6560-50-P
ENVIRONMENTAL PROTECTION AGENCY
40 CFR Parts 9, 59, 60, 85, 86, 88, 89, 90, 91, 92, 94, 1027, 1033, 1036, 1037, 1039, 1042, 1043, 1045, 1048, 1051, 1054, 1060, 1065, 1066, 1068, and 1074
[EPA - HQ - OAR - 2019 - 0307; FRL-10018-52-OAR]
RIN 2060-AU62
Improvements for Heavy-Duty Engine and Vehicle Test Procedures, and other Technical Amendments
AGENCY:  Environmental Protection Agency (EPA).
ACTION:  Final rule.
SUMMARY: The Environmental Protection Agency (EPA) is amending the test procedures for heavy-duty engines and vehicles to improve accuracy and reduce testing burden.  EPA is also making other regulatory amendments concerning light-duty vehicles, heavy-duty vehicles, highway motorcycles, locomotives, marine engines, other nonroad engines and vehicles, and stationary engines.  These amendments affect the certification procedures for exhaust emission standards and related requirements.  EPA is finalizing similar amendments for evaporative emission standards for nonroad equipment and portable fuel containers.  The amendments increase compliance flexibility, harmonize with other requirements, add clarity, correct errors, and streamline the regulations.  Given the nature of the amendments, they will have neither significant environmental impacts nor significant economic impacts for any sector.
DATES: This final rule is effective on [INSERT DATE 30 DAYS AFTER PUBLICATION IN THE FEDERAL REGISTER]. The incorporation by reference of certain publications listed in this regulation is approved by the Director of the Federal Register as of [INSERT DATE 30 DAYS AFTER PUBLICATION IN THE FEDERAL REGISTER].
ADDRESSES: The EPA has established a docket for this action under Docket ID No. EPA-HQ-OAR-2019-0307.  All documents in the docket are listed on the www.regulations.gov web site.  Although listed in the index, some information is not publicly available, e.g., CBI or other information whose disclosure is restricted by statute.  Certain other material, such as copyrighted material, is not placed on the Internet and will be publicly available only in hard copy form.  Publicly available docket materials are available either electronically in www.regulations.gov or in hard copy at Air and Radiation Docket and Information Center, EPA Docket Center, EPA/DC, EPA WJC West Building, 1301 Constitution Ave., N.W., Room 3334, Washington, DC.  Note that the EPA Docket Center and Reading Room were closed to public visitors on March 31, 2020, to reduce the risk of transmitting COVID-19. The Docket Center staff will continue to provide remote customer service via email, phone, and webform. The telephone number for the Public Reading Room is (202) 566 - 1744, and the telephone number for the Air Docket is<PHONE_NUMBER>. For further information on EPA Docket Center services and the current status, go to https://www.epa.gov/dockets.
FOR FURTHER INFORMATION CONTACT: Alan Stout, Office of Transportation and Air Quality, Assessment and Standards Division, Environmental Protection Agency, 2000 Traverwood Drive, Ann Arbor, MI 48105; telephone number:<PHONE_NUMBER>; email address<EMAIL_ADDRESS>
SUPPLEMENTARY INFORMATION:
Table of Contents
I. General Information
II. Heavy-Duty Highway Amendments
   A. Test Procedures and Compliance Model Changes
   B. Heavy-Duty Engine GHG Emission Standards and Flexibility
   C. Heavy-Duty Vehicle GHG Emission Standards and Flexibility
   D. Onboard Diagnostics ("OBD")
III. Other Amendments
   A. Ethanol-Blend Test Fuels for Nonroad Spark-Ignition Engines and Vehicles, Highway Motorcycles, and Portable Fuel Containers
   B. Removing Obsolete CFR Content
   C. Certification Fees (40 CFR Part 1027)
   D. Additional Amendments for Motor Vehicles and Motor Vehicle Engines (40 CFR Parts 85 and 86)
   E. Additional Amendments for Locomotives (40 CFR Part 1033)
   F. Additional Amendments for Land-Based Nonroad Diesel Engines (40 CFR Part 1039)
   G. Additional Amendments for Marine Diesel Engines (40 CFR Parts 1042 and 1043)
   H. Portable Fuel Containers (40 CFR Part 59)
   I. Evaporative Emission Standards for Nonroad Spark-Ignition Engines and Equipment (40 CFR Part 1060)
   J. Additional Amendments for Nonroad Spark-Ignition Engines at or Below 19 kW (40 CFR Part 1054)
   K. Amendments for General Compliance Provisions (40 CFR Part 1068)
   L. Other Requests for Comment
IV. Statutory Authority and Executive Order Reviews
General Information
Does this Action Apply to Me?
      This action relates to companies that manufacture, sell, or import into the United States new heavy-duty engines or Class 2b through 8 trucks, including combination tractors, vocational vehicles, and all types of buses.  Vocational vehicles include municipal, commercial, and recreational vehicles. Additional amendments apply for different manufacturers of light-duty vehicles, light-duty trucks, highway motorcycles, stationary engines, and various types of nonroad engines, vehicles, and equipment. Regulated categories and entities include the following:
                                NAICS Codes[A]
                                 NAICS Titles
                  Examples of Potentially Regulated Entities
333618, 336111, 336112, 336120, 336211, 336212, 336611, 336999
Other Engine Equipment Manufacturing,
Automobile Manufacturing,
Light Truck and Utility Vehicle Manufacturing,
Heavy Duty Truck Manufacturing,
Motor Vehicle Body Manufacturing,
Truck Trailer Manufacturing,
Ship Building and Repairing,
All Other Transportation Equipment Manufacturing
Motor vehicle manufacturers and engine manufacturers
811111, 811112, 811198, 423110
General Automotive Repair,
Automotive Exhaust System Repair,
All Other Automotive Repair and Maintenance,
Automobile and Other Motor Vehicle Merchant Wholesalers
Commercial importers of vehicles and vehicle components
335312, 811198
Motor and Generator Manufacturing,
All Other Automotive Repair and Maintenance
Alternative fuel vehicle converters
326199, 332431
All Other Plastics Product Manufacturing,
Metal Can Manufacturing
Portable fuel container manufacturers
[A] North American Industry Classification System (NAICS)

This list is not intended to be exhaustive, but rather provides a guide for readers regarding entities likely to be regulated by this action.  If you have questions regarding the applicability of this action to a particular entity, consult the person listed in the FOR FURTHER INFORMATION CONTACT section.
What Action Is the Agency Taking?
      This action amends the regulations that implement our air pollutant emission standards for engines, vehicles and mobile equipment. The amendments include corrections, clarifications, and flexibilities for multiple types of vehicles, engines and equipment.
      The majority of these amendments modify existing test procedures for heavy-duty highway engines and vehicles. These test procedure changes improve accuracy, and in some cases, reduce test burden.  They mainly apply for measurement of greenhouse gas pollutants (primarily CO2), though some apply for criteria pollutants (such as NOx), as well. See Section II.A.
      Additional heavy-duty highway amendments update EPA regulations to enhance implementation of existing emission standards. For example, some changes reduce the likelihood that manufacturers would need to duplicate certification efforts to comply with EPA, Canadian, and Californian standards. Some amendments make it easier for manufacturers to more fully account for the emission benefits of advanced emission control technology, which could provide them the opportunity to generate additional emission credits. These heavy-duty highway amendments are described in Section II.B.
      This rule includes other amendments that are generally administrative or technical in nature and include amendments for nonroad engines and vehicles, stationary engines, and portable fuel containers. These amendments are described in Section III. Perhaps the most visible administrative amendment is the elimination of hundreds of pages of obsolete regulations, which is described in Section III.B.
      EPA published a proposed rule on May 12, 2020 (85 FR 28140). This final rule follows from that proposal, with several adjustments that reflect EPA's consideration of comments received. Most of the proposed revisions from that notice are addressed in this final rule. EPA is also issuing a new notice of proposed rulemaking to supplement the earlier proposed rule, published in the Proposed Rules section of today's Federal Register, titled "Improvements for Heavy-Duty Engine and Vehicle Test Procedures," docket number EPA - HQ - OAR - 2019 - 0307; FRL-10018-51-OAR. In the supplemental proposal, EPA proposes further amendments concerning only certain specific aspects of GEM (see Section II of the preamble to the supplemental proposal).
      The proposed rule included requests for comment on a wide range of issues, including some broad areas where we were interested only in gathering information for potential future rulemaking(s). This preamble does not include a discussion of those comment areas where we are not taking any action in this final rule. The "Improvements for Heavy-Duty Engine and Vehicle Test Procedures, and other Technical Amendments Response to Comments" document ("Response to Comments") in the docket for this rulemaking includes a summary of the input received from commenters and EPA's responses.
      In addition, we have prepared a docket memo with redline text to highlight all the changes to the regulations in the proposed rule. This is especially helpful for reviewing provisions that we are removing from the Code of Federal Regulations. For obsolete provisions we are removing, see especially 40 CFR 1027.105, 1033.150, 1042.145, 1045.145, 1048.145, 1051.145, 1054.145, and 1054.625. We prepared additional docket memos to show regulatory changes after the proposed rule.
What are the Incremental Costs and Benefits of this Action?
      This action is limited in scope and does not include amendments that have significant economic or environmental impacts. EPA has therefore not estimated the potential costs or benefits of this Final Rule (and we did not for the proposal).
Heavy-Duty Highway Amendments
Test Procedures and Compliance Model Changes
      Since the promulgation of the Phase 2 regulations, manufacturers have been revising their internal test procedures to ensure they will be able to comply with the new requirements that begin in model year 2021. In doing so, they have identified several areas in which the test procedure regulations could be improved (in terms of overall accuracy, repeatability and clarity) without changing the effective stringency of the standards.
      EPA is making numerous changes to the test procedure regulations to address manufacturers' concerns and other issues we have identified.  These changes are described below.  The list includes numerous editorial changes that simply correct typographical/formatting errors or revise the text to improve clarity.  Although these amendments are being made primarily in the context of heavy-duty engines and vehicles, the amendments to part 1065 will also apply to nonroad engines, and the amendments to part 1066 will also apply to light-duty vehicles.  Since these amendments are mostly editorial or adding flexibility, they will not adversely impact these other sectors.
40 CFR Part 1036 Test Procedures
      EPA proposed several updates to the testing and measurement provisions of 1036 subpart F, and Appendices of part 1036 related to how to measure emissions from heavy-duty engines and requested comment on general improvements to the engine test procedures and compliance provisions (85 FR 28141). This section presents the changes we are adopting to engine test procedures after consideration of comments received. Additional details on some of these and other engine testing and measurement amendments or clarifications requested by commenters and our responses are available in Chapter 2 of our Response to Comments. Amendments to other subparts of part 1036 (i.e., amendments not directly related to test procedures) are discussed in Section II.B.
      These updates are primarily for the purposes of adding flexibility and reducing variability in test results.  Additional information that led to and supports these changes arose from a test program at Southwest Research Institute (SwRI) that was jointly funded by EPA and the Truck and Engine Manufacturers Association (EMA).
       We are generally finalizing revisions as proposed; however, some revisions include further changes and clarifications after consideration of public comments to better ensure clarity, accuracy and consistency with the intent of the proposed rule.
 Section 1036.501(g)  -  Providing a new paragraph (g) to specify duty cycles for testing MY 2016  -  2020 engines, including additional clarifications to the proposed amendment to refer to the steady-state duty cycle as the Supplemental Emission Test ("SET") rather than the Ramped Modal Cycle ("RMC") to avoid confusion as steady-state cycles are run as RMCs in many standard setting parts, and to change a reference for the Federal Test Procedure ("FTP") duty cycle from Appendix II of 40 CFR part 1036 to 40 CFR 1036.510 because 40 CFR 1036.510 gives an overview of the duty cycle and provides the reference to Appendix II of 40 CFR part 1036.
 Section 1036.501(h)  -  Renumbering existing paragraph (g) concerning testing of MY 2021 and later engines as new paragraph (h), modifying paragraph (h)(1) to address restarting the engine during dynamometer testing for engines with stop-start technologies, and adding paragraph (h)(3) (shown as (h)(2) in the proposed rule) to cross-reference transient test cycle specifications, including additional clarifications in final paragraph (h)(2) to refer to the Supplemental Emission Test cycle to avoid confusion as steady-state cycles are run as RMCs in many standard setting parts and in paragraph (h)(2)(ii) that weighting factors for the Supplemental Emission Test are to be applied to CO2 to calculate the composite emission result.
 Section 1036.503  -  Migrating §1036.510 to new 1036.503, renumbering existing paragraph (d) as new paragraph (c), updating paragraphs (b) and (c)(1)-(3) and adding (c)(4)-(5) and (d), including provisions to specify that the engine manufacturer must provide idle speed and torque to the vehicle manufacturer and to provide additional direction on handling data points for a low speed governor where the governor is active.  We further modified proposed paragraph (b) to denote that there are four methods to generate fuel maps with the addition of the hybrid powertrain and hybrid engine testing procedures and to more clearly explain which method(s) apply to which application, paragraphs (b)(1) and (b)(2) to add more specificity to which referenced paragraphs in 1036.535 are applicable,   paragraph (b)(3) to clarify that the option in 1037.520(d)(2) is only allowed for hybrid powertrain testing and not powertrain testing in general, and added paragraph (b)(4) to include a method to perform hybrid engine testing.  We also further updated paragraph (c)(1) to clarify how to measure torque curve for engines that have an RESS and for those that don't.
 Section 1036.505  -  Adding paragraph (b) to give direction on both engine and powertrain testing and modifying Table 1 to include vehicle speed and grade parameters to facilitate the hybrid powertrain testing option. We further modified the proposed language in this section by: adding a new paragraph (b)(2)(v) to calculate curb mass for hybrid powertrain testing as this calculation is needed to determine the linear equivalent mass of rotational moment of inertias in clarified paragraph (b)(vi), adding reference speed determination requirements for powertrain testing in paragraph (c)(2)(i) and (ii) to address underspeed conditions in the hybrid powertrain SET testing, including a removal of default A, B, and C SET speeds and calculation of the A and B speeds based on C speed, modifying Table 1 further to include vehicle speed and grade parameters to facilitate the hybrid powertrain testing option so the road grade equation is now vehicle speed-dependent to address vehicle underspeed concerns corresponding to the determination and use of vehicle C speed, and replacing ramped modal cycle with supplemental emission test for the reason discussed in the first bullet of this subsection of the preamble.
 Section 1036.510  -  Providing a new section regarding transient testing of engines and hybrids to facilitate hybrid certification for both GHG and criteria pollutants.
 Section 1036.525(a)  - Adding a clarification in the final rule that the hybrid engine testing procedure in this section applies only for model year 2014 to 2020 hybrid engines since the new hybrid powertrain and hybrid engine test procedure being adopted in this rulemaking will apply for model year 2021 and later engines.
 Section 1036.525(d)(4)(i)  -  Editorial revisions to equation and the addition of example calculations.
 Section 1036.527  -  Adding a section to provide a means to determine powertrain systems rated power and continuous rated power, to facilitate the hybrid and conventional powertrain testing options.  This test procedure is applicable for powertrain testing defined in 40 CFR 1037.550 for both the engine and vehicle standards. We further modified the proposed language, including modifying how the test is carried out by reducing the number of test intervals from 9 to 1, paragraph (e) to address the determination of Psys for speed and torque measurements at different locations, with new paragraphs (g) and (h) to provide an improved method for determining continuous rated power and vehicle C speed, and addressed typographical errors.
 Section 1036.530(a), (b)(1)(i) and (ii), and (b)(2)(i) and (ii)  -  Updating carbon mass fraction determination to allow analysis by a single lab only to facilitate on-line analysis from pipeline supplied natural gas and adding ASTM method for determination of test fuel mass-specific energy content for natural gas. We have further modified the proposed language by clarifying in paragraph (a) that IRAF is applied to CO2 emission results for all duty-cycles, not just cycle average engine fuel map results, and updating paragraph (b) to require test fuel mass-specific energy content and carbon mass fraction to be analyzed by at least three different labs and the median of all the results to be used in the calculation.  We are also adding a recommendation that you screen your results to determine if additional observations are needed by performing an outlier test and provided critical values for this check.  The critical values were determined as 1.27 times the method reproducibility R.  The R value used for fuel mass-specific energy content is 0.234 which is the published R value for ASTM D4809 and the R value used for carbon mass fraction is 1.23, which was based on analysis of the fuel survey data for ASTM D5291 that was used in the Fuel Mapping Variability Study at SwRI.
 Section 1036.530 Table 1  -  Updating footnote format in table.
 Section 1036.535  -  Generally updating to improve the engine fuel mapping test procedures based on the jointly funded EPA-EMA test program.  The overall result of these updates is to reduce the variability of the emission test results to reduce lab-to-lab variability.  We further modified the proposed language by adding paragraph (h) to describe how EPA will determine the official fuel consumption rate during a confirmatory test, based on carbon balance results, updating paragraph (b)(7)(iv) to require validation of test intervals that were complete prior to a lab equipment or engine malfunction, updating the variable description for wCmeas in paragraph (b)(8) to make clear that you may not account for the contribution to α, β, γ, and δ of diesel exhaust fluid or other non-fuel fluids injected into the exhaust, and clarifying regulatory text and correcting paragraph references.
 Section 1036.540  -  Generally updating to improve the cycle-average engine fuel mapping test procedure as a result of the jointly funded EPA-EMA test program at SwRI.  The overall result of these updates is to reduce the variability of the emission test results to reduce lab-to-lab variability.  We further modified the proposed language in a few ways by adding paragraph (b)(4) to address the ability of gaseous fueled engines with single point fuel injection to pass alternate cycle statistics to validate the transient duty cycle in 40 CFR part 1037, Appendix I, by adding paragraph (e)(2) to describe how EPA will determine the official fuel consumption rate during a confirmatory test, based on carbon balance results, by deleting the requirement for EPA to use an average of indirect measurement of fuel flow with dilute sampling and direct sampling for fuel mapping as EPA will now perform the carbon balance verification in 40 CFR 1065.543, and by generally adding some clarifying text.
 Section 1036.543  -  Adding a section to address carbon balance error verification.  This is a result of the jointly funded EPA-EMA test program.  The overall result of these updates is to reduce the variability of the emission test results to reduce lab-to-lab measurement variability.
 Section 1036.801  -  Adding a definition for hybrid engine to correspond with the addition of the hybrid powertrain test procedures to part 1036.  Modifying the definition from the proposed language to provide examples of hybrid engine architecture and hybrid energy storage systems.
 Section 1036.801  -  Adding definitions for "hybrid powertrain" and "mild hybrid" in the final rule. These definitions are needed as a result of adding hybrid powertrain test procedures to part 1036, subpart F including mild hybrid certification where engine testing can use a transmission model. The definitions make clear what hybrid architectures are covered by each of these terms.
 Section 1036.801  -  Updating definition of "steady-state" to clarify that fuel map and idle tests are steady-state tests.
 Section 1036.805(b)  -  Updating quantity and quantity descriptions, including some changes to those proposed to ensure consistency throughout the part.
 Section 1036.805(c) and (d)  -  Updating table introductory sentence and column headings in the table to be consistent with format in other parts.
 Section 1036.805(e)  -  Updating acronyms and abbreviations, including some changes to those proposed to ensure that the table contained all that were used throughout the part.
 Section 1036.805(f)  -  Adding gravitational constant, including an updated value for the gravitational constant based on consideration of comments received on the proposal.
 Part 1036 Appendix I  -  Adding a new Appendix I to provide a historic summary of previous emission standards which EPA originally adopted under 40 CFR part 85 or part 86, that apply to compression-ignition engines produced before model year 2007 and to spark-ignition engines produced before model year 2008.
 Part 1036 Appendix II(a)  -  Adding a new paragraph (a) of Appendix II to specify transient duty cycles for the engine and powertrain testing described in § 1036.510.
 Part 1036 Appendix II(b)  -  Adding a new paragraph (b) of Appendix II to migrate over the spark-ignition FTP duty cycle from part 86, which includes no changes to the FTP duty-cycle weighting factors or the duty-cycle speed values from the current HDDE FTP duty cycle that applies to criteria pollutant regulation in paragraph (f)(1) of 40 CFR part 86, Appendix I, a change to the negative torque values, and migration of the HDDE FTP drive schedule to paragraph (b) of 40 CFR part 1036, Appendix II, to add vehicle speed and road grade to the duty-cycle to facilitate powertrain testing for compliance with the HD Phase 2 GHG standards. The change to negative torque values is the removal of and footnoting of the negative normalized vehicle torque values over the HDDE FTP duty-cycle.  The footnote denotes that these torque points are controlled using closed throttle motoring, which would then match how negative torque values have been controlled in the HDDE FTP.  This change also reflects the way that engine manufacturers are already controlling to negative torque from spark-ignition engines and harmonizes the methodology with the HDDE FTP, with no effect on stringency.  The spark-ignition engine denormalization equation in 40 CFR 86.1333(a)(1)(ii) includes division by 100 which equates it to the denormalization equation in 40 CFR 1065.610(c)(1) (Equation 1065.610-3), with no effect on stringency.  We have further modified the proposed language in this section by updating the road-grade coefficients to reflect additional refinement of the road-grade development process that is described in Section II.A.7 of the preamble.
 Part 1036 Appendix II(c)  -  Adding a new paragraph (c) of 40 CFR part 1036, Appendix II to migrate over the compression-ignition FTP duty cycle from part 86, which includes no changes to the HDDE FTP weighting factors or the duty-cycle torque values from the duty cycle that currently apply to criteria pollutant regulations in paragraph (f)(2) of 40 CFR part 86, Appendix I, a change to the speed values that does not influence the ultimate denormalized speed, and migration of the HDDE FTP drive schedule to add vehicle speed and road grade to the duty-cycle to facilitate powertrain testing for compliance with the Phase 2 GHG standards.  The change to speed values takes the normalized vehicle speeds over the HDDE FTP duty-cycle and multiplies them by 100/112 to eliminate the need to divide by 112 in the diesel engine denormalization equation in 40 CFR 86.1333(a)(1)(i).  This eliminates the need for use of a denormalization equation and allows commonization (between compression- and spark-ignition engines) of the use of the denormalization equation in 40 CFR 1065.610(c)(1) (Equation 1065.610-3), with no effect on stringency.  We have further modified the proposed language in this section by updating the road grade coefficients to reflect additional refinement of the road grade development process that is described in Section II.A.7 of the preamble.
40 CFR Part 1037 Test Procedures
      EPA proposed several updates to the testing and measurement provisions of 1037 subpart F related to how to measure emissions from heavy-duty vehicles and determine certain GEM inputs and requested comment on general improvements to the vehicle test procedures and compliance provisions (see 85 FR 28142). This section presents the changes we are adopting to vehicle test procedures after consideration of comments received. Chapter 2 of our Response to Comments includes additional details on some of these amendments, as well as other testing and measurement amendments or clarifications requested by commenters and our responses. Amendments for other subparts of part 1037 (i.e., amendments not directly related to test procedures) are discussed in Section II.C.15. We are generally finalizing revisions as proposed; however, some revisions include further changes and clarifications after consideration of public comments to better ensure clarity, accuracy and consistency with the intent of the proposed rule.
 Section 1037.501(i)  - Adding paragraph (i) to note that the declared GEM inputs for fuel maps and aerodynamic drag area typically includes compliance margins to account for testing variability; for other measured GEM inputs, the declared values are typically the measured values without adjustment.
 Section 1037.510(a)(2)  -- Updating the powertrain testing procedure used to generate GEM inputs to reduce the variability of the emission test results and to improve lab-to-lab measurement variability consistent with the results from the jointly funded EPA-EMA test program at SwRI.
 Section 1037.510 Table 1 -- Updating footnote format in table.
 Section 1037.510(d) -- Clarifying the reference to specifically refer to paragraphs "(b) and (c)" of § 1066.425.
 Section 1037.510(e)-- Clarifying to specifically state that the use of cruise control is optional.
 Section 1037.515 Table 2 -- Correcting a table entry to include the proper mathematical symbols in response to a comment by CARB.
 Section 1037.515 Table 3 -- Updating footnote format in table.
 Section 1037.520 -- Updating a reference to reflect the updated version of the GEM model released in conjunction with this rulemaking.
 Section 1037.520(b)(3)(i) -- Adding a reference to §1037.525 to clarify how to determine a high-roof tractor's aerodynamic test results in response to a comment request from EMA.
 Section 1037.520 Table 4  -  Correcting a typographical error in a tractor aerodynamic test result CdA value for Bin III low-roof cabs.
 Section 1037.520 Table 5 -- Correcting a typographical error in a tractor input CdA value for Bin II High-Roof Sleeper Cabs.
 Section 1037.520(c)  -  Adding a clarification to §1037.520(c)(6) and updating the GEM user guide to clarify that a time- and load-weighted average be applied to calculate the rolling resistance of tires installed on liftable axles, given that tires on liftable axles are only in contact with the ground when the axle is in a deployed state in response to a comment from EMA.
 Section 1037.520 Table 6  -  Updating footnote format in table.
 Section 1037.520 Table 7  -  Clarifying that the nonwheel-related weight reductions from alternative materials applied to tractors for non-suspension crossmembers is for a set of three.
 Section 1037.520 Table 8  -  Adding two footnotes to address how weight reduction values apply and what values to use for medium HDVs with 6x4 or 6x2 axle configurations. Also see Section II.C.3.
 Section 1037.520(f) -- Updating a cross-reference.
 Section 1037.520(g) -- Adding and clarifying which vehicle characteristics need to be reported, including providing a better description in paragraph (g)(2)(iv) of the 6x4D drive axle configuration as well as qualifying conditions for use of this configuration. After considering comments received by Allison and Ford, we are further modifying this paragraph by noting in paragraph (g)(1), and similarly in §1037.231(b)(7), that available forward gear means the vehicle has the hardware and software to allow operation in those gears and providing in paragraph (g)(2)(i) that the 4x2 drive axle configuration is available to vehicles with two drive axles where one of them is disconnectable and designed to be connected only when used in off road or slippery road conditions and based on a qualifying condition.
 Section 1037.520(h) -- Adding provisions to determine appropriate vehicle idle speed based on vehicle service class and applicable engine standard, including in the final rule a clarification that the 750 rpm value applies to Light HDV and Medium HDV vocational vehicles and providing an idle speed value of 700 rpm for Medium HDV tractors, corresponding to the idle speed used to set the standards for those vehicles, in response to a comment from EMA. These final provisions incorporated in a new table format, with an updated footnote noting the appropriate adjustable idle speed to choose if an engine cannot operate at the idle speed specified in the table.
 Section 1037.520(i)  -  Adding that a manufacturer can characterize a torque converter, in addition to an axle and transmission, which will improve the accuracy of GEM by replacing default GEM values with more representative values.
 Section 1037.520(j)(2) -- Removing a superfluous reference to tractors in paragraph (j)(2)(i); clarifying paragraph (j)(2)(iii) in response to a comment from EMA to indicate how to demonstrate the performance of high-efficiency air conditioning compressors.
 Section 1037.520(j)(4) Table 9 -- Including additional combinations of idle reduction technologies and their corresponding GEM input values.
 Section 1037.520(j)(5)  -  Correcting typographical error that transposed school and coach bus GEM inputs.
 Section 1037.525 -- See Section II.A.6 for a description of comments and final revisions to this section.
 Section 1037.528 -- Replacing the phrase "primary procedures" with "reference method" for tractors and "alternate procedures" with "an alternate method" for trailers to maintain consistency with terminology used throughout subpart F.
 Section 1037.528(c) -- Clarifying that the conditions listed in paragraph (c) apply to each run separately.
 Section 1037.528(e) -- Removing requirement that the anemometer be "electro-mechanical" to rely instead on the specifications outlined in the existing reference to SAE J1263.
 Section 1037.528(g)(3) -- Clarifying that the measured air direction correction is "from all the high-speed segments."
 Section 1037.528(h)(3)(i) -- Clarifying how to account for measurement noise near the 2 mile/hour boundary.
 Section 1037.528(h)(6) -- Adding a definition of ΔFTRR to the introduction of paragraph (h)(6) to clarify the required calculations; relocating the proposed direction to determine the difference in rolling resistance between 65 mph and 15 mph for each tire and to use good engineering judgment when measuring multiple results to paragraph (v) with the corresponding ΔFTRR equation.
 Section 1037.528 -- Updating equation 11 and the corresponding example to include the appropriate variable to represent inflation pressure variable with a lowercase "p".
 Section 1037.528 -- Updating equation 13 to include appropriate units for the ambient temperature variable.
 Section 1037.528  -  Updating equation 14 to replace a "+" with a "-" to correct a typographical error.
 Section 1037.528(h)(12) -- Updating a variable name to provide consistency with updates made to §1037.525.
 Section 1037.532 -- See Section II.A.6 for a description of comments and final revisions to this section.
 Section 1037.534  -  Updating equation 6 and the corresponding example to include the appropriate variable to represent increments by italicizing the "i".
 Section 1037.540  -  Updating equations 1, 2, and 3 to include the appropriate variable to represent increments by italicizing the "i".
 Section 1037.540 Table 1  -  Updating footnote format in table; updating a parameter name.
 Section 1037.540(e) and (f)  -  Removing incorrect cross-reference to §1036.540(d)(5); adding reference to definition of standard payload.
 Section 1037.550  -  Updating the powertrain testing procedure to reduce the variability of the emission test results and improve lab-to-lab variability consistent with the results from the jointly funded EPA-EMA test program at SwRI.  We further modified this section to include an introduction paragraph and reorganized paragraphs with new paragraph headings to improve navigation. Additional modifications to this section in the final rule include clarifying in paragraph (a)(3) options available to create the models for powertrain testing, adding clarifications in several paragraphs to address where the torque and speed are measured based on powertrain setup, adding a new paragraph (f)(2) to address testing of hybrid engines using the transmission model in GEM, modifying paragraph (b) to give additional clarification on how to set the engine idle speed, adding a new paragraph (f)(2) for testing with torque measurement at the engine's crankshaft and how to calculate the transmission output rotational speed, updating paragraph (j)(2) to describe how to transition between duty cycles if the preceding cycle ends at 0 mi/hr, adding a new paragraph (j)(5) to describe how to warm up the powertrain, adding a new paragraph (o)(2) to describe how EPA will determine the official fuel consumption rate during a confirmatory test, based on carbon balance results, and updating paragraphs (o)(3) through (o)(5) to better define when a vehicle is not moving, moving the text from paragraph (p) into paragraph (o)(1), moving the text of paragraph (q) to the general provisions as a new paragraph (a)(5). The final rule includes additional revisions regulatory text to provide greater clarity and more carefully describe the procedures.
 Section 1037.551(b)  -  Updating a reference.
 Section 1037.555  -  Updating equations 1 and 3 to include the appropriate variable to represent increments by italicizing the "i"; updating a parameter name in Table 1 for consistency in this part.
 Section 1037.560  -  Clarifying that it is optional to drain gear oil after the break in period is complete, providing the option of an alternative temperature range to provide international harmonization of testing, editing the Ploss (i.e., power loss) variable description to improve the readability, and adding paragraph (h) to describe how to derive axle power loss maps for untested configurations in a family. We further modified this section in the final rule by clarifying in paragraph (a) that for tandem axles that can be disconnected, testing both single-drive and tandem axle configurations includes 4x4 axles where one of the axles is disconnectable; adding a new paragraph (h)(4) and modifying (h)(5) to address comments regarding results when multiple gear ratios are tested and one of the points is above the linear regression line, which could cause the regression values to understate power loss, to clarify that you must add the difference between the datapoint and the regression line to the intercept values of the regression line to mitigate this effect; and updating the use of the term "axle" to "axle assembly" throughout the section to provide consistency.
 Section 1037.565  -  Providing an option to map additional test points to provide international harmonization of testing, including edits to improve the readability of the Ploss variable description, and adding paragraph (d)(4) and clarifying paragraphs (e)(6) and (7) regarding the gears the transmission is tested in. After considering comments from Allison, ECJV, and EMA, we further modified this section by: updating the torque transducer accuracy requirements in paragraph (c) to link it to the highest transmission input torque or respective output torque; adding additional detail in paragraph (d)(1) on the maximum transmission input shaft speed to test, specifically the maximum rated input shaft speed of the transmission or the maximum test speed of the highest speed engine paired with the transmission. and the minimum idle speed to test, specifically 600 r/min or the minimum idle speed of the engines paired with the transmission; modifying paragraph (d)(2) in response to comments regarding transmission torque setpoints to optionally allow, in higher gear ratios where output torque may exceed dynamometer torque limits, the use of good engineering judgment to measure loaded test points at input torque values lower than specified (in this case GEM may need to extrapolate values outside of the measured map, however extrapolation time may not exceed 10% for any given cycle and you must describe in the application for certification how you adjusted the torque setpoints); modifying paragraph (e)(9) to allow the use of the maximum loss value achieved from all the repeats of the test points to calculate transmission efficiency if you cannot meet the repeatability requirements; adding a new (e)(11) clarifying what needs to be calculated for each point in the test matrix; modifying paragraph (g) and moving part of existing paragraph (g) to a new paragraph (h) to avoid a potentially never-ending cycle of repeat testing if repeatability requirements are not achieved.  If the repeatability requirement is not met after conducting three or more tests, the maximum loss value may be used to calculate transmission efficiency, or you can continue to test until you pass the repeatability requirement.
 Section 1037.570  -  Adding new section to characterize torque converters to allow a manufacturer to determine their own torque converter capacity factor instead of using the default value provided in GEM. The option to use the default value remains. The final rule includes updated regulatory text to provide greater clarity and more carefully describe the procedures. Final revisions do not change the proposed procedure; instead, they include updates to revise the section heading, reorganize paragraphs, ensure consistent terminology, and clarify measurement points.
40 CFR Part 1065 Test Procedures
      EPA proposed several updates to the testing and measurement provisions of 40 CFR part 1065 related to how to measure emissions from heavy-duty highway and nonroad engines and requested comment on general improvements to the engine test procedures and compliance provisions (see 85 FR 28142). This section presents the changes we are adopting primarily to reduce variability associated with engine test procedures after consideration of comments received. Chapter 2 of our Response to Comments includes additional details on some of these amendments, as well as other testing and measurement amendments or clarifications requested by commenters and our responses.
The regulations in part 1065 rely heavily on acronyms and abbreviations (see 40 CFR 1065.1005 for a complete list).  Acronyms used here are summarized in Table II-1:
Table II-1 Summary of acronyms related to 40 CFR part 1065 that are referenced in these amendments
ASTM
American Society for Testing and Materials
CVS
Constant-Volume Sampler
DEF
Diesel Exhaust Fluid
ECM
Electronic Control Module
NIST
National Institute for Standards and Technology
NMC FID
Nonmethane Cutter with a Flame Ionization Detector
NMHC
Nonmethane Hydrocarbon
NMNEHC
Nonmethane Nonethane Hydrocarbon
RMC
Ramped Modal Cycle
THC FID
Flame Ionization Detector for Total Hydrocarbons

      We are generally finalizing revisions as proposed; however, some revisions include further changes and clarifications after consideration of public comments to better ensure clarity, accuracy and consistency with the intent of the proposed rule.
 Section 1065.1(g)  -  Updating the test procedure URL.
 Section 1065.2(c)  -  Correcting a typographical error by replacing "engines" with "engine".
 Section 1065.130(e)  -  Revising to denote that a carbon balance procedure should be performed to verify exhaust system integrity in place of a chemical balance procedure.
 Section 1065.140(c)(6)(i)  -  Correcting a typographical error by replacing "dew point" with "dewpoint".
 Section 1065.140(e)(2)  -  Clarifying how to determine the minimum dilution ratio for discrete mode testing.
 Section 1065.145(e)(3)(i)  -  Removing the requirement to heat a sample pump if it is located upstream of a NOx converter or chiller and replacing it with a requirement to design the sample system to prevent aqueous condensation to better address concerns with the loss of NO2 in the sampling system where methods other than heating the pump can be used to prevent condensation.
 Section 1065.170  -  Updating to allow you to stop sampling during hybrid tests when the engine is off and allow exclusion of the sampling off portions of the test from the proportional sampling verification, and adding a provision for hybrid testing to allow supplemental dilution air to be added to the bag in the event that sampled volumes are too low for emission analysis.
 Section 1065.205 introductory and Table 1  -  Revising and adding recommended performance specifications for fuel and DEF mass scales and flow meters to reduce fuel flow measurement error.
 Section 1065.220(a) introductory and (a)(3)  -  Updating the application of fuel flow meters to more correctly reflect how and what they are used for in 1065.
 Section 1065.225(a) introductory and (a)(3)  -  Updating the application of intake flow meters to more correctly reflect how and what they are used for in 1065.
 Section 1065.247  -  Revising to add acronym for DEF throughout in place of "diesel exhaust fluid" and in paragraph (c)(2) account for any fluid that bypasses or returns from the dosing unit to the fluid storage tank.
 Section 1065.260(e)  -  Adding the word "some" as a qualifier for gaseous fueled engines with respect to using the additive method for NMHC determination.
 Section 1065.266(a) and (b)  -  Adding flexible fuel engines under the allowance to use FTIR and updating the URL for EPA method 320.
 Section 1065.275  -  Deleting the URL and replacing with a reference to §1065.266(b).
 Section 1065.280(a)  -  Updating to reflect that there is no method in §1065.650 for determining oxygen balance and that you may develop a method using good engineering judgment.
 Section 1065.303 Table 1  -  Updating the formatting and entries in the summary table to reflect revised requirements, including adding Fuel mass scale and DEF mass scale to the linearity verifications in §1065.307, updating the verification in §1065.341 to replace "batch sampler" with "PFD" as PFD is the preferred language, updating one footnote to include the PFD flow verification (propane check) as not being required for measurement systems that are verified by a carbon balance error verification as described in §1065.341(h) and adding two footnotes excluding linearity verification for DEF flow if the ECM is used and for intake air, dilution air, diluted exhaust, batch sampler, and raw exhaust flow rates flow if propane checks or carbon balance is performed.  These are not new exemptions; they are simply relocated to the footnotes.
 Section 1065.307(c)(13)  -  Adding a clarification that the calculation used for arithmetic mean determination in §1065.602 uses a floating intercept.
 Section 1065.307(d)(4)  -  Revising to include DEF mass flow rate and to correct or account for buoyancy effects and flow disturbances to improve the flow measurement.
 Section 1065.307(d)(6)(i)  -  Revising to state that the span gas can only contain one single constituent in balance air (or N2 if using a gas analyzer) as the reference signal for linearity determination.
 Section 1065.307(d)(7)  -  Revising to state that the span gas can only contain one single constituent in balance air (or N2 if using a gas analyzer) as the reference signal for linearity determination.
 Section 1065.307(d)(9)  -  Expanding the paragraph to include fuel and DEF mass scales and requirements for performing the linearity verification on these scales.
 Section 1065.307(e)(3)(i) and (ii)  -  Editing to clarify the intent of the requirements.
 Section 1065.307(e)(3)(iii) through (xi)  -  Defining maximum flowrate for fuel and DEF mass scales and flow meters as well as maximum molar flowrate for intake air and exhaust flow meters and defining maximum for electrical power, current, and voltage measurement.
 Section 1065.307(e)(5)  -  Providing additional information surrounding requirements for using a propane check or carbon balance verification in place of a flow meter linearity verification.
 Section 1065.307(e)(7)(i)(F) and (G)  -  Adding transmission oil and axle gear oil to temperature measurements that require linearity verification.
 Section 1065.307(f)  -  Adding new paragraph (f) to denote that table 1 follows.
 Section 1065.307 Table 1  -  Adding DEF flow rate, fuel mass scale, and DEF mass scale to measurement systems and updating the footnote format.
 Section 1065.307(g)  -  Adding a new paragraph (g) to denote that table 2 follows.
 Section 1065.307 Table 2  -  Adding a new Table 2 to provided additional guidance on when optional verifications to the flow meter linearity verifications can be used.
 Section 1065.309(d)(2)  -  Updating to allow the use of water vapor injection for humidification of gases.  After considering comments from EMA and Auto Innovators, we further modified this section to make language consistent where water vapor injection was added as an alternative.
 Section 1065.320(b)  -  Deleting existing paragraph (b) and marking it "reserved" as this is now adequately covered in 1065.307.
 Section 1065.341  -  Revising section heading, adding introductory text, revising paragraph (a) to clarify which subparagraphs apply to CVS and which apply to PFD, relocating some of existing paragraph (a) to paragraph (f) and reordering existing paragraphs (b) through (f) as paragraphs (a) through (e).
 Section 1065.341(g)  -  Revising to replace "batch sampler" with "PFD" throughout and editing to provide further clarification on the procedure.
 Section 1065.341(h)  -  Adding a new paragraph to reference Table 2 of §1065.307 regarding when alternate verifications can be used.
 Section 1065.342(d)(2)  -  Updating to allow the use of water vapor injection for humidification of gases. After considering comments by EMA and Auto Innovators, we further modified this section to make language consistent where water vapor injection was added as an alternative.
 Section 1065.350(d)(2)  -  Updating to allow the use of water vapor injection for humidification of gases. After considering comments by EMA and Auto Innovators, we further modified this section to make language consistent where water vapor injection was added as an alternative.
 Section 1065.355(d)(2)  -  Updating to allow the use of water vapor injection for humidification of gases. After considering comments by EMA and Auto Innovators, we further modified this section to make language consistent where water vapor injection was added as an alternative.
 Section 1065.360(a)(4)  -  Adding a new option to determine methane and ethane THC FID response factors as a function of exhaust molar water content when measuring emissions from a gaseous fueled engine.  This is to account for the effect water has on non-methane cutters.  We received a comment regarding whether the new regulatory text for the allowance is optional. The intent is that if you decide to use the option to determine the methane and ethane THC FID response factors as a function of exhaust molar water content, you must generate and verify the humidity as described in §1065.365(d)(12).  Paragraph (a)(4) has been modified to make this clear.
 Section 1065.360(d)(12)  -  Adding a process to determine methane and ethane THC FID response factors as a function of exhaust molar water content when measuring emissions from a gaseous fueled engine.  This is to account for the effect water has on non-methane cutters.
 Section 1065.365(a)  - Removing chemical symbol for methane in parenthetical.
 Section 1065.365(d)  -  Adding a requirement to determine NMC FID methane penetration fraction and ethane response factor as a function of exhaust molar water content when measuring emissions from a gaseous fueled engine.  This is to account for the effect water has on non-methane cutters.
 Section 1065.365(d)(9)  - Adding C2H6 before "response factor" and "penetration fraction" to clarify, as intended, that these are the ethane response factor and ethane penetration fraction.
 Section 1065.365(d)(10), (11), and (12)  -  Adding a process to determine NMC FID methane penetration fraction and ethane response factors as a function of exhaust molar water content when measuring emissions from a gaseous fueled engine.  This is to account for the effect water has on non-methane cutters.
 Section 1065.365(f)(9) and (14)  - Adding C2H6 before "response factor" and "penetration fraction" to clarify, as intended, that these are the ethane response factor and ethane penetration fraction.  Adding CH4 before "penetration fraction" to clarify, as intended, that this is the methane penetration fraction.
 Section 1065.370(e)(5)  -  Updating to allow the use of water vapor injection for humidification of gases. After considering comments by EMA and Auto Innovators, we further modified this section to make language consistent where water vapor injection was added as an alternative.
 Section 1065.375(d)(2)  -  Updating to allow the use of water vapor injection for humidification of gases. After considering comments by EMA and Auto Innovators, we further modified this section to make language consistent where water vapor injection was added as an alternative.
 Section 1065.410(c)  - Replacing "bad engine" with "malfunctioning" in relation to engine components after considering a comment by Auto Innovators.
 Section 1065.410(d)  -  Updating to state that you may repair a test engine if the parts are unrelated to emissions without prior approval.  If the part may affect emissions, prior approval is required.
 Section 1065.510(a), (b)(5)(i), (c)(5), and (f)(4)(i)  -  Moving provision for engine stabilization during mapping from §1065.510(a) to §1065.510(b)(5)(i), which lays out the mapping procedure, adding allowance in §1065.510(f)(4)(i) to specify CITT as a function of idle speed in cases where an engine has an adjustable warm idle or enhanced idle. We further modified this section in the final rule by adding a provision in §1065.510(c)(5) for hybrid powertrain testing to map negative torque required to motor the engine with the RESS fully charged.
 Section 1065.512(b)(1) and (2)  -  Updating procedures on how to operate the engine and validate the duty-cycle when an engine utilizes enhanced-idle speed.  This also addresses denormalization of the reference torque when enhanced-idle speed is active.
 Section 1065.514(e)  -  Clarifying that a floating intercept as described in §1065.602 is used to calculate the regression statistics to harmonize with changes made to §1065.602 and further modifying paragraph (e)(3) in the final rule to change "standard estimates of errors" to "standard error of the estimate" for consistency with other parts.
 Section 1065.514 Table 1  -  Updating a parameter name in the final rule for consistency with other parts.
 Section 1065.530(a)(2)(iii)  -  Adding instructions on how to determine that the engine temperature has stabilized for air cooled engines.
 Section 1065.530(g)(5)  -  Adding a new paragraph on carbon balance error verification if it is performed as part of the test sequence.
 Section 1065.543  -  Adding a new section on carbon balance error verification procedure to further reduce measurement variability for the fuel mapping test procedure in part 1036. We have further modified this section in the final rule to make it optional to account for the flow of other non-fuel carbon-carrying fluids into the system as the overall contribution from any such fluids to the total carbon in the system is negligible.
 Section 1065.545 - Revising to clarify that a forcing the intercept through zero as described in §1065.602 is used to calculate the SEE to harmonize with changes to §1065.602.
 Section 1065.602(b), (c), (d), (e), (f), (g), (h), (j), (k)  -  Updating to include the appropriate variable to represent increments by italicizing the "i".
 Section 1065.602 Table 1- Updating footnote format in table.
 Section 1065.602 Table 2  -  Correcting a typographical error where the Nref-1 value should be "22" but was mistakenly listed as "20".
 Section 1065.602(h)  -  Defining the existing Equation 1065.602-9 as a least squares regression slope calculation where the intercept floats, i.e., is not forced through zero, designating this paragraph as (h)(1) and adding a new paragraph (h)(2) for Equation 1065-602-10, a least squares regression slope calculation where the intercept is forced through zero.
 Section 1065.602(i)  -  Editing to state that the intercept calculation Equation 1065.602-11 is for a floating intercept.
 Section 1065.602(j)  -  Defining the existing Equation 1065.602-12 (renumbered from 1065.602-11) as a SEE calculation where the intercept floats, i.e., is not forced through zero, designating this paragraph as (j)(1), adding a new paragraph (j)(2) for Equation 1065.602-13, a SEE calculation where the intercept is forced through zero, and further modifying paragraph (j) in the final rule to change "Standard estimate of error" to "Standard error of the estimate" for consistency with other parts.
 Section 1065.610(a)(1)(iv) - Updating to include the appropriate variable to represent increments by italicizing the "i".
 Section 1065.610(a)(2)  -  Clarifying that the alternate maximum test speed determined is for all duty-cycles.
 Section 1065.610(d)(3)  -  Adding provision to use good engineering judgment to develop an alternate procedure for adjusting CITT as a function of speed.
 Section 1065.640(a), (b)(3), and (d)(1)  -  Deleting a comma in (a), specifying that the least square regression calculation in (b)(3) is with a floating intercept, providing a conversion to kg/mol for Mmix in the example problem for (d)(1), and correcting an error in the example problem in applying Equation 1065.640-10 where Mmix was used with the wrong units.
 Section 1065.640(d)(3)  -  Providing additional guidance on how to calculate SEE for Cd to correspond with the changes made to §1065.602.
 Section 1065.642(b)  -  Correcting a cross-reference.
 Section 1065.642(c)(1)  -  Defining Cf.
 Section 1065.643  -  Adding a new section on carbon balance error verification calculations to support the new §1065.543.
 Section 1065.650(b)(3)  -  Adding DEF to clarify what is needed for chemical balance calculations.
 Section 1065.650(c)(1)  -  Relocating transformation time requirement from §1065.650(c)(2)(i) to §1065.650(c)(1).
 Section 1065.650(c)(3)  -  Updating the equation to include the appropriate variable to represent increments by italicizing the "i".
 Section 1065.650(d)  -  Correcting cross-references.
 Section 1065.650(d)(7)  -  Updating to include the appropriate variable to represent increments by italicizing the "i".
 Section 1065.650(f)(2) - Adding DEF to clarify what is needed for chemical balance calculations.
 Section 1065.650(g)  -  Updating the equations to include the appropriate variable to represent increments by italicizing the "i" and correcting variable name from eNOxcomposite to eNOxcomp.
 Section 1065.655  -  Adding "DEF" to the section heading.
 Section 1065.655(a) and (c) introductory text  -  After considering comments by EMA, we modified this section to clarify that the inclusion of diesel exhaust fluid in the chemical balance is optional.
 Section 1065.655(c)(3)  -  Updating the xCcombdry variable description to include injected fluid.
 Section 1065.655(d)  -  After considering comments by EMA, we modified this section to clarify that the inclusion of diesel exhaust fluid in the wC determination is optional.
 Section 1065.655(e)(1)(i)  -  Clarifying the determination of carbon and hydrogen mass fraction of fuel, specifically to S and N content.
 Section 1065.655(e)(3)  -  Clarifying that nonconstant fuel mixtures also applies to flexible fueled engines.
 Section 1065.655(e)(4)  -  Updating to include the appropriate variable to represent increments by italicizing the "i".
 Section 1065.655(e)(5)  -  Adding new paragraph (e)(5) to denote that table 1 follows.
 Section 1065.655 Table 1  -  Updating cross-reference.
 Section 1065.655(f)(3)  -  Restricting the use of Equation 1065.655-25 if the standard setting part requires carbon balance verification and including the appropriate variable to represent increments by italicizing the "j"; adding in the final rule a description of the variable for carbon mass fraction, as it was missing.
 Section 1065.655(g)(1)  -  Updating cross-reference.
 Section 1065.659(c)(2) and (3)  -  Adding DEF to clarify what is needed for chemical balance chemical balance calculations.
 Section 1065.660(a)(5) and (6)  -  Adding new paragraphs to those proposed codifying existing practice to calculate THC based on measurements made with FTIR for gaseous fueled engines.  EPA intended in previous updates to part 1065 to allow the determination of NMNEHC and NMHC using FTIR from gaseous fueled engines, but the HD Phase 2 rulemaking inadvertently omitted instructional text in paragraph (a) on calculating THC using the two FTIR additive methods.
 Section 1065.660(b)(2) and (3)  -  Correcting typographical errors, including adding missing commas.
 Section 1065.660(b)(4)  -  Correcting a typographical error for the chemical formula of acetaldehyde in a variable.
 Section 1065.660(c)(2)  -  Including NMC FID as allowable option in NMNEHC calculation and further modifying §1065.660(c) in the final rule adding additional information on performing the NMNEHC calculation and to correct typos in variables.
 Section 1065.660(d)  -  Adding missing parentheses.
 Section 1065.665(a)  -  Deleting the variable and description for C# as it is not used in any calculation in this section.
 Section 1065.667(d)  -  Adding DEF to clarify what is needed for chemical balance description.
 Section 1065.675(d)  -  Editing variable descriptions to refer to a humidity generator rather than a bubbler (accommodates both a bubbler and humidity generator).
 Section 1065.695(c)(8)(v)  -  Adding carbon balance verification.
 Section 1065.701(b)  -  Updating name of California gasoline type.
 Section 1065.701 Table 1 - Updating footnote format in table.
 Section 1065.703 Table 1  -  Updating to correct units for kinematic viscosity and updating footnote format in table.
 Section 1065.705 Table 1  -  Updating to correct units for kinematic viscosity and updating footnote format in table.
 Section 1065.710 Table 1  -  Editing format for consistency and updating footnote format in table.
 Section 1065.710 Table 2  -  Editing format for consistency, adding allowance to use ASTM D1319 or D5769 for total aromatic content determination and ASTM D1319 or D6550 for olefin determination because the dye used in ASTM D1319 is becoming scarce and an alternate method is needed, and updating a footnote format in table.
 Section 1065.715 Table 1 - Updating footnote format in table.
 Section 1065.720 Table 1 - Updating footnote format in table and revising Table 1 after considering a comment by EMA to specify ASTM D6667 instead of ASTM D2784 as the reference procedure for measuring sulfur in liquefied petroleum gas. We requested comment on amending the regulation to replace ASTM D2784, which has been withdrawn by ASTM without replacement, received comment from EMA and agree that ASTM D6667 is a suitable method. EPA is similarly changing other regulatory provisions to specify ASTM D6667 as the reference procedure for fuel manufacturers measuring sulfur in butane (see 40 CFR 1090.1350).
 Section 1065.750 Table 1 - Updating footnote format in table.
 Section 1065.790(b)  -  Adding a NIST traceability requirement for calibration weights for dynamometer, fuel mass scale, and DEF mass scale.
 Section 1065.905 Table 1 - Updating footnote format in table.
 Section 1065.910(a)(2)  -  Adding a revision in the final rule to change the requirement to use 300 series stainless steel tubing to connect the PEMS exhaust and/or intake air flow meters into a recommendation because there are other materials that are equally suitable for in-use testing other than stainless steel tubing.
 Section 1065.915 Table 1 - Updating footnote format in table.
 Section 1065.1001  -  Adding a definition for enhanced-idle.
 Section 1065.1001  -  Clarifying definition of test interval as duration of time over which the mass of emissions is determined.
 Section 1065.1005(a) - Updating footnote format in table and parameter names for consistency with other parts.
 Section 1065.1005(c), (d) and (e)  -  Updating to ensure column headings use terminology consistent with NIST SP-811.
 Section 1065.1005(a) and (e)  -  Updating tables of symbols and subscripts to reflect revisions to part 1065.
 Section 1065.1005(f)(2)  -  Adding molar mass of ethane and updating footnote format in table.
 Section 1065.1005(g)  -  Updating acronyms and abbreviations for ASTM, e.g., and i.e.
 Section 1065.1010(b)(23) and (43) - Incorporating by reference ASTM D6667 into the regulations instead of ASTM D2784, consistent with replacing ASTM D2784 with ASTM D6667 as the reference procedure for measuring sulfur in liquefied petroleum gas in §1065.720, as explained above in this section. EPA is similarly specifying ASTM D6667 as the reference procedure for fuel manufacturers measuring sulfur in butane.
40 CFR Part 1066 Test Procedures
      EPA proposed several updates to the testing and measurement provisions of 40 CFR part 1066 related to how to measure emissions from light- and heavy-duty vehicles and requested comment on general improvements to the vehicle test procedures and compliance provisions (see 85 FR 28144). This section presents the changes we are adopting to vehicle test procedures after consideration of comments received. Chapter 2 of our Response to Comments includes additional details on some of these amendments, as well as other testing and measurement amendments or clarifications requested by commenters and our responses.
We are generally finalizing revisions as proposed; however, some revisions include further changes and clarifications after consideration of public comments to better ensure clarity, accuracy and consistency with the intent of the proposed rule.
 Section 1066.1(g)  -  Updating the URL.
 Section 1066.135(a)(1)  -  Revising to widen the range for verifications of a gas divider derived analyzer calibration curve to 10 to 60% to ease lab burden with respect to the number of gas cylinders they must have on hand and revising to make the midspan check optional as the part 1066 requirement for yearly linearity verification of the gas divider has provided more certainty of the accuracy of the gas blending device.
 Section 1066.210(d)(3)  -  Changing the value for acceleration of Earth's gravity from a calculation under 40 CFR 1065.630 to a default value of 9.80665 m/s[2] because the track coastdown doesn't take place in the same location that the dynamometer resides.  Therefore, best practice is to use a default value for gravity.
 Section 1066.255(c)  - Clarifying that the torque transducer zero and span are mathematically done prior to the start of the procedure.
 Section 1066.260(c)(4)  -  Correcting an error in the example problem result.
 Section 1066.265(d)(1)  -  Correcting example equation to replace a subtraction sign that was a typographical error with a multiplication sign.
 Section 1066.270(c)(4)  -  Correcting units for force in mean force variable description and correcting example problem solution.
 Section 1066.270(d)(2)  -  Adding corrections in the final rule of typographical errors on maximum allowable error where error tolerances were indicated as "+-", but paragraph is clear that the allowable error is a maximum value as Equation 1066.270-2 determines error as an absolute value.  Therefore, the error values are positive and not a positive and negative range.
 Section 1066.275  -  Extending the dynamometer readiness verification interval from within 1 day before testing to an optional 7 days prior to testing if historic data from the test site supports an interval of more than 1 day.  Adding corrections in the final rule of typographical errors in paragraph (d)(1) and (2) on allowable error where error tolerances were indicated as "+-", but paragraph is clear that the allowable error is a maximum value as Equation 1066.270-2 determines error as an absolute value.  Therefore, the error values are positive and not a positive and negative range.
 Section 1066.405  -  Updating heading to include "maintenance".
 Section 1066.405(a)-(c)  -  Designating existing text as paragraph (a), adding new paragraphs (b) and (c) to address test vehicle inspection, maintenance and repair, consistent with 1065.410, and, after considering a comment by Auto Innovators, replacing "bad engine" with "malfunctioning" in relation to engine components in paragraph (b).
 Section 1066.420 Table 1 - Updating footnote format in table and, after considering comments from Auto Innovators and VW, clarifying that SC03 humidity tolerance is an "average" value consistent with 40 CFR 86.161-00(b)(1) and inadvertently not carried over in part 1066.  All SC03 capable test cells have been designed to meet the humidity requirement in 86.161-00 which is on an average basis.
 Section 1066.605  -  Correcting a typographical error in paragraph (c)(4) where NMHC should read NMHCE and editing Equation 1066.605-10 adding italics for format consistency.
 Section 1066.610  -  Editing Equation 1066.610-4 adding italics for format consistency.
 Section 1066.710(c)  -  Clarifying to reflect how HVAC control systems operate in vehicles and how they should be operated for the test.  Further modifying paragraph (c)(1)(i)(A) in the final rule to state that for automatic temperature control systems that allow the operator to select a specific temperature, set the air temperature at 72 °F or higher, which the vehicle then maintains by providing air at that selected constant temperature.  Further modifying paragraph (c)(2) in the final rule to state that for full automatic temperature control systems that allow the operator to select a specific temperature, set the air temperature at 72 °F, which the vehicle then maintains by varying temperature, direction and speed of air flow.  Clarifying terminology is consistent with EPA compliance guidance CD-2020-04.
 Section 1066.801 Figure 1  -  Updating to reflect that the initial vehicle soak, as outlined in the regulations, is a 6-hour minimum and not a range of 6 to 36 hours.
 Section 1066.835(a)  -  Clarifying that the last drain and fill operation is after the most recent FTP or HFET measurement (with or without evaporative emission measurements).
 Section 1066.835(f)(2)  -  Deleting the word "instantaneous" to reflect that the SC03 temperature and humidity tolerances in paragraph (f)(1) are not all instantaneous in response to comments received from Auto Innovators and VW.  This was an inadvertent error in part 1066.
 Section 1066.930  -  Adding a period to the end of the sentence.
 Section 1066.1005(a)  -  Updating a parameter name to be consistent with use in other parts.
 Section 1066.1005(c) and (d)  -  Updating to ensure column headings use terminology consistent with NIST SP-811.
 Section 1066.1005(f)  -  Updating footnote format in table.
Greenhouse Gas Emissions Model (GEM)
      EPA proposed several updates to the GEM model related to how to measure emissions from heavy-duty engines and requested comment on whether the differences in GEM would impact the effective stringency of the standards and, if so, whether either GEM or the regulations need to be revised to address the changes (see 85 FR 28145, May 12, 21020). This section presents the changes we are adopting to GEM after consideration of comments received. Additional details on these and other amendments or clarifications requested by commenters and our responses are available in Chapter 2 of our Response to Comments.
      GEM is a computer application that estimates the greenhouse gas (GHG) emissions and fuel efficiency performance of specific aspects of heavy-duty (HD) vehicles. GEM is used to determine compliance with the Phase 2 standards from several vehicle-specific inputs, such as engine fuel maps, aerodynamic drag coefficients, and vehicle weight rating.  GEM simulates engine operation over two cruise cycles, one transient cycle, and for vocational vehicles, idle operation.  These results are weighted by GEM to provide a composite GEM score that is compared to the standard.
      EPA proposed to update GEM, in a revised version 3.5 to replace the current version 3.0, and requested comment on whether the differences in GEM would impact the effective stringency of the standards and, if so, whether either GEM or the regulations need to be revised to address the changes.  We received one comment on the proposal on this topic from the California Air Resources Board (CARB), stating the importance of GEM results being consistent with the current program standards to ensure stringency is maintained and recommending that EPA revise GEM to maintain this consistency.
      After considering the comment and further evaluating the performance of GEM 3.5 with the input files used to set the Phase 2 vehicle standards, EPA is finalizing GEM version 3.5.1 applicable for MY 2021 vehicles that includes the changes proposed in version 3.5 as well as changes that correct three errors in the GEM 3.5 code. The following changes were proposed in version 3.5 and are finalized in version 3.5.1 to allow additional compliance flexibilities and improve the vehicle simulation:
       Corrected how idle emission rates are used in the model.
       Increased the allowable weight reduction range to 25,000 pounds.
       For powertrain input, added an input for powertrain rated power to scale default engine power.
       Recalibrated driver over speed allowance on cruise cycles from 3 mph to 2.5 mph.
       Revised engine cycle generation outputs with corrected engine cycle generation torque output from model based on simulated inertia and rate limited speed target.
       Added scaling of powertrain simulation default engine and transmission maps based on new rated power input.
       Changed interpolation of fuel map used in post processing to be consistent with one used in simulation.
       Corrected accessory load value on powertrain test when coasting or decelerating.
       Added torque converter k-factor input option.
       Cycle average cycles: added flag for points that are to be considered "idle."
       Improved handling of large input tables.
       Allow hybrid engine input.
      The three additional changes in GEM 3.5.1 correct the following errors in GEM 3.5 code: (1) A typographical error, where GEM used a weighting factor of 0.25 instead of 0.23 for the HHD Multipurpose vehicle subcategory; (2) an idle map error when the cycle average fuel mapping procedure is used for all three drive cycles; and (3) a functional error that unnecessarily required transmission power loss data when using the option to enter a unique (instead of default) k-factor for the torque converter. The GEM version we are releasing with and incorporating by reference in this final rule is identified as "3.5.1."
      EPA is also issuing a supplemental proposal published in the Proposed Rules section of today's Federal Register, titled "Improvements for Heavy-Duty Engine and Vehicle Test Procedures," docket number EPA - HQ - OAR - 2019 - 0307; FRL-10018-51-OAR.  This supplemental proposal provides notice and opportunity for comment on a proposed further updated version of GEM for MY 2022 and later, proposes to allow use of the updated model for MY 2021 for demonstrating compliance with the Phase 2 standards, including obtaining a certificate of conformity and submitting end-of-year reports, and requests comment on whether this version of GEM should be required for MY2021 end-of-year reports. This proposed revised version in the supplemental notice includes corrections, clarifications, additional flexibilities, and adjustment factors to the Greenhouse gas Emissions Model (GEM) compliance tool for heavy-duty vehicles after consideration of comments received on the proposed rule. The supplemental notice proposes limiting the use of GEM 3.5.1 to MY 2021 vehicles only, except where this MY 2021 data can be used for carryover requests for certificates of conformity for MY 2022 and future years for qualifying vehicles under §1036.235(d); however, manufacturers would still need to use GEM 3.8 for end-of-year reporting for MY 2022 and future years.
      EPA is finalizing GEM 3.5.1 after considering comments, further evaluating the performance of GEM 3.5.1 with the input files used to set the Phase 2 vehicle standards, considering the corrections and improvements made in GEM 3.5.1, and identifying potential additional corrections and improvements for GEM. Evaluation of GEM 3.5.1 indicated that there was some difference in output 96results for both tractor and vocational vehicles when compared to GEM 3.0.  To assess the magnitude of any differences between using GEM 3.0 and GEM 3.5.1, we repeated the process used in 2016 to calculate the numerical level of the vehicle standards, replacing GEM 3.0 with GEM 3.5.1.  On average, the differences in the resulting standards from using GEM 3.5.1 instead of GEM 3.0 are decreases of 0.09 percent and 0.54 percent for the tractor and vocational vehicle standards, respectively.  The tractor standards resulting from GEM 3.5.1 ranged from 0.29 percent below to 0.15 percent above the GEM 3.0 standards. The vocational vehicle standards resulting from GEM 3.5.1 ranged from 0.32 percent above to 1.45 percent below the GEM 3.0 standards. A summary of the process taken to calculate the vehicle standards using GEM and a comparison of the results generated by GEM 3.0 and GEM 3.5.1 are provided in a docket memo.
      We are finalizing GEM 3.5.1 without adopting adjustment factors in the related test procedures. In the same memo noted previously, we compare the GEM 3.8 results to those from GEM 3.0. In the supplemental notice, EPA proposes GEM 3.8 and corresponding adjustment factors to adjust the results to more closely match the results produced by the original GEM 3.0 version and we intend to issue a final rule before the start of model year 2022. If finalized as proposed, we would limit the potential impact on effective stringency due to a change in GEM versions to model year 2021 only, which should have a minimal impact on the effective stringency and environmental benefits of the overall Phase 2 program.
Aerodynamic Test Procedures
      EPA proposed several updates to the testing and modeling provisions of 1037 subpart F related to aerodynamic testing and requested comment on general improvements to the aerodynamic test procedures and compliance provisions (see 85 FR 28147). This section presents the changes we are adopting to aerodynamic test 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.
Aerodynamic Measurements for Tractors
      The aerodynamic drag of a vehicle is determined by the vehicle's coefficient of drag (Cd), frontal area, air density and speed.  The regulations in §1037.525 allow manufacturers to use a range of techniques, including wind tunnel testing, computational fluid dynamics, and constant speed tests.  This broad approach is appropriate given that no single test procedure is superior in all aspects to other approaches.  However, we also recognized the need for consistency and a level playing field in evaluating aerodynamic performance.  To address the consistency and level playing field concerns, EPA adopted an approach that identified coastdown testing as the reference aerodynamic test method, and specified a procedure to align results from other aerodynamic test procedures with the reference method by applying a correction factor (Falt-aero) to results from alternative methods (§1037.525(b)). We are adding a sentence to the introductory text of §1037.525 to clarify that coastdown testing is the "reference method for aerodynamic measurements".
      In the proposed rule, we proposed to separate paragraph §1037.525(b)(1) into a paragraph (b)(1) defining Falt-aero and a new paragraph (b)(2) allowing manufacturers to assume Falt-aero is constant for a given alternate method. We are finalizing two separate paragraphs and the subsequent renumbering of the remaining paragraphs as proposed except as explained here. Our proposed update to the definition of Falt-aero in Equation 1037.525-1 and the related text in §1037.525(b)(1) inadvertently removed the definition of effective yaw, ψeff, which is used throughout §1037.525 and incorrectly replaced the CdA variables measured at ψeff with wind-averaged CdA values, as noted in comment by EMA. We agree that Equation 1037.525-1 should continue to be based on the definition from HD GHG Phase 2 final rule such that Falt-aero is a function of the coefficient of drag areas at the effective yaw angle.  We are finalizing (b)(1) with the same Equation 1037.525-1 as the current requirement but with the updated variable names throughout §1037.525 (and where referenced in §1037.525(h)(12)(v)) to more clearly relate the drag areas to the defined effective yaw variable, as recommended by EMA. We are also adding a "Where:" statement to Equation 1037.525-1 to define the variables in that equation and are restoring the existing language we proposed to remove that defines the effective yaw angle to apply for Phase 1 and Phase 2 compliance.
      We proposed and received no adverse comments on two additional changes in §1037.525(b). In paragraph (b)(3), we proposed and are finalizing removal of the sentence "Where you have test results from multiple vehicles expected to have the same Falt-aero, you may either average the Falt-aero values or select any greater value." By removing this statement, we are allowing manufacturers the flexibility to propose a method for calculating their Falt-aero from multiple test vehicles that suits their unique compliance margin targets. In paragraph (b)(5), we proposed to add a statement that manufacturers may test earlier model years than the 2021, 2024, and 2027 model years specified and are finalizing additional clarifying text and a new example. We are finalizing two additional typographical edits correcting references to our renumbered paragraphs in the paragraph (b)(5). The reference to "paragraph (b)(2)" was corrected to (b)(3) and the reference to "this paragraph (b)(4)" was corrected to (b)(5). Finally, we are adding the phrase "drag area from your alternate method" to describe the previously undefined term, CdAalt.
      EPA proposed a change to §1037.525(b)(7), to clarify that the use of good engineering judgment with respect to the specified tractor-trailer gap dimension "applies for all testing, including confirmatory and SEA testing". Both EMA and Volvo requested further clarification through use of an example. We are finalizing three clarifying changes to §1037.525(b)(7). First, we are adding a reference to the tractor-trailer gap specifications in §1037.501(g)(1)(ii), as requested. Second, we provide an example of good engineering judgment that could be applied to correct a difference between the specified and tested tractor-trailer gaps. Lastly, we clarify that the allowance applies "for certification, confirmatory testing, SEA, and all other testing to demonstrate compliance with standards."
      We also proposed a provision to our regulations at §1037.525(b)(8) to encourage manufacturers to proactively coordinate with EPA to have compliance staff present when a manufacturer conducts its coastdown testing to establish Falt-aero values.  Section 208 of the Clean Air Act provides EPA broad oversight authority for manufacturer testing. Being present for the testing would give EPA greater confidence that the test was conducted properly, and thus, would make it less likely that EPA would need to conduct aerodynamic confirmatory testing on the vehicle. Consistent with the intent of the proposed revision and EPA's authority under section 208, we are finalizing in §1037.525(b)(8) a provision that refers to the existing preliminary approval provisions of §1037.210 with the note that EPA may witness the testing. Section §1037.210 provides an established protocol for manufacturers to coordinate with EPA for testing.
      EMA's comment requested additional modifications to the yaw sweep correction provisions in §1037.525(c), suggesting that coastdown results do not need to be corrected to wind-averaged and that all of paragraph (c)(2) was "unnecessary" because another regulatory provision "serves that function". Their request appears to be a misunderstanding of the existing regulations. Wind-averaged drag area (CdAwa) is a required input for GEM in Phase 2. Paragraph (c)(1) specifies how to calculate CdAwa when using an alternate test method and paragraph (c)(2) specifies how to calculate it for coastdown testing. EPA may use coastdown for confirmatory testing and manufacturers may choose to use coastdown testing for all aerodynamic testing. Consequently, paragraph (c)(2) is needed to properly calculate the wind-averaged input required by GEM in these situations. To address any potential confusion on the necessity of both paragraphs under the current regulatory text, we are finalizing three updates to §1037.525(c) as follows:
       Clarifying the use of the yaw correction provisions by revising paragraph (c) introductory text to add "as specified in §1037.520" and to remove the phrase "differences from coastdown testing" that only applies to paragraph (c)(1).
       Updating the text of paragraphs (c)(1) and (c)(2) to more clearly communicate that they are two separate options that apply based on which testing method is chosen.
       Adopting the updated drag area variable names from §1037.525(b).
Aerodynamic Measurements for Vocational Vehicles
      We did not specifically propose changes to or request comment on our procedures for measuring aerodynamic performance of vocational vehicles in §1037.527. EMA commented that the existing provisions of §1037.527 to determine a ΔCdA value for vocational vehicles refer to the trailer provisions in §1037.526; however, §1037.526 does not specify how to choose an appropriate baseline for vocational vehicles. EMA requested that manufacturers should be able to "choose an appropriate baseline vehicle for the technology and applications". We are not taking any final action on this issue at this time. However, we are providing a summary of the current provisions and their original intent in this preamble to assist manufacturers.
      The current §1037.527(a) states that ΔCdA is determined for vocational vehicles as follows: "Determine ΔCdA values by performing A to B testing as described for trailers in §1037.526, with any appropriate adjustments, consistent with good engineering judgment." The A to B testing provisions for trailers are specified in §1037.526(a), where paragraph (a)(1) describes the baseline trailer, paragraph (a)(2) describes the general intent of the A to B test, and paragraph (a)(3) describes how to calculate the ΔCdA from the test results.
      We acknowledge that the reference to a "standard trailer" in §1037.526(a)(1) may cause confusion to vocational vehicle manufacturers, since it would be a challenge to identify a single "standard" vehicle to represent the range of vocational applications. However, the baseline trailer description in that paragraph equates to a trailer without aerodynamic components, which is the key aspect of that baseline description the regulatory cross-reference in §1037.527(a) applies to vocational vehicles. The trailer provision of §1037.526(a)(2) states that the general intent of the A to B test is to "demonstrate the reduction in aerodynamic drag associated with the improved design", which can be directly applied to vocational vehicles. The general process of calculating ΔCdA in §1037.526(a)(3) could be applied to vocational vehicles as well, but its reference to test trailer and baseline trailer may cause confusion for reasons similar to those discussed for §1037.526(a)(1).
      Similar to the trailer provision, a vocational vehicle's aerodynamic performance is based on a ΔCdA value relative to a baseline vehicle. Manufacturers wishing to perform aerodynamic testing on their vocational vehicles are encouraged to coordinate with their Designated Compliance Officer and use the existing provision in §1037.527, including its reference to the description of how to do so for the trailer-specific provision in §1037.526.  As noted in §1037.527(a), we expect manufacturers to make "appropriate adjustments" when applying the cross-referenced provision to vocational vehicle testing consistent with good engineering judgment. When followed, this should result in a manufacturer choosing an appropriate baseline vehicle, similar to the clarification requested by the commenter.  For example, a manufacturer may choose an aerodynamic test method, determine a baseline CdA value (in m[2]) using a vehicle that represents a production configuration without the aerodynamic improvement, then repeat the same aerodynamic method for a test vehicle that is a nearly equivalent configuration but includes the aerodynamic improvement of interest. In this case, the manufacturer would calculate ΔCdA by subtracting the measured drag area for the test vehicle from the drag area for the baseline vehicle. Calculating ΔCdA in this manner would generally be consistent with the intent that the test "accurately demonstrate the reduction in aerodynamic drag associated with the improved design" for the vocational vehicle since any improvement to aerodynamic performance would be attributable to the aerodynamic technology on the test vehicle.
Computational Fluid Dynamics Procedures
      We proposed one correction to our computational fluid dynamics (CFD) provisions of §1037.532 that replaced the incorrect "or" in paragraph (a)(1) with "and" to include yaw angles of +4.5° and  - 4.5°. EMA requested three additional modifications related to our CFD provisions. In §1037.532(a)(3), they requested that we clarify our specified Reynolds number of 5.1 million is based on the 102-inch trailer width as the characteristic length. We agree with this suggestion and updated the language in §1037.532(a)(3) for clarity that the Reynolds number is based on a 102-inch trailer width consistent with our specifications for a "standard trailer" in §1037.501(g)(1)(i).  EMA also suggested the phrase "the General On-Road Simulation" in §1037.532(a)(4) be replaced with "an open-road simulation" to avoid confusion with SAE International's revisions of SAE J2966 to incorporate the impact of traffic. We agree that open-road simulation is representative of our initial intent and are updating the regulatory text of §1037.532(a)(4). See Chapter 2 of our Response to Comments for additional details.
      EMA's third request was that we remove the requirement to set the "free stream turbulence intensity to 0.0 percent" in §1037.532(a)(5), and instead recommended we replace that requirement with a "uniform inlet velocity profile." EPA is not taking any final action on revision to that paragraph at this time. Furthermore, EPA disagrees with the requested change to paragraph (5). Turbulence intensity is a common parameter in CFD packages and, as described in Chapter <IP_ADDRESS> of the Final Regulatory Impact Analysis for the HD Phase 2 Rule, we evaluated a range of turbulence intensities and intentionally specified a value of zero to ensure consistency, stating that "Turbulence intensity must be 0.0 percent." Manufacturers who wish to use alternative parameters and criteria related to their CFD models, which includes seeking to substitute the specified turbulence intensity with a uniform inlet velocity profile, continue to have the option to seek to do so through requesting EPA approval under §1037.532(f).
      CARB requested EPA add provisions that set a requirement for a maximum limit of computational elements to perform Computational Fluid Dynamics (CFD) simulation, define a specific transient averaging methodology, quantify the uncertainty in using CFD simulation, and assess CFD simulation credibility. We are not taking any final action on these requests, but may consider the changes suggested by the commenter in an appropriate future rulemaking with notice and comment. See our complete response in Chapter 2 of our Response to Comments.
Hybrid Powertrain Test Procedures
      As explained above in Sections II.A.1 and II.A.2, EPA proposed several updates to the hybrid powertrain test procedures that apply to engine and vehicle standards provisions in 40 CFR 1036.503, 1036.505, 1036.510, and 1036.527, 40 CFR part 1036, Appendix II, and 40 CFR 1037.550 related to how to perform hybrid powertrain testing and requested comment on general improvements to the hybrid powertrain test procedure provisions (see 85 FR 28152). This section further explains, in addition to the specific descriptions in Sections II.A.1. and II.A.2. above, the changes we are adopting to hybrid powertrain test procedures after consideration of comments received. Additional details on these and other hybrid powertrain testing and measurement amendments or clarifications requested by commenters and our responses are available in Chapter 2 of our Response to Comments.
Hybrid Test Procedures for Engine Standards
      EPA worked with industry prior to proposal and also considered input provided during this rulemaking to develop a powertrain test procedure that includes the addition of a transmission model to GEM and options in GEM to test without the transmission present, using the model in its place to be used to certify a hybrid powertrain to the FTP and SET HD GHG Phase 2 greenhouse gas engine standards.  The two primary goals of this development process were to make sure that the powertrain version of each test cycle was equivalent to the respective engine cycle in terms of positive power demand versus time and that the powertrain cycle had appropriate levels of negative power demand.
      Our current regulations do not have a certification procedure for powertrain certification of heavy-duty hybrid vehicles to any engine standards. The powertrain certification test for certification to both the FTP and SET is carried out by following 40 CFR 1037.550 as described in 40 CFR 1036.505 and 1036.510 and is applicable for powertrain systems located in the P0, P1, P2, and P3 positions.
      For this test procedure, EPA is finalizing addition of a vehicle speed and road grade profile to the existing HDDE FTP and HDOC FTP duty-cycles in 40 CFR part 1036, Appendix II, and to the SET in 40 CFR 1036.505.  EPA also is finalizing vehicle parameters to be used in place of those in 40 CFR 1037.550; namely vehicle test mass, vehicle frontal area, vehicle drag area, coefficient of rolling resistance, drive axle ratio, tire radius, vehicle curb mass, and linear equivalent mass of rotational moment of inertias.  Under the final test procedure, determination of system and continuous rated power along with the maximum vehicle speed (C speed) is also required using 40 CFR 1036.527.  Under the final test procedure, the combination of the generic vehicle parameters, the engine duty-cycle vehicle speed profile, and road grade profile fully defines the system load and this is designed to match up the powertrain load with the compression-ignition engine vFTP, spark ignition engine vFTP, and vSET load for an equally powered engine.
      The development of this test procedure was based on the process contained in Global Technical Regulation No. 4.,  Generally speaking, the final test procedure is powertrain in the loop using a vehicle-based cycle (vehicle speed vs. time and grade vs. time).  The final vehicle speed profiles were developed by following SAE 2012-01-0878.
      The engine operational profile for engines installed in vehicles depends on the entire vehicle setup, including the use of hybrid systems if applicable, thus the entire vehicle must be considered when certifying a powertrain.  Given that heavy duty vehicles can vary quite a bit even though the powertrain configuration remains unchanged, testing of every conceivable configuration is not possible; therefore, a representative average vehicle, consisting of generic vehicle parameters, is used to provide a representative configuration for certification testing.  Generic vehicle parameters were developed with the intent of maintaining the same system load for engines installed in conventional vehicles and hybrid systems with the same power rating to maintain comparability in terms of emissions.
      EPA is finalizing vehicle parameters for hybrid powertrain testing in place of those in 40 CFR 1037.550 to be used in the vehicle model in 40 CFR 1037.550(f).  These final parameters can be found in 40 CFR 1036.505 (via reference from 40 CFR 1036.510 for FTP testing) and included vehicle test mass, M, vehicle frontal area, Afront, vehicle drag area, CdA, coefficient of rolling resistance, Crr, drive axle ratio, ka, tire radius, r, transmission efficiency if the hybrid powertrain is being tested without the transmission, axle efficiency, Effaxle, vehicle curb mass, Mcurb, and linear equivalent mass of rotational moment of inertias, Mrotating.  The requirements for the determination of these parameters were taken from the Global Technical Regulation (GTR) No. 4 referenced above.
      Under the final test procedure, to align the system demands for conventional and hybrid engines, the generic vehicle parameters are defined as a function of the system's power rating.  40 CFR 1036.527 provides the procedure for determining the peak rated power, Prated, and continuous rated power of the hybrid system, Pcontrated, that goes into the vehicle test mass determination.  These revisions also provide a procedure for the determination of the maximum vehicle speed (C speed), vrefC.  In general, the process for determining both Prated and Pcontrated is very similar to the GTR No. 4 hybrid system rated power determination procedure with a few exceptions.  In the final 40 CFR 1036.527 procedure, the default axle efficiency is 0.955 because that is the default value in GEM.  The determination of continuous rated power in the final EPA process versus the system rated power in the GTR No. 4 process is to address the lack of a steady state vehicle test cycle in GTR No. 4.  The full throttle test to determine system rated power in GTR No. 4 lasts 50 to 150 seconds and GTR No. 4 determines rated power as peak power during these tests.  While this process is appropriate for the FTP, the SET is 2400 seconds long and the extended operation at some high speed and load points can lead to some hybrid systems not being able to sustain peak power over the course of the test due to thermal limitations on the motor generator (generally due to material limitations) and limitations on the battery storage capacity and available usable energy.  Under these scenarios, the hybrid system will typically derate the motor generator to thermally protect it, resulting in a sustained peak power that is lower than that determined using the GTR No. 4 process.
      Under the final test procedure, the powertrain system rated power determination in 40 CFR 1036.527 includes the determination of both peak and continuous rated power.  The peak rated power (Prated) is used in the transient FTP test procedure, while the continuous rated power (Pcontrated) is used in the steady-state SET test procedure.  The vehicle C speed, vrefC, is also determined as a result of this process.  This is the maximum vehicle speed at which Psys equals Pcontrated.
      The final compression-ignition vFTP duty cycle vehicle speed profile was derived from the compression-ignition FTP vehicle duty-cycle developed in SAE 2012-01-0878.  In this work, a vehicle FTP cycle and a vehicle SET cycle were created based on the transient diesel engine FTP and engine SET duty cycles. The vehicle cycles are the same duration and have similar power requirements and performance when compared to the engine cycles. The alignment of the engine and vehicle cycles maintain a consistency within vehicle and engine emissions evaluations.  The compression-ignition FTP vehicle speed profile is not applicable to the spark-ignition FTP vehicle speed profile due to differences in the engine duty-cycle lengths, speed profiles, and torque profiles.  Thus, a separate vehicle speed profile had to be developed for the spark-ignition FTP duty cycle.  Using the methodology in SAE 2012-01-0878, a vehicle speed profile was developed for the spark-ignition FTP duty cycle and a comparison between the two cycles can be found in Table II-2.  The vehicle speed profiles can be found in Figure II-1 and Figure II-2.
Table II-2 Comparison Between HDDE FTP and HDOC FTP Vehicle Duty Cycle Metrics
Cycle Metric
Compression-Ignition FTP Vehicle Duty Cycle
Spark-Ignition FTP Vehicle Duty Cycle
Maximum acceleration (m/s[2])
1.55
1.47
Maximum deceleration (m/s[2])
-2.26
-2.15
Average speed (mph)
20.1
19.2
Maximum speed (mph)
60.6
60.8
Stop duration (%)
3.3
4.7
Distance (miles)
6.4
6.4

Figure II-1 Compression-Ignition FTP duty cycle vehicle speed profile.

Figure II-2 Spark-Ignition FTP duty cycle vehicle speed profile.

      The road gradient profile is designed to further align the powertrain system load for engines installed in conventional vehicles and hybrid systems to eliminate the deviations in cumulative work done between the engine and powertrain test.  The grade profiles were developed to align the power versus time and cycle work of the vehicle profiles (compression-ignition vFTP, spark-ignition vFTP, and vSET) to the compression-ignition and spark-ignition FTPs, and SET.  The general process was based on the development of the grade profile for the World Harmonized Vehicle Cycle (WHVC).  A reference normalized power curve was generated using denormalized torque and speed curves from 50 different compression-ignition engines with multiple engine ratings for the compression-ignition FTP, and SET.  The denormalized curves were normalized individually for each engine based on the engine's rated power.  The normalized power curves were then averaged to define the final reference normalized power curve.  Ten different spark-ignition engine torque curves were used for the spark-ignition FTP.  The duty-cycle velocity profile over time was then divided into multiple mini-cycles. Within each mini-cycle, a constant grade was defined in such a way that the energy calculated from the normalized power curve was matched for a given engine power rating.  Power ratings between 100 and 500 kW were used to develop the compression-ignition vFTP, spark-ignition vFTP, and vSET duty-cycles.  The average slope was calculated from the road grade profiles generated for the power ratings between 100 and 500 kW.  The average fixed slope was calculated for every time step along the drive cycle, and a second order polynomial was chosen for the FTP duty-cycles to describe correlation between, and account for the differences in, the average fixed and individual slopes based on the rated power (Prated) of the powertrain.  The equation and coefficient descriptions follow:
Equation II-1
Road Grade=a∙Prated2+b∙Prated+c

      Where a is error compensation in %/kW[2], b is error compensation in %/kW, and c is the average fixed slope pattern.  Negative road grade is included in the profile to ensured that a representative amount of recuperation energy is provided by the test cycle for hybrid applications.  This enables accurate cycle power/work alignment for all vehicles with the engine HDDE and HDOC FTP duty-cycles.  Example vehicle road grade profiles for a 350 kW compression-ignition and 400 kW spark-ignition engine can be found in Figure II-3 and Figure II-4.

Figure II-3 Compression-Ignition FTP vehicle grade profile for a 350 kW engine.

Figure II-4 Spark-Ignition FTP vehicle grade profile for a 400 kW engine.
      During additional review of the development of the road grade profile for vSET included in the proposal, it became apparent that the powertrain might not be able to achieve the default vehicle C speed of 75.0 mph.  To provide a representative maximum vehicle speed and vehicle A and B speeds that are scaled to the C speed in the final test procedure, the determination of vehicle C speed was added as an additional revision to 40 CFR 1036.527.  This maximum achievable vehicle speed is used as the vehicle C speed in Table 1 of §1036.505 and A and B speed are calculated as described in 40 CFR 1036.505.  The final test procedure replaces the proposed maximum vehicle C speed and the default vehicle A and B speeds in the proposed additions to Table 1 of §1036.505 with these calculated speeds.  Adding the allowance to scale the vSET test speeds based on the vehicle maximum achievable speed required an accounting of the effect of these lower speeds on the road grade determination.  This resulted in an expansion of the proposed second order polynomial equation for the vFTP to include vehicle speed in the final test procedure.  The expanded equation and coefficient descriptions follow:
Equation II-2
Road Grade=a∙Pcontrated3+b∙Pcontrated2∙vrefspeed+c∙Pcontrated2+d∙vrefspeed2+e∙Pcontrated∙vrefspeed+f∙Pcontrated+g∙vrefspeed+h

      Where a is error compensation in %/kW[3], b is error compensation in %/kW[2]·mi/hr, c is error compensation in %/kW[2], d is error compensation in %/(mi/hr)[2], e is error compensation in %/kW·mi/hr, f is error compensation in %/kW, g is error compensation in %/mi/hr, and h is the average fixed slope pattern.  Negative road grade is included in the profile to ensure that a representative amount of recuperation energy is provided by the test cycle for hybrid applications.  This enables accurate cycle power/work alignment for all vehicles with the engine SET duty-cycle.
      The final test procedure also includes updates to the road grade coefficients for the compression-ignition and spark-ignition vFTP duty cycles from those proposed.  EPA further reviewed the GTR No. 4 process and noted that the work in mini cycles number 4 and 6 was set to zero.  This was a policy decision made during the GTR No. 4 process but is not appropriate for the generation of EPA's duty-cycles, which should include the actual work for these two mini cycles.  While this improvement results in only a marginal difference from that proposed, it provides a more aligned comparison of work between the engine and vehicle duty-cycles.  The result of this was included in the final test procedure in updated coefficients for the compression-ignition vFTP, spark-ignition vFTP, and vSET duty cycles (vSET improvements are in addition to the road grade coefficient updates already discussed).  Figure II-5 and Figure II-6 show a comparison of the effect on work matching from changing the mini cycle work in mini cycles number 4 and 6 from zero to the actual work for a 300 kW engine. Note, this final test procedure is limited to hybrid powertrains to avoid having two different testing pathways for non-hybrid engines for the same standards.

Figure II-5 Comparison of vSET work from the engine normalized power curve to the vehicle road load equation prior to code correction for a 300 kW engine.

Figure II-6 Comparison of vSET work from the engine normalized power curve to the vehicle road load equation after code correction for a 300 kW engine.
Hybrid Test Procedures for Vehicle Standards
Hybrid Fuel Maps
We are finalizing an option, after consideration of comments received, to generate fuel maps for engine hybrids using the powertrain test procedure in 40 CFR 1037.550. This was done by updating the hybrid engine test procedures finalized in 40 CFR parts 1036.503, 1036.505, 1036.527, and 1037.550 and include the addition of a transmission model to GEM and options in GEM to test without the transmission present, using the model in its place.
Mild Hybrid Certification
Under the Phase 2 regulations, manufacturers must conduct powertrain testing if they wish to take credit for hybrid systems, including mild hybrid systems.  However, manufacturers have expressed concerns about the cost of powertrain testing and that the existing procedure may not measure improvements from certain mild hybrid systems.  EPA requested comment on alternative means of evaluating mild hybrids noting that manufacturers have asked EPA to consider the following options:
 Allow manufacturers to test a powertrain and apply analytically derived scaling factors to others (e.g., scale by fraction of battery capacity or motor capacity) under 40 CFR 1037.235(h).
 Allow manufacturers to use international test procedures for battery capacity, motor power, and motor efficiency.
 Provide smaller credit (potentially with a volume limit and/or only for limited time) in exchange for less testing (e.g., reduced benefit when using the simplified model spreadsheet that is available under docket no. EPA-HQ-OAR-2014-0827-2109).
Commenters generally responded with support for EPA addressing mild hybrid certification but did not provide any concrete means to address concerns surrounding the cost of powertrain testing. In addition, commenters stated that the existing procedures in the proposal may not measure improvements from certain mild hybrid systems. This section presents the changes we are adopting to hybrid test procedures after consideration of comments received. Additional details on these and other hybrid test procedure amendments or clarifications requested by commenters and our responses are available in Chapter 2 of our Response to Comments.
After further consideration, including the lack of additional input on these mild-hybrid certification options, we have concluded that the engine hybrid test procedure proposed in this rule, is the best pathway for these hybrids.  This will allow a manufacturer to test a mild hybrid engine without having to certify the hybrid with a transmission under the powertrain testing option.  Finalizing these changes allows the test results to better reflect the performance of mild hybrid's that are not integrated into the transmission, without requiring that the transmission be part of the certified configuration.  Finalizing this procedure also allows the test results to be used for additional appropriate vehicles, since the test results will not be limited to the transmission that was included during the test, as is required for non-hybrid powertrains utilizing 40 CFR 1037.550.  This mild hybrid engine test procedure was finalize via additions to the hybrid powertrain test procedure revisions in 40 CFR parts 1036.503, 1036.505, 1036.510, 1036.527, and 1037.550 and includes the addition of a transmission model to GEM and options in GEM to test without the transmission present, using the model in its place.
Heavy-Duty Engine GHG Emission Standards and Flexibility
Revisions to Credit Provisions for Vocational Engine Emissions Standards
EPA proposed several updates to the credit provisions related to credit provisions for vocational engines and requested comment on these credit provisions (see 85 FR 28145). This section presents the changes we are adopting to vocational engine credit provisions after consideration of comment received. Additional details on comment on these credit provisions and our response are available in Chapter 2.4 of our Response to Comments.
In developing the baseline emission rates for vocational engines in the final Phase 2 rulemaking, we considered MY 2016 FTP certification data for diesel engines, which showed an unexpected step-change improvement in engine fuel consumption and CO2 emissions compared to data considered in the proposed rule.  The proposed baseline emission rates came from the Phase 1 standards, which in turn were derived from our estimates of emission rates for 2010 engines.  The underlying reasons for this shift in the 2016 Phase 2 final rule were mostly related to manufacturers optimizing their SCR thermal management strategy over the FTP in ways that we (mistakenly) thought they already had in MY 2010 (i.e., the Phase 1 baseline).
As background, the FTP includes a cold-start, a hot-start and significant time spent at engine idle. During these portions of the FTP, the NOx SCR system can cool down and lose NOx reducing efficiency.  To maintain SCR temperature, manufacturers initially used a simplistic strategy of burning extra fuel to heat the exhaust system. However, during the development of Phase 1, EPA believed manufacturers were using more sophisticated and efficient strategies to maintain SCR temperature.  EPA's misunderstanding of the baseline technology for Phase 1 provided engine manufacturers the opportunity to generate windfall credits against the FTP standards.
For the Phase 2 final rule, EPA revised the baseline emission rate for vocational engines to reflect the actual certified emission levels. The Phase 2 vocational engine final CO2 baseline emissions are shown in the table below. More detailed analyses on these Phase 2 baseline values of tractor and vocational vehicles can be found in Chapter 2.7.4 of the Phase 2 Final RIA.
Table II-3 Phase 2 Vocational Engine CO2 and Fuel Consumption Baseline Emissions
Units
HHD
MHD
LHD
g/bhp-hr
525
558
576
gal/100 bhp-hr
5.1572
5.4813
5.6582

EPA did not allow the carryover of Phase 1 vocational engine credits into the Phase 2 program, consistent with these adjustments to the baselines. Since this issue does not apply for RMC emissions, the restriction was applied only for engines certified exclusively to the FTP standards (rather than both FTP and RMC standards).  We believed that allowing engine credits generated against the Phase 1 diesel FTP standards to be carried over into the Phase 2 program would have inappropriately diluted the Phase 2 engine program.  However, this was in the context of unadjusted credits.
After further consideration, we now believe that it would not dilute the program if the credits were appropriately adjusted to more accurately reflect improvement over the true baseline levels.
Allowing the portion of the credits that represent actual emission improvements to be carried forward is consistent with our rationale from Phase 2.  Thus, we are allowing in §1036.701(j), for the purpose of carrying Phase 1 credits into the Phase 2 program, and not compliance with Phase 1 standards, that manufacturers may recalculate the credits in their initial Phase 1 ABT vocational engine averaging set relative to the Phase 2 baseline engine values.  The recalculated vocational engine credits for an ABT averaging set will be allowed into the Phase 2 engine program to the same extent as tractor engine credits. Cummins submitted a late comment (see Docket ID EPA-HQ-OAR-2019-0307-0066) requesting clarification of whether manufacturers would have the option of applying these vocational carryover provisions to one ABT averaging set but not another (i.e. that EPA would not require the recalculation of all averaging sets.) This final rule affirms that recalculation of vocational credits is to be applied to all engines within an individual ABT averaging set and that other averaging sets, such as tractors, are not affected by these vocational carryover provisions. EMA commented that manufacturers should be able to opt in to recalculating credits on an engine family by engine family basis, as applying this adjustment to all engine families could affect existing Phase 1 compliance for engines above the Phase 2 baseline value. However, EPA is only allowing this recalculation for the purpose of determining the amount of credit that can be carried into the Phase 2 program, and adjusting the credits for all the engine families a manufacturer chose to include in their initial ABT averaging set for Phase 1 program properly accounts for the net credits that can be carried forward. In the ABT program, all engine families within an averaging set are used in the calculation of credits, and manufacturers cannot pick and choose which engine families are used in that calculation.
As noted in the Phase 2 final rule, allowing additional flexibility for compliance with engine standards does not cause any increase in emissions because the manufacturers must still comply with the vehicle standards (See 81 FR 73499, October 25, 2016).  However, this flexibility could allow some manufacturers to find a less expensive compliance path.
Special Flexibility for Vocational Engines and Credits
EPA requested comment on several updates to the special flexibility provisions for vocational engines (see 85 FR 28145). This section presents the regulatory changes we are adopting after consideration of comments received. Additional details on comments received on these provisions and our responses are available in Chapter 2.4 of our Response to Comments.
In the existing regulations at 40 CFR 1036.150(p), EPA provided special flexibility for engine manufacturers that certify all their model year 2020 engines within an averaging set to the model year 2021 FTP and SET standards and requirements.  Where 40 CFR 1036.150(p) applies, subparagraph (p)(1) specifies that GHG emission credits that manufacturers generate with model year 2018 through 2024 engines may be used through model year 2030, instead of being limited to a five-year credit life as specified in 40 CFR 1036.740(d). Note that under the Phase 2 final rule this provision in effect only applies to manufacturers of tractor engines, as under 40 CFR 1036.701(j) EPA did not allow the carryover of Phase 1 vocational engine credits into the Phase 2 program (81 FR 73499, October 25, 2016). Where 40 CFR 1036.150(p) applies, subparagraph (p)(2) specifies that manufacturers are also allowed to certify model year 2024 through 2026 tractor engines to alternative standards that are slightly higher than the otherwise applicable standards. Note that in the table of alternative standards in the Phase 2 final rule EPA included values for medium and heavy heavy-duty vocational engines, but these values are identical to the Phase 2 standards and not slightly higher due to our concerns about windfall credits if carryover of Phase 1 credits were allowed.
The applicability of 40 CFR 1036.150(p) is based on the choices manufacturers made when certifying their MY 2020 engines. Instead of certifying engines to the final year of the Phase 1 engine standards, manufacturers electing the alternative instead certified to the MY 2021 Phase 2 engine standards. Because these engine manufacturers reduced emissions of engines that would otherwise have been subject to the more lenient MY 2020 Phase 1 engine standards, there can be a net benefit to the environment. These engines do not generate credits relative to the Phase 1 standards but instead generate credits relative to the pulled ahead MY 2021 Phase 2 engine standards.  Because the vehicle standards themselves are unaffected, the alternative MY 2024-2026 engine standards will not dilute or diminish the overall GHG reductions or fuel savings of the program. Vehicle manufacturers using engines subject to the alternative MY 2024 - 2026 standards would need to adopt additional vehicle technology (i.e., technology beyond that projected to be needed to meet the engine standards) to meet the applicable vehicle GHG standards. The result is that the vehicles would still achieve the same GHG emissions in use.
The proposed rule included an amendment to address the concern regarding Phase 1 windfall credits and requested comment on the possibility of a similar set of alternative standards for vocational engines. CARB and Volvo commented that they support these changes and flexibilities. Cummins commented opposing both the alternative MY 2024 through 2026 vocational engine standards and extending the life of credits generated from early compliance with Phase 2 vocational standards. ACEEE commented opposing extending the life of vocational engine credits generated in Phase 1, stating that doing so does not result in emission reductions but would increase emissions and reduce the rule's overall stringency. Cummins also commented that manufacturers had already developed and certified MY 2020 products without consideration of these changes, and even if post hoc recertification was possible, allowing them now would potentially be an advantage or disadvantage to individual manufacturers.
As discussed in section II.B.1, we are finalizing provisions on calculating credits relative to a baseline that addresses these windfall credit concerns, which also results in the extended credit life flexibility under 40 CFR 1036.150(p)(1) now being available to vocational vehicles that qualify under 40 CFR 1036.150(p). We are also finalizing a set of alternative standards for vocational engines, as shown in Table II-4.
Table II-4 Alternative Standards for Vocational Engines
Model Years
Medium Heavy-Duty Vocational (g/hp-hr)
Heavy Heavy-Duty Vocational (g/hp-hr)
2024-2026
542
510

The Phase 2 standards are implemented in three MY steps: 2021, 2024, and 2027. The largest step change in stringency occurs in MY 2024, where approximately two-thirds of the total numeric reduction in the MY 2021 through MY 2027 standards is achieved, with the remaining one-third occurring in MY 2027. For the alternative tractor engine standards, EPA reversed the magnitude of the MY 2024 and MY 2027 step changes, where the MY 2024 alternative standard represents one-third of the total numeric reduction and is slightly higher than the Phase 2 standard. The standards at the beginning (MY 2021) and ending (MY 2027) steps of the Phase 2 program remain the same in either case, and only the level of decrease in standard for MY 2024 changes with the alternative standards. EPA determined the alternative standards for vocational engines by adjusting the magnitude of the MY 2024 standard in the same manner as used to determine the alternative tractor engine standards in the Phase 2. The Phase 2 vocational engine standards decrease by 10 g/hp-hr between MY 2021 and MY 2027, with a 7 g/hp-hr step change in the MY 2024 standard (approximately two-thirds of the total numeric reduction) and a 3 g/hp-hr step change in MY 2027. For the alternative vocational engine standards in MY 2024-2026, we are adopting a 3 g/hp-hr reduction from the MY 2021 standard (from 545 to 542 g/hp-hr for medium heavy-duty and 513 to 510 g/hp-hr for heavy heavy-duty) instead of 7 g/hp-hr.  EPA believes that allowing these slightly higher (approximately 0.7 to 0.8 % compared to the Phase 2 final rule) engine standards for vocational vehicles is justified, as the overall vehicle standards will still be met. Engine development and vehicle technology choices are pathways to meeting overall vehicle standards, as is the use of credits generated by early compliance. EPA's alternative engine standards provisions for vocational vehicles for MYs 2024-2026 allows manufacturers flexibility to choose the mix of engine and vehicle technologies that will comply with the standards. As noted in the Phase 2 final rule and this rule's proposal, EPA views this type of alternative as being positive from the environmental and energy conservation perspectives, as vehicle-level emission standards remain the same, but manufacturers are provided with significant flexibility on engine emission standards and credit life provisions that may reduce their compliance costs
      Regarding the adverse comments received, including whether or not manufacturers had the opportunity to consider these changes prior to MY 2020, these changes correspond to the corrected approach to Phase 1 credit calculations explained in Section II.B.1 above. At the time of the Phase 2 final rule, we believed that allowing Phase 1 vocational engine credits, without adjustment, to be carried over to the Phase 2 program would result in "windfall" credits, or dilution of the benefits of the Phase 2 program, and we adopted restrictions to limit their use. However, after the Phase 2 final rule we recognized that an alternative to restricting Phase 1 vocational engine credits because of windfall concerns would be to adjust credits earned in Phase 1 downward, relative to a baseline of the lower Phase 2 emissions standards, and in doing so, we would be extending to vocational engine manufactures the same flexibilities that were provided to tractor engine manufacturers. In this final rule we are allowing the vocational engine credits generated in Phase 1 to be adjusted downward and used in Phase 2 program through MY 2030, just as they were for tractors. In setting lower baseline emission values for Phase 1 vocational engine credits and providing the corresponding program flexibilities, EPA does not intend to advantage or disadvantage any manufacturer. Rather, we are removing restrictions that were applied only to vocational engines but no longer should be applied now that we are finalizing provisions that provide a proper accounting of the emission improvements realized by manufacturers who chose to certify their MY 2020 engines to the MY 2021 Phase 2 standards, so vocational and tractor engines are treated the same. In addition, the revised MY 2024-2026 alternative standards for vocational engines, while slightly higher than those in the Phase 2 final rule by 0.7 to 0.8 %, do not reduce the overall stringency of the Phase 2 program, but instead reflect the alternative standards we would have adopted in the Phase 2 final rule alongside the similar tractor provisions, and for the same reasons we finalized those tractor provisions, had we considered adjusting baseline emission rates used for calculating Phase 1 credits. Manufacturers that qualify to use the alternative MYs 2024 - 2026 engine standards accelerated their compliance with the more stringent MY 2021 Phase 2 standards by one model year. As we explained in the Phase 2 final rule, because the vehicle standards themselves are unaffected, these alternative engine standards will not dilute or diminish the overall GHG reductions or fuel savings of the program. Vehicle manufacturers using engines subject to the alternative MYs 2024 - 2026 standards will need to adopt additional vehicle technology (i.e., technology beyond that projected to be needed to meet the engine standard) to meet the applicable vehicle GHG standards. The result is that the vehicles using engines that comply with the alternative standards will still achieve the same overall GHG emissions in use. EPA believes that these alternative standards are appropriate, and allowing alternative engine standards for vocational vehicles that qualify is justified, for these reasons, and that vocational engine manufacturers who met the Phase 2 engine standards one year in advance of the MY 2021 implementation date should have the same flexibility as tractors to earn and use those credits through MY 2030.
Confirmatory Testing of Engines and Measurement Variability
EPA proposed updates to the procedure for confirmatory testing of the fuel mapping test procedure related to providing an interim 2% allowance during confirmatory testing of the fuel mapping test procedure finalized in the Phase 2 final rule and requested comment on "...whether it appropriately balances the impacts of testing variability for fuel maps" (see 85 FR 28146, May 12, 2020). This section presents the changes we are adopting to the confirmatory testing portion of the fuel mapping test procedure after consideration of comments received. Additional details on these comments and our responses are available in Chapter 2 of our Response to Comments.