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. 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:
 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%).
 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.
 Measuring CO2 and fuel consumption at idle is particularly challenging.
 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:
Equation II-3
difference=i=1NeCO2compEPAi-eCO2compManuieCO2compManuiN⋅100 %
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.
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 §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 §1036.705(b)(5).  The second sentence of §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 §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 I 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.
Heavy-Duty Vehicle GHG Emission Standards and Flexibility
Aerodynamic Compliance Provisions
In addition to the aerodynamic test procedure amendments described in Section II.A.6, we proposed several updates to §1037.150(s) as it relates to EPA's confirmatory testing of aerodynamic parameters and §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.
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 §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 §1037.305. In keeping with the principle that good engineering judgment 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 §1037.150(s).
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 §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 §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 §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 §1037.305 and the coastdown test procedures of §1037.528 and we updated §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 §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 §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 §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 §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 §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 §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."
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 §1037.305. We are finalizing those three edits as proposed and additional editorial edits as follows:
 §1037.305  -  Replaced reference to 40 CFR 1068.420 with the range "40 CFR 1068.415 through 1068.425" as proposed.
 §1037.305(a)  -  Rephrased "whether or not a tractor fails to meet" to the more concise "whether a tractor meets".
 §1037.305(a)(2)  -  Corrected "coastdown effective" to "coastdown effective yaw angle" as proposed.
 §1037.305(a)(7)  -  Added a missing "m[2]" 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 §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 §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 §1037.501(g)(1).
As noted in Section II.C.1.a, we proposed and are finalizing a provision in §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 §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 §1037.305(a)(7)(v) allowing manufacturers to continue testing and to generate additional data that EPA may consider in our pass/fail determinations.
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.
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 §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
Technology
                               GEM Input Values

                                  Adjustable
                               Tamper-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

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.
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 §1037.660(b)(1)(ii) (cross-referenced under the existing regulations for vocational vehicles in §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 §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 §1037.660(b)(2)(i) to that particular provision in §1037.660(b)(1) and replaces it with a new provision in §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 paragraph §1037.660(b)(2)(ii), which is redundant with the existing cross-reference to paragraph (b)(1) in (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 §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.
We are finalizing editorial revisions to §1037.660(b) so the paragraphs consistently begin with "When". Additionally, we reordered the paragraphs of §1037.660(b)(1) to move the servicing provision previously located at §1037.660(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).
Neutral Idle Overrides
EPA proposed and is finalizing a provision in §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 §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 §1037.660(b).
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 §1037.205(b)(5), manufacturers are required to include a description of their idle reduction technology, including the override conditions of §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 §1037.660(b)(4) cross-reference the provisions for vocational vehicle AES (paragraph (b)(2)) and neutral idle (paragraphs (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 §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 §1037.660(b)).
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 §1037.520(e)(5), this process is available in the existing off-cycle provisions of §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 §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.
Self-contained air conditioning units.
We proposed a revision to §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 §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 §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."
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, §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 §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 §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.
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 §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.
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 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 §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.
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 §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 III, 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.
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 §1037.140).  This is not an issue for tractors, which are classified based on 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 §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 §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 (§1037.105(e)) and warranty (§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 §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.
§1037.140(g)(5) references §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 §1037.140(g)(1) regarding hybrid and electric tractors interacts with the cross-referenced §1037.106(f). Consistent with our explanation at proposal that the current requirements in  §1037.140(g) applied to all tractors, we are also finalizing a corresponding clarification in §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.
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.  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.
Vocational vehicles are classified based upon the gross vehicle weight rating (GVWR) as defined in §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 §1037.140(h). There are constraints for vocational duty cycle and regulatory subcategory, specified in §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 §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 §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 §1037.140(h) and throughout §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 §1037.150(bb); specifically, the paragraph that allows manufacturers to select the Multi-purpose subcategory for any vocational vehicle, unless otherwise specified in 1037.150(z). 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 §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 §1037.150(bb)(2) of the proposed safe harbor provision. Instead, as discussed further below, we continue to rely on the constraints listed in §1037.150(z) to guide manufacturers in identifying an appropriate duty cycle, with the addition of a Multi-purpose safe harbor.
§1037.150(z) outlines the constraints manufacturers apply when determining the appropriate vocational subcategory for their vehicles as described in §1037.140. Instead of adding a new paragraph (bb) as proposed, we are reordering §1037.150(z) and incorporating a new paragraph to allow the Multi-purpose classification. The modified §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 §1037.150(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 §1037.510. Where it is unclear, we would evaluate whether a manufacturer has applied the good engineering judgment required under §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 §1037.140(h) and the constraints listed in §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 §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 §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 §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 §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.
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.  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 §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 §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.
 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 §1037.150(y)(4). Our final revisions include  minor edits to the proposed credit-related provision in §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 paragraph §1037.150(c)(4) where the applicable standards and implementation dates for qualifying small businesses are introduced.
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 §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 §1037.621(g), as proposed.
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.  Since the purpose of these standards was to facilitate certification of vehicles intended for Canada, we  proposed optional standards in §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 §1037.670. Note that these standards are not directly comparable to either the normal Class 8 standards or the heavy haul standards of §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.
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 §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.
Transmission Calibrations
Manufacturers with advanced transmission calibrations may use the powertrain test option in §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, §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 §1037.550 as described in amendments made in §1037.235(a). See Chapter 2 of the Response to Comments for further details on comments received and our responses.
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 §1037.245 describes..." to refer to §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 § 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 §1037.150(y)(4) provision. Also moving the certification-focused portion of the early certification provision proposed as part of §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 §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.
 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 §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 §1037.520, after consideration of comment by CARB.
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 §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 §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 §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 §86.010-18(j)(3)(i) - (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 §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 §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.
Other Amendments
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). 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.
We have issued guidance for marine spark-ignition engines (40 CFR part 1045) and for recreational vehicles (40 CFR part 1051) 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 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.
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. 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.
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.
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 part 86 and part 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 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.
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 engines
40 CFR part 89
40 CFR part 1039
Nonroad spark-ignition engines at or below 19 kW
40 CFR part 90
40 CFR part 1054
Marine spark-ignition engines
40 CFR part 91
40 CFR part 1045
Locomotives and locomotive engines
40 CFR part 92
40 CFR part 1033
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 §1039.740 allow for limited use of Tier 2 and Tier 3 credits from part 89 for certifying Tier 4 engines. We are revising §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, subpart IIII and subpart 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 §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 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.
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.
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 §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: 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 PM standard.
 Section 86.1813-01: We are clarifying that electric vehicles and fuel cell vehicles are not subject to evaporative and refueling emission standards. The preamble to the final rule adopting the light-duty Tier 3 standards stated that these emission standards apply only for volatile fuels, but we did not include a clear statement excluding electric vehicles and fuel cell vehicles in the regulations (79 FR 23514, April 28, 2014).
 Section 86.1818-12:  We are clarifying that manufacturers calculate the in-use CO2 standard using the appropriate test result for carbon-related exhaust emissions after adjustment with the deterioration factor to account for durability effects. In many cases, the deterioration factor is 0 (additive) or 1 (multiplicative), in which case the deterioration factor does not change the calculated in-use CO2 standard.
 Section 86.1838-01: We are restoring text that was inadvertently removed in an earlier amendment. The restored text specifies which mileage provisions from §86.1845 do not apply for small-volume manufacturers doing in-use verification testing.
 Section 86.1868: We are adopting detailed provisions describing how reduced air conditioning test requirements apply for electric vehicles and plug-in hybrid electric vehicles. These provisions are consistent with current practice described in EPA guidance. We specify that plug-in hybrid electric vehicles qualify for relief from AC17 testing, like electric vehicles, if they have an adjusted all electric range of 60 miles or more and they do not need engine power for cabin cooling during vehicle operation represented by the AC17 procedure; in response to a comment on the proposed rule, we have revised the amended regulatory text to clarify that the specified driving range applies for combined city/highway driving. Specifying a 60-mile range is intended to include vehicles for which an owner can typically expect to avoid using the engine for daily commuting, including commutes on a hot summer day. Finally, we are clarifying that manufacturers do not need to make a demonstration to qualify for air conditioning efficiency credits for pure electric vehicles or for plug-in hybrid electric vehicles, provided that those vehicles qualify for waived AC17 testing as described above. This is due to the complexity of quantifying credit quantities in grams CO2 per mile for driving without engine power. We also specify that AC17 testing with plug-in hybrid electric vehicles, if required, always be done in charge-sustaining mode to avoid the confounding effect of intermittent engine operation during the test.
Additional Amendments for Locomotives (40 CFR Part 1033)
EPA is updating 40 CFR part 1033 to remove references to specific content in 40 CFR part 92, as described in Section III.B.2. In addition, we are adopting the following minor corrections and changes:
 Section 1033.150: Remove the interim provisions that no longer apply. This leaves paragraphs (e) and (k) as the only remaining paragraphs in this section.
 Section 1033.255: Clarify that doing anything to make information false or incomplete after submitting an application for certification is the same as submitting false or incomplete information.  For example, if there is a change to any corporate information or engine parameters described in the manufacturer's previously submitted application for certification, the manufacturer must amend the application to include the new information. Amendments include additional minor changes to align regulatory text across programs.
 Section 1033.601: Correct references to specific provisions in 40 CFR part 1068.
 Section 1033.701: Correct a paragraph reference.
 Section 1033.740: Remove the reference to part 92 because the emission credit provisions of part 92 are being removed from the CFR. We are replacing the reference to emission credits from part 92 with the equivalent statement saying that manufacturers may continue to use emission credits from locomotives certified in 2008 and earlier model years. EPA's recordkeeping will not identify credits as being from either part 92 or part 1033. Any credits generated under part 92 will continue to be available for certifying locomotives under part 1033.
 Section 1033.901: Name the date, January 1, 2000, that marked the start of the original locomotive emission standards, rather than describing the date with reference to publication of the original final rule and its effective date (18978 FR 63, April 16, 1998).
 Section 1033.925: Removing text in paragraph (e) that is already in paragraph (b) of the same section.
Additional Amendments for Land-Based Nonroad Diesel Engines (40 CFR Part 1039)
EPA's emission standards and certification requirements for land-based nonroad compression-ignition (CI) engines are identified in 40 CFR part 1039.  We refer to these as Nonroad CI engines. Several changes to 40 CFR part 1039 that apply broadly are described above. Specifically, Section III.B.2 describes how we are removing regulatory content related to the Tier 1, Tier 2, and Tier 3 standards originally adopted in 40 CFR part 89. We are accordingly amending 40 CFR part 1039 to remove references to 40 CFR part 89 that no longer apply.
This section describes additional amendments for EPA's Nonroad CI program:
 Section 1039.20: Remove the option to use a branded name instead of the engine manufacturer's corporate name for uncertified stationary engines. Since these engines are not certified, there is no way for EPA to document any relationship between the engine manufacturer and the branded company. We also are not aware of anyone using this provision.
 Section 1039.20: Revise the label statement for stationary engines covered by §1039.20 to avoid references to specific parts of the CFR. This is intended to prevent confusion. We can approve continued use of labels with the older previous statement under the provisions of §1039.135(f). This may be needed, for example, if manufacturers have remaining labels in their inventory.
 Section 1039.101: Add a table entry to clarify how standards apply for engines with maximum engine power above 560 kW. The current rendering in the Code of Federal Regulations can be misleading.
 Section 1039.102: Correct the heading of Table 6 to include engines at or below 560 kW. The table was published in a way that inadvertently excluded 560 kW engines.
 Section 1039.135: Discontinue the equipment labeling requirement to state that engines must be refueled with ultra low-sulfur diesel fuel (ULSD). Since in-use diesel fuel for these engines must universally meet ULSD requirements, there is no longer a benefit to including this label information.
 Section 1039.205: Add text to clarify how engine manufacturers should identify information in the application for certification related to engine diagnostic systems that are required under §1039.110.
 Section 1039.255: Clarify that doing anything to make information false or incomplete after submitting an application for certification is the same as submitting false or incomplete information.  For example, if there is a change to any corporate information or engine parameters described in the manufacturer's previously submitted application for certification, the manufacturer must amend the application to include the new information. Amendments include additional minor changes to align regulatory text across programs.
 Section 1039.740: Remove the reference to emission credits from part 89. There is no need for this since the records related to credit accounting do not identify credits as being from part 89 or part 1039.
 Section 1039.801: Revise the definition of "low-hour" to state that engines with NOx aftertreatment should qualify as "low-hour" up to 300 hours, with other engines qualifying as "low-hour" up to only 125 hours. This is intended to ensure that engines tested to establish the low-hour emission result for an engine family are properly represented as new engines that have not started to experience deterioration of emission controls. In line with the comments from EMA, we understand the longer stabilization period to be appropriate for engines with NOx aftertreatment. In contrast, engines without NOx aftertreatment reach a point of stabilized emission levels much sooner, which supports the shorter duration for low-hour testing before starting service accumulation. This does not preclude continued testing beyond 125 hours for engines without NOx aftertreatment, but it would prevent manufacturers from planning test programs that extend well beyond 125 hours. This is similar to provisions that already apply for marine diesel engines under 40 CFR part 1042; however, we are also adjusting the definition of "low-hour" for marine diesel engines to reference NOx aftertreatment instead of a power cutoff.
 Section 1039.801: Revise the definition of "small-volume engine manufacturer" to remove the requirement to have certified engines in the United States before 2003. This limitation was related to the transition to meeting the Tier 4 standards. Now that those phase-in provisions have expired, the remaining provisions relate to reporting CH4 and N2O emissions and using assigned deterioration factors. We believe these provisions can reasonably be applied to start-up small businesses meeting the Tier 4 standards.
Additional Amendments for Marine Diesel Engines (40 CFR Parts 1042 and 1043)
EPA's emission standards and certification requirements for marine diesel engines under the Clean Air Act are set out in 40 CFR part 1042.  Emission standards and related fuel requirements that apply internationally are set out in 40 CFR part 1043.
Several changes to 40 CFR part 1042 that apply more broadly are described above. Specifically, Section III.B.2 describes how we are removing regulatory content related to the Tier 1 and Tier 2 standards originally adopted in 40 CFR part 94. We are accordingly amending 40 CFR part 1042 to remove references to 40 CFR part 94 that no longer apply.
This section describes additional amendments for our marine diesel engine program.
Marine Replacement Engine Exemption
We are adopting several adjustments to the replacement engine exemption in §1042.615.
EPA's Advance Determination for Tier 4 Marine Replacement Engines
The proposed rule described that we were intending to clarify the regulatory determination that applies for cases involving new replacement engines that are normally subject to Tier 4 standards (see §1042.615(a)(1)). In the 2008 final rule to adopt the Tier 4 standards, we finalized a determination "that Tier 4 engines equipped with aftertreatment technology to control either NOx or PM are not required for use as replacement engines for engines from previous tiers in accordance with this regulatory replacement engine provision."  The preamble to that final rule made it clear that the determination was limited to "Tier 4 marine diesel replacement engines that comply with the Tier 4 standards through the use of catalytic aftertreatment systems." (73 FR 37157)  However, that limitation was not copied into the regulatory text. The development involving Tier 4 engines that rely on EGR instead of aftertreatment led us to revisit the discrepancy from the 2008 rule. The 2008 rule also stated that "[s]hould an engine manufacturer develop a Tier 4 compliant engine solution that does not require the use of such technology, then this automatic determination will not apply."
EMA and the California Air Resources Board (CARB) both commented on the proposed change to the replacement engine exemption in §1042.615(a)(1). EMA's comment suggested that we should leave the regulatory text in §1042.615(a)(1) unchanged from what we adopted in 2008. CARB suggested that we entirely abandon the advance determination that Tier 4 engines are not suitable as replacements for earlier engines, regardless of aftertreatment, which would require a case-by-case engineering analysis in all cases to demonstrate that an exemption is appropriate.
As we explained in the 2008 rulemaking, an engine manufacturer is generally prohibited from selling a marine engine that does not meet the standards that are in effect when that engine is produced.  However, we recognized that there may be situations in which a vessel owner may require an engine certified to an earlier tier of standards, including (1) when a vessel has been designed to use a particular engine such that it cannot physically accommodate a different engine due to size or weight constraints (e.g., a new engine model will not fit into the existing engine compartment); or (2) when the engine is matched to key vessel components such as the propeller, or when a vessel has a pair of engines that must be matched for the vessel to function properly.  Our 2008 rule allows the engine manufacturer to make the relevant determinations, but we adopted a provision that requires the engine manufacturer to consider all previous tiers and use any of their own engine models from the most recent tier that meets the vessel's physical and performance requirements.  If an engine manufacturer produces an engine that meets a previous tier of standards representing better control of emissions than that of the engine being replaced, the manufacturer would need to supply the engine meeting the tier of standards with the lowest emission levels.
At that time, we made an advance determination that Tier 4 engines would not be required as replacement engines for previous tier engines.  As we explained in Section IV.C.2 of the final rule preamble, we expected that installing such a Tier 4 engine in a vessel that was originally designed and built with a previous tier engine could require extensive vessel modifications (e.g., addition of a urea tank and associated plumbing; extra room for a SCR or PM filter; additional control equipment) that may affect important vessel characteristics such as vessel stability.  We stated that we were not implying Tier 4 engines would never be appropriate as replacements for engines from previous tiers; rather, the determination was intended to simplify the search across engines and was based on the presumption that Tier 4 engines would not fit in most cases.    We also stated that the advance determination was made solely for Tier 4 marine diesel replacement engines that comply with the Tier 4 standards through the use of catalytic aftertreatment systems.  We stated: "Should an engine manufacturer develop a Tier 4 compliant engine solution that does not require the use of such technology, then this automatic determination will not apply.  Instead our existing provision will apply and it would be necessary to show that a non-catalytic Tier 4 engine would not meet the required physical or performance needs of the vessel."
We were also not intending to prevent states or local entities from including Tier 4 engines in incentive programs that encourage vessel owners to replace existing previous tier engines with new Tier 4 engines or to retrofit control technologies on existing engines, since those incentive programs often are designed to offset some of the costs of installing or using advanced emission control technology solutions. However, on a national basis, we continue to believe our original approach described in the 2008 final rule is appropriate.  The characteristics of the national fleet are likely different from the fleet of vessels affected in California; taking away the Tier 4 determination should not be made lightly or without a thorough understanding of the impact on existing boats.  It would therefore be appropriate for us to include the advance determination that Tier 4 engines with aftertreatment are not suitable as replacement for earlier engines. In particular, we stand by our 2008 assessment that it is appropriate to automatically consider SCR-equipped engines to not have "the appropriate physical or performance characteristics to repower" pre-Tier 4 vessels, which in turn qualifies the repower for an exempt replacement engine.
EMA objected to the proposed clarification to apply the advance determination only for engines that meet Tier 4 standards with aftertreatment. The EMA comment suggests that the same presumption and regulatory burden should apply for EGR-equipped engines because compliant engines with EGR instead of aftertreatment also necessarily involve significant costs and vessel redesigns. EGR-equipped engines use exhaust gas recirculation (EGR) instead of SCR to control NOx emissions. Engines with EGR include additional hardware to manage airflow in and through the engine, and to manage wastewater.
Revising the regulation to make clear that the advance determination was not intended to include EGR-equipped engines from the advance determination is in fact a very minor change in policy. Engine manufacturers may still qualify for the replacement engine exemption based on a showing that an EGR-equipped engine does not have "the appropriate physical or performance characteristics to repower the vessel."  However, there are two reasons to believe that EGR-equipped engines may be suitable for repower. First, all EGR-equipped Tier 4 engines are locomotive-sized Category 2 engines. Vessels with Category 2 engines generally have engine compartments that have room for additional hardware and other componentry. Second, the additional hardware for EGR-equipped engines would generally involve a greater design effort than upgrading to a Tier 3 engine, but this kind of change would often fit within the scope of vessel repower projects. Vessel owners would also need to follow new protocols for maintaining the engines and dealing with wastewater and other technical issues. None of these challenges create any inherent conflict with installing the Tier 4 engines to replace earlier engines.
These factors together support a policy in which an EGR-equipped engine can be considered unsuitable for repower based on its physical or performance characteristics, but this conclusion should not be presumed. We would accomplish that policy objective by revising §1042.615(a)(1) as proposed.
Other Amendments Related to Marine Replacement Engines