 1 emission credits are based
on the degree to which the Family Emission Limit is below the Phase 1
standard.
    We received no adverse comment to either proposal for small
manufacturers in Sec.  1037.150(y)(4). Our final revisions include
minor edits to the proposed credit-related provision in Sec.
1037.150(y)(4) to create a standalone sentence and moving the proposed
provision that describes the certification flexibility for these small
manufacturers to a new Sec.  1037.150(c)(4) where the applicable
standards and implementation dates for qualifying small businesses are
introduced.
12. Delegated Assembly
    In 40 CFR 1037.621, EPA specifies provisions to allow manufacturers
to ship incomplete vehicles and delegate the final assembly to another
entity. Manufacturers previously expressed the concern that these
``delegated assembly'' requirements are too burdensome in some cases,
particularly in cases such as auxiliary power units and natural gas
fuel tanks. EPA requested comment on this issue and proposed a single
clarifying edit in Sec.  1037.621(g). CARB encouraged EPA to maintain
the existing delegated assembly provisions. We received no comments
adverse these existing provisions or providing suggestions for updated
text. The final rule adopts only the single clarifying edit in Sec.
1037.621(g), as proposed.
13. Canadian Vehicle Standards
    During the Phase 2 rulemaking, Environment and Climate Change
Canada (ECCC) emphasized that the highway weight limitations in Canada
are much greater than those in the U.S. Where the U.S. Federal highways
have limits of 80,000 pounds gross combined weight, Canadian provinces
have weight limits up to 140,000 pounds. This difference could
potentially limit emission reductions that could be achieved if ECCC
were to fully harmonize with the U.S.'s HD Phase 2 standards because a
significant portion of the tractors sold in Canada have GCWR (Gross
Combined Weight Rating) greater than EPA's 120,000-pound weight
criterion for ``heavy-haul'' tractors.
    EPA addressed this in Phase 2 by adopting provisions that allow the
manufacturers the option for vehicles above 120,000 pounds GCWR to meet
the more stringent standards that reflect the ECCC views on appropriate
technology improvements, along with the powertrain requirements that go
along with higher GCWR (see 81 FR 73582, October 25, 2016). Vehicles in
the 120,000 to 140,000 pound GCWR range would normally be treated as
simple ``heavy haul'' tractors in GEM, which eliminates the GEM input
for aerodynamics. However, vehicles certified to the optional standards
would be classified as ``heavy Class 8'' tractors in GEM, which then
requires an aerodynamic input. Nevertheless, they both use the heavier
payload for heavy haul.
    ECCC has since adopted final standards for these 120,000 to 140,000
pound GCWR tractors, which differ from the optional standards finalized
in Phase 2.\24\ Since the purpose of these standards was to facilitate
certification of vehicles intended for Canada, we proposed optional
standards in Sec.  1037.670 that would be the same as the final ECCC
standards. We did not receive any comments adverse the proposed
optional standards and we are finalizing the optional standards as
proposed in Sec.  1037.670. Note that these standards are not directly
comparable to either the normal Class 8 standards or the heavy haul
standards of Sec.  1037.106 because GEM uses different inputs for them.
Manufacturers who choose to opt into meeting the Canadian standards
would achieve greater emission reductions compared to EPA's program.
---------------------------------------------------------------------------

    \24\ Government of Canada. Regulations Amending the Heavy-duty
Vehicle and Engine Greenhouse Gas Emission Regulations and Other
Regulations Made Under the Canadian Environmental Protection Act,
1999: SOR/2018-98, Canada Gazette, Part II, Volume 152, Number 11,
May 16, 2018. Available online: http://gazette.gc.ca/rp-pr/p2/2018/2018-05-30/html/sor-dors98-eng.html.
---------------------------------------------------------------------------

    ECCC has also adopted new standards for tractors in the 97,000 to
120,000 pound GCWR category. In general, EPA would classify a tractor
in the 97,000 to 120,000 lb GCWR range in one of its Class 8 tractor
subcategories. EPA's Class 8 tractor standards, which cover up to
120,000 lb GCWR, have standards that are more stringent than ECCC's
standards for their 97,000 to 120,000 lb GCWR subcategory. We did not
propose special provisions for these tractors, but requested comment on
the need for special provisions for these vehicles. Both EMA and Volvo
commented that special provisions are necessary to facilitate
certification of 97,000 to 120,000-pound GCWR tractors for export to
Canada. EMA suggested a similar approach for these 97,000 to 120,000-
pound GCWR tractors as the one provided for the optional certification
for tractors at or above 120,000 pounds GCWR, proposed in Sec.
1037.670. Similarly, Volvo requested that EPA provide subcategories and
standards for these tractors that align with the ECCC regulations. We
have concerns with the suggestion of providing an option for tractor
standards that are less stringent than our current standards. EPA did
not propose and is not taking any final action on special provisions
for such vehicles at this time.
14. Transmission Calibrations
    Manufacturers with advanced transmission calibrations may use the
powertrain test option in Sec.  1037.550 to demonstrate the performance
of their transmissions. We adopted this option to provide an incentive
for the development of advanced transmissions with sophisticated
calibrations.
    Transmission manufacturers have developed some new efficient
calibrations, but must also maintain less efficient calibrations to
address special types of operation. Due to concerns about resale value,
most customers want to retain the ability to select the correct
calibration for their operation. For transmissions with such selectable
calibrations, Sec.  1037.235(a) requires that they test using the
worst-case calibration, which can undermine the incentive to continue
improving the calibrations. We received comment requesting that we
allow averaging of the worst-case and best-case performance, however
this request would be a significant departure from how engine families
are certified and what 40 CFR part 1037 currently requires for
transmissions. We also received comment on weighting the

calibration performance based on the actual use of these calibrations
in the field. We believe that this option will give the most
representative use of these calibrations and their impact on
CO2 emissions. After consideration of these comments, we are
finalizing a change to allow manufacturers to measure both the best-
and worst-case calibrations and weight them by prior model year based
on survey data, prior model year sales volume, or other appropriate
means. This weighting will be accomplished by testing both calibrations
and weighting the results in Table 2 of Sec.  1037.550 as described in
amendments made in Sec.  1037.235(a). See Chapter 2 of the Response to
Comments for further details on comments received and our responses.
15. Other Minor Heavy-Duty Vehicle Amendments
    We received no adverse comments to the following proposed
amendments. EPA is finalizing the following amendments to part 1037 as
proposed:
     Section 1037.103(c)--Adding phrase ``throughout the useful
life''.
     Section 1037.105 Table 5--Updating footnote format in
table.
     Section 1037.106 Table 1--Updating footnote format in
table.
     Section 1037.120(b)--Correcting the text with respect to
tires and Heavy Heavy-Duty vehicles.
     Section 1037.150(c)--Adding a sentence pointing to
additional interim provisions for small manufacturers.
     Section 1037.150(aa)--Clarifying the production limit for
drayage tractors under the custom chassis allowance.
     Section 1037.201(h)--Correcting phrase ``except that Sec.
1037.245 describes . . .'' to refer to Sec.  1037.243.
     Section 1037.205(e)--Correcting parenthetical ``(see 40
CFR 1036.510)'' to refer to 40 CFR 1036.503.
     Section 1037.225(e)--Reorganizing paragraph with the
introduction noting starting data, paragraph (e)(1) with existing text,
and a new paragraph (e)(2) regarding the requirement that the amended
application be ``correct and complete''.
     Section 1037.230(a)(2)--Adding two clarifying paragraphs
for optional tractor subcategories.
     Section 1037.243(c)--Rephrasing for consistency with other
paragraphs in the section.
     Section 1037.255--Replacing the possessive ``your'' with
articles a/an/the throughout this section and added clarifying
statements related to the information submitted in an application for a
certificate of conformity.
     Section 1037.301(b)--Removing phrase ``matches or exceeds
the efficiency improvement''.
     Section 1037.635(c)(1)--Editorial, adding a missing
``the''.
     Section 1037.701(h)--Editorial, fixing reference.
     Section 1037.705(c)(2)--Adding a clarification for
exported vehicles.
     Section 1037.801--Correcting punctuation in Compression-
ignition and Low rolling resistance tires definitions; adding the word
``motor'' to definition of Electric vehicle; adding definition of
electronic control module; clarifying Heavy-duty vehicle definition
with respect to incomplete vehicles; adding definition of High-strength
steel; clarifying Light-duty truck definition; adding Tonne definition.
     Section 1037.805(c) and (d)--Editorial; updating to be
consistent with format in other parts.
    EPA is also finalizing the following additional amendments, that
include revisions we are finalizing as proposed but with additional
clarifications, editorial improvements, or to fix typographical errors,
after consideration of comments, as noted. Chapter 2 of our Response to
Comments includes additional details on some of these amendments, as
well as other amendments or clarifications requested by commenters and
our responses.
     Section 1037.150(c)--Reorganizing the section into
subparagraphs; removing ``qualifying'' throughout; moving reference to
NAICS codes into definition of ``small manufacturer'' in Sec.
1037.801; and combining the statements regarding the MY 2022
implementation date for tractor and vocational vehicles and the
additional delays in later years for alternatively-fueled tractors and
vocational vehicles into the new paragraph (c)(2) to provide further
clarification in response to CARB's seeming misinterpretation of the
regulations in a submitted comment related to our proposed Sec.
1037.150(y)(4) provision. Also moving the certification-focused portion
of the early certification provision proposed as part of Sec.
1037.150(y)(4) to a new paragraph (c)(4) as discussed in Section
II.C.11.
     Section 1037.231(b)(7)--Adding an additional revision to
provide clarification on forward gear availability, noting that
available forward gear means the vehicle has the hardware and software
to allow operation in those gears, consistent with our final revision
to Sec.  1037.520(g) as noted in Section II.A.2.
     Section 1037.235(h)--Providing an example of an ``untested
configuration'' in response to EMA's request for clarification.
     Section 1037.601(a)(2)--Removing limit of ``up to 50'' and
added a more general statement that we will limit the number of
engines.
     Section 1037.615--Clarifying that fuel cells powered by
hydrogen should have a Family Emission Limit of 0 g/ton-mile for
calculating CO2 credits. Vehicles fueled by hydrogen are
inherently carbon-free, which supports treating these vehicles the same
as electric vehicles. This clarification is responsive to a comment
from EMA.
     Section 1037.660(a)(2)--Revising to specify the
permissible delay before engaging neutral idle when the vehicle is
stopped; updating from proposed value of two seconds to the final value
of five seconds after consideration of a request from Ford that
suggested ``two seconds is too short to account for normal stops and
restarts in real on-road driving''. This request was posed in an email
to EPA following the proposed rule.\25\
---------------------------------------------------------------------------

    \25\ Memorandum to Docket EPA-HQ-OAR-2019-0307, Email from Ken
McAlinden (Ford) Requesting Regulatory Change for Neutral Idle
Credit, Christopher Laroo, September 23, 2020.
---------------------------------------------------------------------------

     Section 1037.740(b)--Updated naming convention to match
vehicle service classes Our revised delay of five seconds for neutral
idle accommodates Ford's request and is consistent with the permissible
Sec.  1037.740(b)--Updating the naming convention to match vehicle
service classes.
     Section 1037.801--Updating the proposed definitions for
``hybrid engine or powertrain'' and ``hybrid vehicle'' to be consistent
with the proposed and further developed hybrid powertrain test
procedure revisions to part 1036, subpart F, and the definitions of
``hybrid powertrain'' and ``mild hybrid'' added to 40 CFR part 1036.
These revisions add examples of systems that qualify as hybrid engines
or powertrains, specifically systems that recover kinetic energy and
use it to power an electric heater in the aftertreatment. Updating
model year definition as discussed in Section II.C.6 and small
manufacturer definition as discussed in II.C.11.
     Section 1037.805(b)--Updating quantity and quantity
descriptions including additional revisions to those proposed to ensure
that these descriptions were consistent throughout the part.
     Section 1037.805(f)--Adding an additional revision to
those proposed to update gravitational constant after consideration of
comments received on the proposal.
     Appendix III to part 1037--Updating the definition of the
emission control identifier ``DWSW'' to clarify

high-strength steel wheel and maintain consistency with the related
requirements in Table 6 of Sec.  1037.520, after consideration of
comment by CARB.

D. Onboard Diagnostics (``OBD'')

    EPA proposed several updates to the onboard diagnostic (OBD)
provisions of 40 CFR part 86, subpart A, related to onboard diagnostic
requirements for heavy-duty engines and requested comment on general
improvements and efforts to harmonize EPA and CARB OBD requirements
(see 85 FR 28152). This section presents the changes we are adopting to
OBD requirements after consideration of comments received. Additional
details on these and other OBD amendments or clarifications requested
by commenters and our responses are available in Chapter 2 of our
Response to Comments document.
    EPA's OBD regulations for heavy-duty engines are contained in 40
CFR 86.010-18, and were promulgated February 24, 2009 (74 FR 8310).
Although these regulations were originally harmonized with CARB's OBD
program, CARB has since updated and made changes to their regulations
which EPA has not adopted. Most recently, in October 2019, CARB
approved revisions to the onboard diagnostics requirements that include
implementation of real emissions assessment logging (REAL) for heavy-
duty engines and other vehicles.
    The proposed rule requested comment on differences between existing
EPA and CARB OBD regulations and included specific proposed revisions
intended to reduce these differences. EPA proposed six specific
revisions to update existing OBD regulations and harmonize with CARB
requirements. We received comments supportive of these proposals, as
well as comments indicating that EPA should reconsider certain
proposals to ensure the regulations are clear and have the desired
effect. After further evaluation and consideration of comments, EPA is
finalizing four of these six proposed revisions:
    (1) Adopting as proposed the CARB 5% threshold for misfire in Sec.
86.010-18(g)(2). This would allow manufacturers to not detect misfires
under certain conditions, such as during aftertreatment regeneration
and some low temperature operation.
    (2) Adopting as proposed CARB's misfire flexibilities in
1971.1(e)(2.3.3) which include identifying when it is reasonable for a
manufacturer to seek approval for systems that cannot detect all
misfire under all required speed and load conditions and where they
seek approval to disable misfire detections.
    (3) Adopting with a clarification the proposed revision to our in-
use compliance standards in Sec.  86.010-18(p) to reflect the CARB
approach for minimum ratios for representative samples where a system
would be considered noncompliant if the representative test sample (or
performance group) indicates that the in-use ratio is below 0.088. A
clarification was added to specify that the in-use ratio is based on
the ``average'' value for the test sample group.
    (4) Adopting as proposed the allowance to use CARB OBD reporting
templates for EPA OBD requirements.
    EPA received comments on the 5% threshold for misfire indicating
concern that the provision as proposed does not reflect CARB's most
recent requirements. EPA's proposal in Sec.  86.010-18(g)(2)(iii)(C)
was to require misfire detection on those engines equipped with sensors
that can detect misfire occurrences. Existing CARB requirements state
that all diesel engines are required to continuously monitor for
misfire, not just those engines equipped to detect for misfire. EPA is
finalizing the misfire provision as proposed but may further review
this provision and may consider harmonizing with existing CARB
requirements that require misfire detection for all diesel engines as a
part of a future rulemaking. For example, the Cleaner Trucks Initiative
(``CTI'') rulemaking intends to consider updating existing EPA OBD
regulations and harmonizing further with CARB OBD requirements as noted
in the advance notice of proposed rulemaking (ANPR) (85 FR 3306,
January 21, 2020). EPA received comment on the proposal to revise our
in-use compliance standards that recommended adding a clarification to
the proposed language to indicate that the in-use ratio is based on the
average in-use ratio of the engines in the test sample group. The
comment pointed out that the regulations as proposed were not clear as
to how the in-use ratio would be determined. Existing EPA regulations
in Sec.  86.010-18(j)(3)(i) and (ii) specify that manufacturers must
collect and report in-use monitoring performance data representative of
production vehicles, separate production vehicles into monitoring
performance groups and submit data that represents each of these
groups. The purpose of this requirement is to analyze in-use data from
more than one vehicle to ensure that the OBD system is functioning
properly. The frequency that some OBD monitors run can vary depending
on the duty cycle of a particular vehicle, therefore, using the average
in-use ratio from to evaluate performance is most appropriate. Adding
this clarification also increases the alignment of EPA and CARB OBD
requirements. After consideration of these factors we have added the
word ``average'' to Sec.  86.010-18(p)(4)(ii) to provide this clarity.
Comments were also received on the in-use requirements stating that an
additional provision should be included to Sec.  86.010-18(p)(4)(ii) to
ensure that compliance with the in-use ratio requirement is not
influenced by engines with very high ratios which could lower the
average value. We are not finalizing this change at this time but
intend to review whether or not revisions to this provision should be
considered as a part of the CTI rulemaking effort. EPA received no
adverse comments on the proposal to allow the use of CARB's OBD
reporting template. Using the CARB template will help streamline
certification processes and reduce the time manufacturers may spend
entering duplicative information on different forms. EPA is finalizing
this provision as proposed to help harmonize requirements and
streamline the certification process.
    EPA is not taking final action at this time on two proposed
revisions: (1) To allow CARB certified configurations to not count as
separate engines families for the purposes of determining OEM test
requirements, and (2) to allow a simplified carryover OBD certification
path intended for special engine families. We received comments
indicating concern that these proposals were not clear. For example,
CARB noted that the proposed regulatory requirements for both carryover
certification and for determining required OBD demonstration testing
requirements relied on the term ``special engine family'' which is not
defined in EPA regulations. EPA intends to review these two issues and
other comments received on existing OBD requirements as part of a more
comprehensive effort to consider updating our existing OBD regulations
in the intended CTI rulemaking.

II. Other Amendments

A. Ethanol-Blend Test Fuels for Nonroad Spark-Ignition Engines and
Vehicles, Highway Motorcycles, and Portable Fuel Containers

    EPA adopted exhaust and evaporative emission standards for
gasoline-fueled nonroad engines, vehicles, and equipment before there
was a Federal gasoline test fuel with 10 percent

ethanol (E10). Most of those programs therefore relied on testing with
neat gasoline (E0) or with a splash-blended mix of neat gasoline and
ethanol to make E10. In the meantime, EPA adopted a Federal gasoline
test fuel with 10 percent ethanol for testing motor vehicles (79 FR
23414, April 28, 2014).
    California ARB adopted its own specification for an E10 test fuel
for testing motor vehicles, referred to as ``LEV III E10.'' California
ARB revised its nonroad emission control programs to require
manufacturers to start using LEV III E10 test fuel for certification
starting in model year 2020, without allowing for carryover of previous
data from testing with neat gasoline. California ARB's move to require
use of LEV III E10 test fuel for certification has led manufacturers to
express a concern about the test burden associated with separate
testing to demonstrate compliance with EPA and California ARB emission
standards.
    The concern for aligning test requirements related to test fuel
applies for marine spark-ignition engines (40 CFR part 1045), nonroad
spark-ignition engines above 19 kW (40 CFR part 1048), and recreational
vehicles (40 CFR part 1051).\26\ We expect a similar situation to apply
for highway motorcycles in the 2022-2025 time frame based on California
ARB's plans for further rulemaking activity.
---------------------------------------------------------------------------

    \26\ EPA adopted amendments to address these concerns for
nonroad spark-ignition engines at or below 19 kW in an earlier
rulemaking (80 FR 9114, February 19, 2015).
---------------------------------------------------------------------------

    We have issued guidance for marine spark-ignition engines (40 CFR
part 1045) \27\ and for recreational vehicles (40 CFR part 1051) \28\
describing how we may approve certification based on emission
measurements with an E10 test fuel. We are revising 40 CFR parts 1045,
1048, and 1051, consistent with the recently issued guidance documents,
to allow for certification based on emission measurements with EPA's
E10 test fuel without requiring EPA approval, and without adjusting
emission standards to account for fuel effects. For marine spark-
ignition engines (40 CFR part 1045), this merely replaces the existing
provision allowing for the alternative of using a splash-blended E10
test fuel. For recreational vehicles (40 CFR part 1051) and Large
spark-ignition (Large SI) engines (40 CFR part 1048), naming EPA's E10
specification as the alternative test fuel is a new provision. We are
not prepared in this rulemaking to justify adopting new emission
standards or to otherwise change the stringency of the existing
standards. It is therefore necessary for EPA to be able to do
confirmatory testing with either the original E0 test fuel, or the
manufacturer's selected alternative fuel.
---------------------------------------------------------------------------

    \27\ ``Marine Spark Ignition Engine Certification Testing with
California ARB E10 Test Fuel,'' EPA guidance document CD-18-15,
December 24, 2018.
    \28\ ``Off-Highway Recreational Vehicle Certification Testing
with California ARB E10 Test Fuel,'' EPA guidance document CD-19-03,
April 22, 2019.
---------------------------------------------------------------------------

    We are also allowing the same approach for certification based on
emission measurements with EPA's E10 test fuel for highway motorcycles
(including EPA confirmatory testing with either E0 or E10).
    We expect this approach of allowing E10 as an alternative test fuel
to adequately address concerns for the identified sectors. Many of
these engines have closed-loop fuel controls that reduce the effect of
fuel variables on exhaust emissions. Many also have relatively large
compliance margins relative to the standards that apply. These factors
help manufacturers confidently test with E10 as an alternative fuel,
knowing that they continue to be liable for meeting emission standards
on the specified E0 test fuel.
    In the proposed rule we described a process for approving the use
of California ARB's LEV III E10 test fuel instead of EPA's E10 test
fuel as the alternative test fuel. That process is detailed in the
existing regulations at 40 CFR 1065.701(b). The National Marine
Manufacturers Association, the Motorcycle Industry Council, and Polaris
requested that we revise the regulation to include California ARB's LEV
III E10 as an alternative test fuel. The two sets of fuel
specifications are nearly identical, with the notable difference being
that California ARB's LEV III E10 test fuel has a lower volatility,
which corresponds to the fuel regulations that apply in California. For
testing hot-stabilized engines, volatility has a very small effect on
exhaust emissions.
    We are not revising the regulation to specify California ARB's LEV
III E10 test fuel as an alternative test fuel. We expect the approval
process described in 40 CFR 1065.701(b) to allow for review that will
typically result in approval to use the California test fuel. However,
we remain concerned that there may be some limited circumstances in
which testing with the California fuel may not be appropriate for EPA
certification. For example, engine manufacturers might name a Family
Emission Limit to earn emission credits with a very narrow compliance
margin. In that case, we would want to be able to explore with the
manufacturer whether its testing adequately supports the proposed
application for certification. As another example, some nonroad sectors
include standards and testing requirements for controlling off-cycle
emissions. It may be appropriate for the manufacturer to perform some
of this off-cycle testing for certification using EPA's E0 or E10 test
fuel in addition to testing over specified duty cycles with California
ARB's LEV III E10 test fuel. To illustrate this point, we observed from
a recent experience exploring potential noncompliance that an engine
that has electronic feedback control can have a sensitivity to fuel
parameters that is much greater than we would expect based on a simple
assessment of combustion chemistry. We also note that the experience of
implementing these changes in test fuel requirements will inform our
ongoing approach for approving requests. Data supporting the
equivalence of EPA and California test fuels would lead us to reduce
our concerns for approving requests. In contrast, if we learn that fuel
effects are greater than expected, we would review requests more
carefully. This more careful review could be limited to a single
manufacturer or a single type of engine (or engine technology), or it
may apply more broadly.
    We specify evaporative emission standards and test procedures for
portable fuel containers and nonroad spark-ignition equipment in 40 CFR
part 59, subpart F, and 40 CFR part 1060, respectively. The gasoline
test fuel is splash-blended E10. California ARB specifies their LEV III
gasoline test fuel for the analogous procedures in California, but they
allow manufacturers to submit data instead using EPA's specified test
fuel. Accordingly, we believe manufacturers do not face the same burden
of needing to perform duplicate measurements for the two agencies. We
are therefore not changing the EPA test fuel for portable fuel
containers.
    Commenters largely affirmed the proposed approach for increased
flexibility for using E10 test fuels.\29\ We understand this approach--
allowing testing with E10 testing as an alternative procedure--to be an
interim measure. We expect to continue the move toward adopting E10
test fuel specifications, without referencing an E0 test fuel
specification, as we consider updating emission standards for each
sector over time. When we establish new standards, we would expect to
evaluate the stringency of those standards based on

testing with E10 test fuel, which will allow for adopting a singular
test fuel.
---------------------------------------------------------------------------

    \29\ See the Response to Comments for detailed input from
commenters.
---------------------------------------------------------------------------

B. Removing Obsolete CFR Content

    EPA first adopted emission standards for light-duty motor vehicles
and heavy-duty highway engines in the 1970s. Emission standards for the
first categories of nonroad engines started to apply in the 1990s. Each
of these programs include emission standards that apply by model year.
For most of these programs over time, engines and vehicles were subject
to increasingly stringent standards and improved certification and
testing requirements. All these standards and regulatory provisions are
codified in the Code of Federal Regulations. As time passes, the
regulations for past model years become obsolete, but it remains in
print until there is a rulemaking change to remove it from print. We
are removing large portions of this regulatory content that no longer
applies. The following sections describe these changes for different
sectors.
    Note that Section III.D describes several amendments to emission
control programs for motor vehicles in 40 CFR parts 85 and 86. These
amendments include several provisions that also remove obsolete
regulatory content.
1. Clean Fuel Fleet Standards (40 CFR Part 88)
    The Clean Air Act Amendments of 1990 included numerical standards
for the Clean Fuel Fleet program that were intended to encourage
innovation and reduce emissions for fleets of motor vehicles in certain
nonattainment areas as compared to conventionally fueled vehicles
available at the time. As originally adopted, those Clean Fuel Fleet
standards were substantially more stringent than the standards that
applied to vehicles and engines generally.
    Now that we have begun implementing Tier 3 standards in 40 CFR part
86, subpart S, the Clean Fuel Fleet standards are either less stringent
than or equivalent to the standards that apply to vehicles and engines
generally. Because the statute continues to require Clean Fuel Fleet
standards for state clean-fuel vehicle programs, we cannot simply
remove the Clean Fuel Fleet program from the regulations. Rather, we
are implementing the Clean Fuel Fleet standards in 40 CFR part 88 with
a compliance option where vehicles and engines certified to current
standards under 40 CFR parts 86 and 1036 would be deemed to comply with
the Clean Fuel Fleet standards as Ultra Low-Emission Vehicles. Further,
the Clean Fuel Fleet program as adopted included labeling requirements
for engine and vehicle manufacturers to identify compliant engines and
vehicles, and a restriction against including such engines or vehicles
when calculating emission credits. Both provisions would also no longer
be applicable because of the earlier mentioned increased stringency of
standards for engines and vehicles, and under the compliance option we
are establishing. Therefore, we are also removing these regulations.
This will give clear instructions to vehicle and engine manufacturers
as well as states that continue to have Clean Fuel Fleet provisions in
their State Implementation Plans or become subject to these
requirements in the future under the Clean Air Act (CAA) sections
182(c)(4)(A) and 246(a).
    For states with areas that become subject to the clean-fuel vehicle
program requirements in the future based on a new designation as an
ozone nonattainment area, the required state implementation plan
submission for the program or for a substitute measure is due within 42
months after the effective date of an area's nonattainment designation.
The clean-fuel vehicle program requirements apply for ozone
nonattainment areas with an initial designation as Serious, Severe, or
Extreme. For marginal and moderate ozone nonattainment areas that are
reclassified as Serious, Severe, or Extreme, the required state
implementation plan submission for the program or for a substitute
measure is due on the date specified in the EPA rulemaking finalizing
the area's reclassification.
    The Clean Fuel Fleet program also depends on vehicle
classifications that include Zero Emission Vehicles and Inherently Low-
Emission Vehicles. We are therefore preserving these defined terms in
40 CFR part 88. Under the new provisions, we will consider as Zero
Emission Vehicles all electric vehicles and any vehicle that does not
emit NOX, PM, HC, CO, or formaldehyde (including evaporative
emissions). We are simplifying the definition of Inherently Low-
Emission Vehicles to mean any certified vehicle that is designed to not
vent fuel vapors to the atmosphere.
2. Legacy Nonroad Standards (40 CFR Parts 89 Through 94)
    The 1990 amendments to the Clean Air Act authorized EPA to set
emission standards for nonroad engines. This led to a series of
rulemakings to adopt emission control programs for different nonroad
sectors. From 1994 through 1999, EPA adopted these emission control
programs in 40 CFR parts 89, 90, 91, 92, and 94 (all part of subchapter
C).
    Starting in 2002, EPA adopted emission standards for additional
nonroad emission control programs in a new subchapter, which allowed
for improved organization and harmonization across sectors. We codified
these new standards and related provisions in 40 CFR parts 1048, 1051,
1065, and 1068 (all part of subchapter U). Since then, we have migrated
the ``legacy'' emission control programs from subchapter C to
subchapter U. In each case, the migration corresponded to new emission
standards and substantially updated compliance and testing provisions.
This applies for the following sectors:

------------------------------------------------------------------------
             Sector                Legacy regulation  Current regulation
------------------------------------------------------------------------
Land-based nonroad diesel         40 CFR part 89....  40 CFR part 1039.
 engines.
Nonroad spark-ignition engines    40 CFR part 90....  40 CFR part 1054.
 at or below 19 kW.
Marine spark-ignition engines...  40 CFR part 91....  40 CFR part 1045.
Locomotives and locomotive        40 CFR part 92....  40 CFR part 1033.
 engines.
Marine diesel engines...........  40 CFR part 94....  40 CFR part 1042.
------------------------------------------------------------------------

    As a result of this migration, engine manufacturers have not
certified engines under the legacy parts for the last 5-10 years.
Removing these legacy parts reduces the cost to the Agency and prevents
confusion for readers who think that the old provisions still apply.
    While EPA's engine certification programs don't rely on these
obsolete provisions, the new programs refer to the legacy parts for
some specific provisions. For example, the new standard-setting part
for each type of engine/equipment allows manufacturers to continue to
certify carryover engine families based on test data from procedures
specified in the legacy parts.

We are not discontinuing further use of carryover data from engines
originally certified under the legacy parts. On the other hand, this
provision will gradually sunset itself as manufacturers update engine
designs and perform new testing for their engine families to meet
current standards.
    Another example of relying on the legacy parts in the new
regulations is emission credits generated under the legacy parts. In
most cases, current programs either disallow using those credits for
certification, or they allow it without keeping separate accounts for
credits generated under the legacy parts. We are making no changes
where credits from legacy parts are either unavailable or
indistinguishable from currently generated credits. One exception is
for land-based nonroad diesel engines certified under 40 CFR parts 89
and 1039. Current provisions in Sec.  1039.740 allow for limited use of
Tier 2 and Tier 3 credits from part 89 for certifying Tier 4 engines.
We are revising Sec.  1039.740, as proposed, to continue to allow
manufacturers to use credits generated from Tier 2 and Tier 3 engines
by simply changing the relevant references 40 CFR part 89 to 40 CFR
part 1039, appendix I.
    We are also aware that other Federal and state regulations and
compliance programs include numerous references to 40 CFR parts 89
through 94. To address this, we are replacing the full text of
regulations in the legacy parts with a paragraph describing the
historical scope and purpose for each part. The remaining paragraph
also directs readers to the new regulations that apply in subchapter U
and clarifies how the regulatory requirements transition to the new
content. As an example, the statute and regulations prohibit tampering
with certified engines throughout an engine's lifetime, even if the
original text describing that prohibition no longer resides in its
original location in the Code of Federal Regulations.
    We are also including the emission standards from the legacy parts
as reference material in an appendix in the appropriate CFR parts. This
allows for readily citing the historical standards in our own emission
control programs, and in any other Federal or state regulations or
compliance materials that depend on citing emission standards that are
no longer current for purposes of gaining EPA certification as part of
our nonroad emission control program.
    In addition to removing references to the legacy parts, we are
taking the opportunity to remove additional obsolete content from the
newer regulations. Most of these changes were adopted to address
temporary concerns as part of transitioning to new standards or other
new requirements. We adopted these changes in isolated regulatory
sections as ``interim provisions.'' Most of these interim provisions
have been obsolete for several years.
    References to the legacy parts are especially common for stationary
engines EPA regulates under 40 CFR part 60, subparts IIII and JJJJ. The
emission standards for stationary engines in many cases rely on current
or past nonroad emission standards in 40 CFR parts 89, 90, and 94.
Including all the iterations of these emission standards as reference
material allows us to preserve the existing set of standards and
requirements for stationary engines. This rule includes numerous
amendments to 40 CFR part 60 to change regulatory cites from the legacy
parts to the new regulatory parts in subchapter U, or to copy
referenced text directly into 40 CFR part 60.
    Most of the changes for stationary engines in 40 CFR part 60 are
intended to update references without changing standards or other
provisions. We are making three more substantive changes. First, we are
allowing all manufacturers of emergency stationary compression-ignition
internal combustion engines and stationary emergency spark-ignition
engines to certify using assigned deterioration factors. Since these
emergency engines generally serve in standby status in anticipation of
emergency situations, they often have lifetime operation that is much
less extensive than non-emergency engines. Assigned deterioration
factors would allow manufacturers to demonstrate the durability of
emission controls without performing testing that might otherwise
exceed the operating life of the engines being certified. We are
prepared to publish assigned deterioration factors based on currently
available information. We may need to revise those values in the future
as additional information becomes available, so we are not including
specific values for assigned deterioration factors in this rulemaking.
We are adopting these provisions as proposed, except that we are
referencing the relevant nonroad regulations that apply and we are
clarifying that assigned deterioration factors for stationary engines
are not limited to small-volume manufacturers.
    Second, stationary spark-ignition engines are currently subject to
emission standards and certification procedures adopted under 40 CFR
part 90 for Phase 1 engines. Revising the requirements for these
engines to instead rely on the certification procedures in 40 CFR part
1054 requires that we identify the Phase 1 standards as not including
the following provisions that apply for Phase 3 engines (as noted in
the amended regulatory text for appendix I of part 1054):
     The useful life and corresponding deterioration factors.
     Evaporative emission standards.
     Altitude adjustments.
     Warranty assurance provisions in Sec.  1054.120(f).
     Emission-related installation instructions.
     Bonding.
    Third, in response to a comment from the EMA, we are revising the
instruction regarding VOC measurement methods to allow manufacturers to
use any method that is specified for highway or nonroad engines in 40
CFR part 1065, subpart C. The current regulation at 40 CFR 60.4241(i)
identifies specific measurement procedures. When we revised 40 CFR part
1065 to include fourier transform infrared analyzers as an additional
measurement method, it would have been appropriate to modify 40 CFR
60.4241(i) to identify this additional measurement method. We are
addressing that in this rule by broadly referencing test methods in 40
CFR part 1065, subpart C, which includes fourier transform infrared
analyzers.
    In addition, following the proposed rule, we realized that 40 CFR
part 89 includes content that is, in fact, not obsolete. Specifically,
there is an interpretation of the Clean Air Act regarding the
preemption of state regulations related to nonroad engines in 40 CFR
part 89, subpart A, appendix A (62 FR 67736, December 30, 1997). This
interpretation describes EPA's belief that states may regulate the use
and operation of nonroad engines within certain parameters. This final
rule preserves appendix A by copying it into 40 CFR part 1074, where we
more broadly describe a range of issues related to preemption of state
regulation of nonroad engines.

C. Certification Fees (40 CFR Part 1027)

    EPA is making several minor changes in 40 CFR part 1027 to update
the procedures and align the instructions with current practices. None
of these changes involve change or reconsideration of fee policies. We
are finalizing the following changes:
     Correcting the name of the compliance program.
     Replacing the schedule of fees from 2005 with the fees
that apply for applications submitted in 2020.
     Revising the timeline for announcing adjusted fees for the
upcoming year from a January 31

deadline to a March 31 deadline. This will allow for a more orderly
process of calculating the new fees using the information from the
previous year.
     Correcting the equation for non-evaporative certificates
to no longer apply the inflation adjustment to operating costs. This
corrects a publishing error that mistakenly introduced parentheses in
the equation.
     Correcting the internet address for the consumer price
index used for inflation adjustments.
     Removing the sample calculation for determining fees for
2006.
     Revising submission and payment instructions to refer only
to electronic forms and transactions through www.Pay.gov.
     Clarifying that deficient filings must be resolved before
the end of the model year, and that the time limit for requesting
refunds applies equally to deficient filings.
    We received no comments on the proposed amendments to 40 CFR part
1027 and are adopting these amendments without modification.

D. Additional Amendments for Motor Vehicles and Motor Vehicle Engines
(40 CFR Parts 85 and 86)

    Motor vehicles and motor vehicle engines are subject to emission
standards and certification requirements under 40 CFR part 86. This
applies for light-duty vehicles, light-duty trucks, heavy-duty vehicles
and engines, and highway motorcycles. There are additional compliance
provisions in 40 CFR part 85. We are adopting the following amendments
to these provisions:
     Part 85: We are amending the provisions for
importation, exemptions, and model year to clarify that they no longer
apply for heavy-duty engines. Those engines are already subject to
analogous provisions under 40 CFR part 1068. While the two sets of
provisions are largely the same, we want to avoid the ambiguity of
having overlapping requirements. One aspect of this migration involves
discontinuing the provisions that apply for Independent Commercial
Importers for heavy-duty engines. No one has used these provisions for
several years, and we have no reason to believe anyone will start to
use these provisions. We are revising the regulatory text for the final
rule, based on a comment, to clarify that the importation provisions
continue to apply for highway motorcycles, and that references to
engines in 40 CFR part 85, subpart P, continue to apply for replacement
engines intended for installation in motor vehicles subject to the same
importation provisions.
     Part 85: We are making several minor corrections
to (1) refer to provisions in 40 CFR part 1068 related to confidential
business information and hearing procedures, and (2) clarify
organization names and addresses for submitting information.
     Part 85, subpart O: This subpart set emission
standards for 1993 and older model year urban buses undergoing engine
rebuilding. We have confirmed with the American Public Transportation
Association that there are very few such urban buses still operating,
and that none of them will have engine rebuilds. We are therefore
removing this content from the CFR.
     Section 85.1902(b)(2): We are clarifying that
defect-reporting requirements under paragraph (b)(2) apply for defects
related to noncompliance with greenhouse gas emission standards, not
criteria emission standards. This corrects an earlier amendment that
inadvertently described the provisions as applying to noncompliance
with any kind of emission standard. Defects related to criteria
emission standards are covered by Sec.  85.1902(b)(1).
     Sections 86.113-04, 86.213, and 86.513: Adding
optional reference procedures for measuring aromatic and olefin content
of E0 gasoline test fuel. These changes align with the reference
procedures for EPA's Tier 3 E10 gasoline test fuel at 40 CFR
1065.710(b). These changes are needed because material limitations
prevent laboratories from using the procedures in ASTM D1319. This
change also applies for the E0 gasoline test fuel specified in 40 CFR
1065.710(c),
     Section 86.129-00: Revising the description of
test weight basis to be loaded vehicle weight for all light-duty
vehicles and light-duty trucks. This is a correction to align the
regulation with current practice.
     Section 86.130-96: We are correcting the
reference to a testing flowchart that was moved to 40 CFR 1066.801.
     Sections 86.401-97 and 86.413-78: We are
removing obsolete sections to prevent confusion.
     Sections 86.419-2006 and 86.427-78: We are
revising the table with service accumulation parameters to clarify how
to perform testing separately for Class I-A and Class I-B, rather than
treating them as a single class.
     Sections 86.435-78 and 86.436-78: We are
correcting references to the regulation to clarify that a motorcycle is
compliant if measured test results are at or below the standards.
     Section 86.531-78: We are adding instruction to
seal exhaust system leaks as needed before testing highway motorcycles.
The amendment also applies for testing off-highway motorcycles and all-
terrain vehicles under 40 CFR part 1051. This same instruction also
applies for light-duty vehicle testing under 40 CFR 1066.110(b)(1)(vi).
We made minor wording changes after the proposed rule to clarify that
manufacturers need to close all known leaks as part of the effort to
prevent exhaust leaks from affecting the compliance demonstration.
     Part 86, subpart P: The idle test procedures for
spark-ignition engine and vehicles are no longer needed for
certification or other compliance demonstrations. We are therefore
removing this content from the CFR.
     Part 86, subpart Q: Engine technology has
advanced to include internal feedback controls and compensation to
allow for operation at a wide range of altitudes. The certification
requirements related to altitude adjustments are therefore mostly or
completely obsolete. We are finalizing a simplified version of the
altitude provisions for highway motorcycles at 40 CFR 86.408-78(c) and
(d) in case there are some very small motorcycles that require
adjustment for altitude.
     Section 86.1803-01: We are revising the
definition for heavy-duty vehicle, with a conforming revision to the
definition for light-duty truck, to clarify that the sole regulatory
criterion for whether a complete vehicle is a heavy-duty vehicle for
purposes of the regulation is whether its gross vehicle weight rating
is above 8,500 pounds. The current approach remains unchanged for
incomplete vehicles; that is, heavy-duty vehicles also include
incomplete vehicles even if their gross vehicle weight rating is at or
below 8,500 pounds, if their curb weight is above 6,000 pounds or if
their basic vehicle frontal area is greater than 45 square feet. The
revisions are intended to (1) prevent light-duty trucks from becoming
heavy-duty vehicles in a configuration involving a hybrid powertrain
due to the extra weight related to energy storage and (2) avoid an
incentive for manufacturers to add vehicle weight or frontal area
simply to avoid the standards that apply for light-duty vehicles. In
these cases, under the current definition, the curb weight or frontal
area would artificially increase to the point that the vehicle would
qualify as a heavy-duty vehicle, even though it otherwise has the
characteristics of a light-duty truck. This same change is not
necessary for incomplete vehicles because certifying manufacturers have
the option to select

the appropriate vehicle classification for those vehicles. Note that
the change applies only for future certification; any certified heavy-
duty vehicle that would no longer fit the description will not be
affected by the amended definition.
     Section 86.1811-17: The Federal Register
mistakenly published a reference to the Tier 3 p.m. standard. Since we
intended for the standard to apply at all times, we are amending the
regulation to properly refer to that as the Tier 3 p.m. standard.
     Section 86.1813-01: We are clarifying that
electric vehicles and fuel cell vehicles are not subject to evaporative