0.5 percent benefit coming from improved water pump efficiency.\277\ It
should be noted that water pump improvements include both pump
efficiency improvement and variable speed or on/off controls. Lube pump
improvements are primarily achieved using variable displacement pumps
and may also include efficiency improvement. All of these results shown
in this paragraph are demonstrated through the DOE SuperTruck program
at a single operating point on the engine map, and therefore the
overall expected reduction of these technologies is less than the
single point result. The agencies proposed that compared to 2017 MY air
conditioners, air conditioners with improved efficiency compressors
will reduce CO2 emissions by 0.5 percent. Improvements in
accessories, such as power steering, can lead to an efficiency
improvement of one percent over the 2017 MY baseline. 80 FR 40218.
---------------------------------------------------------------------------

    \277\ See the RIA Chapter 2.4 for details.
---------------------------------------------------------------------------

    Navistar commented that the proposed ``electrically powered pumps
for engine cooling'' be revised to include ``electronically controlled
variable speed coolant pumps'' to align with the Preamble descriptions
and technology under development as part of the SuperTruck program.
Navistar commented that shifting to fully electronic pump creates
reliability concerns and adds additional complexity due to the size of
the necessary pumps (2+ horsepower) and that the increased power load
will require a larger alternator and upgraded wiring. Navistar
suggested that in addition to a fully electric pump, Dual Displacement
power steering should also be included as an accessory improvement
because this technology reduces parasitic loads by applying power
proportional to steering demand. ZF TRW Commercial Steering commented
that they are developing a power steering pump that uses a secondary
chamber deactivation during highway cruise operations that reduce the
pump drive torque by 30 to 40 percent. Navistar also commented that the
effectiveness for an electrified air conditioning compressor is
understated in the NPRM. Navistar's estimates are closer to 1.5 percent
when in use which will be during the use of air conditioning and during
defrost; therefore, the effective benefit should be one percent.
Daimler commented that the proposed high efficiency air conditioning
effectiveness should be refined and that other opportunities to reduce
losses, such as blend air systems, should be considered. In response to
the comments, the agencies evaluated a set of accessories that can be
designed to reduce accessory losses. Due to the complexity in
determining what qualifies as an efficient accessory, we are
maintaining the proposed language for accessories for tractors which
provides defined effectiveness values for only electric air
conditioning compressors and electric power steering pumps and coolant
pumps. Manufacturers have the option to apply for off-cycle credits for
the other types and designs of high efficiency accessories.
    Intelligent Controls: Skilled drivers know how to control a vehicle
to obtain maximum fuel efficiency by, among other things, considering
road terrain. For example, the driver may allow the vehicle to slow
down below the target speed on an uphill and allow it to go over the
target speed when going downhill, to essentially smooth out the engine
demand. Electronic controls can be developed to essentially mimic this
activity. The agencies proposed to provide a two percent reduction in
fuel consumption and CO2 emissions for vehicles configured
with intelligent controls, such as predictive cruise control. 80 FR
40218. ICCT found in their workshop that opportunities exist for road
load optimization through predictive cruise, GPS, and driver feedback
that could lead to a zero to five percent improvement in fuel
consumption.\278\ Daimler commented that eCoast should also be
recognized as an intelligent control within GEM. Eaton offers similar
technology, known as Neutral Coast Mode. Neutral coast is an electronic
feature that places an automated transmission in neutral on downhill
grades which allows the engine speed to go idle speed. A fuel savings
is recognized due to the difference in engine operating conditions due
to the reduced load on the engine due to the transmission.
---------------------------------------------------------------------------

    \278\ Delgado, Oscar. N. Lutsey. Advanced Tractor-Trailer
Efficiency Technology Potential in the 2020-2030 Timeframe. April
2015. Docket EPA-HQ-OAR-2014-0827.
---------------------------------------------------------------------------

    Based on literature information, intelligent controls such as
predictive cruise control will reduce CO2 emissions by two
percent, and the agencies are assuming this level of improvement in
considering the level of the tractor standard. In addition, the
agencies' review of literature and confidential business information
provided based on the SuperTruck demonstration vehicles indicates that
neutral coasting will reduce fuel consumption and CO2
emissions by 1.5 percent.
    Solar Load Management: The agencies received a letter from the
California Air Resources Board prior to the proposal requesting
consideration of including technologies that reduce solar heating of
the cab (to reduce air conditioning loads) in setting the Phase 2
tractor standards. Solar reflective paints and solar control glazing
technologies are discussed in RIA Chapter <IP_ADDRESS>. The agencies
requested comment on the Air Resources Board's letter and
recommendations.\279\ The agencies received some clarifications from
ARB on our evaluation of solar technologies and some CBI from Daimler,
but not a sufficient amount of information to evaluate the baseline
level of solar control that exists in the heavy-duty market today,
determine the effectiveness of each of the solar technologies, or to
develop a definition of what qualifies as a solar control technology
that could be used in the regulations. Therefore, the agencies would
consider solar control to be a technology that manufacturers may
consider pursuing through the off-cycle credit program. As such, the
agencies did not include solar load management technologies in the
technology packages used in setting the final Phase 2 tractor standard
stringencies.
---------------------------------------------------------------------------

    \279\ California Air Resources Board. Letter from Michael Carter
to Matthew Spears dated December 3, 2014. Solar Control: Heavy-Duty
Vehicles White Paper. Docket EPA-HA-OAR-2014-0827.
---------------------------------------------------------------------------

(ix) Weight Reduction
    Reductions in vehicle mass lower fuel consumption and GHG emissions
by decreasing the overall vehicle mass that is moved down the road.
Weight reductions also increase vehicle payload capability which can
allow additional tons to be carried by fewer trucks consuming less fuel
and producing

lower emissions on a ton-mile basis. We treated such weight reduction
in two ways in Phase 1 to account for the fact that combination
tractor-trailers weigh-out approximately one-third of the time and
cube-out approximately two-thirds of the time. Therefore in Phase 1 and
also as finalized for Phase 2, one-third of the weight reduction will
be added payload in the denominator while two-thirds of the weight
reduction is subtracted from the overall weight of the vehicle in GEM.
See 76 FR 57153.
    In Phase 1, we reflected mass reductions for specific technology
substitutions (e.g., installing aluminum wheels instead of steel
wheels). These substitutions were included where we could with
confidence verify the mass reduction information provided by the
manufacturer. The weight reductions were developed from tire
manufacturer information, the Aluminum Association, the Department of
Energy, SABIC and TIAX. The agencies proposed to expand the list of
weight reduction components which can be input into GEM in order to
provide the manufacturers with additional means to comply via GEM with
the combination tractor standards and to further encourage reductions
in vehicle weight. As in Phase 1, we recognize that there may be
additional potential for weight reduction in new high strength steel
components which combine the reduction due to the material substitution
along with improvements in redesign, as evidenced by the studies done
for light-duty vehicles.\280\ The agencies however do not agree with
all of the recommendations in this report. See Section I.C.1 and RTC
Section 1 for a discussion on lifecycle emissions. In the development
of the high strength steel component weights, we are only assuming a
reduction from material substitution and no weight reduction from
redesign, since we do not have any data specific to redesign of heavy-
duty components nor do we have a regulatory mechanism to differentiate
between material substitution and improved design. Additional weight
reduction would be evaluated as a potential off-cycle credit. As
described in Section III.E.2 below, the agencies discuss the weight
reduction component comments received and are adopting an expanded list
of weight reduction options which could be input into the GEM by the
manufacturers to reduce their certified CO2 emission and
fuel consumption levels.
---------------------------------------------------------------------------

    \280\ American Iron and Steel Institute. ``A Cost Benefit
Analysis Report to the North American Steel Industry on Improved
Material and Powertrain Architectures for 21st Century ``Trucks.''
---------------------------------------------------------------------------

(x) Vehicle Speed Limiter
    Fuel consumption and GHG emissions increase proportional to the
square of vehicle speed. Therefore, lowering vehicle speeds can
significantly reduce fuel consumption and GHG emissions. A vehicle
speed limiter (VSL), which limits the vehicle's maximum speed, is
another technology option for compliance that is already utilized today
by some fleets (though the typical maximum speed setting is often
higher than 65 mph).
    CARB recommended not giving any credit for VSLs because the
available data do not fully support whether VSLs result in real-world
fuel consumption and GHG reductions. CARB referenced Oakridge National
Laboratory's Transportation Energy Data Book, Table 5.11 that shows
CO2 emissions decrease with increased speed. CARB also
stated that the draft GEM model appears to offer up to 22 percent
credit for use of VSL set to 45 mph, which they consider to be
unreasonably high. Before including VSLs as a technology, CARB staff
suggests that EPA and NHTSA should thoroughly evaluate whether they
would result in real-world CO2 and fuel consumption
benefits.
    The agencies conducted in-use tractor testing at different speeds
and in turn used this data to validate the GEM simulations of VSL, as
discussed in more detail in RIA Chapter 4. The agencies are confident
that GEM appropriately recognizes the impact of VSL on CO2
emissions and fuel consumption. The agencies have limited the range of
inputs to the VSL in Phase 2 GEM to a minimum of 55 mph to align with
the regulations in 40 CFR 1037.631 that provide exemptions for
vocational vehicles intended for off-road use. A 55 mph VSL installed
on a typical day cab tractor would reduce the composite grams of
CO2 emitted per ton-mile by seven percent. Similarly, a 55
mph VSL on a sleeper cab would reduce the composite grams of
CO2 per ton-mile emitted by 10 percent. Please see RIA
Chapter 2.8 for additional detail of technology impacts.
(xi) Hybrid Powertrains
    In Phase 2, hybrid powertrains are generally considered a
conventional rather than innovative technology, especially for
vocational vehicles. However, hybrid powertrain development in Class 7
and 8 tractors has been limited to a few manufacturer demonstration
vehicles to date. One of the key benefit opportunities for fuel
consumption reduction with hybrids is less fuel consumption when a
vehicle is idling, but the standard is already premised on use of
extended idle reduction so use of hybrid technology will duplicate many
of the same emission reductions attributable to extended idle
reduction. NAS estimated that hybrid systems would cost approximately
$25,000 per tractor in the 2015 through the 2020 time frame and provide
a potential fuel consumption reduction of ten percent, of which six
percent is idle reduction that can be achieved (less expensively)
through the use of other idle reduction technologies.\281\ The limited
reduction potential outside of idle reduction for Class 8 sleeper cab
tractors is due to the mostly highway operation and limited start-stop
operation. Due to the high cost and limited benefit during the model
years at issue in this action, the agencies did not include hybrids in
assessing stringency of the proposed tractor standard.
---------------------------------------------------------------------------

    \281\ See the 2010 NAS Report, Note 229, page 128.
---------------------------------------------------------------------------

    In addition to the high cost and limited utility of hybrids for
many tractor drive cycles noted above, the agencies believe that hybrid
powertrains systems for tractors may not be sufficiently developed and
the necessary manufacturing capacity put in place to base a standard on
any significant volume of hybrid tractors. Unlike hybrids for
vocational vehicles and light-duty vehicles, the agencies are not aware
of any full hybrid systems currently developed for long haul tractor
applications. To date, hybrid systems for tractors have been primarily
focused on extended idle shutdown technologies and not on the broader
energy storage and recovery systems necessary to achieve reductions
over typical tractor drive cycles. The Phase 2 sleeper cab tractor
standards instead reflect the potential for extended idle shutdown
technologies. Further, as highlighted by the 2010 NAS report, the
agencies do believe that full hybrid powertrains may have the potential
in the longer term to provide significant improvements in long haul
tractor fuel efficiency and to greenhouse gas emission reductions. With
respect to day cab tractors, the types of tractors that would receive
the benefit from hybrid powertrains would be those such as beverage
delivery tractors which could be treated as vocational vehicles through
the Special Purpose Tractor provisions (40 CFR 1037.630).
    Several stakeholders commented on hybrid powertrain development for
tractor applications. Allison agreed with the agencies' overall
assessment of hybrids in tractors, as discussed in the

NPRM. Bendix agreed that hybrid systems for tractors have not been
focused on. Bendix believed that mild hybrid systems should be included
in GEM for credit, including stop-start and electrification of
accessories. Daimler commented that in SuperTruck, a tractor that was
tested on line haul-type highway routes, the hybrid system provided
little benefit beyond what eCoast achieved because it competes with
hybrids for energy that might be lost on hills. Overall, Daimler's view
was that hybrid systems proved too costly relative to their benefit.
Eaton stated that hybrids have not penetrated the commercial trucking
landscape, primarily due to the costs but that there may be potential
in the future for hybrids in tractor applications driven by improved
aerodynamics and lower rolling resistance tires because it would lead
to longer coasting times and higher braking loads, therefore greater
regeneration opportunities. PACCAR commented that their history with
hybrid technology was a niche market application appealing to ``green''
companies as long as incentives offset the cost of the technology.
PACCAR stated that the low sales volumes were not based on performance,
but rather on the combination of the payback of the high initial cost
based on the limited number of gallons saved in low mileage pick up-
and-delivery applications and on the concern over resale value, since
at some point in the vehicle's life the battery must be replaced at a
significant cost to the owner.
    After considering the comments, the agencies are continuing the
Phase 1 approach of not including hybrid powertrains in our feasibility
analysis for Phase 2. Because the technology for tractor applications
is still under development we cannot confidently assess the
effectiveness of this technology at this point in time. In addition,
due to the high cost, limited benefit during highway driving, and
lacking any existing systems or manufacturing base, we cannot conclude
that such technology will be available for tractors in the 2021-2027
timeframe. However, manufacturers will be able to use powertrain
testing to capture the performance of a hybrid system in GEM if systems
are developed in the Phase 2 timeframe, so this technology remains a
potential compliance option (without requiring an off-cycle
demonstration).
(xii) Operational Management
    The 2010 NAS report noted many operational opportunities to reduce
fuel consumption, such as driver training and route optimization. The
agencies have included discussion of several of these strategies in RIA
Chapter 2, but are not using these approaches or technologies in the
Phase 2 standard setting process. The agencies are looking to other
resources, such as EPA's SmartWay Transport Partnership and regulations
that could potentially be promulgated by the Federal Highway
Administration and the Federal Motor Carrier Safety Administration, to
continue to encourage the development and utilization of these
approaches. In addition, the agencies have also declined to base
standard stringencies on technologies which are largely to chiefly
driver-dependent, and evaluate such potential improvements through the
off-cycle credit mechanism. See, e.g., 77 FR 62838/3 (Oct. 12, 2012).
(xiii) Consideration of Phase 1 Credits in Phase 2 Stringency Setting
    The agencies requested comment regarding the treatment of Phase 1
credits, as discussed in Section I.C.1.b. See 80 FR 40251. As examples,
the agencies discussed limiting the use of Phase 1 credits in Phase 2
and factoring credit balances into the 2021 standards. Daimler
commented that allowing Phase 1 credits in Phase 2 is necessary to
smooth the transition into a new program that is very complex and that
HD manufacturers cannot change over an entire product portfolio at one
time. The agencies evaluated the status of Phase 1 credit balances in
2015 by sector. For tractors, we found that manufacturers are
generating significant credits, and that it appears that many of the
credits result from their use of an optional provision for calculating
aerodynamic drag. However, we also believe that manufacturers will
generate fewer credits in MY 2017 and later when the final Phase 1
standards begin. Still, the agencies believe that manufacturers will
have significant credit balances available to them for MYs 2021-2023,
and that much of these balances would be the result of the test
procedure provisions rather than pull ahead of any technology. Based on
confidential product plans for MYs 2017 and later, we expect this total
windfall amount to be three percent of the MY 2021 standards or more.
Therefore, the agencies are factoring in a total credit amount
equivalent to this three percent credit (i.e. three years times 1
percent per year). Thus, we are increasing the stringency of the
CO2 and fuel consumption tractor standards for MYs 2021-2023
by 1 percent to reflect these credits.
(xiv) Summary of Technology Performance
    Table III-10 describes the performance levels for the range of
Class 7 and 8 tractor vehicle technologies.

                                                         Table III-10--Phase 2 Technology Inputs
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                    Class 7                                                    Class 8
                                    --------------------------------------------------------------------------------------------------------------------
                                                    Day cab                                Day cab                              Sleeper cab
                                    --------------------------------------------------------------------------------------------------------------------
                                       Low roof     Mid roof    High roof     Low roof     Mid roof    High roof     Low roof     Mid roof    High roof
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                         Engine
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                          2021MY       2021MY       2021MY       2021MY       2021MY       2021MY       2021MY       2021MY       2021MY
                                      11L Engine   11L Engine   11L Engine   15L Engine   15L Engine   15L Engine   15L Engine   15L Engine   15L Engine
                                          350 HP       350 HP       350 HP       455 HP       455 HP       455 HP       455 HP       455 HP       455 HP
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                Aerodynamics (CdA in m2)
--------------------------------------------------------------------------------------------------------------------------------------------------------
Bin I..............................         6.00         7.00         7.45         6.00         7.00         7.45         6.00         7.00         7.15
Bin II.............................         5.60         6.65         6.85         5.60         6.65         6.85         5.60         6.65         6.55
Bin III............................         5.15         6.25         6.25         5.15         6.25         6.25         5.15         6.25         5.95
Bin IV.............................         4.75         5.85         5.70         4.75         5.85         5.70         4.75         5.85         5.40
Bin V..............................         4.40         5.50         5.20         4.40         5.50         5.20         4.40         5.50         4.90
Bin VI.............................         4.10         5.20         4.70         4.10         5.20         4.70         4.10         5.20         4.40
Bin VII............................         3.80         4.90         4.20         3.80         4.90         4.20         3.80         4.90         3.90
--------------------------------------------------------------------------------------------------------------------------------------------------------

                                                           Steer Tires (CRR in kg/metric ton)
--------------------------------------------------------------------------------------------------------------------------------------------------------
Base...............................          7.8          7.8          7.8          7.8          7.8          7.8          7.8          7.8          7.8
Level 1............................          6.6          6.6          6.6          6.6          6.6          6.6          6.6          6.6          6.6
Level 2............................          5.7          5.7          5.7          5.7          5.7          5.7          5.7          5.7          5.7
Level 3............................          4.9          4.9          4.9          4.9          4.9          4.9          4.9          4.9          4.9
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                           Drive Tires (CRR in kg/metric ton)
--------------------------------------------------------------------------------------------------------------------------------------------------------
Base...............................          8.1          8.1          8.1          8.1          8.1          8.1          8.1          8.1          8.1
Level 1............................          6.9          6.9          6.9          6.9          6.9          6.9          6.9          6.9          6.9
Level 2............................          6.0          6.0          6.0          6.0          6.0          6.0          6.0          6.0          6.0
Level 3............................          5.0          5.0          5.0          5.0          5.0          5.0          5.0          5.0          5.0
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                              Idle Reduction (% reduction)
--------------------------------------------------------------------------------------------------------------------------------------------------------
Tamper Proof AESS..................          N/A          N/A          N/A          N/A          N/A          N/A            4            4            4
Tamper Proof AESS with Diesel APU..          N/A          N/A          N/A          N/A          N/A          N/A            4            4            4
Tamper Proof AESS with Battery APU.          N/A          N/A          N/A          N/A          N/A          N/A            6            6            6
Tamper Proof AESS with Automatic             N/A          N/A          N/A          N/A          N/A          N/A            3            3            3
 Stop-Start........................
Tamper Proof AESS with FOH.........          N/A          N/A          N/A          N/A          N/A          N/A            3            3            3
Adjustable AESS....................          N/A          N/A          N/A          N/A          N/A          N/A            1            1            1
Adjustable AESS with Diesel APU....          N/A          N/A          N/A          N/A          N/A          N/A            3            3            3
Adjustable AESS with Battery APU...          N/A          N/A          N/A          N/A          N/A          N/A            5            5            5
Adjustable AESS with Automatic Stop-         N/A          N/A          N/A          N/A          N/A          N/A            5            5            5
 Start.............................
Adjustable AESS with FOH...........          N/A          N/A          N/A          N/A          N/A          N/A            2            2            2
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                               Transmission (% reduction)
--------------------------------------------------------------------------------------------------------------------------------------------------------
Manual.............................            0            0            0            0            0            0            0            0            0
AMT................................            2            2            2            2            2            2            2            2            2
Auto...............................            2            2            2            2            2            2            2            2            2
Dual Clutch........................            2            2            2            2            2            2            2            2            2
Top Gear Direct Drive..............            2            2            2            2            2            2            2            2            2
Trans Efficiency...................            1            1            1            1            1            1            1            1            1
Neutral Idle.......................   Modeled in   Modeled in   Modeled in   Modeled in   Modeled in   Modeled in   Modeled in   Modeled in   Modeled in
                                         GEM          GEM          GEM          GEM          GEM          GEM          GEM          GEM          GEM
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                 Driveline (% reduction)
--------------------------------------------------------------------------------------------------------------------------------------------------------
Axle Efficiency....................            2            2            2            2            2            2            2            2            2
6x2, 6x4 Axle Disconnect or 4x2              N/A          N/A          N/A   Modeled in   Modeled in   Modeled in   Modeled in   Modeled in   Modeled in
 Axle..............................                                             GEM          GEM          GEM          GEM          GEM          GEM
Downspeed..........................   Modeled in   Modeled in   Modeled in   Modeled in   Modeled in   Modeled in   Modeled in   Modeled in   Modeled in
                                         GEM          GEM          GEM          GEM          GEM          GEM          GEM          GEM          GEM
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                          Accessory Improvements (% reduction)
--------------------------------------------------------------------------------------------------------------------------------------------------------
A/C Efficiency.....................          0.5          0.5          0.5          0.5          0.5          0.5          0.5          0.5          0.5
Electric Access....................            1            1            1            1            1            1            1            1            1
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                            Other Technologies (% reduction)
--------------------------------------------------------------------------------------------------------------------------------------------------------
Predictive Cruise Control..........            2            2            2            2            2            2            2            2            2
Automated Tire Inflation System....          1.2          1.2          1.2          1.2          1.2          1.2          1.2          1.2          1.2
Tire Pressure Monitoring System....            1            1            1            1            1            1            1            1            1
Neutral Coast......................          1.5          1.5          1.5          1.5          1.5          1.5          1.5          1.5          1.5
--------------------------------------------------------------------------------------------------------------------------------------------------------
Note:
``Modeled in GEM'' means that a manufacturer will input information into GEM, such as ``Yes or No'' for neutral idle, and GEM will simulate that
  condition. The values listed in the table above as percentages reflect a post-processing done within GEM after the simulation runs the drive cycles.

(c) Tractor Technology Adoption Rates
    As explained above, tractor manufacturers often introduce major
product changes together, as a package. In this manner the
manufacturers can optimize their available resources, including
engineering, development, manufacturing and marketing activities to
create a product with multiple new features. Since Phase 1 began, this
approach also has allowed manufacturers to consolidate testing and
certification requirements. In addition, manufacturers recognize that a
truck design will need to remain competitive over the intended life of
the design and meet future regulatory requirements. In some limited
cases, manufacturers may implement an individual technology outside of
a vehicle's redesign cycle.
    With respect to the levels of technology adoption used to develop
the HD Phase 2 standards, NHTSA and EPA established technology adoption
constraints. The first type of constraint was established based on the
application of fuel consumption and CO2 emission reduction
technologies into the different types of tractors. For example,
extended idle reduction technologies are limited to Class 8 sleeper
cabs using the reasonable assumption that day cabs are not used for
overnight hoteling. Day cabs typically idle for shorter durations
throughout the day.
    A second type of constraint was applied to most other technologies
and limited their adoption based on factors reflecting the real world
operating conditions that some combination tractors encounter (so that
the standards are not based on use of technologies which do not provide
in-use benefit). This second type of constraint was applied to the
aerodynamic, tire, powertrain, vehicle speed limiter technologies, and
other technologies. NHTSA and EPA believe that within each of these
individual vehicle categories there are particular applications where
the use of the identified technologies will be either ineffective or
not technically feasible. For example, the agencies are not predicating
these standards on the use of full aerodynamic vehicle treatments on
100 percent of tractors because we know that in some applications (for
example, gravel trucks engaged in local delivery) the added weight of
the aerodynamic technologies will increase fuel consumption and hence
CO2 emissions to a greater degree than the reduction that
will be accomplished from the more aerodynamic nature of the tractor.
General considerations of needed lead time also play a significant role
in the agencies' determination of technology adoption rates.
    In the development of the standards, we generally focused initially
on what technology could be adopted in 2027 MY after ten years of lead
time, consistent with the general principles discussed above. Based on
our detailed discussions with manufacturers and technology suppliers,
we can project that the vast majority of technologies will be fully
developed and in widespread use by 2027 MY. (One notable exception to
this is Rankine cycle waste heat recovery, which we project to be less
widespread in 2027). Having identified what could be achieved in 2027
MY, we projected technology steps for 2021 MY and 2024 MY to reflect
the gradual development and deployment of these technologies.
    This is also consistent with how manufacturers will likely approach
complying with these standards. In general, we would expect a
manufacturer to first identify technology packages that would allow
them to meet the 2027 MY standards, then to structure a development
plan to make steady progress toward the 2027 MY standards. To some
extent, it was easier to project the technology for 2027 MY, because it
represents a maximum feasible adoption of most technologies. The
agencies' projections for MYs 2021 and 2024 are less certain because
they reflect choices manufacturers would likely make to reach the 2027
levels. As such, we have more confidence that the levels of our MYs
2021 and 2024 standards are appropriate than we do that each
manufacturer will follow our specific technology development path in
2021 MY or 2024 MY.
    Table III-13, Table III-14, and Table III-15 specify the adoption
rates that EPA and NHTSA used to develop these standards.
(i) Aerodynamics Adoption Rate
    The impact of aerodynamics on a tractor-trailer's efficiency
increases with vehicle speed. Therefore, the usage pattern of the
vehicle will determine the benefit of various aerodynamic technologies.
Sleeper cabs are often used in line haul applications and drive the
majority of their miles on the highway travelling at speeds greater
than 55 mph. The industry has focused aerodynamic technology
development, including SmartWay tractors, on these types of trucks.
Therefore the agencies proposed standards that reflect the most
aggressive aerodynamic technology application rates to this regulatory
subcategory, along with the high roof day cabs. 80 FR 40227. All of the
major manufacturers today offer at least one SmartWay sleeper cab
tractor model, which is represented as Bin III aerodynamic performance.
The agencies requested comment on the proposed aerodynamic assessment.
    The agencies received significant comment from the manufacturers
regarding our assessment of aerodynamics in the most aerodynamic bins
for high roof sleeper cabs. EMA commented that the assumptions that
Class 7 and Class 8 high-roof vehicles will achieve a 35 percent
penetration rate into Bin V, a 20 percent penetration rate into Bin VI,
and a 5 percent penetration rate into Bin VII by 2027 are over-stated
and unreasonable. Volvo and EMA commented that it is impossible to
achieve the targeted aerodynamic drag reductions that ultimately are
predicated on 60 percent of tractors achieving aero bins V, VI, and
VII. According to their analysis, the manufacturers stated that it is
not possible to achieve these low drag levels with any tractor design
coupled to the non-aerodynamic test trailer prescribed in this
proposal. Caterpillar commented that given the proposed aerodynamic
testing procedures, the Phase 2 test trailer, and the lack of any audit
margin for these highly variable test processes, it is infeasible to
design tractors that can achieve bin V, and so would not be able to
achieve bins VI and VII. Caterpillar also stated that none of the
vehicles developed within the Department of Energy's SuperTruck program
are capable of meeting the proposed aerodynamic targets.
    In Phase 1, the agencies determined the stringency of the tractor
standards through the use of a mix of aerodynamic bins in the
technology packages. For example, we included 10 percent Bin II, 70
percent Bin III, and 20 percent Bin IV in the high roof sleeper cab
tractor standard. The weighted average aerodynamic performance of this
technology package is equivalent to Bin III. 76 FR 57211. In
consideration of the comments, the agencies have adjusted the
aerodynamic adoption rate for Class 8 high roof sleeper cabs used to
set the final standards in 2021, 2024, and 2027 MYs (i.e., the degree
of technology adoption on which the stringency of the standard is
premised). Upon further analysis of simulation modeling of a SuperTruck
tractor with a Phase 2 reference trailer with skirts, we agree with the
manufacturers that a SuperTruck tractor technology package would only
achieve the Bin V level of CdA, as discussed above and in
RIA Chapter <IP_ADDRESS>. Consequently, as noted above, the final standards
are not premised on any adoption of Bin VI and VII technologies.
Accordingly, we

determined the adoption rates in the technology packages developed for
the final rule using a similar approach as Phase 1--spanning three
aerodynamic bins and not setting adoption rates in the most aerodynamic
bin(s)--to reflect that there are some vehicles whose operation limits
the applicability of some aerodynamic technologies. We set the MY 2027
high roof sleeper cab tractor standards using a technology package that
included 20 percent of Bin III, 30 percent Bin IV, and 50 percent Bin V
reflecting our assessment of the fraction of high roof sleeper cab
tractors that we project could successfully apply these aerodynamic
packages with this amount of lead time. The weighted average of this
set of adoption rates is equivalent to a tractor aerodynamic
performance near the border between Bin IV and Bin V. We believe that
there is sufficient lead time to develop aerodynamic tractors that can
move the entire high roof sleeper cab aerodynamic performance to be as
good as or better than today's SmartWay designated tractors.
    The agencies phased-in the aerodynamic technology adoption rates
within the technology packages used to determine the MY 2021 and 2024
standards so that manufacturers can gradually introduce these
technologies. The changes required for Bin V performance reflect the
kinds of improvements projected in the Department of Energy's
SuperTruck program. That program has demonstrated tractor-trailers in
2015 with significant aerodynamic technologies. For the final rule, the
agencies are projecting that truck manufacturers will be able to begin
implementing some of these aerodynamic technologies on high roof
tractors as early as 2021 MY on a limited scale. For example, in the
2021 MY technology package, the agencies have assumed that 10 percent
of high roof sleeper cabs will have aerodynamics better than today's
best tractors. This phase-in structure is consistent with the normal
manner in which manufacturers introduce new technology to manage
limited research and development budgets as well as to allow them to
work with fleets to fully evaluate in-use reliability before a
technology is applied fleet-wide. The agencies believe the phase-in
schedule will allow manufacturers to complete these normal processes.
Overall, while the agencies are now projecting slightly less benefit
from aerodynamic improvements than we did in the NPRM, the actual
aerodynamic technologies being projected are very similar to what was
projected at the time of NPRM (however, these vehicles fall into Bin V
in the final rule, instead of Bin VI and VII in the NPRM). Importantly,
our averaging, banking and trading provisions provide manufacturers
with the flexibility (and incentive) to implement these technologies
over time even though the standard changes in a single step.
    The agencies also received comment regarding our aerodynamic
assessment of the other tractor subcategories. Daimler commented that
due to their shorter length, day cabs are more difficult to make
aerodynamic than sleeper cabs, and that the bin boundaries and adoption
rates should reflect this. EMA commented that the assumed aerodynamic
performance improvements to be achieved by day cab and mid and low-roof
vehicles are over-estimated by at least one bin. Daimler commented that
the agencies should adjust the average bin down in recognition of the
fact that mid/low-roof vehicles should have lower penetration rates of
aerodynamic vehicles to reflect market needs, reflecting these
vehicles' use in rough environments or in hauling non-aerodynamic
trailers.
    Aerodynamic improvements through new tractor designs and the
development of new aerodynamic components is an inherently slow and
iterative process. The agencies recognize that there are tractor
applications that require on/off-road capability and other truck
functions which restrict the type of aerodynamic equipment applicable.
We also recognize that these types of trucks spend less time at highway
speeds where aerodynamic technologies have the greatest benefit. The
2002 VIUS data ranks trucks by major use.\282\ The heavy trucks usage
indicates that up to 35 percent of the trucks may be used in on/off-
road applications or heavier applications. The uses include
construction (16 percent), agriculture (12 percent), waste management
(5 percent), and mining (2 percent). Therefore, the agencies analyzed
the technologies to evaluate the potential restrictions that will
prevent 100 percent adoption of more advanced aerodynamic technologies
for all of the tractor regulatory subcategories and developed standards
with new penetration rates reflecting that these vehicles spend less
time at highway speeds. For the final rule, the agencies evaluated the
certification data to assess how the aerodynamic performance of high
roof day cabs compare to high roof sleeper cabs. In 2014, the high roof
day cabs on average are certified to one bin lower than the high roof
sleeper cabs.\283\ Consistent with the public comments, and the
certification data, the aerodynamic adoption rates used to develop the
final Phase 2 standards for the high roof day cab regulatory
subcategories are less aggressive than for the Class 8 sleeper cab high
roof tractors. In addition, the agencies are also accordingly reducing
the adoption rates in the highest bins for low and mid roof tractors to
follow the changes made to the high roof subcategories because we
neither proposed nor expect the aerodynamics of a low or mid roof
tractor to be better than a high roof tractor.
---------------------------------------------------------------------------

    \282\ U.S. Department of Energy. Transportation Energy Data
Book, Edition 28-2009. Table 5.7.
    \283\ U.S. EPA. Memo to Docket. Coefficient of Rolling
Resistance and Coefficient of Drag Certification Data for Tractors.
See Docket EPA-HQ-OAR-2014-0827.
---------------------------------------------------------------------------

(ii) Low Rolling Resistance Tire Adoption Rate
    For the tire manufacturers to further reduce tire rolling
resistance, the manufacturers must consider several performance
criteria that affect tire selection. The characteristics of a tire also
influence durability, traction control, vehicle handling, comfort, and
retreadability. A single performance parameter can easily be enhanced,
but an optimal balance of all the criteria will require improvements in
materials and tread design at a higher cost, as estimated by the
agencies. Tire design requires balancing performance, since changes in
design may change different performance characteristics in opposing
directions. Similar to the discussion regarding lesser aerodynamic
technology application in tractor segments other than sleeper cab high
roof, the agencies believe that the proposed standards should not be
premised on 100 percent application of Level 3 tires in all tractor
segments given the potential interference with vehicle utility that
could result. 80 FR 40223.
    Several stakeholders commented about the level of rolling
resistance used in setting the proposed level of tractor stringencies
because the agencies used a single level for all tractor subcategories.
ATA, First Industries, National Association of Manufacturers, PACCAR,
Navistar and Daimler commented that the agencies erred by using the
same rolling resistance for all types of day and sleeper cab tractors.
They stated that the tire stringency levels should account for fleet
and class variations and different duty-cycle needs. Caterpillar stated
that tires need to meet demands of all conditions, including

unpaved roads, sloped loading docks which are frequently not treated in
winter conditions. Caterpillar also stated that tire casings must have
adequate durability to allow for as many as five retreads. NADA
commented current LRRT tractor adoption rates are low and are not
expected to increase significantly any time soon unless significant
improvements in design are forthcoming and that there is no realistic
means of ensuring that customers (or subsequent owners) will continue
to use LRR tires. OOIDA commented that the LRR tire may be beneficial
on flat terrain, but may pose a safety concern in many geographical
regions. OOIDA also stated that a LRR tire achieves much of its
potential fuel savings benefit by reducing the very component of
friction or resistance that a truck driver may rely upon. PACCAR
commented that customers with low- and mid-roof configurations
typically operate more in urban areas where tires must withstand the
abuse of curbs and other obstacles or in more on/off road conditions
that are typical for flatbed, tanker, and low-boy operations, which use
the low and mid-roof configuration vehicles. PACCAR stated that the
tires for low and mid roof tractors vehicles are designed with
additional side wall protection and generally have a higher coefficient
of rolling resistance. Volvo commented with respect to tractor
penetration and stringency setting the agencies show penetration of
Level 3 tires starting in MY 2021. Volvo stated that they continue to
hear customer feedback that low rolling resistance tires often lack
adequate traction under many of the demanding conditions that trucks
and tractors experience, such as snow and off-road. Schneider commented
that fleet uses low rolling resistance tires on dual wheels for the
majority of the standard fleet while using wide-based single tires for
weight sensitive portions of the fleet. Schneider commented that
regulations should not force the use of wide based single tires based
solely on rolling resistance advantages without considering the overall
performance because it may increase waste, the number of scrapped tire
casings and landfill requirements. The commenter's view is that LRR
dual tires are very comparable to wide based single tires (WBS) tires
in fuel efficiency while providing better overall operating and
economic efficiency.
    For the final rulemaking, the agencies evaluated the tire rolling
resistance levels in the Phase 1 certification data.\284\ We found that
high roof sleeper cabs are certified today with steer tire rolling
resistance levels that ranged between 4.9 and 7.6 kg/ton and with drive
tires ranging between 5.1 and 9.8 kg/ton. In the same analysis, we
found that high roof day cabs are certified with rolling resistance
levels ranging between 4.9 and 9.0 kg/ton for steer tires and between
5.1 and 9.8 kg/ton for drive tires. This range spans the baseline
through Level 3 rolling resistance performance levels. Therefore, for
the final rule we took an approach similar to the one taken in Phase 1
and proposed in Phase 2 that considers adoption rates across a wide
range of tire rolling resistance levels to recognize that operators may
have different needs. 76 FR 57211 and 80 FR 40227. The adoption rates
for the technology packages used to determine the MY 2027 standards for
each high roof tractor subcategory are shown in Table III-15.
---------------------------------------------------------------------------

    \284\ Memo to Docket. Coefficient of Rolling Resistance and
Coefficient of Drag Certification Data for Tractors. Docket EPA-HQ-
OAR-2014-0827.
---------------------------------------------------------------------------

    In our analysis of the Phase 1 certification data, we found that
the drive tires on low and mid roof sleeper cab tractors on average had
10 to 17 percent higher rolling resistance than the high roof sleeper
cabs. But we found only a minor difference in rolling resistance of the
steer tires between the tractor subcategories. Based on comments
received and further consideration of our own analysis of the
difference in tire rolling resistance levels that exist today in the
certification data, the agencies are adopting Phase 2 standards using a
technology pathway that utilizes higher rolling resistance levels for
low and mid roof tractors than the levels used to set the high roof
tractor standards. This is also consistent with the approach that we
took in setting the Phase 1 tractor standards. 76 FR 57211. In
addition, the final rule reflects a reduction in Level 3 adoption rates
for low and mid roof tractors from 25 percent in MY 2027 used at
proposal (80 FR 40227) to zero percent adoption rate. The technology
packages developed for the low and mid roof tractors used to determine
the stringency of the MY 2027 standards in the final rule do not
include any adoption rate of Level 3 drive tires to recognize the
special needs of these applications, consistent with the comments noted
above raising concerns about applications that limit the use of low
rolling resistance tires.
    The agencies phased-in the low rolling resistance tire adoption
rates within the technology packages used to determine the MY 2021 and
2024 standards so that manufacturers can gradually introduce these
technologies. In addition, the levels of rolling resistance used in all
of the technology packages are achievable with either dual or wide
based single tires, so the agencies are not forcing one technology over
another. The adoption rates for the technology packages used to
determine the MY 2021, 2024, and 2027 standards for each tractor
subcategory are shown in Table III-13, Table III-14, and Table III-15.
(iii) Tire Pressure Monitoring and Automatic Tire Inflation System
(ATIS) Adoption Rate
    The agencies used a 20 percent adoption rate of ATIS in MY 2021 and
a 40 percent adoption rate in setting the proposed Phase 2 MY 2024 and
2027 tractor standards. 80 FR 40227.
    ATA commented that as of 2012, roughly one percent of tractors used
ATIS. Caterpillar and First Industries stated that the agencies should
not force ATIS into the market by assuming any penetration rate. EMA
commented that the assumption that 40 percent of all Class 7 and 8
vehicles will utilize automated tire inflation systems lacked support
and failed to account for the prevalence of tire inflation monitoring
systems. NADA stated that they can support a 40 percent tractor
adoption rate for MY 2027 if TPMS are considered. Volvo commented that
given the poor reliability of past ATIS systems, they are skeptical of
supplier's claims of current or future reliability improvements to
these systems. Volvo stated that fleets are even more skeptical than
truck OEMs, as an ATIS air leak results in increased fuel consumption
due to a compressor cycling more frequently and also in potentially
significant downtime of the vehicle. Volvo also commented that to
incentivize truck operators to maintain tire pressure on vehicles
equipped with a TPMS system, fleets have the ability to monitor fuel
consumption remotely, including the ability to identify causes for
increased fuel consumption which would be expected to motivate drivers
to properly maintain tire pressure on TPMS equipped vehicles.
    The agencies find the comments related to a greater acceptance of
TPMS in the tractor market to be persuasive. However, available
information indicates that it is feasible to utilize either TPMS or
ATIS to reduce the prevalence on underinflated tires in-use on all
tractors. As a result, we are finalizing tractor standards that are
predicated on the performance of a mix of TPMS and ATIS adoption rates
in all tractor subcategories. The agencies are

using adoption rates of 30 percent of ATIS and 70 percent of TPMS in
the technology packages used in setting the final Phase 2 MY 2027
tractor standards. This represents a lower adoption rate of ATIS than
used in the NPRM, but the agencies have added additional adoption rate
of TPMS because none of the comments or available information disputed
the ability to use it on all tractors. The agencies have developed
technology packages for setting the 2021 and 2024 MY standards which
reflect a phase in of adoption rates of each of these technologies. In
2021 MY, the adoption rates consist of 20 percent TPMS and 20 percent
ATIS. In 2024 MY, the adoption rates are 50 percent TPMS and 25 percent
ATIS.
(iv) Idle Reduction Technology Adoption Rate
    Idle reduction technologies provide significant reductions in fuel
consumption and CO2 emissions for Class 8 sleeper cabs and
are available on the market today. There are several different
technologies available to reduce idling. These include APUs, diesel
fired heaters, and battery powered units. Our discussions with
manufacturers prior to the Phase 2 NPRM indicated that idle
technologies are sometimes installed in the factory, but that it is
also a common practice to have the units installed after the sale of
the truck. We want to continue to incentivize this practice and to do
so in a manner that the emission reductions associated with idle
reduction technology occur in use. We proposed to continue the Phase 1
approach into Phase 2 where we recognize only idle emission reduction
technologies that include a tamper-proof automatic engine shutoff
system (AESS) with some override provisions.\285\ However, we welcomed
comment on other approaches that will appropriately quantify the
reductions that will be experienced in the real world. 80 FR 40224.
---------------------------------------------------------------------------

    \285\ The agencies are retaining the HD Phase 1 AESS override
provisions included in 40 CFR 1037.660(b) for driver safety.
---------------------------------------------------------------------------

    We used an overall 90 percent adoption rate of tamper-proof AESS
for Class 8 sleeper cabs in setting the proposed MY 2024 and 2027
standards. Id. The agencies stated in the Phase 2 NPRM that we were
unaware of reasons why AESS with extended idle reduction technologies
could not be applied to this high fraction of tractors with a sleeper
cab, except those deemed a vocational tractor, in the available lead
time.
    EMA, Volvo, Daimler, and Navistar commented that the agencies
should consider that customers are not accepting the tamper-proof AESS
in Phase 1, therefore the adoption rates included in the proposal were
too high and that resale concerns remain a significant issue for
customers. PACCAR and EMA commented that the proposed 90 percent
penetration rate of tamper-proof AESS is unachievable. Many comments
also focused on the need for adjustable AESS. OOIDA commented that 90
percent APU adoption is unreasonable and that the 400 pound weight
exemption for APUs is not provided in California, Washington DC,
Hawaii, Kentucky, Massachusetts, North Carolina, and Rhode Island.
OOIDA also raised concerns about situations where an AESS could have
negative consequences--such as team drivers where the co-driver was
left asleep in the berth while the truck was shut off, or drivers with
certain medical conditions, or pets.
    The agencies find the comments regarding the concerns for using 90
percent adoption rates of tamper-proof AESS to be persuasive. For the
final rule, the agencies developed a menu of idle reduction
technologies that include both tamper-proof and adjustable AESS (as
discussed in Section III.D.1.b) that are recognized at different levels
of effectiveness in GEM. As discussed in the discussion of tractor
baselines (Section III.D.1.a), the latest NACFE confidence report found
that 96 percent of HD vehicles are equipped with adjustable automatic
engine shutdown systems.\286\ Therefore, the agencies built this level
of idle reduction into the baseline for sleeper cab tractors. Due to
the high percentage acceptance of adjustable AESS today, the agencies
project that by 2027 MY it is feasible for 100 percent of sleeper cabs
to contain some type of AESS and idle reduction technology to meet the
hoteling needs of the driver. However, we recognize that there are a
variety of idle reduction technologies that meet the various needs of
specific customers and not all customers will select diesel powered
APUs due to the cost or weight concerns highlighted in the comments.
Therefore, we developed an idle reduction technology package for each
MY that reflects this variety. The idle reduction packages developed
for the final rule contain lower AESS adoption rates than used at
proposal. The AESS used during the NPRM assumed that it also included a
diesel powered APU in terms of determining the effectiveness and costs.
In the final rule, the idle reduction technology mix actually has an
overall lower cost (even after increasing the diesel APU technology
cost estimate for the final rule) than would have been developed for
the final rule. In addition, the stringency of the tractor standards
are not affected because the higher penetration rate of other idle
reduction technologies, which are not quite as effective, but will be
deployed more. We developed the technology package to set the 2027 MY
sleeper cab tractor standards that includes 15 percent adoption rate of
adjustable AESS only, 40 percent of adjustable AESS with a diesel
powered APU, 15 percent adjustable AESS with a battery APU, 15 percent
adjustable AESS with automatic stop/start, and 15 percent adjustable
AESS with a fuel operated heater. We continued the same approach of
phasing in different technology packages for the 2021 and 2024 MY
standards, though we included some type of idle reduction on 100
percent of the sleeper cab tractors. The 2021 MY technology package had
a higher adoption rate of adjustable AESS with no other idle reduction
technology and lower adoption rates of adjustable AESS with other idle
reduction technologies. Details on the idle reduction technology
adoption rates for the MY 2021 and 2024 standards are included in Table
III-13 and Table III-14.
---------------------------------------------------------------------------

    \286\ North American Council for Freight Efficiency. Confidence
Report: Idle-Reduction Solutions. 2014. Page 13.
---------------------------------------------------------------------------

(v) Transmission Adoption Rates
    The agencies' proposed standards included a 55, 80, and 90 percent
adoption rate of automatic, automated manual, and dual clutch
transmissions in MYs 2021, 2024, and 2027 respectively. 80 FR 40225-7.
The agencies did not receive any comments regarding these proposed
transmission adoption rates, and have not found any other information
suggesting a change in approach. Therefore, we are including the same
level of adoption rates in setting the final rule standards. The MY
2021 and 2024 standards are likewise premised on the same adoption
rates of these transmission technologies as at proposal.
    The agencies have added neutral idle as a technology input to GEM
for Phase 2 in the final rulemaking. The TC10 that was tested by the
agencies for the final rule included this technology. Therefore, we
projected that neutral idle would be included in all of the automatic
transmissions and therefore the adoption rates of neutral idle match
the adoption rates of the automatic transmission in each of the MYs.
    Transmissions with direct drive as the top gear and numerically
lower axles are

better suited for applications with primarily highway driving with flat
or low rolling hills. Therefore, this technology is not appropriate for
use in 100 percent of tractors. The agencies proposed standards
reflected the projection that 50 percent of the tractors would have
direct drive in top gear in MYs 2024 and 2027. 80 FR 40226-7. The
agencies did not receive any comments regarding the adoption rates of
transmissions with direct drive in those MYs. We therefore are
including the same level of adoption rates in setting the final rule
standards for MYs 2024 and 2027. Transmissions with direct drive top
gears exist in the market today, therefore, the agencies determined it
is feasible to also include this technology in the package for setting
the 2021 MY standards. For the final rule, the agencies included a 20
percent adoption rate of direct drive in the 2021 MY technology
package.
    The agencies received comments supporting establishing a
transmission efficiency test that measures the efficiency of each
transmission gear and could be input into GEM. In the final rule, the
agencies are adopting Phase 2 standards that project that 20, 40, and
70 percent of the AMT and DCT transmissions will be tested and achieve
a fuel consumption and CO2 emissions reduction of one
percent in MYs 2021, 2024, and 2027, respectively.
    The adoption rates for the technology packages used to determine
the MY 2021, 2024, and 2027 standards for each tractor subcategory are
shown in Table III-13, Table III-14, and Table III-15.
(vi) Engine Downspeeding Adoption Rates
    The agencies proposed to include lower final drive ratios in
setting the Phase 2 standards to account for engine downspeeding. In
the NPRM, we used a transmission top gear ratio of 0.73 and baseline
drive axle ratio of 3.70 in 2017 going down to a rear axle ratio of
3.55 in 2021 MY, 3.36 in 2024 MY, and 3.20 in 2027 MY. 80 FR 40228-30.
    UCS commented that downspeeding was only partially captured as
proposed. The agencies also received additional information from
vehicle manufacturers and axle manufacturers that we believe supports
using lower numerical drive axle ratios in setting the final Phase 2
standards for sleeper cabs that spend more time on the highway than day
cabs, directionally consistent with the UCS comment. For the final
rules, the agencies have used 3.70 in the baseline and 3.16 for sleeper
cabs and 3.21 for day cabs in MY 2027 to account for continued
downspeeding opportunities. The final drive ratios used for setting the
other model years are shown in Table III-11. These values represent the
``average'' tractor in each of the MYs, but there will be a range of
final drive ratios that contain more aggressive engine downspeeding on
some tractors and less aggressive on others.

                         Table III-11--Final Drive Ratio for Tractor Technology Packages
----------------------------------------------------------------------------------------------------------------
                                                                                Transmission
                           Model year                                Rear axle       top gear       Final drive
                                                                       ratio           ratio           ratio
----------------------------------------------------------------------------------------------------------------
                                                  Sleeper Cabs
----------------------------------------------------------------------------------------------------------------
2018............................................................            3.70            0.73            2.70
2021............................................................            3.31            0.73            2.42
2024............................................................            3.26            0.73            2.38
2027............................................................            3.16            0.73            2.31
----------------------------------------------------------------------------------------------------------------
                                                    Day Cabs
----------------------------------------------------------------------------------------------------------------
2018............................................................            3.70            0.73            2.70
2021............................................................            3.36            0.73            2.45
2024............................................................            3.31            0.73            2.42
2027............................................................            3.21            0.73            2.34
----------------------------------------------------------------------------------------------------------------

(vii) Drivetrain Adoption Rates
    The agencies' proposed standards included 6x2 axle adoption rates
in high roof tractors of 20 percent in 2021 MY and 60 percent in MYs
2024 and 2027. Because 6x2 axle configurations could raise concerns of
traction, the agencies proposed standards that reflected lower adoption
rates of 6x2 axles in low and mid roof tractors recognizing that these
tractors may require some unique capabilities. The agencies proposed
standards for low and mid roof tractors that included 6x2 axle adoption
rates of 10 percent in MY 2021 and 20 percent in MYs 2024 and 2027. 80
FR 40225-7.
    ATA and others commented that limitations to a high penetration
rate of 6x2 axles include curb cuts, other uneven terrain features that
could expose the truck to traction issues, lower residual values,
traction issues, driver dissatisfaction, tire wear, and the legality of
their use. The commenters stated that recent surveys indicate current
market penetration rates of new line-haul 6x2 tractor sales are only in
the range of two percent, according to a NACFE confidence report. The
commenters also stated that while recent improvements in traction
control systems can automatically shift weight for short periods of
time from the non-driving axle to the driving axle during low-traction
events, concerns remain over the impacts to highways caused by such
shifting of weight between axles. EMA, ATA, OOIDA, Volvo, Daimler,
PACCAR, First Industries, National Association of Manufacturers,
Caterpillar, and others discussed that 6x2 axles are not legal in all
U.S. states and Canadian provinces. Caterpillar and Daimler also stated
the agencies should not assume more than 5 percent penetration rates of
6x2 through 2027. EMA forecasts a 6x2 penetration rate of less than 5
percent.
    Upon further consideration, the agencies have reduced the adoption
rate of 6x2 axles and projected a 30 percent adoption rate in the
technology package used to determine the Phase 2 2027 MY standards. The
2021 MY standards include an adoption rate of 15 percent and the 2024
MY standards include an adoption rate of 25 percent 6x2 axles. This
adoption rate represents a combination of liftable 6x2 axles (which as
noted in ATA's comments are allowed in all states but Utah, and Utah is
expected to revise their law) and 4x2 axles. In addition, it is worth
recognizing that state regulations related to 6x2 axles could change
significantly

over the next ten years. It is also worth noting that the issue related
to the legality of 6x2 axles was not mentioned as a barrier to adoption
by fleets in the NACFE Confidence Report on 6x2 axles.\287\
---------------------------------------------------------------------------

    \287\ North American Council for Freight Efficiency.
``Confidence Findings on the Potential of 6x2 Axles.'' 2014. Page
16.
---------------------------------------------------------------------------

    In the NPRM, the agencies projected that 20 percent of 2021 MY and
40 percent of the 2024 and 2027 MY axles would use low friction axle
lubricants. 80 FR 40225-7. In the final rule, we are requiring that
manufacturers conduct an axle efficiency test if they want to include
the benefit of low friction lubricant or other axle design improvements
when certifying in GEM. The axle efficiency test will be optional, but
will allow manufacturers to reduce CO2 emissions and fuel
consumption if the manufacturers have improved axle gear designs and/or
mandatory use of low friction lubricants. The agencies' assessment of
axle improvements found that 80 percent of the axles built in MY 2027
could be two percent more efficient than a 2017 baseline axle. Because
it will take time for axle manufacturers to make improvements across
the majority of their product offerings, the agencies phased in the
amount of axle efficiency improvements in the technology packages in
setting the 2021 and 2024 MY standards to include 30 and 65 percent
adoption rates, respectively.
(viii) Accessories and Other Technology Adoption Rates
    In the NPRM, the agencies projected adoption rates as show in Table
III-12. 80 FR 40227. The agencies are adopting the same level of
adoption rates for setting the final Phase 2 standards because we did
not receive any comments or new data to support a change in the
adoption rates used in the proposal.

                Table III-12--Adoption Rates Used in the Tractor Technology Packages in the NPRM
----------------------------------------------------------------------------------------------------------------
                                                                                Higher efficiency
                  Model year                     Predictive  cruise        Electrified        air conditioning
                                                    control  (%)        accessories  (%)             (%)
----------------------------------------------------------------------------------------------------------------
2021..........................................                    20                    10                    10
2024..........................................                    40                    20                    20
2027..........................................                    40                    30                    30
----------------------------------------------------------------------------------------------------------------

(ix) Weight Reduction Technology Adoption Rates
    In the NPRM, the agencies proposed to allow manufacturers to use
tractor weight reduction to comply with the standards. 80 FR 40223. A
number of organizations commented generally in favor of the inclusion
of light weight components for compliance, including the Aluminum
Association, Meritor, American Die Casting Association, and the
American Chemistry Council saying light-weight materials are durable
and their use in heavy-duty vehicles can reduce weight and fuel
consumption.
    Unlike in HD Phase 1, the agencies proposed the 2021 through 2027
model year tractor standards without using weight reduction as a
technology to demonstrate the feasibility of the standards. The ICCT
stated that the agencies should include light weight components in
setting the stringency of the standards, citing an ICCT tractor and
trailer study showing specific light weight benefits for tractor
components. Meritor argued that weight reduction should not be included
in setting stringency, given the high cost to benefit ratio for weight
reduction.
    The agencies view weight reduction as a technology with a high cost
that offers a small benefit in the tractor sector. For example, our
estimate of a 400 pound weight reduction will cost $2,050 (2012$) in
2021 MY, but offers a 0.3 percent reduction in fuel consumption and
CO2 emissions. The agencies are excluding the use of weight
reduction components for the tractor stringency calculation due to the
high cost associated with this technology. As noted above, Meritor in
their comments expressed agreement with this approach.
(x) Vehicle Speed Limiter Adoption Rate
    Consistent with Phase 1, we proposed to continue the approach where
vehicle speed limiters may be used as a technology to meet the Phase 2
standard. See 80 FR 40224. In setting the Phase 2 proposed standard,
however, we assumed a zero percent adoption rate of vehicle speed
limiters. Although we expect there will be some use of VSL, currently
it is used when the fleet involved decides it is feasible and
practicable and increases the overall efficiency of the freight system
for that fleet operator. To date, the compliance data provided by
manufacturers indicate that none of the tractor configurations include
a tamper-proof VSL setting less than 65 mph.
    At this point the agencies are not in a position to determine in
how many additional situations use of a VSL will result in similar
benefits to overall efficiency or how many customers will be willing to
accept a tamper-proof VSL setting. Although we believe vehicle speed
limiters are a simple, easy to implement, and inexpensive technology,
we want to leave the use of vehicle speed limiters to the truck
purchaser. In doing so, we are providing another means of meeting the
standard that can lower compliance costs and provide a more optimal
vehicle solution for some truck fleets or owners. For example, a local
beverage distributor may operate trucks in a distribution network of
primarily local roads. Under those conditions, aerodynamic fairings
used to reduce aerodynamic drag provide little benefit due to the low
vehicle speed while adding additional mass to the vehicle. A vehicle
manufacturer could choose to install a VSL set at an optimized speed
for its intended application and use this technology to assist in
complying with our program all at a lower cost to the ultimate tractor
purchaser.\288\
---------------------------------------------------------------------------

    \288\ Ibid.
    \288\ The agencies note that because a VSL value can be input
into GEM, its benefits can be directly assessed with the model and
off cycle credit applications therefore are not necessary even
though the standard is not based on performance of VSLs (i.e. VSL is
an on-cycle technology).
---------------------------------------------------------------------------

    We welcomed comment on whether the use of a VSL would require a
fleet to deploy additional tractors, but did not receive responsive
comment. ARB stated that if EPA and NHTSA decide to give credit in
Phase 2 GEMs for VSLs, VSL benefit should also be reflected in the
standard's stringency. Daimler supported the approach of not including
VSLs in setting the stringency because of the resistance in the market
to accept tamperproof VSLs. OOIDA commented that the agencies must
consider the significant negative consequences of VSLs, such as safety
impact from

differential speeds between light duty vehicles and trucks.
    After considering the comments, we still could not make a
determination regarding the reasonableness of setting a standard based
on a particular VSL adoption rate, for the same reasons articulated at
proposal. Therefore, the agencies are not premising these final Phase 2
standards on use of VSL, and instead will continue to rely on the
industry to select VSL when circumstances are appropriate for its use
(in which case there is an input in GEM reflecting VSL efficiency).
(d) Summary of the Adoption Rates Used To Determine the Final Phase 2
Tractor Standards
    Table III-13 through Table III-16 provide the adoption rates of
each technology broken down by weight class, cab configuration, and
roof height.

                        Table III-13--Technology Adoption Rates for Class 7 and 8 Tractors for Determining the 2021 MY Standards
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                    Class 7                                                    Class 8
                                    --------------------------------------------------------------------------------------------------------------------
                                                    Day cab                                Day cab                              Sleeper cab
                                    --------------------------------------------------------------------------------------------------------------------
                                       Low roof     Mid roof    High roof     Low roof     Mid roof    High roof     Low roof     Mid roof    High roof
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                         Engine
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                     2021 MY 11L  2021 MY 11L  2021 MY 11L  2021 MY 15L  2021 MY 15L  2021 MY 15L  2021 MY 15L  2021 MY 15L  2021 MY 15L
                                      engine 350   engine 350   engine 350   engine 455   engine 455   engine 455   engine 455   engine 455   engine 455
                                          HP           HP           HP           HP           HP           HP           HP           HP           HP
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                      Aerodynamics
--------------------------------------------------------------------------------------------------------------------------------------------------------
Bin I..............................          10%          10%           0%          10%          10%           0%           0%          10%           0%
Bin II.............................          10%          10%           0%          10%          10%           0%          20%          10%           0%
Bin III............................          70%          70%          60%          70%          70%          60%          60%          70%          60%
Bin IV.............................          10%          10%          35%          10%          10%          35%          20%          10%          30%
Bin V..............................           0%           0%           5%           0%           0%           5%           0%           0%          10%
Bin VI.............................           0%           0%           0%           0%           0%           0%           0%           0%           0%
Bin VII............................           0%           0%           0%           0%           0%           0%           0%           0%           0%
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                       Steer Tires
--------------------------------------------------------------------------------------------------------------------------------------------------------
Base...............................           5%           5%           5%           5%           5%           5%           5%           5%           5%
Level 1............................          35%          35%          35%          35%          35%          35%          35%          35%          35%
Level 2............................          50%          50%          50%          50%          50%          50%          50%          50%          50%
Level 3............................          10%          10%          10%          10%          10%          10%          10%          10%          10%
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                       Drive Tires
--------------------------------------------------------------------------------------------------------------------------------------------------------
Base...............................          15%          15%           5%          15%          15%           5%          15%          15%           5%
Level 1............................          35%          35%          35%          35%          35%          35%          35%          35%          35%
Level 2............................          50%          50%          50%          50%          50%          50%          50%          50%          50%
Level 3............................           0%           0%          10%           0%           0%          10%           0%           0%          10%
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                     Idle Reduction
--------------------------------------------------------------------------------------------------------------------------------------------------------
Tamper Proof AESS..................          N/A          N/A          N/A          N/A          N/A          N/A           0%           0%           0%
Tamper Proof AESS with Diesel APU..          N/A          N/A          N/A          N/A          N/A          N/A           0%           0%           0%
Tamper Proof AESS with Battery APU.          N/A          N/A          N/A          N/A          N/A          N/A           0%           0%           0%
Tamper Proof AESS with Automatic             N/A          N/A          N/A          N/A          N/A          N/A           0%           0%           0%
 Stop-Start........................
Tamper Proof AESS with FOH.........          N/A          N/A          N/A          N/A          N/A          N/A           0%           0%           0%
Adjustable AESS....................          N/A          N/A          N/A          N/A          N/A          N/A          40%          40%          40%
Adjustable AESS with Diesel APU....          N/A          N/A          N/A          N/A          N/A          N/A          30%          30%          30%
Adjustable AESS with Battery APU...          N/A          N/A          N/A          N/A          N/A          N/A          10%          10%          10%
Adjustable AESS with Automatic Stop-         N/A          N/A          N/A          N/A          N/A          N/A          10%          10%          10%
 Start.............................
Adjustable AESS with FOH...........          N/A          N/A          N/A          N/A          N/A          N/A          10%          10%          10%
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                      Transmission
--------------------------------------------------------------------------------------------------------------------------------------------------------
Manual.............................           0%           0%           0%           0%           0%           0%           0%           0%           0%
AMT................................          40%          40%          40%          40%          40%          40%          40%          40%          40%
Auto...............................          10%          10%          10%          10%          10%          10%          10%          10%          10%
Dual Clutch........................           5%           5%           5%           5%           5%           5%           5%           5%           5%
Top Gear Direct Drive..............          20%          20%          20%          20%          20%          20%          20%          20%          20%
Trans. Efficiency..................          20%          20%          20%          20%          20%          20%          20%          20%          20%
Neutral Idle.......................          10%          10%          10%          10%          10%          10%          10%          10%          10%
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                        Driveline
--------------------------------------------------------------------------------------------------------------------------------------------------------
Axle Efficiency....................          30%          30%          30%          30%          30%          30%          30%          30%          30%
6x2, 6x4 Axle Disconnect or 4x2              N/A          N/A          N/A          15%          15%          15%          15%          15%          15%
 Axle..............................
Downspeed (Rear Axle Ratio)........         3.36         3.36         3.36         3.36         3.36         3.36         3.31         3.31         3.31
--------------------------------------------------------------------------------------------------------------------------------------------------------

                                                                 Accessory Improvements
--------------------------------------------------------------------------------------------------------------------------------------------------------
A/C Efficiency.....................          10%          10%          10%          10%          10%          10%          10%          10%          10%
Electric Access....................          10%          10%          10%          10%          10%          10%          10%          10%          10%
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                   Other Technologies
--------------------------------------------------------------------------------------------------------------------------------------------------------
Predictive Cruise Control..........          20%          20%          20%          20%          20%          20%          20%          20%          20%
Automated Tire Inflation System....          20%          20%          20%          20%          20%          20%          20%          20%          20%
Tire Pressure Monitoring System....          20%          20%          20%          20%          20%          20%          20%          20%          20%
Neutral Coast......................           0%           0%           0%           0%           0%           0%           0%           0%           0%
--------------------------------------------------------------------------------------------------------------------------------------------------------

                        Table III-14--Technology Adoption Rates for Class 7 and 8 Tractors for Determining the 2024 MY Standards
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                    Class 7                                                    Class 8
                                    --------------------------------------------------------------------------------------------------------------------
                                                    Day cab                                Day cab                              Sleeper cab
                                    --------------------------------------------------------------------------------------------------------------------
                                       Low roof     Mid roof    High roof     Low roof     Mid roof    High roof     Low roof     Mid roof    High roof
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                         Engine
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                     2024 MY 11L  2024 MY 11L  2024 MY 11L  2024 MY 15L  2024 MY 15L  2024 MY 15L  2024 MY 15L  2024 MY 15L  2024 MY 15L
                                      engine 350   engine 350   engine 350   engine 455   engine 455   engine 455   engine 455   engine 455   engine 455
                                          HP           HP           HP           HP           HP           HP           HP           HP           HP
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                      Aerodynamics
--------------------------------------------------------------------------------------------------------------------------------------------------------
Bin I..............................           0%           0%           0%           0%           0%           0%           0%           0%           0%
Bin II.............................          20%          20%           0%          20%          20%           0%          20%          20%           0%
Bin III............................          60%          60%          40%          60%          60%          40%          60%          60%          40%
Bin IV.............................          20%          20%          40%          20%          20%          40%          20%          20%          40%
Bin V..............................           0%           0%          20%           0%           0%          20%           0%           0%          20%
Bin VI.............................           0%           0%           0%           0%           0%           0%           0%           0%           0%
Bin VII............................           0%           0%           0%           0%           0%           0%           0%           0%           0%
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                       Steer Tires
--------------------------------------------------------------------------------------------------------------------------------------------------------
Base...............................           5%           5%           5%           5%           5%           5%           5%           5%           5%
Level 1............................          25%          25%          15%          25%          25%          15%          25%          25%          15%
Level 2............................          55%          55%          60%          55%          55%          60%          55%          55%          60%
Level 3............................          15%          15%          20%          15%          15%          20%          15%          15%          20%
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                       Drive Tires
--------------------------------------------------------------------------------------------------------------------------------------------------------
Base...............................          10%          10%           5%          10%          10%           5%          10%          10%           5%
Level 1............................          25%          25%          15%          25%          25%          15%          25%          25%          15%
Level 2............................          65%          65%          60%          65%          65%          60%          65%          65%          60%
Level 3............................           0%           0%          20%           0%           0%          20%           0%           0%          20%
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                     Idle Reduction
--------------------------------------------------------------------------------------------------------------------------------------------------------
Tamper Proof AESS..................          N/A          N/A          N/A          N/A          N/A          N/A           0%           0%           0%
Tamper Proof AESS with Diesel APU..          N/A          N/A          N/A          N/A          N/A          N/A           0%           0%           0%
Tamper Proof AESS with Battery APU.          N/A          N/A          N/A          N/A          N/A          N/A           0%           0%           0%
Tamper Proof AESS with Automatic             N/A          N/A          N/A          N/A          N/A          N/A           0%           0%           0%
 Stop-Start........................
Tamper Proof AESS with FOH.........          N/A          N/A          N/A          N/A          N/A          N/A           0%           0%           0%
Adjustable AESS....................          N/A          N/A          N/A          N/A          N/A          N/A          30%          30%          30%
Adjustable AESS with Diesel APU....          N/A          N/A          N/A          N/A          N/A          N/A          40%          40%          40%
Adjustable AESS with Battery APU...          N/A          N/A          N/A          N/A          N/A          N/A          10%          10%          10%
Adjustable AESS with Automatic Stop-         N/A          N/A          N/A          N/A          N/A          N/A          10%          10%          10%
 Start.............................
Adjustable AESS with FOH...........          N/A          N/A          N/A          N/A          N/A          N/A          10%          10%          10%
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                      Transmission
--------------------------------------------------------------------------------------------------------------------------------------------------------
Manual.............................           0%           0%           0%           0%           0%           0%           0%           0%           0%
AMT................................          50%          50%          50%          50%          50%          50%          50%          50%          50%
Auto...............................          20%          20%          20%          20%          20%          20%          20%          20%          20%

Dual Clutch........................          10%          10%          10%          10%          10%          10%          10%          10%          10%
Top Gear Direct Drive..............          50%          50%          50%          50%          50%          50%          50%          50%          50%
Trans. Efficiency..................          40%          40%          40%          40%          40%          40%          40%          40%          40%
Neutral Idle.......................          20%          20%          20%          20%          20%          20%          20%          20%          20%
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                        Driveline
--------------------------------------------------------------------------------------------------------------------------------------------------------
Axle Efficiency....................          65%          65%          65%          65%          65%          65%          65%          65%          65%
6x2, 6x4 Axle Disconnect or 4x2              N/A          N/A          N/A          25%          25%          25%          25%          25%          25%
 Axle..............................
Downspeed (Rear Axle Ratio)........         3.31         3.31         3.31         3.31         3.31         3.31         3.26         3.26         3.26
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                 Accessory Improvements
--------------------------------------------------------------------------------------------------------------------------------------------------------
A/C Efficiency.....................          20%          20%          20%          20%          20%          20%          20%          20%          20%
Electric Access....................          20%          20%          20%          20%          20%          20%          20%          20%          20%
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                   Other Technologies
--------------------------------------------------------------------------------------------------------------------------------------------------------
Predictive Cruise Control..........          40%          40%          40%          40%          40%          40%          40%          40%          40%
Automated Tire Inflation System....          25%          25%          25%          25%          25%          25%          25%          25%          25%
Tire Pressure Monitoring System....          50%          50%          50%          50%          50%          50%          50%          50%          50%
Neutral Coast......................           0%           0%           0%           0%           0%           0%           0%           0%           0%
--------------------------------------------------------------------------------------------------------------------------------------------------------

                        Table III-15--Technology Adoption Rates for Class 7 and 8 Tractors for Determining the 2027 MY Standards
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                    Class 7                                                    Class 8
                                    --------------------------------------------------------------------------------------------------------------------
                                                    Day cab                                Day cab                              Sleeper cab
                                    --------------------------------------------------------------------------------------------------------------------
                                       Low roof     Mid roof    High roof     Low roof     Mid roof    High roof     Low roof     Mid roof    High roof
--------------------------------------------------------------------------------------------------------------------------------------------------------
Engine
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                     2027 MY 11L  2027 MY 11L  2027 MY 11L  2027 MY 15L  2027 MY 15L  2027 MY 15L  2027 MY 15L  2027 MY 15L  2027 MY 15L
                                      Engine 350   Engine 350   Engine 350   Engine 455   Engine 455   Engine 455   Engine 455   Engine 455   Engine 455
                                          HP           HP           HP           HP           HP           HP           HP           HP           HP
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                      Aerodynamics
--------------------------------------------------------------------------------------------------------------------------------------------------------
Bin I..............................           0%           0%           0%           0%           0%           0%           0%           0%           0%
Bin II.............................          20%          20%           0%          20%          20%           0%          20%          20%           0%
Bin III............................          50%          50%          30%          50%          60%          30%          40%          50%          20%
Bin IV.............................          30%          30%          30%          30%          20%          30%          40%          30%          30%
Bin V..............................           0%           0%          40%           0%           0%          40%           0%           0%          50%
Bin VI.............................           0%           0%           0%           0%           0%           0%           0%           0%           0%
Bin VII............................           0%           0%           0%           0%           0%           0%           0%           0%           0%
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                       Steer Tires
--------------------------------------------------------------------------------------------------------------------------------------------------------
Base...............................           5%           5%           5%           5%           5%           5%           5%           5%           5%
Level 1............................          20%          20%          10%          20%          20%          10%          20%          20%          10%
Level 2............................          50%          50%          50%          50%          50%          50%          50%          50%          50%
Level 3............................          25%          25%          35%          25%          25%          35%          25%          25%          35%
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                       Drive Tires
--------------------------------------------------------------------------------------------------------------------------------------------------------
Base...............................           5%           5%           5%           5%           5%           5%           5%           5%           5%
Level 1............................          10%          10%          10%          10%          10%          10%          10%          10%          10%
Level 2............................          85%          85%          50%          85%          85%          50%          85%          85%          50%
Level 3............................           0%           0%          35%           0%           0%          35%           0%           0%          35%
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                     Idle Reduction
--------------------------------------------------------------------------------------------------------------------------------------------------------
Tamper Proof AESS..................          N/A          N/A          N/A          N/A          N/A          N/A           0%           0%           0%
Tamper Proof AESS with Diesel APU..          N/A          N/A          N/A          N/A          N/A          N/A           0%           0%           0%
Tamper Proof AESS with Battery APU.          N/A          N/A          N/A          N/A          N/A          N/A           0%           0%           0%
Tamper Proof AESS with Automatic             N/A          N/A          N/A          N/A          N/A          N/A           0%           0%           0%
 Stop-Start........................
Tamper Proof AESS with FOH.........          N/A          N/A          N/A          N/A          N/A          N/A           0%           0%           0%
Adjustable AESS....................          N/A          N/A          N/A          N/A          N/A          N/A          15%          15%          15%
Adjustable AESS with Diesel APU....          N/A          N/A          N/A          N/A          N/A          N/A          40%          40%          40%

Adjustable AESS with Battery APU...          N/A          N/A          N/A          N/A          N/A          N/A          15%          15%          15%
Adjustable AESS with Automatic Stop-         N/A          N/A          N/A          N/A          N/A          N/A          15%          15%          15%
 Start.............................
Adjustable AESS with FOH...........          N/A          N/A          N/A          N/A          N/A          N/A          15%          15%          15%
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                      Transmission
--------------------------------------------------------------------------------------------------------------------------------------------------------
Manual.............................           0%           0%           0%           0%           0%           0%           0%           0%           0%
AMT................................          50%          50%          50%          50%          50%          50%          50%          50%          50%
Auto...............................          30%          30%          30%          30%          30%          30%          30%          30%          30%
Dual Clutch........................          10%          10%          10%          10%          10%          10%          10%          10%          10%
Top Gear Direct Drive..............          50%          50%          50%          50%          50%          50%          50%          50%          50%
Trans. Efficiency..................          70%          70%          70%          70%          70%          70%          70%          70%          70%
Neutral Idle.......................          30%          30%          30%          30%          30%          30%          30%          30%          30%
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                        Driveline
--------------------------------------------------------------------------------------------------------------------------------------------------------
Axle Efficiency....................          80%          80%          80%          80%          80%          80%          80%          80%          80%
6x2, 6x4 Axle Disconnect or 4x2              N/A          N/A          N/A          30%          30%          30%          30%          30%          30%
 Axle..............................
Downspeed (Rear Axle Ratio)........         3.21         3.21         3.21         3.21         3.21         3.21         3.16         3.16         3.16
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                 Accessory Improvements
--------------------------------------------------------------------------------------------------------------------------------------------------------
A/C Efficiency.....................          30%          30%          30%          30%          30%          30%          30%          30%          30%
Electric Access....................          30%          30%          30%          30%          30%          30%          30%          30%          30%
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                   Other Technologies
--------------------------------------------------------------------------------------------------------------------------------------------------------
Predictive Cruise Control..........          40%          40%          40%          40%          40%          40%          40%          40%          40%
Automated Tire Inflation System....          30%          30%          30%          30%          30%          30%          30%          30%          30%
Tire Pressure Monitoring System....          70%          70%          70%          70%          70%          70%          70%          70%          70%
Neutral Coast......................           0%           0%           0%           0%           0%           0%           0%           0%           0%
--------------------------------------------------------------------------------------------------------------------------------------------------------

(e) Adoption Rates Used To Set the Heavy-Haul Tractor Standards
    The agencies recognize that certain technologies used to determine
the stringency of the Phase 2 tractor standards are less applicable to
heavy-haul tractors. Heavy-haul tractors are not typically used in the
same manner as long-haul tractors with extended highway driving, and
therefore will experience less benefit from aerodynamics. Aerodynamic
technologies are very effective at reducing the fuel consumption and
GHG emissions of tractors, but only when traveling at highway speeds.
At lower speeds, the aerodynamic technologies may have a detrimental
impact due to the potential of added weight. The agencies therefore
proposed not considering the use of aerodynamic technologies in the
development of the Phase 2 heavy-haul tractor standards. Moreover,
because aerodynamics will not play a role in the heavy-haul standards,
the agencies proposed to combine all of the heavy-haul tractor cab
configurations (day and sleeper) and roof heights (low, mid, and high)
into a single heavy-haul tractor subcategory. We welcomed comment on
this approach. 80 FR 40233.
    The agencies received comments regarding the applicability of
aerodynamic technologies on heavy-haul vehicles. Daimler commented that
heavy-haul vehicles are designed to meet high cooling needs, therefore
have large radiators and grilles, and are not designed primarily for
hauling standard trailers on the highway. Daimler also stated that
these vehicles are designed to operate off-road or on difficult
terrain, which also limits the application of aerodynamic fairings, and
that requiring aerodynamic improvements on these vehicles, may
compromise the vehicles' work. EMA supported the agencies' proposed
approach of not requiring the use of aerodynamic technologies as a
component of the proposed Phase 2 heavy-haul tractor standards. EMA
stated that those vehicles are already quite heavy (by virtue of need),
are designed to meet high-cooling needs (thus having, for example,
large grilles), and generally are not designed for hauling standard
trailers on highways. EMA also stated that those vehicles are often
designed to be capable of operation off-road or on difficult terrain.
Volvo supported the addition of a heavy-haul subcategory since heavy-
haul tractors require large engines and increased cooling capacity that
limits aerodynamic improvements. Volvo also stated the most heavy-haul
rigs have some requirement for off-road access to pick up machinery,
bulk goods, and unusual loads that also inhibit aerodynamic
improvements. These comments largely echo the agencies' own concerns
voiced at proposal. After considering these comments, the agencies are
using a technology package that does not use aerodynamic improvements
in setting the Phase 2 heavy-haul tractor standards, as we
proposed.\289\
---------------------------------------------------------------------------

    \289\ Since aerodynamic improvements are not part of the
technology package, the agencies likewise are not adopting any aero
bin structure for the heavy-haul tractor subcategory.
---------------------------------------------------------------------------

    Certain powertrain and drivetrain components are also impacted
during the design of a heavy-haul tractor,

including the transmission, axles, and the engine. Heavy-haul tractors
typically require transmissions with 13 or 18 speeds to provide the
ratio spread to ensure that the tractor is able to start pulling the
load from a stop. Downspeed powertrains are typically not an option for
heavy-haul operations because these vehicles require more torque to
move the vehicle because of the heavier load. Finally, due to the
loading requirements of the vehicle, it is not likely that a 6x2 axle
configuration can be used in heavy-haul applications. We requested
comments on all aspects of our heavy-haul tractor technology packages.
80 FR 40233.
    We received comments from stakeholders about the application of
technologies other than aerodynamics for heavy-haul tractors. Daimler
commented that the low rolling resistance levels in the NPRM are overly
aggressive because heavy-haul tractors require unusually high traction
and stopping power. Daimler agreed with the agencies' assessment in the
NPRM that did not include weight reduction because these vehicles
require strong frames and axles to carry heavy loads. Volvo commented
that heavy-haul tractors would not likely be able to utilize current
SmartWay tires; would see no benefit from predictive cruise; sometimes
utilize an auxiliary transmission for further reduction or closer
ratios; and nearly all heavy-haul tractors have deeper drive axle
ratios than the agencies assumed in the NPRM. After considering these
comments and the information regarding the tire rolling resistance
improvement opportunities, discussed in Section III.D.1.b.iii, the
agencies have adjusted the adoption rate of low rolling resistance
tires. Consistent with the changes made in the final rule for the
adoption of low rolling resistance tires in low and mid roof tractors,
the agencies did not project any adoption of Level 3 tires for heavy-
haul tractors in the final rule.
    Allison commented that AMTs in the NPRM receive a 1.8 percent
credit in GEM for heavy-haul tractors, yet there is no similar credit
for ATs. Allison commented that since ATs offer similar, if not
greater, benefits, they should also receive credit and that neutral-
idle recognition should be available. The final version of Phase 2 GEM
treats ATs and AMTs the same for heavy-haul tractors as for the other
tractors.
    The agencies used the following heavy-haul tractor adoption rates
for developing the final Phase 2 2021, 2024, and 2027 MY standards, as
shown in Table III-16.

                        Table III-16--Application Rates for Heavy-Haul Tractor Standards
                                     [Heavy-haul tractor application rates]
----------------------------------------------------------------------------------------------------------------
                                               2021 MY                  2024 MY                  2027 MY
                                      --------------------------------------------------------------------------
                Engine                 2021 MY 15L engine with  2024 MY 15L engine with  2027 MY 15L engine with
                                            600 HP with 2%          600 HP with 4.2%         600 HP with 5.4%
                                        reduction over 2018 MY   reduction over 2018 MY   reduction over 2018 MY
----------------------------------------------------------------------------------------------------------------
                                                Aerodynamics--0%
----------------------------------------------------------------------------------------------------------------
                                                   Steer Tires
----------------------------------------------------------------------------------------------------------------
Phase 1 Baseline:                                          15%                      10%                       5%
    Level I..........................                      35%                      30%                      10%
    Level 2..........................                      50%                      60%                      85%
    Level 3..........................                       0%                       0%                       0%
----------------------------------------------------------------------------------------------------------------
                                                   Drive Tires
----------------------------------------------------------------------------------------------------------------
Phase 1 Baseline:                                          15%                      10%                       5%
    Level I..........................                      35%                      30%                      10%
    Level 2..........................                      50%                      60%                      85%
    Level 3..........................                       0%                       0%                       0%
----------------------------------------------------------------------------------------------------------------
                                                  Transmission
----------------------------------------------------------------------------------------------------------------
AMT..................................                      40%                      50%                      50%
Automatic with Neutral Idle..........                      10%                      20%                      20%
DCT..................................                       5%                      10%                      10%
----------------------------------------------------------------------------------------------------------------
                                               Other Technologies
----------------------------------------------------------------------------------------------------------------
6x2 Axle.............................                       0%                       0%                       0%
Transmission Efficiency..............                      20%                      40%                      70%
Axle Efficiency......................                      30%                      65%                      80%
Predictive Cruise Control............                      20%                      40%                      40%
Accessory Improvements...............                      10%                      20%                      20%
Air Conditioner Efficiency                                 10%                      20%                      20%
 Improvements........................
Automatic Tire Inflation Systems.....                      20%                      25%                      30%
Tire Pressure Monitoring System......                      20%                      50%                      70%
----------------------------------------------------------------------------------------------------------------

    The agencies are also adopting in Phase 2 provisions that allow the
manufacturers to meet an optional heavy Class 8 tractor standard that
reflects both aerodynamic improvements, along with the powertrain
requirements that go along with higher GCWR. Table III-17 reflects the
adoption rates for each of the technologies for each of the
subcategories in MY 2021. The technology packages closely reflect those
in the primary Class 8 tractor program. The exceptions include less
aggressive targets for low rolling

resistance tires, no 6x2 axle adoption rates, and no downspeeding due
to the heavier loads of these vehicles.

        Table III-17--Adoption Rates Used To Develop the 2021 MY Optional Heavy Class 8 Tractor Standards
                           [Optional heavy class 8 tractor application rates--2021 MY]
----------------------------------------------------------------------------------------------------------------
                                                   Low/mid roof    High roof day   Low/mid roof      High roof
                                                      day cab           cab         sleeper cab     sleeper cab
                                                 ---------------------------------------------------------------
                     Engine                         2021 MY 15L     2021 MY 15L     2021 MY 15L     2021 MY 15L
                                                    Engine with     Engine with     Engine with     Engine with
                                                      600 HP          600 HP          600 HP          600 HP
----------------------------------------------------------------------------------------------------------------
                                                  Aerodynamics
----------------------------------------------------------------------------------------------------------------
Bin I...........................................             10%              0%             10%              0%
Bin II..........................................             10%              0%             10%              0%
Bin III.........................................             70%             60%             70%             60%
Bin IV..........................................             10%             35%             10%             30%
Bin V...........................................              0%              5%              0%             10%
Bin VI..........................................              0%              0%              0%              0%
Bin VII.........................................              0%              0%              0%              0%
----------------------------------------------------------------------------------------------------------------
                                                   Steer Tires
----------------------------------------------------------------------------------------------------------------
Phase 1 Baseline                                             10%              5%             10%              5%
Level I.........................................             25%             35%             25%             35%
Level 2.........................................             65%             60%             65%             60%
Level 3.........................................              0%              0%              0%              0%
----------------------------------------------------------------------------------------------------------------
                                                   Drive Tires
----------------------------------------------------------------------------------------------------------------
Phase 1 Baseline                                             20%             10%             20%             10%
Level I.........................................             40%             30%             40%             30%
Level 2.........................................             40%             60%             40%             60%