Owners of vocational vehicles that are upfitted with high-priced bodies that are purpose-built for particular applications tend to keep them longer, on average, than owners of vehicles such as pickups, vans, and tractors, which are traded in broad markets that include many potential secondary markets.  The fact that vocational vehicles also generally accumulate far fewer annual miles than tractors further contributes to lengthy trade cycles among owners of these vehicles.  To the extent vocational vehicle owners may be similar to owners of tractors in terms of business profiles, they would be more likely to resemble private fleets or owner-operators than for-hire fleets.  A 2013 survey conducted by NACFE found that the trade cycle of private tractor fleets ranged from seven to 12 years.
The Phase 1 standards for this vocational vehicle category generally apply at the chassis manufacturer level. For the same reasons given in Phase 1, the agencies propose to apply the Phase 2 vocational vehicle standards at the chassis manufacturer level.
The Phase 1 regulations prohibit the introduction into commerce of any heavy-duty vehicle without a valid certificate or exemption.  Title 40 CFR §1037.620 allows for a temporary exemption for the chassis manufacturer if it produces the chassis for a secondary manufacturer that holds a certificate.  Further discussion of temporary exemptions and possible obligations of secondary manufacturers can be found in Section V. E.
In Phase 1, the agencies adopted two equivalent sets of standards for Class 2b-8 vocational vehicles.  For vehicle-level (chassis) emissions, EPA adopted CO2 standards expressed in grams per ton-mile. For fuel efficiency, NHTSA adopted fuel consumption standards expressed in gallons per 1,000 ton-miles.  The Phase 1 engine-based standards vary based on the expected weight class and usage of the vehicle into which the engine will be installed.  We adopted Phase 1 vehicle-based standards that vary according to one key attribute, GVWR, based on the same groupings of vehicle weight classes used for the engine standards -- light heavy-duty (LHD, Class 2b-5), medium heavy-duty (MHD, Class 6-7), and heavy heavy-duty (HHD, Class 8).
In Phase 1, the agencies defined a special regulatory category called vocational tractor, which generally operate more like vocational vehicles than line haul tractors.  As described above in Section III.C.3, under the Phase 1 rules, a vocational tractor is certified under standards for vocational vehicles, not those for tractors.  In Phase 2, the agencies propose to retain the vocational tractor definition, and to allow vocational tractors to certify over any of the proposed vocational vehicle duty cycles, following the same decision-tree as other vocational chassis.  Vocational tractors would continue to satisfy the proposed engine standard and vocational vehicle GEM-based standard, rather than the proposed tractor standard.
Manufacturers are required to use GEM to determine compliance with the Phase 1 vocational vehicle standards, where the primary vocational vehicle manufacturer-generated input is the measure of tire rolling resistance.  The GEM assumes the use of a typical representative, compliant engine in the simulation, resulting in one overall value for CO2 emissions and one for fuel consumption.  The manufacturers of engines intended for use in vocational vehicles are subject to separate Phase 1 engine-based standards. Manufacturers also may demonstrate compliance with the CO2 standards in whole or in part using credits reflecting CO2 reductions resulting from technologies not reflected in the GEM testing regime.  See 40 CFR Section 1037.610.
In Phase 1, EPA and NHTSA also adopted provisions designed to give manufacturers a degree of flexibility in complying with the standards.  Most significantly, we adopted an ABT program to allow manufacturers within the same averaging set to comply on average. See 40 CFR Section 1037 subpart H. These provisions enabled the agencies to adopt overall standards that are more stringent than we could have considered with a less flexible program.
Proposed Phase 2 Standards for Vocational Vehicles
The agencies have held dozens of meetings with manufacturers, suppliers, non-governmental organizations (NGOs), and other stakeholders to identify and understand the opportunities and challenges involved with regulating vocational vehicles.  These meetings have helped us to better understand the performance demands of the customers, the fuel-saving and GHG reducing technologies that are being investigated, as well as some challenges that are being encountered.  In addition, we updated our industry characterization to better understand the vocational vehicle manufacturing process, including the component suppliers and body builders.  We believe these information exchanges have enabled us to develop this proposal with an appropriate balance of reasonably achievable goals and a reasonably small risk of unintended consequences.
Proposed Subcategories and Test Cycles
The proposed Phase 2 vocational vehicle standards are based on the performance of a wider array of control technologies than the Phase 1 rules.  In particular, the agencies are proposing to recognize detailed characteristics of powertrains and drivelines in the proposed Phase 2 vocational vehicle standards. As described below, driveline improvements present a significant opportunity for reducing fuel consumption and CO2 emissions from vocational vehicles.  However, there is no single package of driveline technologies that would be equally suitable for the majority of vocational vehicles, because there is an extremely broad range of driveline configurations available in the market.  This is due in part to the variety in build processes, ranging from a purpose built custom chassis to a commercial chassis that may be intended as a multi-purpose stock vehicle.  Further, the wide range of applications and driving patterns of these vehicles leads manufacturers to offer a variety of drivelines, as each performs differently in use.  For example, depending on whether the transmission has an overdrive gear, drive axle ratios for Class 7 and 8 tractors can be found in the range of 2.5:1 to 4.1:1.  By contrast, across all types of vocational vehicles, drive axle ratios can be as low as 3.1:1 (delivery vehicle) and as high as 9.8:1 (transit bus).  Other components of the driveline also have a broader range of product in vocational vehicles than in tractors, including transmission gears, tire sizes, and engine speeds.  Each of these design features affects the GHG emission rate and fuel consumption of the vehicle.  It therefore is reasonable to define more than one baseline configuration of vocational vehicle, to encompass a range of drivelines and recognize that the agencies cannot use a one-size-fits-all approach.  A detailed list of the technologies the agencies project could be adopted to meet the proposed vocational vehicle standards is described in Section V.C, and in the draft RIA Chapter 2.  The agencies have determined that these technologies perform differently depending on the drivelines and driving patterns, further supporting the need to subcategorize this segment.
For these reasons, the agencies are proposing to create additional subcategories of vocational vehicles in Phase 2.  By creating additional subcategories we would essentially be setting separate baselines and separate numerical performance standards for different groups of vocational vehicle chassis over different test cycles.  This would enable the technologies that perform best at highway speeds and those that perform best in urban driving to each to be fully recognized over appropriate test cycles, while avoiding the unintended consequence of forcing vocational vehicles that are designed to serve in a wide variety of applications to be measured against a single baseline.  The attributes we believe could define these chassis groups are described below.
The agencies are proposing to split groups of chassis into subcategories based generally on vehicle use patterns in which the CO2 emissions and fuel consumption standards vary as a consequence.  Compliance with these standards would be demonstrated through test cycles reflecting these use patterns, to best assure that actual in-use benefits occur.  An ideal test cycle is one in which the performance improvements achieved by the adopted technologies are recognized over the cycle. As described in Section V.C and in the draft RIA Chapter 2.9, the agencies have found that most of the technologies considered do perform differently under different driving conditions.  For example, the effectiveness of lower tire rolling resistance is different depending on the degree of highway or transient driving, but the differences are very small compared to the difference in effectiveness for a hybrid drivetrain under different driving conditions.  The agencies have found that the measurable changes in performance of a majority of the technologies are significant enough to merit creation of different subcategories with different test cycles.
Idle reduction technology is one type of technology that is particularly duty-cycle dependent. The composite test cycle for vocational vehicles in Phase 1 includes a 42 percent weighting on the ARB Transient test cycle, which comprises nearly 17 percent of idle time.  However, no single idle event in this test cycle is longer than 36 seconds, which may not be enough time to adequately recognize the benefits of some idle reduction technologies. For Phase 2, the agencies propose to recognize this important fuel saving technology by evaluating workday idle reduction technologies through a new idle-only cycle as described in the draft RIA Chapter 3.
The agencies are proposing three different composite test cycles for vocational vehicles in Phase 2: Regional, Multi-Purpose, and Urban.  The agencies believe these three cycles balance the competing pressures to recognize the varying performance of technologies, serve the varying needs of customers, and maintain reasonable regulatory simplicity.  Table V-1 below presents the nine proposed subcategories of vocational vehicles: three weight class groupings, each with three composite duty cycles.  Each of these proposed composite duty cycles has a different weighting of the new idle cycle, the highway cruise cycles, and the ARB Transient cycle, as shown in Table V-2.  The CALSTART HD Truck Fuel Economy Task Group met in June 2013 to discuss vocational vehicle segmentation, and suggested an approach very similar to this.  The task group generally supported a limited number of duty cycles that would be sufficient to cover the basic applications while allowing new technology to demonstrate its worth.  They recognized that a few meaningful duty cycles could "bound" how vocational vehicles are generally used, while recognizing that this approach would not perfectly match how every vocational vehicle is actually used.  Their recommendations included three vocational vehicle duty-cycle-based subcategories: Urban, Regional, and Work Site.  A detailed discussion of the CALSTART recommendations, as well as reasoning why the agencies selected the proposed composite cycle weightings can be found in the draft RIA Chapter 2.  Continuing the averaging scheme from Phase 1, each manufacturer would be able to average within each vehicle weight class.
Table V-1: Proposed Regulatory Subcategories for Vocational Vehicles
Weight Class
Light Heavy-Duty
                                  Class 2b-5
                          Medium Heavy-Duty Class 6-7
Heavy Heavy-Duty
                                    Class 8
Duty Cycle
Regional
Regional
Regional

Multi-Purpose
Multi-Purpose
Multi-Purpose

Urban
Urban
Urban

Table V-2: Proposed Composite Test Cycle Weightings (in Percent) for Vocational Vehicles

                                 ARB Transient
                       55 mph Cruise with Road Grade[a]
                       65 mph Cruise with Road Grade[a]
                                     Idle
Regional
50
28
22
10
Multi-Purpose
82
15
3
15
Urban
94
6
0
20
Note:
a As described in Section III.E.2.b, the agencies are proposing to add road grade to the highway cruise test cycles.
The agencies are proposing criteria for determining the applicability of these subcategories.  This is not as straightforward an exercise as with tractors, where attributes such as cab type are obvious physical properties that indicate reasonably well how a vehicle is intended to be used.  The agencies have identified the final drive ratio of a vocational vehicle as a possible attribute that may indicate how the vehicle is intended to be used.  As described in Section V. E. (1) (d), we expect that most vocational chassis could be assigned to a duty cycle by estimating the percent of maximum engine test speed that is achieved over highway cruise cycles, by use of an equation that relates engine speed to vehicle speed.  To simplify this assignment process, the agencies propose that a vocational chassis would be presumed to certify using the Multi-Purpose duty cycle unless some criteria were met that indicated either the Regional or Urban cycle would be more appropriate.  Those criteria could include the objective calculation described in Section V.E., or a mix of physical attributes and knowledge of intended use.  The agencies are also proposing that chassis manufacturers would be able to request a different duty cycle.
We understand that even within certain vocational vehicle types, vehicle use varies significantly.  By employing the agencies' recommended assignment process, it is our expectation that a delivery truck and a dump truck could both be certified over the same duty cycle while still yielding accurate technology effectiveness, if they had similar chassis and driveline characteristics.  Further, while intended service class may help a manufacturer decide how to classify some vehicles, we do not believe that intended service class would be a sufficient indicator by itself.  An example of this is the refuse service class.  A neighborhood collection refuse truck would not need to be assigned to the same subcategory as a roll-off refuse straight/dump truck that makes daily highway trips to a landfill.
The agencies request comment on the method for assigning vocational chassis to regulatory subcategories. We believe the proposed approach is aligned with the objective to allow manufacturers to certify their chassis over appropriate duty cycles, while maintaining the ability of the market to offer a variety of products to meet customer demand.
Alternative Approach to Subcategorization
The U.S. Department of Energy and EPA are partnering to support a project aimed at evaluating, refining and/or developing duty cycles for tractors and vocational vehicles to be used in the certification of heavy-duty vehicles to GHG emission standards.  This project is underway at the National Renewable Energy Laboratory (NREL) and includes a task to develop alternative subcategorization options for vocational vehicles, along with new drive cycles and/or cycle composite weightings. NREL is continuing to collate available vehicle activity data and vehicle characteristics, and the public is invited to submit information to the docket in support of this work to identify possible alternative GEM test cycles and segmentation options for vocational vehicles.  Preliminary work under this project indicates that two or three test cycles may adequately represent most vocational vehicles.  Preliminary work also indicates that in-use drive cycles may include more idle operation for all types of vocational vehicles than is represented by the currently proposed GEM test cycles.  Depending on comments and additional information received during the comment period, it may be within the agencies' discretion to adopt one or more alternative vocational vehicle test cycles, or re-weight the current test cycles, to better represent real world driving and better reflect performance of the technology packages.
Proposed GHG and Fuel Consumption Standards for Vocational Vehicles
EPA is proposing CO2 standards and NHTSA is proposing fuel consumption standards for manufacturers of chassis for new vocational vehicles.  As described in Sections II.C.1 and II.D.1 above, the agencies are proposing test procedures so that engine performance would be evaluated within the GEM simulation tool.  These test procedures include corrections for the test fuel, enabling vocational vehicles to be certified with many different types of CI and SI engines. In addition, EPA is proposing to establish HFC leakage standards for air conditioning systems in vocational vehicles, as described below and in the draft RIA Chapters 2 and 5.
This section describes the standards and implementation dates that the agencies are proposing for the nine subcategories of vocational vehicles.  The agencies have performed a technology analysis to determine the level of standards that we believe would be available at reasonable cost, and would be cost-effective, technically feasible, and appropriate in the lead time provided.  More details of this analysis are described in the draft RIA Chapter 2. This analysis considered the following for each of the proposed regulatory subcategories:
the level of technology that is incorporated in current new vehicles,
forecasts of manufacturers' product redesign schedules,
the available data on CO2 emissions and fuel consumption for these vehicles,
technologies that would reduce CO2 emissions and fuel consumption and that are judged to be feasible and appropriate for these vehicles through the 2027 model year,
the effectiveness and cost of these technologies,
a projection of the technologically feasible application rates of these technologies, in this time frame, and
projections of future U.S. sales for different types of vehicles and engines.

The proposal described here and throughout the rulemaking documents is the preferred alternative, referred to as Alternative 3 in Section X and the draft RIA Chapter 11.  However, the agencies are seriously considering another alternative for all segments, including vocational vehicles, referred to as Alternative 4.  The agencies believe that Alternative 4 has the potential to be the maximum feasible and reasonable alternative.  However, based on the evidence currently before the agencies, EPA and NHTSA have outstanding questions regarding relative risks and benefits of Alternative 4 due to the time frame envisioned by that alternative.   Alternative 4 is predicated on the same general market adoption rates of the same technologies as the proposal, but would provide three years less lead time than the proposal.  Details of Alternative 4 are presented in Section V.D, Section X, and in the draft RIA Chapter 11.
The agencies seek comment on the feasibility of Alternative 4 for vocational vehicles, including empirical data on its appropriateness, cost-effectiveness, and technological feasibility.  It would be helpful if comments addressed these issues separately for each type of technology.
Additional information and feedback could further inform our assumptions and, by extension, our analysis of feasibility.  The agencies believe it is possible that it could be within the agencies' discretion to determine in the final rules that Alternative 4 could be maximum feasible and appropriate under CAA section 202 (a)(1) and (2).  If the agencies receive relevant information supporting the feasibility of Alternative 4, or regarding technology pathways different than those in Alternatives 3 and 4, the agencies may consider establishing final fuel consumption and GHG emissions standards at levels that provide more overall reductions than what we are proposing if we deem them to be maximum feasible and reasonable for NHTSA and EPA, respectively.
    Proposed Fuel Consumption and CO2 Standards
The agencies are proposing standards that would phase in over a period of seven years, beginning in the 2021 model year, consistent with the requirement in EISA that NHTSA's standards provide four full model years of regulatory lead time and three full model years of regulatory stability, and provide sufficient time "to permit the development and application of the requisite technology" for purposes of CAA section 202 (a)(2).  The proposed Phase 2 program would progress in three-year stages with an intermediate set of standards in MY 2024 and would continue to reduce fuel consumption and CO2 emissions well beyond the full implementation year of MY 2027.  The agencies have identified a technology path for each of these levels of improvement, as described below.
Combining engine and vehicle technologies, vocational vehicles powered by CI engines would be projected to achieve improvements of 16 percent in MY 2027 over the MY 2017 baseline, as described below and in the draft RIA Chapter 2.  The agencies project up to 13 percent improvement in fuel consumption and CO2 emissions in MY 2027 from SI-powered vocational vehicles, as shown in Table V-3.  The incremental Phase 2 vocational vehicle standards would ensure steady progress toward the MY2027 standards, with improvements in MY 2021 of up to seven percent and improvements in MY 2024 of up to 11 percent over the MY 2017 baseline vehicles, as shown in Table V-3.
 The agencies' analyses, as discussed in this preamble and in the draft RIA Chapter 2, show that the proposed standards would be appropriate under each agency's respective statutory authority.
Table V-3: Projected Vocational Vehicle CO2 and Fuel Use Reductions (in Percent) from 2017 Baseline
Model Year
 Engine Type
Heavy Heavy-Duty Class 8
Medium Heavy-Duty Class 6-7
Light Heavy-Duty Class 2b-5
2021
CI Engine
7
7
6

SI Engine
5
5
4
2024
CI Engine
11
11
10

SI Engine
7
7
7
2027
CI Engine
16
16
16

SI Engine
12
13
12

Based on our analysis and research, the agencies believe that the improvements in vocational vehicle fuel consumption and CO2 emissions can be achieved through deployment and utilization of a greater set of technologies than formed the technology basis for the Phase 1 standards.  In developing the proposed standards, the agencies have evaluated the current levels of fuel consumption and emissions, the kinds of technologies that could be utilized by manufacturers to reduce fuel consumption and emissions, the associated lead time, the associated costs for the industry, fuel savings for the owner/operator, and the magnitude of the CO2 reductions and fuel savings that may be achieved.  After examining the possibilities of vehicle improvements, the agencies are basing the proposed standards on the performance of workday idle reduction technologies, improved transmissions including hybrid powertrains, axle technologies, weight reduction, and further tire rolling resistance improvements.  The EPA-only air conditioning standard is based on leakage improvements.
The agencies' evaluation indicates that some of the above vehicle technologies are commercially available today, though often in limited volumes.  Other technologies would need additional time for development.  Those that we believe are available today and may be adopted to a limited extent in some vehicles include improved tire rolling resistance, weight reduction, some types of conventional transmission improvements, neutral idle, and air conditioning leakage improvements.  However, EPA is not proposing standards predicated on performance of these technologies until MY 2021.  The agencies consider any potential benefits that could be achieved by implementing rules requiring some technologies on vocational vehicles earlier than MY 2021 to be outweighed by several disadvantages.  For one, manufacturers would need lead time to develop compliance tracking tools.  Also, if the Phase 2 vocational vehicle standards began in a different year than the tractor standards, this could create unnecessary added complexity, and could strongly detract from the fuel savings and GHG emission reductions that could otherwise be achieved.  Therefore we anticipate that the Phase 1 standards will continue to apply in model years 2018 to 2020.
Vehicle technologies that we believe will become available in the near term include improved axle lubrication and 6x2 axles.  Vehicle technologies that we understand would benefit from even more development time include stop-start idle reduction and hybrid powertrains.  The agencies have analyzed the technical feasibility of achieving the fuel consumption and CO2 standards, based on projections of what actions manufacturers would be expected to take to reduce fuel consumption and emissions to achieve the standards, and believe that the standards would be technologically feasible throughout the regulatory useful life of the program.  EPA and NHTSA estimated vehicle package costs are found in Section V. C. (2) .
Table V-4 and Table V-5 present EPA's proposed CO2 standards and NHTSA's proposed fuel consumption standards, respectively, for chassis manufacturers of Class 2b through Class 8 vocational vehicles for the beginning model year of the program, MY 2021.  As in Phase 1, the standards would be in the form of the mass of emissions, or gallons of fuel, associated with carrying a ton of cargo over a fixed distance.  The EPA standards would be measured in units of grams CO2 per ton-mile and the NHTSA standards would be in gallons of fuel per 1,000 ton-miles. With the mass of freight in the denominator of this term, the program is designed to measure improved efficiency in terms of freight efficiency. As in Phase 1, the Phase 2 program would assign a fixed default payload in GEM for each vehicle weight class group (heavy heavy-duty, medium heavy-duty, and light heavy-duty).  Even though this simplification does not allow individual vehicle freight efficiencies to be recognized, the general capacity for larger vehicles to carry more payload is represented in the numerical values of the proposed standards for each weight class group.
EPA's proposed vocational vehicle CO2 standards and NHTSA's proposed fuel consumption standards for the MY 2024 stage of the program are presented in Table V-6 and Table V-7, respectively.  These reflect broader adoption rates of vehicle technologies already considered in the technology basis for the MY 2021 standards.  The standards for vehicles powered by CI engines also reflect that in MY 2024, the separate engine standard would be more stringent, so the vehicle standard keeps pace with the engine standard.
EPA's proposed vocational vehicle CO2 standards and NHTSA's proposed fuel consumption standards for the full implementation year of MY 2027 are presented in Table V-8 and Table V-9, respectively.  These reflect even greater adoption rates of the same vehicle technologies considered in the basis for the previous stages of the Phase 2 standards.   The proposed MY 2027 standards for vocational vehicles powered by CI engines reflect additional engine technologies consistent with those on which the separate proposed MY 2027 CI engine standard is based.  The proposed MY 2027 standards for vocational vehicles powered by SI engines reflect improvements due to additional engine friction reduction technology, which is not among the technologies on which the separate SI engine standard is based.
The proposed standards are based on highway cruise cycles that include road grade, to better reflect real world driving and to help recognize engine and driveline technologies.  See Section III.E.  The agencies have evaluated some alternate road grade profiles, including several recommended by NREL and two developed independently by the agencies, and have prepared possible alternative vocational vehicle standards based on these profiles.  The agencies request comment on this analysis, which is available in a memorandum to the docket.
  As described in Section I, the agencies are proposing to continue the Phase 1 approach to averaging, banking and trading (ABT), allowing ABT within vehicle weight classes.  For Phase 2, continuing this approach means allowing averaging between CI-powered vehicles and SI-powered vehicles that belong to the same weight class group and have the same regulatory useful life.
Table V-4: Proposed EPA CO2 Standards for MY2021 Class 2b-8 Vocational Vehicles
EPA Standard for Vehicle with CI Engine Effective MY2021 (gram CO2/ton-mile)
Duty Cycle
Light Heavy-Duty
Class 2b-5
Medium Heavy-Duty Class 6-7
Heavy Heavy-Duty
Class 8
Urban
296
188
198
Multi-Purpose
305
190
200
Regional
318
186
189
EPA Standard for Vehicle with SI Engine Effective MY2021 (gram CO2/ton-mile)
Duty Cycle
Light Heavy-Duty
Class 2b-5
Medium Heavy-Duty Class 6-7
Heavy Heavy-Duty
Class 8
Urban
320
203
214
Multi-Purpose
329
205
216
Regional
343
201
204

Table V-5: Proposed NHTSA Fuel Consumption Standards for MY2021 Class 2b-8 Vocational Vehicles
NHTSA Standard for Vehicle with CI Engine Effective MY 2021 (Fuel Consumption gallon per 1,000 ton-mile)
Duty Cycle
Light Heavy-Duty
Class 2b-5
Medium Heavy-Duty Class 6-7
Heavy Heavy-Duty
Class 8
Urban
29.0766
18.4676
19.4499
Multi-Purpose
29.9607
18.6640
19.6464
Regional
31.2377
18.2711
18.5658
NHTSA Standard for Vehicle with SI Engine Effective MY 2021 (Fuel Consumption gallon per 1,000 ton-mile)
Duty Cycle
Light Heavy-Duty
Class 2b-5
Medium Heavy-Duty Class 6-7
Heavy Heavy-Duty
Class 8
Urban
36.0077
22.8424
24.0801
Multi-Purpose
37.0204
23.0674
24.3052
Regional
38.5957
22.6173
22.9549
Table V-6: Proposed EPA CO2 Standards for MY2024 Class 2b-8 Vocational Vehicles
EPA Standard for Vehicle with CI Engine Effective MY2024 (gram CO2/ton-mile)
Duty Cycle
Light Heavy-Duty
Class 2b-5
Medium Heavy-Duty Class 6-7
Heavy Heavy-Duty
Class 8
Urban
284
179
190
Multi-Purpose
292
181
192
Regional
304
178
182
EPA Standard for Vehicle with SI Engine Effective MY2024 (gram CO2/ton-mile)
Duty Cycle
Light Heavy-Duty
Class 2b-5
Medium Heavy-Duty Class 6-7
Heavy Heavy-Duty
Class 8
Urban
312
197
208
Multi-Purpose
321
199
210
Regional
334
196
199

Table V-7: Proposed NHTSA Fuel Consumption Standards for MY2024 Class 2b-8 Vocational Vehicles
NHTSA Standard for Vehicle with CI Engine Effective MY 2024 (Fuel Consumption gallon per 1,000 ton-mile)
Duty Cycle
Light Heavy-Duty
Class 2b-5
Medium Heavy-Duty Class 6-7
Heavy Heavy-Duty
Class 8
Urban
27.8978
17.5835
18.6640
Multi-Purpose
28.6837
17.7800
18.8605
Regional
29.8625
17.4853
17.8782
NHTSA Standard for Vehicle with SI Engine Effective MY 2024 (Fuel Consumption gallon per 1,000 ton-mile)
Duty Cycle
Light Heavy-Duty
Class 2b-5
Medium Heavy-Duty Class 6-7
Heavy Heavy-Duty
Class 8
Urban
35.1075
22.1672
23.4050
Multi-Purpose
36.1202
22.3923
23.6300
Regional
37.5830
22.0547
22.3923

Table V-8: Proposed EPA CO2 Standards for MY2027 Class 2b-8 Vocational Vehicles
EPA Standard for Vehicle with CI Engine Effective MY2027 (gram CO2/ton-mile)
Duty Cycle
Light Heavy-Duty
Class 2b-5
Medium Heavy-Duty Class 6-7
Heavy Heavy-Duty
Class 8
Urban
272
172
182
Multi-Purpose
280
174
183
Regional
292
170
174
EPA Standard for Vehicle with SI Engine Effective MY2027 (gram CO2/ton-mile)
Duty Cycle
Light Heavy-Duty
Class 2b-5
Medium Heavy-Duty Class 6-7
Heavy Heavy-Duty
Class 8
Urban
299
189
196
Multi-Purpose
308
191
198
Regional
321
187
188

Table V-9: Proposed NHTSA Fuel Consumption Standards for MY2027 Class 2b-8 Vocational Vehicles
NHTSA Standard for Vehicle with CI Engine Effective MY 2027 (Fuel Consumption gallon per 1,000 ton-mile)
Duty Cycle
Light Heavy-Duty
Class 2b-5
Medium Heavy-Duty Class 6-7
Heavy Heavy-Duty
Class 8
Urban
26.7191
16.8959
17.8782
Multi-Purpose
27.5049
17.0923
17.9764
Regional
28.6837
16.6994
17.0923
NHTSA Standard for Vehicle with SI Engine Effective MY 2027 (Fuel Consumption gallon per 1,000 ton-mile)
Duty Cycle
Light Heavy-Duty
Class 2b-5
Medium Heavy-Duty Class 6-7
Heavy Heavy-Duty
Class 8
Urban
33.6446
21.2670
22.0547
Multi-Purpose
34.6574
21.4921
22.2797
Regional
36.1202
21.0420
21.1545
As with the other regulatory categories of heavy-duty vehicles, NHTSA and EPA are proposing standards that apply to Class 2b-8 vocational vehicles at the time of production, and EPA is proposing standards for a specified period of time in use (e.g., throughout the regulatory useful life of the vehicle).  The derivation of the standards for these vehicles, as well as details about the proposed provisions for certification and implementation of these standards, are discussed in more detail later in this notice and in the draft RIA.
    Proposed HFC Leakage Standards
The Phase 1 GHG standards do not include standards to control direct HFC emissions from air conditioning systems on vocational vehicles.  EPA deferred such standards due to "the complexity in the build process and the potential for different entities besides the chassis manufacturer to be involved in the air conditioning system production and installation".  76 FR 57194/3.  During our stakeholder outreach conducted for Phase 2, we learned that the majority of vocational vehicles are sold as cab-completes with the dashboard-mounted air conditioning systems installed by the chassis manufacturer.  For those vehicles that have A/C systems installed by a second stage manufacturer, EPA is proposing revisions to our regulations that would resolve the issues identified in Phase 1, in what we believe is a practical and feasible manner, as described below in Section V.E.
For the above reasons, in Phase 2, EPA now believes that it is reasonable to propose A/C refrigerant leakage standards for Class 2b-8 vocational vehicles, beginning with the 2021 model year.  Chassis sold as cab-completes typically have air conditioning systems installed by the chassis manufacturer.  For these configurations, the process for certifying that low leakage components are used would follow the system in place currently for comparable systems in tractors.  In the case where a chassis manufacturer would rely on a second stage manufacturer to install a compliant air conditioning system, the chassis manufacturer must follow the proposed delegated assembly provisions described below in Section V.E.
Proposed Exemptions and Exclusions
    Proposed Standards for Emergency Vehicles
Emergency vehicles are covered by the Phase 1 program at the same level of stringency as any other vocational vehicle.  In discussions with representatives of the Fire Apparatus Manufacturers Association, the agencies have learned that chassis manufacturers of fire apparatus are currently able to obtain compliant engines and tires with the coefficient of rolling resistance allowing compliance with the Phase 1 standards. The agencies are proposing in Phase 2 to allow emergency vehicles to meet less stringent standards than other vocational vehicles.  There are two reasons for doing so.  First, as the level of complexity of Phase 2 would increase with the need for additional technologies aimed to improve driveline efficiency, the compliance burden would be disproportionately high for a company that manufactures small volumes of specialized chassis. The ability of such a company to benefit from averaging would be limited, as would be the ability to spread compliance costs across many vehicles. The second and more important reason is that emergency vehicles, which are necessarily built for high levels of performance and reliability, would likely sacrifice some levels of function to attain the proposed Phase 2 standards.  For example, vehicles with large engines, high-torque powertrains, and tires designed with deep tread would likely be deficit-producing vehicles if manufacturers needed to certify an emergency vehicle family to the primary proposed standards.
In the MY 2017-2025 light-duty rule, the agencies adopted an exclusion for emergency and police vehicles from GHG and fuel economy standards.  As described in that rule, the unique features of purpose-built emergency vehicles, such as high rolling resistance tires, reinforced suspensions, and special calibrations of engines and transmissions, have the effect of raising their GHG emissions.  The agencies determined in that rule that an exemption was appropriate because the technical feasibility issues for emergency vehicles went beyond those of other high-performance vehicles, and vehicles with these performance characteristics must continue to be made available in the market.  The agencies do not believe that non-emergency vocational vehicles are designed for the severe duty cycles that are experienced by emergency vehicles, and therefore do not face the same potential constraints in terms of vehicle design and the application of technology.
In conducting an independent technical feasibility assessment for heavy-duty emergency vehicles, the agencies believe that some GHG and fuel saving technologies could reasonably be applied without compromising vehicle utility.  However, these vehicles are designed, built, and operated so differently than other vocational vehicles that we believe keeping them in the same averaging sets as other vocational vehicles in Phase 2 would not be appropriate and thus a separate standard (evaluated from a baseline specific to these vehicles) is warranted.
Our feasibility analysis and the available tire data indicate that emergency vehicle manufacturers can reasonably continue to apply tires with the Phase 1 level tire CRR performance, in the Phase 2 program.  We have also learned that a variety of vehicle-level technologies are being developed specifically for emergency vehicles, to maintain on-board electronics without excessive idling.  Modern fire apparatus and ambulances typically have multiple computers and other electronic devices on-board, each of which requires power and continues to draw electricity when the vehicle is parked and the crew is responding to an emergency, which could take several hours.  Most on-board batteries and alternators are not capable of sustaining these power demands for any length of time, so emergency vehicles must either operate in a high-idle mode or adopt one of several possible technologies that can assist with electrical load management.  Some of these technologies can enable an emergency vehicle to shut down the main engine and drastically reduce idle emissions.  NHTSA and EPA have not based the proposed emergency vehicle standards on use of idle reduction technologies because we do not believe the regular neutral idle and stop-start technologies we project for other vocational vehicles could apply equally to emergency vehicles, and we do not have enough information about this subset of idle reduction technologies that is designed for extended electrical load management to either estimate an effectiveness value or determine an appropriate market adoption rate.  The agencies request comment on whether we should include any market adoption rate of idle reduction technologies for emergency vehicles, as part of the basis for the Phase 2 emergency vocational vehicle standard.
To address both the technical feasibility and the compliance burden, the agencies are proposing less stringent standards that also have a simplified compliance method.  Because the potential trade-offs between performance and fuel efficiency apply equally to any emergency vehicle manufacturer, the agencies propose that these less stringent standards would apply for commercial chassis manufacturers of emergency vehicles, as well as for custom chassis manufacturers.  The standard for vehicles identified at the time of certification as being intended for emergency service would be predicated solely on the continued use of lower rolling resistance tires, at the Phase 2 baseline level (i.e. compliant with Phase 1).
With respect to standards for engines used in these emergency vehicles, based on what we have learned from discussions with engine manufacturers, we understand that engines designed for heavy-duty emergency vehicles are generally higher-emitting than other engines. However, if we maintain a separate engine standard and regulatory flexibility such as ABT, fire apparatus manufacturers would be able to obtain engines that, on average, meet the proposed Phase 2 engine standards.  The agencies further recognize that the proposed engine map inputs to GEM in the primary program would pose a difficulty for emergency vehicle manufacturers.  If we required engine-specific inputs then these manufacturers would have to apply extra vehicle technologies to compensate for the necessary but higher-emitting engine.  The agencies are therefore not proposing to recognize engine performance as part of the vehicle standard for emergency vehicles.  Manufacturers of these vehicles would be expected to install an engine that is certified to the applicable separate Phase 2 engine standard.  However, under the simplified compliance method we are proposing, emergency vehicle manufacturers would not follow the otherwise applicable Phase 2 proposed approach of entering an engine map in GEM.  Instead a Phase 1 style GEM interface would be made available, where an EPA default engine specified by rule would be simulated in GEM.
This approach is consistent with the approach recommended by the Small Business Advocacy Review Panel, which believed it would be feasible for small emergency vehicle manufacturers to install a Phase 2-compliant engine, but recommended a simplified certification approach to reduce the number of required GEM inputs.  Consistent with the recommendations of this panel, the agencies are asking for comments on whether there would be enough fuel consumption and CO2 emissions benefits achieved by use of LRR tires in emergency vehicles to justify requiring small business emergency chassis manufacturers to adopt them.
We expect some commercial chassis manufacturers that serve the emergency vehicle market may have the ability to meet the proposed Phase 2 standards of our primary program when including emergency vehicles in their averaging sets.  Even so, we are proposing that they have the option to comply with the less stringent standards, because there are fewer opportunities to improve fuel efficiency on emergency vehicles, which (as noted) are designed for high levels of performance and severe duty.  The agencies expect that this compliance path would be most needed by custom chassis manufacturers who serve the emergency vehicle market.  Custom chassis manufacturers typically offer a narrow range of products with low sales volumes. Therefore, fleet averaging would provide a lower level of compliance flexibility, and there would be less opportunity to spread the costs of developing advanced technologies across a large number of vehicles.  Further, many custom chassis manufacturers do not qualify as small entities under the SBA regulations.  Thus, the agencies believe that existence of program-wide ABT does not vitiate the need to propose alternative, less stringent standards for emergency vehicles.
Table V-10 below presents the proposed numerical standards to which an emergency vehicle chassis would be certified under this provision.  Emergency vehicles certified to these proposed emergency vehicle standards would be ineligible to generate credits.  The proposed standards shown below were derived by building a model of three baseline vehicles (LHD, MHD, HHD) using attributes similar to those developed for the primary program as assigned to the Urban drive cycle subcategories.  By modeling a 2021-compliant engine and tires with CRR of 7.7, the MY 2021 standards were derived using GEM.  Details of these configurations are provided in the draft RIA Chapter 2.
Table V-10: Proposed Standards for Class 2b-8 Emergency Vehicles for MY 2021 and Later
Proposed EPA Emergency Vehicle Standard (gram CO2/ton-mile)
Implementation Year
Light Heavy-Duty
Class 2b-5
Medium Heavy-Duty Class 6-7
Heavy Heavy-Duty
Class 8
MY2021
312
195
215
Proposed NHTSA Emergency Vehicle Standard (Fuel Consumption gallon per 1,000 ton-mile)
Implementation Year
Light Heavy-Duty
Class 2b-5
Medium Heavy-Duty Class 6-7
Heavy Heavy-Duty
Class 8
MY2021
30.6483
19.1552
21.1198
The agencies have estimated the costs of vocational vehicle technology packages, as presented below in Table V-20 to Table V-22.  The technologies on which the proposed emergency vehicle standards are based include engines, LRR tires, and leak-tight air conditioning systems.  Using the estimated costs of those technologies as presented, the agencies estimate that the average cost for a heavy heavy-duty or medium-heavy-duty emergency vehicle to meet the proposed emergency vehicle standards would be approximately $463 in MY 2027, and the average cost for a light heavy-duty emergency vehicle would be approximately $497 in MY 2027.  To derive these estimates, the agencies have combined the $7 cost of LRR tires that is presented in Table V-20 with the engine and air conditioning costs presented in Table V-22.  The agencies are not aware of any emergency vehicle manufacturer that produces engines, thus most of these costs would be borne by engine manufacturers.  While some of the added engine costs may be passed on to emergency vehicle manufacturers and vehicle owners/operators, the overall costs of these technologies are on the order of the Phase 1 vocational vehicle program costs, which are highly cost-effective.
To ensure that only emergency vehicle chassis would be able to certify to these less stringent standards, the agencies propose that manufacturers identify vehicles using the definition at 40 CFR 86.1803-01, which for Phase 2 purposes would be an ambulance or a fire truck. Manufacturers have informed us that it is feasible to identify such vehicles using sales codes or the presence of specialty attributes.  The agencies request comment on the merits and drawbacks of aligning the definition of emergency vehicle for purposes of the Phase 2 program with the definition of emergency vehicle for purposes of the light-duty GHG provisions under 40 CFR 86.1818, which includes additional vehicles such as those used by law enforcement.
According to the International Council on Clean Transportation (ICCT), less than one percent of all new heavy-duty truck registrations from 2003 to 2007 were emergency vehicles. On average, the ICCT's data suggest that approximately 5,700 new emergency vehicles are sold in the U.S. each year; about 0.8 percent of the 3.4 million new heavy-duty trucks registered between 2003 and 2007.  According to the Fire Apparatus Manufacturers Association, the annual VMT of the newest emergency vehicles ranges from approximately 2,000 to 8,000 miles, as documented in their 2004 Fire Apparatus Duty Cycle White Paper.  Because there are relatively few of these vehicles and they travel a relatively small number of miles, the agencies believe that setting less stringent GHG and fuel consumptions standards for these vehicles would not detract from the greater benefits of this rulemaking, and such separate standards are warranted in any case.
    Possible Standards for Other Custom Chassis Manufacturers
The agencies request comment on extending the above simplified compliance procedure and less stringent Phase 2 standards to other custom chassis manufacturers  -  those who offer such a narrow range of products that averaging is not of practical value as a compliance flexibility, and for whom there are not large sales volumes over which to distribute technology development costs. Custom chassis manufacturers that are not small businesses must comply with the Phase 1 standards and are generally doing so, by installing tires with the required coefficient of rolling resistance.  We are aware of a handful of U.S. chassis manufacturers serving the recreational vehicle and bus markets who we believe would have a disproportionate compliance burden, should we require compliance with the primary proposed Phase 2 standards.
According to the MOVES model forecast, there will be approximately 1,000 commercial intercity coach buses, 5,000 transit buses, 40,000 school buses, and 90,000 recreational vehicles manufactured new for MY 2018.  In each of these markets, specialty chassis manufacturers compete with large vertically integrated manufacturers. We request comment on the merits of offering less stringent standards to small volume chassis manufacturers, and seek comment as well as to other factors the agencies should consider to ensure this approach would not have unintended consequences for businesses competing in the vocational vehicle market.
If the agencies were to adopt less stringent standards for custom non-emergency chassis manufacturers, we would expect to limit this by setting a maximum number of eligible vocational chassis annually for each such manufacturer.  The agencies request comment on an appropriate sales volume to qualify for these possible standards, and also request comment as to whether the sales volume thresholds should be different for different markets. We further request comment on whether it would adversely affect business competitiveness if custom chassis manufacturers were held to a different standard than commercial chassis manufacturers, and whether the agencies should consider allowing commercial chassis manufacturers competing in these markets to sell a limited number of chassis certified to a less stringent standard.
As an alternative approach, the agencies request comment on providing custom chassis manufacturers with additional lead time to comply.  For example, we could offer such manufacturers an additional one or two years to meet each level of the primary proposed vocational vehicle standards.
If the agencies pursued the approach of less stringent standards, we would offer a simplified compliance procedure similar to the one proposed for emergency vehicles.  Custom chassis manufacturers would not follow the otherwise applicable Phase 2 proposed approach of entering an engine map in GEM.  Instead, a Phase 1 style GEM interface would be made available, where an EPA default engine specified by rule would be simulated in GEM.  The vehicle-level standard would be predicated on a simpler set of technologies than the primary proposed Phase 2 standard, most likely lower rolling resistance tires and idle reduction.  Because these would not be emergency vehicles, we believe the performance of these vehicles would not be compromised by requiring improvement in tire CRR beyond that of the Phase 1 level. The agencies request comment on whether we should develop separate standards for different vehicle types such as recreational vehicles and buses.
The Small Business Advocacy Review Panel recommended that EPA seek comment on how to design a small business vocational vehicle exemption by means of a custom chassis volume exemption and what sales volume would be an appropriate threshold.  The agencies seek comments on all aspects of an approach for custom vocational vehicle chassis manufacturers that would enable us to adopt a final Phase 2 program that would be consistent with the recommendations of the panel.
    Off-Road and Low-Speed Vocational Vehicle Exemptions
The agencies are proposing to continue the exemptions in Phase 1 for off-road and low-speed vocational vehicles, with revision. See generally 76 FR 57175.  These provisions currently apply for vehicles that are defined as "motor vehicles" per 40 CFR 85.1703, but may conduct most of their operations off-road, such as drill rigs, mobile cranes and yard hostlers.  Vehicles qualifying under these provisions must be built with engines certified to meet the applicable engine standard, but need not comply with a vehicle-level GHG or fuel consumption standard.  In Phase 1, this typically means not needing to install tires with a lower coefficient of rolling resistance.  Because manufacturers choosing to exempt vehicles (but not engines) based on the criteria for heavy-duty off road vehicles at 40 CFR §1037.631 and 49 CFR §523.2 will for the first time provide a description to the agencies of how they meet the qualifications for this exemption in their end-of-the year reports in the spring of 2015, we do not have information beyond what we knew at the time of the Phase 1 rules regarding how broadly this provision is being used.  Nonetheless, we are proposing to discontinue the criterion for exemption based solely on use of tires with maximum speed rating at or below 55 mph.  The agencies are concerned that tires are so easily replaced that this would be an unreliable way to identify vehicles that truly need special consideration.  We are proposing to retain the qualifying criteria related to design and use of the vehicle.  We invite comments on the proposed revisions to the qualifying criteria in the regulations, including whether the rated speed of the tires should be retained, and whether vehicles intended to be covered by this provision have characteristics that are captured by the proposed criteria.
Feasibility of the Proposed Vocational Vehicle Standards
This section describes the agencies' technical feasibility and cost analysis in greater detail.  Further detail on all of these technologies can be found in the draft RIA Chapter 2.4 and Chapter 2.9.  The variation in the design and use of vocational vehicles has led the agencies to project different technology solutions for each regulatory subcategory.  Manufacturers may also find additional means to reduce emissions and lower fuel consumption than the technologies identified by the agencies, and of course may adopt any compliance path they deem most advantageous.  The focus of this section is on the feasibility of the proposed standards for non-emergency vocational vehicles.  Further, the agencies project that these technology packages would also be feasible for vocational tractors.  With typical driving patterns having limited operation at highway speeds, vocational tractors would appropriately be classified as vocational vehicles, with proposed standards that would not be predicated on the performance of aerodynamic devices.  The agencies propose to allow vocational tractors to follow the same subcategory assignment process as other vocational vehicles.  For example, a beverage tractor intended for local delivery routes may have a driving pattern that is reasonably represented by the proposed Urban test cycle.  The agencies request comment on whether vocational tractors would be deficit-generating vehicles if certified as vocational vehicles, where performance would be measured against the proposed vocational vehicle baseline configurations.  For example, if a tractor were designed with a higher power engine to carry a heavier payload than presumed in the GEM baseline for that subcategory, would GEM return a value that poorly represents the real world performance of that vehicle, and if so, would that merit a different certification approach for vocational tractors?
NHTSA and EPA collected information on the cost and effectiveness of fuel consumption and CO2 emission reducing technologies from several sources.  The primary sources of information were the Southwest Research Institute evaluation of heavy-duty vehicle fuel efficiency and costs for NHTSA,  the 2010 National Academy of Sciences report of Technologies and Approaches to Reducing the Fuel Consumption of Medium- and Heavy-Duty Vehicles, TIAX's assessment of technologies to support the NAS panel report,  the technology cost analysis conducted by ICF for EPA, and the 2009 report from Argonne National Laboratory on Evaluation of Fuel Consumption Potential of Medium and Heavy Duty Vehicles through Modeling and Simulation.
What Technologies Are the Agencies Considering to Reduce the CO2 Emissions and Fuel Consumption of vocational vehicles?
In assessing the feasibility of the proposed Phase 2 vocational vehicle standards, the agencies evaluated a suite of technologies, including workday idle reduction, improved tire rolling resistance, improved transmissions, improved axles, and weight reduction, as well as their impact on reducing fuel consumption and GHG emissions.  The agencies also evaluated aerodynamic technologies and full electric vehicles.
As discussed above, vocational vehicles may be powered by either SI or CI engines. The technologies and feasibility of the proposed engine standards are discussed in Section II.  At the vehicle level, the agencies have considered the same suite of technologies and have applied the same reasoning for including or rejecting these vehicle-level technologies as part of the basis for the proposed standards, regardless of whether the vehicle is powered by a CI or SI engine. With the exception of the MY 2027 proposed standards, the analysis below does not distinguish between vehicles with different types of engines.  The resulting proposed vehicle standards do reflect the differences arising from the performance of different types of engines over the GEM cycles.
    Vehicle Technologies Considered in Standard-Setting
 The agencies note that the effectiveness values estimated for the technologies may represent average values, and do not reflect the potentially-limitless combination of possible values that could result from adding the technology to different vehicles.  For example, while the agencies have estimated an effectiveness of 0.5 percent for low friction axle lubricants, each vehicle could have a unique effectiveness estimate depending on the baseline axle's oil viscosity rating.  For purposes of this proposed rulemaking, NHTSA and EPA believe that employing average values for technology effectiveness estimates is an appropriate way of recognizing the potential variation in the specific benefits that individual manufacturers (and individual vehicles) might obtain from adding a given technology. There may be real world effectiveness that exceeds or falls short of the average, but on-balance the agencies believe this is the most practicable approach for determining the wide ranging effectiveness of technologies in the diverse vocational vehicle arena.
Transmissions
Transmission improvements present a significant opportunity for reducing fuel consumption and CO2 emissions from vocational vehicles.  Transmission efficiency is important for many vocational vehicles as their duty cycles involve high percentages of driving under transient operation.  The three categories of transmission improvements the agencies considered for Phase 2 are driveline optimization, architectural improvements, and hybrid powertrain systems.
The agencies believe an effective way to derive efficiency improvements from a transmission is by optimizing it with the engine and other driveline components to balance both performance needs and fuel savings.  However, many vocational vehicles today are not operating with such optimized systems.  Because customers are able to specify their preferred components in a highly customized build process, many vocational vehicles are assembled with components that were designed more for compatibility than for optimization.  To some extent, vertically integrated manufacturers are able to optimize their drivelines.  However, this is not widespread in the vocational vehicle sector, resulting primarily, from the multi-stage manufacture process.  The agencies project transmission and driveline optimization will yield a substantial proportion of vocational vehicle fuel efficiency and GHG emissions reduction improvements for Phase 2.  On average, we anticipate that efficiency improvements of about five percent can be achieved from optimization, or deep integration of drivelines.  However, we are not assigning a fixed level of improvement; rather we have developed a test procedure, the powertrain test, for manufacturers to use to obtain improvement factors representative of their systems. See Section V.E and the draft RIA Chapter 3 for a discussion of this proposed test procedure.  Depending on the test cycle and level of integration, the agencies believe improvement factors greater than ten percent above the baseline vehicle performance could be achieved.  To obtain such benefits across more of the vocational vehicle fleet, the agencies believe there is opportunity for manufacturers to form strategic partnerships and explore commercial pathways to deeper driveline integration.  For example, one partnership of an engine manufacturer and a transmission manufacturer has led to development of driveline components that deliver improved fuel efficiency based on optimization that could not be realized without sharing of critical data.
The agencies project other related transmission technologies would be recognized over the powertrain test along with driveline optimization. These include improved mechanical gear efficiency, more sophisticated shift strategies, more aggressive torque converter lockups, transmission friction reduction, and reduced parasitic losses, as described in the 2009 TIAX report at 4.5.2.  Each of these attributes would be simulated in GEM using default values, unless the powertrain test were employed.  The draft RIA Chapter 4 explains each parameter that would be set as a fixed value in GEM.  The expected benefits of improved gear efficiency, shift logic, and torque converter lockup are included in the total projected effectiveness of optimized conventional transmissions using the powertrain test.
Transmission efficiency could also be improved in the time frame of the proposed rules by changes in the architecture of conventional transmissions.  Most vocational vehicles currently use torque converter automatic transmissions (AT), especially in Classes 2b-6.  According to the 2009 TIAX report, approximately 70 percent of Class 3-6 box and bucket trucks use AT, and all refuse trucks, urban buses, and motor coaches use AT. Automatic transmissions offer acceleration benefits over drive cycles with frequent stops, which can enhance productivity.  However, with the diversity of vocational vehicles and drive cycles, other kinds of transmission architectures can meet customer needs, including automated manual transmissions (AMT) and even some manual transmissions (MT).
One type of architectural improvement the agencies project will be developed by manufacturers of all transmission architectures is increased number of gears. The benefit of adding more gears varies depending on whether the gears are added in the range where most operation occurs.  The TIAX 2009 report projected that 8-speed transmissions could incrementally reduce fuel consumption by 2 to 3 percent over a 6-speed automatic transmission, for Class 3-6 box and bucket trucks, refuse haulers, and transit buses.  Although the agencies estimate the improvement could on average be about two percent for the adding of two gears in the range where significant vehicle operation occurs, we are not assigning a fixed improvement based solely on number of transmission gears.  Manufacturers would enter the number of gears and gear ratios into GEM and the model would simulate the efficiency benefit over the applicable test cycle.  Because a public version of proposed GEM is being released with these proposed rules, stakeholders are free to use this tool to explore the effectiveness of different numbers of gears and gear ratios over the proposed test cycles.  The agencies request comment on all aspects of the GEM tool, including how it models transmissions and shifting strategies.  More details on GEM are available in the draft RIA Chapter 4.
Other architectural changes that the agencies project will offer efficiency improvements include improved automated manual transmissions (AMT) and introduction of dual clutch transmissions (DCT).  Newer versions of AMT are showing significant improvements in reliability, such that the current generation of transmissions with this architecture is more likely to retain resale value and win customer acceptance than early models.  The agencies believe AMT generally compare favorably to manual transmissions in fuel efficiency, and while the degree of improvement is highly driver-dependent, it can be two percent or greater, depending on the drive cycle. See Section III for additional discussion of AMT.  The agencies are not assigning fixed average performance levels to compare an AMT with a traditional automatic transmission. Although the lack of a torque converter offers AMT an efficiency advantage in one respect, the lag in power during shifts is a disadvantage.  For Phase 2, the agencies have developed validated models of both AMT and AT, as described in the draft RIA Chapter 4. Manufacturers installing AMT or AT would enter the relevant inputs to GEM and the simulation would calculate the performance.  Dual clutch transmissions (DCT) designed for medium heavy-duty vocational vehicles are already in production, and could reasonably be expected to be adapted for other weight classes of vocational vehicles during the time frame of Phase 2.  Based on supplier conversations, manufacturers intend to match varying DCT designs with the diverse needs of the heavy-duty market.  The agencies do not yet have a validated DCT model in GEM, and we are not assigning a fixed performance level for DCT, though we expect the per-vehicle fuel efficiency improvement due to switching from automatic to DCT to be in the range of three percent over the GEM vocational vehicle test cycles.  Selection of transmission architecture type (Manual, AMT, AT, DCT) would be made by manufacturers at the time of certification, and GEM would either use this input information to simulate that transmission using algorithms as described in the draft RIA Chapter 4, or fixed improvements may be assigned.  The agencies are assigning fixed levels of improvement that vary by test cycle in GEM for AMT when replacing a manual, which for vocational vehicles would be in the HHD Regional subcategory.  If a manufacturer elected not to conduct powertrain testing to obtain specific improvements for use of a DCT, GEM would simulate a DCT as if it were an AMT, with no fixed assigned benefit. The draft RIA at Chapter 2.9 describes the projected effectiveness of each type of transmission improvement for each vocational vehicle test cycle.
Hybrid powertrain systems are included under transmission technologies because, depending on the design and degree of hybridization, they may either replace a conventional transmission or be deeply integrated with a conventional transmission. Further, these systems are often manufactured by companies that also manufacture conventional transmissions.
The agencies are including hybrid powertrains as a technology on which some of the proposed vocational vehicle standards are predicated.  We project a variety of mild and strong hybrid systems, with a wide range of effectiveness.  Mild hybrid systems that offer an engine stop-start feature are discussed below under workday idle reduction.  For hybrid powertrains, we are estimating a 22 to 25 percent fuel efficiency improvement over the powertrain test, depending on the duty cycle in GEM for the applicable subcategory. The agencies obtained these estimates by projecting a 27 percent effectiveness over the ARB Transient cycle, and zero percent over the constant-speed highway cruise cycles.  With the proposed cycle weightings, this calculates to a 25 percent improvement over the Urban cycle, and 22 percent over the Multi-Purpose cycle. According to the NREL Final Evaluation of UPS Diesel Hybrid-Electric Delivery Vans, the improvement of a hybrid over a conventional diesel in gallons per ton-mile on a chassis dynamometer over the NYC Composite test cycle was 28 percent.  NREL characterizes the NYC Composite cycle as more aggressive than most of the observed field data points from the study, and may represent an ideal hybrid cycle in terms of low average speed, high stops per mile, and high kinetic intensity.  NREL noted that most of the observed field data points were reasonably represented by the HTUF4 cycle, over which the chassis dynamometer results showed a 31 percent improvement in gallons per ton-mile.  In units of grams CO2 per mile, NREL reported these test results as 22 percent improvement over the NYC Composite cycle and 26 percent improvement over the HTUF4 cycle.  Based on these results, and the fact that any improvement from strong hybrids in Phase 2 would not be simulated in GEM, but rather would be evaluated using the powertrain test, the agencies deemed it reasonable to estimate a conservative 27 percent effectiveness over the ARB Transient in setting the stringency of the proposed standards.
The Phase 1 standards were not predicated on any adoption of hybrid powertrains in the vocational vehicle sector.  Because the first implementation year of Phase 1 came just three years after promulgation, there was insufficient lead time for development and deployment of the technology.  In addition, our proposed Phase 2 vocational vehicle GEM test cycles are expected to better recognize hybrid technology effectiveness than the Phase 1 hybrid test cycle, especially in the Urban subcategory.  Further, our Phase 2 cost analysis shows that hybrid systems designed for LHD and MHD vocational vehicles would cost less than the costs we were projecting in Phase 1.  The agencies believe the Phase 2 rulemaking timeframes would offer sufficient lead time to develop, demonstrate, and conduct reliability testing for technologies that are still maturing, including these hybrid technologies.
Several types of vocational vehicles are well suited for hybrid powertrains, and tend to be early adopters of this technology.  Vehicles such as utility or bucket trucks, delivery vehicles, refuse haulers, and buses have operational usage patterns with either a significant amount of stop-and-go activity or spend a large portion of their operating hours idling the main engine to operate a PTO unit.
The industry is currently developing many variations of hybrid powertrain systems. There are a few hybrid systems in the market today and several more under development.  In addition, energy storage systems are improving.  Heavy-duty customers are getting used to these systems with the number of demonstration products on the road.  Even so, some manufacturers may be uncertain how much investment to make in this technology without clear signals about future market demand.  A list of hybrid manufacturers and their products intended for the vocational market is provided in the draft RIA Chapter 2.9.
Some low cost products on the simple end of the hybrid spectrum are available that minimize battery demand through the use of ultracapacitors or only provide power assist at low speeds.  Our regulations define a hybrid system as one that has the capacity for energy storage.  In the light-duty GHG program a mild hybrid is defined as including an integrated starter generator, a high-voltage battery (above 12v), and a capacity to recover at least 15 percent of the braking energy.  In such systems some accessories are usually electrified.  Strong hybrids are typically referred to as those that have larger energy recovery and storage capacity, defined at 65 percent braking energy recovery in the light-duty GHG program.  Although integration of a strong hybrid system may enable installation of a downsized engine in some cases, the agencies have not projected any vocational engine downsizing for any hybrid systems as part of our Phase 2 technology assessment.  Depending on the drive cycle and units of measurement, strong hybrids developed to date have seen fuel consumption and CO2 emissions reductions between 20 and 50 percent in the field.
The agencies are working to reduce barriers related to hybrid vehicle certification.  In Phase 1, there is a significant test burden associated with demonstrating the GHG and fuel efficiency performance of vehicles with hybrid powertrain systems.  Manufacturers must obtain a conventional vehicle that is identical to the hybrid vehicle in every way except the transmission, test both, and compare the results.  In Phase 2, the agencies are proposing that manufacturers would conduct powertrain testing on the hybrid system, and the results of that testing would become inputs to GEM for simulation of the non-powertrain features of the hybrid vehicle, removing a significant test burden.
In discussions with manufacturers during the development of Phase 2, the agencies have learned that meeting the on-board diagnostic requirements for criteria pollutant engine certification continues to be a potential impediment to adoption of hybrid systems.  See Section XIV.A.1 for a discussion of regulatory changes proposed to reduce the non-GHG certification burden for engines paired with hybrid powertrain systems.
Axles
The agencies are considering two axle technologies for the vocational vehicle sector. The first is advanced low friction axle lubricants. SwRI tested improved driveline lubrication and found measurable improvements by switching from current mainstream products to newer formulations focusing on modified viscometric effects.  Synthetic lubricant formulations can offer superior thermal and oxidative stability compared to petroleum or mineral based lubricants. The agencies believe that a 0.5 percent improvement in vocational vehicle efficiency (as for tractors) is achievable through the application of low friction axle lubricants, and have included that value as a fixed value in GEM.  Beyond the use of different lubricant formulations, some axle manufacturers are offering products that achieve efficiency improvements by varying the lubrication levels with vehicle speed, reducing churning losses.  The agencies request comment on whether we could accept these systems as qualifying for a fixed GEM improvement value.  If a manufacturer wishes to demonstrate the benefit of a specific axle technology, an off-cycle technology credit would be necessary.  To support such an application, manufacturers could conduct a rear axle efficiency test, as described in the draft RIA Chapter 3.8.  Proposed regulations for this test procedure can be found at 40 CFR 1037.515.   Our estimated axle lubricating costs do not include operational costs such as refreshing lubricants on a periodic basis.  Based on supplier information, it is likely that some advanced lubricants may have a longer drain interval than traditional lubricants.  We are estimating the axle lubricating costs for HHD to be the same as for tractors since those vehicles likewise typically have three axles.  However, for LHD and MHD vocational vehicles, we scaled down the cost of this technology to reflect the presence of a single rear axle.
The second axle technology the agencies are considering is a design that enables one of the rear axles to disconnect or otherwise behave as if it's a non-driven axle, on vehicles with two rear (drive) axles, commonly referred to as a 6x2 configuration.  The agencies have considered two types of 6x2 configurations for vocational vehicles:  those that are engaged full time on a vehicle, and those that may be engaged only during some types of vehicle operation, such as only when operating at highway cruise speeds.  Some early versions of 6x2 technology offered by manufacturers were not accepted by vehicle owners.  When the second drive axle is no longer powered, traction may be sacrificed in some cases.  Vehicles with earlier versions of this technology have seen reduced residual values in the secondary market.  Over the model years covered by the Phase 2 rules, the agencies expect the market to offer significantly improved versions of this technology, with traction control maintained at lower speeds and efficiency gains at highway cruise speeds.  Further information about this technology is provided in the feasibility of the tractor standards, Section III, as well as in draft RIA Chapter 2.4.
The efficiency benefit of a 6x2 axle configuration can be duty-cycle dependent.  In many instances, vocational vehicles need to operate off-highway, such as at a construction site delivering materials or dumping at a refuse collection facility.  In these cases, vehicles with two drive axles may need the full tractive benefit of both drive axles.  The part-time 6x2 axle technology is not expected to measurably improve a vehicle's efficiency for vehicles whose normal duty cycle involves performing significant off-highway work, but the agencies do expect this technology to be recognized over a highway cruise cycle.
Some vocational vehicles in the HHD Regional subcategory may see a 6x2 axle configuration as a reasonable option for improving fuel efficiency.  As in Phase 1, our vehicle simulation model assumes that only HHD vehicles have two rear axles, so only these could be recognized for adopting this technology.  Further, the agencies don't believe the Multipurpose and Urban subcategories include a significant enough highway cycle weighting in the composite cycle for vehicles that operate in this manner to experience a benefit from adopting this technology.  The agencies project this can achieve 2 percent benefit at highway cruise, thus we propose to assign a fixed value in GEM for part-time 6x2 technology of 2.5 percent over the highway cruise cycles, where the specific improvement would be calculated according to the composite weighting of the applicable vocational vehicle test cycle.  We request comment on the best way to recognize this technology in Phase 2, either through a GEM calculation or a fixed assigned value, for vocational vehicles.
Lower Rolling Resistance Tires
Tires are the second largest contributor to energy losses of vocational vehicles, as found in the energy audit conducted by Argonne National Lab.  There is a wide range of rolling resistance of tires used on vocational vehicles today.  This is in part due to the fact that the competitive pressure to improve rolling resistance of vocational vehicle tires has been less than that found in the line haul tire market.  In addition, the drive cycles typical for these applications often lead vocational vehicle buyers to value tire traction and durability more heavily than rolling resistance.  The agencies acknowledge there can be tradeoffs when designing a tire for reduced rolling resistance.  These tradeoffs can include characteristics such as wear resistance, cost and scuff resistance.  However, based on input from tire suppliers, the agencies expect that the LRR tires that will be available in the Phase 2 timeframe will not compromise performance parameters such as traction, handling, wear, retreadability, or structural durability.
After the Phase 1 rules were promulgated, NHTSA and EPA conducted supplemental tire testing.  Other data that have become available to the agencies since Phase 1 include pre-certification data provided to manufacturers by tire suppliers in preparation for MY 2014 vehicle certification.   The agencies categorized the data by tire position and vehicle application, so that we have a representation of the variety of LRR vocational vehicle tires that are available in the market for the drive position, steer and all-position tires, as well as wide base singles in all positions.  Based on our data set that includes results from multiple laboratories, drive tires that are intended for vocational vehicles have an average CRR of 7.8, and steer and all-position tires that are intended for vocational vehicles have an average CRR of 6.7.  The results also indicate that there are a variety of wide based single tires that are intended for vocational vehicles, with an average CRR of 6.6.  Each of these data sets shows several models of commercial tires are available at levels of CRR ranging generally from 20 percent worse than average to 20 percent better than average.  Further details are presented in the draft RIA Chapter 2.
According to the 2014 SwRI report, vocational vehicles are likely to see the most benefits from reduced tire rolling resistance when they are driving at 55 mph.  This report also found an influence of vehicle weight on the benefits of LRR tires. The study found that both vocational vehicles tested had greater benefits of LRR tires at 100 percent payload than when empty.  Also, the T270 delivery box truck that was 4,000 pounds heavier when fully loaded saw slightly greater efficiency gains from LRR tires than the F650 flatbed tow truck over the same cycles.  At higher speeds, aerodynamic drag grows, which reduces the rolling resistance share of total vehicle power demand.  In highly transient cycles, the power required to accelerate the vehicle inertia overshadows the rolling resistance power demand.  In simulation, GEM represents vocational vehicles with fixed vehicle weights, payloads and aerodynamic coefficients.  Thus, the benefit of LRR tires will be reflected in GEM differently for vehicles of different weight classes.  There will also be further differences arising from the different test cycles.  Based on preliminary simulations, it appears the vehicles in GEM most likely to see the greatest fuel efficiency gains from use of LRR tires are those in the MHD weight classes tested over the Regional or Multipurpose duty cycles, where one percent efficiency improvement could be achieved by reducing CRR by four to five percent.  Those seeing the least benefit from LRR tires would likely be Class 8 vehicles tested over the Urban or Multipurpose cycles, where one percent efficiency improvement could be achieved by reducing CRR by seven to eight percent.
The agencies propose to continue the light truck (LT) tire CRR adjustment factor that was adopted in Phase 1.  See generally 76 FR 57172-74.  In Phase 1, the agencies developed this adjustment factor by dividing the overall vocational test average CRR of 7.7 by the LT vocational average CRR of 8.9. This yielded an adjustment factor of 0.87.  After promulgation of the Phase 1 rules, the agencies conducted additional tire CRR testing on a variety of LT tires, most of which were designated as all-position tires.  In addition, manufacturers have submitted to the agencies pre-certification data that include CRR values provided by tire suppliers.  For the small subset of newer test tires that were designated as steer tires, the average CRR was 7.8 kg/ton.  For the subset of newer test tires that were designated as drive tires, the average CRR was 8.6 kg/ton. However all-position tires had an average CRR of 8.9 kg/ton.  Therefore, for LT vocational vehicle tires, we propose to continue allowing the measured CRR values to be multiplied by a 0.87 adjustment factor before entering the values in the GEM for compliance, because this additional testing has not revealed compelling information that a change is needed.  We request comment on whether the adjustment factor should be retained, as well as data on which to base a possible update of its numerical value.
As described above in V. B. (4) (c), the agencies are proposing to continue the Phase 1 off-road and low speed exemptions in Phase 2, with the proposed revision of discontinuing the option to qualify for this exemption solely if the vehicle is fitted with tires that have a maximum speed rating at or below 55 mph.  The agencies welcome comments on this revision.
Workday Idle Reduction
The Phase 2 idle reduction technologies considered for vocational vehicles are those that reduce workday idling, unlike the overnight idling of combination tractors.  There are many potential technologies.  The agencies in particular evaluated neutral idle and stop-start technologies, and the proposed standards are predicated on projected amounts of penetrations of these technologies, described in Section V. C. (2) .  While neutral idle is necessarily a transmission technology, stop-start could range from an engine technology to one that would be installed by a secondary manufacturer under a delegated assembly agreement.
The agencies are aware that for a vocational vehicle's engine to turn off during workday driving conditions, there must be a reserve source of energy to maintain functions such as power steering, cabin heat, and transmission pressure, among others. Stop-start systems can be viewed as having a place on the low-cost end of the hybridization continuum. As described in Section V. C. (2)  and in the draft RIA Chapter 2.9, the agencies are including the cost of energy storage sufficient to maintain critical onboard systems and restart the engine as part of the cost of vocational vehicle stop-start packages.  The technologies to capture this energy could include a system of photovoltaic cells on the roof of a box truck, or regenerative braking. The technologies to store the captured energy could include a battery or a hydraulic pressure bladder.  More discussion of stop-start technologies is found in the draft RIA Chapter 2.4.
The agencies intend for the technologies that would qualify to be recognized in GEM as stop-start to be broadly defined, including those that may be installed at different stages in the manufacturing process. The agencies request comment on an appropriate definition of stop-start technologies for vocational vehicles.
The agencies are also proposing a certification test cycle that measures the amount of fuel saved and CO2 reduced by these two primary types of idle reduction technologies:  neutral idle and stop-start. Vocational vehicles frequently also idle while cargo is loaded or unloaded, and while operating a PTO such as compacting garbage or operating a bucket.  In these rules, the agencies are proposing that the Regional duty cycle have ten percent idle, the Multi-purpose cycle have 15 percent idle, and the Urban cycle have 20 percent idle. These estimates are based on publically available data published by NREL.  To bolster this information, EPA entered into an interagency agreement with NREL to characterize workday idle among vocational vehicles. One task of this agreement is to estimate the nationally representative fraction of idle operation for vocational vehicles for each proposed regulatory subcategory including a distinction between idling while driving or stopping in gear, and idling while parked.  The preliminary range of total idle operation indicated by this work is from 15 percent to 70 percent.  The agencies request comment regarding the nature of vocational workday idle operation, including how much of it is in traffic and how much is while the vehicle is parked.  Depending on comments and additional information received during the comment period, it may be within the agencies' discretion to adopt different final test cycles, or re-weight the current test cycles, to better represent real world driving and better reflect performance of the technology packages.
Based on GEM simulations using the currently proposed vocational vehicle test cycles, the agencies estimate neutral idle for automatic transmissions to provide fuel efficiency improvements ranging from one percent to nearly four percent, depending on the regulatory subcategory.  The agencies estimate stop-start to provide fuel efficiency improvements ranging from 0.5 percent to nearly seven percent, depending on the regulatory subcategory.  Because of the higher idle weighting factor in the Urban test cycle, vehicles certified in these subcategories would derive the greatest benefit from applying idle reduction technologies.
Although the primary program would not simulate vocational vehicles over a test cycle that includes PTO operation, the agencies are proposing to continue, with revisions, the hybrid-PTO test option that was in Phase 1. See 40 CFR 1037.525 and 76 FR 57247.  Recall that we are proposing to regulate vocational vehicles at the incomplete stage when a chassis manufacturer may not know at the time of certification whether a PTO will be installed or how the vehicle will be used.  Based on stakeholder input, chassis manufacturers are expected to know whether a vehicle's transmission is PTO-enabled.  However, that is very different from knowing whether a PTO will actually be installed and how it will be used.  Chassis manufacturers may rarely know whether the PTO-enabled vehicle will use this capability to maneuver a lift gate on a delivery vehicle, to operate a utility boom, or merely to keep it as a reserve item to add value in the secondary market.  In cases where a manufacturer can certify that a PTO with an idle-reduction technology will be installed either by the chassis manufacturer or by a second stage manufacturer, the hybrid-PTO test cycle may be utilized by the certifying manufacturer to measure an improvement factor over the GEM duty cycle that would otherwise apply to that vehicle.  In addition, the delegated assembly provisions would apply.  See Section V.E for a description of the delegated assembly provisions.  See draft RIA Chapter 3 for a discussion of the proposed revisions to the PTO test cycle.
The agencies have reason to believe there may be a NOX co-benefit to stop-start idle reduction technologies, e-PTO, and possibly also to neutral idle.  For this to be true, the benefits of reduced fuel consumption and retained aftertreatment temperature would have to outweigh any extra emissions due to re-starts.  In the draft RIA Chapter 5, there is a more detailed discussion of the relationship between idle reduction and NOX co-benefits.  The agencies request comments and relevant test data that can help inform this issue.
Weight Reduction
The agencies believe there is opportunity for weight reduction in some vocational vehicles. According to the 2009 TIAX report, there are freight-efficiency benefits to reducing weight on vocational vehicles that carry heavy cargo, and tax savings potentially available to vocational vehicles that remain below excise tax weight thresholds.  This report also estimates that the cost effectiveness of weight reduction over urban drive cycles is potentially greater than the cost effectiveness of weight reduction for long haul tractors and trailers.  On a city duty cycle, 89 percent of the vehicle's road load is weight dependent, compared to 38 percent on a steady-state 55 mph duty cycle.  The 2014 SwRI report found that weight reduction provides a greater fuel efficiency benefit for vehicles driving under transient conditions than for those operating under constant speeds.  In simulation, the study found that the two Class 6 trucks improved fuel efficiency by over two percent on the ARB transient cycle by removing 1,100 lbs. Further, SwRI observed that the improvements due to weight reduction behaved linearly.  The proposed menu of components available for a vocational vehicle weight credit in GEM is presented in Section V.E and in the draft RIA Chapter 2.9.  It includes fewer options than for tractors, but the agencies believe there are a number of feasible material substitution choices at the chassis level, which could add up to weight savings on the order of a few hundred pounds. The agencies project that refuse trucks, construction vehicles, and weight-limited regional delivery vehicles could reasonably apply material substitution for weight reduction.  We do not expect this to be broadly applicable across many types of vocational vehicles.  Based on the assumed payload in GEM, and depending on the vocational vehicle subcategory, the agencies believe a reduction of 200 pounds may offer a fuel efficiency improvement of approximately 1 to 2 percent.
Without more specific data on which to base our assumptions, the agencies are proposing to allocate 50 percent of any mass reduction to increased payload, and 50 percent to reduce the chassis weight. We considered the data on which the tractor weight allocation (1/3:2/3) is based, but determined this would not be valid for vocational vehicles, as the underlying data pertained only to long haul tractor-trailers.  The agencies propose that 50 percent of weight removed from vocational vehicle chassis would be added back as additional payload in GEM. This suggests an equal likelihood that a vehicle would be reducing weight for benefits of being lighter, or reducing weight to carry more payload.  The agencies welcome data that could better inform the fraction of weight reduced for vocational vehicles that is added back as payload.
The agencies request comment on whether the HD Phase 2 program should recognize that weight reduction of rotating components provides an enhanced fuel efficiency benefit over weight reduction on static components.  In theory, as components such as brake rotors, brake drums, wheels, tires, crankshafts, camshafts, and piston assemblies become lighter, the power consumption to rotate the masses would be directly proportional to the mass decrease.  Using physical properties of a rotating component such as a wheel, it is relatively straightforward to calculate an equivalent mass.  However, we do not have enough information to derive industry average values for equivalent mass, nor have we evaluated the best way for GEM to account for this.
HFC Refrigerant from Cabin Air Conditioning (A/C) Systems
Manufacturers can reduce direct A/C leakage emissions by utilizing leak-tight components. EPA's proposed HFC direct emission leakage standard would be independent of the CO2 vehicle standard.  Manufacturers could choose components from a menu of leak-reducing technologies sufficient to comply with the standard, as opposed to using a test to measure performance.  See 76 FR 57194/3.
In Phase 1, EPA adopted a HFC leakage standard to assure that high-quality, low-leakage components are used in each air conditioning system installed in HD pickup trucks, vans, and combination tractors (see 40 CFR 1037.115(c)).  We did not adopt a HFC leakage standard in Phase 1 for systems installed in vocational vehicles.  EPA is proposing in Phase 2 to extend the HFC leakage standard that exists due to Phase 1 requirements to all vocational vehicles.  Beginning in the 2021 model year, EPA proposes that vocational vehicle air conditioning systems with a refrigerant capacity of greater than 733 grams meet a leakage rate of 1.50 percent leakage per year and systems with a refrigerant capacity of 733 grams or lower meet a leakage standard of 11.0 grams per year.  EPA believes this proposed approach of having a leak rate standard for lower capacity systems and a percent leakage per year standard for higher capacity systems would result in reduced refrigerant emissions from all air conditioning systems, while still allowing manufacturers the ability to produce low-leak, lower capacity systems in vehicles which require them.
EPA believes that reducing A/C system leakage is both highly cost-effective and technologically feasible.  The availability of low leakage components is being driven by the air conditioning program in the light-duty GHG rule which began in the 2012 model year and the HD Phase 1 rule that began in the 2014 model year.  The cooperative industry and government Improved Mobile Air Conditioning program has demonstrated that new-vehicle leakage emissions can be reduced by 50 percent by reducing the number and improving the quality of the components, fittings, seals, and hoses of the A/C system.  All of these technologies are already in commercial use and exist on some of today's systems, and EPA does not anticipate any significant improvements in sealing technologies for model years beyond 2021. However, EPA has recognized some manufacturers utilize an improved manufacturing process for air conditioning systems, where a helium leak test is performed on 100 percent of all o-ring fittings and connections after final assembly. By leak testing each fitting, the manufacturer or supplier is verifying the o-ring is not damaged during assembly (which is the primary source of leakage from o-ring fittings), and when calculating the yearly leak rate for a system, EPA will allow a relative emission value equivalent to a `seal washer' can be used in place of the value normally used for an o-ring fitting, when 100 percent helium leak testing is performed on those fittings.  The agencies request comment on other possible improvements in the design of air conditioning systems that EPA could recognize for the purposes of compliance with this proposed standard.  For example, should the agency recognize electrified compressors as having a zero leak rate, and should we allow vehicles fitted with electrified compressors to use a simplified version of the compliance reporting form?  Please see Section I.F.1 (b) of this preamble for a description of proposed program-wide revisions to EPA's HFC leakage standards that would address air conditioning systems designed for alternative refrigerants.
The HFC control costs presented in the draft RIA Chapter 2.9 and 2.12 are applied to all heavy-duty vocational vehicles.  EPA views these costs as minimal and the reductions of potent GHGs to be easily feasible and reasonable in the lead times provided by the proposed rule.
    Engine Technologies Considered in Vehicle Standard-Setting
Section II explains the technical basis for the agencies' proposed separate engine standards.  The agencies are not proposing to predicate the vocational vehicle standards on different diesel engine technology packages than those presumed for compliance with the separate diesel engine standards.  However, for the proposed MY 2027 vocational vehicle standards, the agencies are predicating the SI-powered vocational vehicle standards on a gasoline engine technology package that includes additional friction reduction beyond that presumed for compliance with the MY 2016 gasoline engine standard.  Chapter 2 of the draft RIA provides more details on each of the technologies that can be applied to both gasoline and diesel engines.
The vehicle-level standards would vary depending on whether the engines powering those vehicles are compression-ignition or spark-ignition.  In Phase 1, this was not the case because GEM used a default engine that was the same for every vehicle configuration, regardless of the actual engine being installed.  As described above in Section II, the Phase 2 vehicle certification tool, GEM, would require manufacturers to enter specific engine performance data, where emissions and fuel consumption profiles would differ significantly depending on the engine's architecture.
As explained in Section II.A.2, engines would continue to be certified over the FTP test cycle.  The FTP test cycle that is applicable for bare vocational engines is very different than the proposed test cycles for vocational vehicles in GEM.  That test is a very demanding transient cycle that exercises the engine over its full range of capabilities.  In contrast, the cycles evaluated by GEM measure emissions over more frequently used engine operating ranges.  The ARB Transient vehicle cycle represents city driving, and the highway cruise cycles measure engine operation that is closer to steady state.  Each of these cycles is described in the draft RIA Chapter 3.  A consequence of recognizing engine performance at the vehicle level would be that further engine improvements (i.e. improvements measureable by duty cycles that more precisely represent driving patterns for specific subcategories of vocational vehicles) could be evaluated as possible components of a technical basis for a vocational vehicle standard.  For this reason, the agencies considered whether any different engine technologies should be included in the feasibility analysis for the vehicle standards (and potentially, in the proposed standard stringency).
One CI engine technology that might be recognized over a vehicle highway cruise cycle would be waste heat recovery (WHR).  However, the agencies do not consider this to be a feasible technology for vocational engines.  As described in Section II of this preamble and Chapter 2.3 of the draft RIA, there currently are no commercially available WHR systems for diesel engines, although most engine manufacturers are exploring this technology.  While it would be possible to capture excess heat from a vocational engine operating at highway speeds, many vocational vehicles spend insufficient time at highway speeds to generate enough excess heat to make this technology worthwhile.  As explained in Section II.D, the agencies are projecting a very small adoption rate of WHR even in the tractor engine market.  Because the research is currently being conducted to apply this technology for tractors, it is logical that future research may reveal ways to adapt this technology for those vocational engines that are intended for on-highway applications.  The agencies do not believe this technology will be developed to the point of commercial readiness for vocational vehicles in the time frame of these proposed rules.
The agencies assessed three SI engine technologies for possible inclusion in the vocational vehicle technology packages:  cylinder deactivation, variable valve timing, and advanced friction reduction.  These might be recognized over the proposed vocational vehicle test cycles in GEM through use of the proposed engine mapping procedures.  To the extent either cylinder deactivation or variable valve timing would be adopted for complete heavy-duty pickups and vans, they would be recognized over the complete chassis test specified for that segment and possibly over the GEM highway cruise cycles, however the aggressive bare engine FTP test is unlikely to put the engine into operating modes that activate either of those technologies.  Based on stakeholder input, the agencies project that the SI engines certified over the FTP and fitted into vocational vehicles would most likely be designed as overhead valve engines, for which the only kind of VVT available is dual cam phasing.  Dual cam phasing is already included at 100 percent adoption rate in the feasibility and stringency of the MY 2016 bare engine standard.  If manufacturers choose to fit vocational vehicles with coaxial camshaft SI engines, additional VVT options would be feasible and could be recognized over the vocational vehicle test cycles.  Based on stakeholder input, the agencies project that some SI engines certified over the FTP and fitted into vocational vehicles may be designed with cylinder deactivation by MY 2021.  However, the agencies do not have enough information at this time to quantify the potential fuel efficiency improvements over the vocational vehicle test cycles for engines with cylinder deactivation or various designs implementing VVT.  Therefore we are not proposing to predicate the SI-powered vocational vehicle standards on use of these technologies.
In Section II.D, the agencies explain why we are not proposing a more stringent separate SI vocational engine standard in Phase 2 based on additional engine technologies beyond those assumed for the Phase 1 MY 2016 standard.  The agencies are instead proposing to include adoption and performance of advanced engine friction reduction technology as a basis for the proposed SI-powered vocational vehicle standards.  Based on Volpe model results, the agencies project that manufacturers of some SI engines for complete HD pickups would apply advanced friction reduction.  Level 2 engine friction reduction is listed in Table VI-3, and costs are presented in the draft RIA Chapter 2.12.  We expect some engines with this technology would be engine-certified and sold for use in vocational vehicles.  We are projecting an overall effectiveness of 0.6 percent improvement over the GEM cycles for this technology, calculated using a per-vehicle effectiveness of 1.1 percent and a vocational vehicle adoption rate of 56 percent.  We request comment on the merits of setting a SI-based vocational vehicle standard predicated on adoption of SI engine technologies.
    Technologies the Agencies Assessed but did not Use In Standard-Setting
Aerodynamics
The Argonne National lab work shows that aerodynamics has less of an impact on vocational vehicle energy losses than do engines or tires. Further, when a vehicle spends significant time at slower speeds, the disbenefit of the added weight of the aero devices diminishes the benefit obtained when driving at high speeds.  In addition, the aerodynamic performance of a complete vehicle is significantly influenced by the body of the vehicle.  As noted above, the agencies are not proposing to regulate body builders for the reasons discussed in Phase 1.
The NAS 2010 report estimated a one percent fuel efficiency improvement could be achieved from a full aerodynamic package on a box truck with an average speed of 30 mph.  Both from the NAS 2010 report and from experiences of EPA's SmartWay team, the agencies expect the potential benefits of aerodynamics at an average speed of 60 mph would be diminished by 50 percent or more when average speeds are closer to 40 mph. The proposed Regional composite duty cycle in GEM for vocational vehicles (the test cycle with the most highway weighting) has a weighted average speed of 39 mph.
The 2014 SwRI technology assessment simulated a Class 6 box truck with a coefficient of aerodynamic drag that had been improved by 15 percent.  Over transient test cycles, this produced a one percent fuel efficiency benefit, though this produced results of approximately seven percent improvement over the 55 mph and eight percent over the 65 mph cycle. SwRI conducted coastdown testing to determine the baseline CdA of the truck, of 5.0.   However, it is unknown what aerodynamic technologies could be applied to yield a 15 percent improvement in CdA. Using these simulation results and the proposed Regional cycle weightings of 22 percent at 65 mph and 28 percent at 55 mph, the agencies estimate the fuel efficiency benefit of improving the CdA of a Class 6 box truck by 15 percent could be approximately four percent. This assumes no penalty for carrying the weight of the aerodynamic devices while operating under transient driving conditions.
Because we do not have information on specific technologies that could be applied to vocational vehicles to yield a 15 percent improvement in CdA, or their costs, we are not basing any of the proposed standards for vocational vehicles on aerodynamic improvements.  Nonetheless, we are working with CARB to incorporate into GEM some data from testing that is being conducted by CARB through NREL.  A test plan is underway to assess the fuel efficiency benefit of three different devices to improve the aerodynamic performance of a Class 6 box truck and one device on a Class 4 box truck.  The agencies request comment on allowing  a manufacturer to obtain an improved GEM result by certifying that a final vehicle configuration will closely match one of the configurations on which this testing was conducted, where the improvement would be based on installation of specific aerodynamic devices for which we have pre-defined effectiveness through this testing program.  The amount of improvement would be set by EPA and NHTSA based on NREL's test results.  This credit provision would apply only to vocational vehicles certified over the Regional duty cycle. Manufacturers wishing to receive credit for other aerodynamic technologies or on other vehicle configurations would be able to seek credit for it as an off-cycle technology. See Section V.E, for a description of regulatory flexibilities such as off-cycle technology credits.
A description of vehicles and aerodynamic technologies that could be eligible for this option, as well as a description of the testing conducted to obtain the assigned GEM improvements due to these technologies, can be found in a memorandum to the docket.  The agencies seek comment on this potential approach to providing credits for aerodynamic aids to vocational box trucks.
Full Electric Trucks
Some heavy-duty vehicles can be powered exclusively by electric motors.  Electric motors are efficient and able to produce high torque, giving e-trucks strong driving characteristics, particularly in stop-and-go or urban driving situations, and are well-suited for moving heavy loads.  Electric motors also offer the ability to operate with very low noise, an advantage in certain applications.  Currently, e-trucks have some disadvantages over conventional vehicles, primarily in cost, weight and range.  Components are relatively expensive, and storing electricity using currently available technology is expensive, bulky, and heavy.
The West Coast Collaborative, a public-private partnership, has estimated the incremental costs for electric Class 3-6 trucks in the Los Angeles, CA, area.  Compared to a conventional diesel, the WCC estimates a BEV system would cost between $70,000 and $90,000 more than a conventional diesel system. The CalHEAT Technology Roadmap includes an estimate that the incremental cost for a fully-electric medium- or heavy- duty vehicle would be between $50,000 and $100,000.  This roadmap report also presents several actions that must be taken by manufacturers and others, before heavy-duty e-trucks can reach what they call Stage 3 Deployment.
Early adopters of electric drivetrain technology are medium-heavy-duty vocational vehicles that are not weight-limited and have drive cycles where they don't need to go far from a central garage.  Examples include Frito-Lay. CalHEAT has published results of a comprehensive performance evaluation of three battery electric truck models using information and data from in-use data collection, on road testing and chassis dynamometer testing.
Given the high costs and the developing nature of this technology, the agencies do not project fully electric vocational vehicles to be widely commercially available in the time frame of the proposed rules.  For this reason, the agencies have not based the proposed Phase 2 standards on adoption of full-electric vocational vehicles.  To the extent this technology is able to be brought to market in the time frame of the Phase 2 program, there is currently a certification path for these chassis from Phase 1, as described in Section V.E and in EPA's regulations at 40 CFR 1037.150 and NHTSA's regulations at 49 CFR 535.8.
Electrified Accessories
Accessories that are traditionally gear- or belt-driven by a vehicle's engine can be optimized and/or converted to electric power. Examples include the engine water pump, oil pump, fuel injection pump, air compressor, power-steering pump, cooling fans, and the vehicle's air-conditioning system.  Optimization and improved pressure regulation may significantly reduce the parasitic load of the water, air and fuel pumps.  Electrification may result in a reduction in power demand, because electrically-powered accessories (such as the air compressor or power steering) operate only when needed if they are electrically powered, but they impose a parasitic demand all the time if they are engine-driven.  In other cases, such as cooling fans or an engine's water pump, electric power allows the accessory to run at speeds independent of engine speed, which can reduce power consumption.  Electrification of accessories can individually improve fuel consumption, regardless of whether the drivetrain is a strong hybrid. The TIAX study used 2 to 4 percent fuel consumption improvement for accessory electrification, with the understanding that electrification of accessories will have more effect in short haul/urban applications and less benefit in line-haul applications.
Electric power steering (EPS) or Electrohydraulic power steering (EHPS) provides a potential reduction in CO2 emissions and fuel consumption over hydraulic power steering because of reduced overall accessory loads.  This eliminates the parasitic losses associated with belt-driven power steering pumps which consistently draw load from the engine to pump hydraulic fluid through the steering actuation systems even when the wheels are not being turned.  EPS is an enabler for all vehicle hybridization technologies since it provides power steering when the engine is off.  EPS is feasible for most vehicles with a standard 12V system.  Some heavier vehicles may require a higher voltage system which may add cost and complexity.
The agencies are projecting that some electrified accessories will be necessary as part of the development of stop-start idle reduction systems for vocational vehicles.  However, the agencies have not developed a pre-defined credit-generating option for manufacturers to directly receive credit in GEM for electrified accessories on vocational vehicles.  Manufacturers wishing to conduct independent testing may apply for off-cycle credits derived from electrified accessories.
E-PTO
There are products available today that can provide auxiliary power, usually electric, to a vehicle that needs to work in PTO mode for an extended time, to avoid idling the main engine.  There are different designs of electrified PTO systems on the market today.  Some designs have auxiliary power sources, typically batteries, with sufficient energy storage to power an onboard tool or device for a short period of time, and are intended to be recharged during the workday by operating the main engine, either while driving between work sites, or by idling the engine until a sufficient state of charge is reached that the engine may shut off.  Other designs have sufficient energy storage to power an onboard tool or device for many hours, and are intended to be recharged as a plug-in hybrid at a home garage.  The agencies are proposing to continue the hybrid-PTO test option that was available in Phase 1, with a few revisions.  See the proposed regulations at 40 CFR 1037.525.  The current test procedure is a charge-sustaining procedure, meaning the test is not complete until the energy storage system is depleted and brought back to its original state of charge.  The agencies request comment and data relating to the population and energy storage capacity of plug-in e-PTO systems, for which a charge-depleting test cycle may be more appropriate.  For the reasons described above, the agencies are not basing the proposed vocational vehicle standards on use of electrified PTO or hybrid PTO technology.  Manufacturers wishing to conduct testing as specified may apply for off-cycle credits derived from e-PTO or hybrid PTO technologies.
Projected Vehicle Technology Package Effectiveness and Cost
    Baseline Vocational Engine and Vehicle Performance
The proposed baseline vocational vehicle configurations for each of the nine proposed regulatory subcategories are described in draft RIA Chapter 2.9 and Chapter 4.4.  The agencies propose to set the baseline rolling resistance coefficient for the 2017 vocational vehicle fleet at 7.7 kg/metric ton, which assumes 100 percent of tires meet the Phase 1 standard.
 In the agencies' proposed baseline configurations, we include torque converter automatics with five forward gears in eight of the nine subcategories. In the Regional HHD subcategory, the baseline includes a manual transmission with ten forward gears.  No additional vehicle-level efficiency-improving technology is included in the baseline vehicles, nor in the agencies' analyses for the no-action reference case.  Specifically, we have assumed zero adoption rates for other types of transmissions, increased numbers of gears, idle reduction, and technologies other than Phase 1 compliant LRR tires in both the nominally flat baseline and the dynamic baseline reference cases.  Technology adoption rates for Alternative 1a (nominally flat baseline) can be found in the draft RIA Chapter 2.12.  Chapter 2.12.8 presents the adoption rates for tires on vocational vehicles with different levels of rolling resistance, including the 100 percent adoption rate of tires with Level 1 CRR in the reference case and in model years preceding Phase 2.  In this manner, we have defined a reference vocational vehicle fleet that meets the Phase 1 standards and includes reasonable representations of vocational vehicle technology and configurations.  Details of the vehicle configurations, including reasons why they are reasonably included as baseline technologies, are discussed in the draft RIA Chapter 2.9.
 The agencies note that the baseline performance derived for the proposed rules varies between regulatory subcategories. This is due to the range of attributes and modeling parameters, such as transmission characteristics, final drive ratio, and vehicle weight, which were selected to represent a range of performance across this diverse segment. The agencies request comment on whether the proposed configurations adequately represent a reasonable range of vocational chassis configurations likely to be manufactured in the implementation years of the Phase 2 program.  We especially are interested in comments regarding the following driveline parameters:  transmission gear ratios, axle ratios, and tire radii.
The baseline engine fuel consumption represents improvements beyond currently available engines to achieve the efficiency of what the agencies believe would be a 2017 model year diesel engine, as described in the draft RIA Chapter 2.  Using the values for compression-ignition engines, the baseline performance of vocational vehicles is shown in Table V-11.
Different types of diesel engines are used in vocational vehicles, depending on the application.  They fall into the categories of Light, Medium, and Heavy Heavy-duty Diesel engines.  The Light Heavy-duty Diesel engines typically range between 4.7 and 6.7 liters displacement.  The Medium Heavy-duty Diesel engines typically have some overlap in displacement with the Light Heavy-duty Diesel engines and range between 6.7 and 9.3 liters.  The Heavy Heavy-duty Diesel engines typically are represented by engines between 10.8 and 16 liters.  Because of these differences, the GEM simulation of baseline vocational CI engines includes four engines - one for LHD, one for MHD, and two for HHD.  Detailed descriptions can be seen in Chapter 4 of the draft RIA. These four engine models have been employed in setting the vocational vehicle baselines, as described in the draft RIA Chapter 2.9.
Table V-11: Baseline Vocational Vehicle Performance with CI Engines
Baseline Emissions Performance in CO2 gram/ton-mile
Duty Cycle
Light Heavy-Duty
Class 2b-5
Medium Heavy-Duty Class 6-7
Heavy Heavy-Duty
Class 8
Urban
316
201
212
Multi-Purpose
325
203
214
Regional
339
199
203
Baseline Fuel Efficiency Performance in gallon per 1,000 ton-mile
Duty Cycle
Light Heavy-Duty
Class 2b-5
Medium Heavy-Duty Class 6-7
Heavy Heavy-Duty
Class 8
Urban
31.0413
19.7446
20.8251
Multi-Purpose
31.9253
19.9411
21.0216
Regional
33.3006
19.5481
19.9411
The agencies intend to develop a model in GEM of a MY 2016-compliant gasoline engine, but we have been unable to obtain sufficient information to complete this process.  The agencies request comments on the process for mapping gasoline engines for simulation purposes, as well as information about the power rating and displacement that should be considered as a baseline SI engine for vocational vehicle standard-setting purposes.  In lieu of a SI engine map, the agencies have applied a correction factor to the GEM CI vocational simulation results, to approximate the baseline performance of a SI-powered vocational vehicle.  The SI-powered vocational vehicle baseline performance shown in Table V-12 was calculated from applying an adjustment factor to the respective CI-powered vocational vehicle baseline values.  This CI to SI baseline adjustment factor is derived from the Phase 1 HD pickup and van stringency curves, as described in the draft RIA Chapter 2.9.1.  The correction factor approach is not the agencies' preferred approach, as it has many drawbacks.  One key drawback with this approach is that it does not account for the fact that SI engines operate very differently than CI engines at idle.  Our current model includes information on CI engine idle performance, and assumes transmissions and torque converters appropriate for CI engines. We expect these driveline parameters would be very different for SI powered vehicles, which would affect performance over all the GEM duty cycles.
The baseline performance levels for HHD vocational vehicles powered by SI engines were derived using the same procedures described above for the MHD and LHD vehicles, adjusting the performance of the HHD CI powered vocational vehicles by the same degree as for the other vehicles.  However, we expect that any gasoline Class 8 vocational vehicle would be powered by a MHD SI engine, as there are no HHD gasoline engines on the market.  Further, we expect that if we were to develop an engine map for use in simulating heavier SI vocational vehicles in GEM, we could establish a more representative baseline performance level by calculating the work done by the MHD engine to move the heavier vehicle over the test cycles.  The agencies request comments on the merits of developing separate baseline levels and numerical standards for HHD vocational vehicles powered by SI engines, including any benefits that could be obtained by addressing this unlikely occurrence and other ways in which the agencies could avoid the instance of an orphaned SI vocational vehicle.  Commenters who favor separate numerical standards are encouraged to submit information related to appropriate default vehicle characteristics such as weight and payload.  Depending on comments, the agencies could choose to require all Class 8 vocational vehicles to certify to the standards for CI powered HHD vocational vehicles, or we could require SI powered Class 8 vocational vehicles to certify to the MHD standards for SI vocational vehicles.
Table V-12: Baseline Vocational Vehicle Performance with SI Engines
Baseline Emissions Performance in CO2 gram/ton-mile
Duty Cycle
Light Heavy-Duty
Class 2b-5
Medium Heavy-Duty Class 6-7
Heavy Heavy-Duty
Class 8
Urban
334
213
224
Multi-Purpose
344
215
226
Regional
358
211
214
Baseline Fuel Efficiency Performance in gallon per 1,000 ton-mile
Duty Cycle
Light Heavy-Duty
Class 2b-5
Medium Heavy-Duty Class 6-7
Heavy Heavy-Duty
Class 8
Urban
37.5830
23.9676
25.2054
Multi-Purpose
38.7082
24.1926
25.4304
Regional
40.2836
23.7425
24.0801
    Technology Packages for Derivation of Proposed Standards
Prior to developing the numerical values for the proposed standards, the agencies projected the mix of new technologies and technology improvements that would be feasible within the proposed lead time.  We note that for some technologies, the adoption rates and effectiveness may be very similar across subcategories.  However, for other technologies, either the adoption rate, effectiveness, or both differ across subcategories.  The standards being proposed reflect the technology projected for each service class.  Where a technology performs differently over different test cycles, these differences are reflected to some extent in the derivation of the stringency of the proposed standard.  However, the proposed standard stringency does reflect, to some extent, the ability of manufacturers to utilize credits.  For example, we project that hybrid vehicles would generally be certified in the Urban subcategory and would generate emission credits that would most likely be used in the other subcategories within the weight class group.
As part of the derivation of the numerical standards, we performed a benchmarking analysis to inform our development of standards that would have roughly equivalent stringency among the duty-cycle-based subcategories within each weight class group.  To do this, the agencies assessed the performance of broadly applicable technologies, such as low rolling resistance tires, on each of the selected baseline vehicles over each of the duty cycles. We then evaluated how much improvement could be achieved over the various duty cycles for a vehicle that incorporated all the broadly applicable technologies, but which did not include a hybrid powertrain. We simulated neutral idle for benchmarked vehicles for MY 2021 and MY 2024, and simulated stop-start idle reduction on the benchmarked MY 2027 vehicles.  From this, we learned that a vehicle with neutral idle and a deeply integrated conventional powertrain, with moderately low rolling resistance tires and some weight reduction could easily meet the proposed standards in the early implementation years of the program, in any weight class or duty cycle.  We also learned how the effectiveness of tire rolling resistance and weight reduction vary in GEM (i.e. and therefore likely in actual operation) across the different subcategories.  We also found that a vehicle with a deeply integrated conventional powertrain, tires with even lower CRR, some weight reduction, and stop-start idle reduction could achieve the MY 2027 proposed standards.  However, our technology feasibility does not presume that 100 percent of vocational vehicles can reasonably apply deep powertrain integration, nor do we project 100 percent adoption of LRR tires or weight reduction.
The technologies assumed for the benchmarked vehicles are summarized in Table V-13, Table V-14, and Table V-15.  Note that the agencies are not projecting that these are the vehicles that would actually be produced.  Rather, these theoretical vehicles are being evaluated to compare the relative stringency of the standards for each subcategory.
Table V-13: GEM Inputs for Benchmarked MY 2021 Vocational Vehicles
                                  Class 2b-5
                                   Class 6-7
                                    Class 8
                                     Urban
                                 Multi-Purpose
                                   Regional
                                     Urban
                                 Multi-Purpose
                                   Regional
                                     Urban
                                 Multi-Purpose
                                   Regional
                                 Transmission
 100% Deep Transmission Integration for 7% Urban, 6% Multipurpose, 5% Regional
                                     5s AT
                                     5s AT
                                     5s AT
                                     5s AT
                                     5s AT
                                     5s AT
                                     5s AT
                                     5s AT
                                    10s AMT
                                 CI Engine[a]
                           2021 MY 7L, 200 hp Engine
                           2021 MY 7L, 270 hp Engine
                          2021 MY 11L, 345 hp Engine
                           2021 MY 15L 455hp Engine
                      100% Idle Reduction = Neutral Idle
                     100% improved axle lubrication: 0.5%
                  100% Steer Tires with CRR 6.9 kg/metric ton
                  100% Drive Tires with CRR 7.3 kg/metric ton
                            Weight Reduction 200 lb
Note:
[a] SI engines were not simulated in GEM

Table V-14: GEM Inputs for Benchmarked MY 2024 Vocational Vehicles
                                  Class 2b-5
                                   Class 6-7
                                    Class 8
                                     Urban
                                 Multi-Purpose
                                   Regional
                                     Urban
                                 Multi-Purpose
                                   Regional
                                     Urban