existing engines with minor or moderate changes to the engines, but
many engine technologies require an entirely new engine architecture.
    We divide engine technologies into two categories, ``basic engine
technologies'' and ``advanced engine technologies.'' ``Basic engine
technologies'' refer to technologies adaptable to an existing engine
with minor or moderate changes to the engine. ``Advanced engine
technologies'' refer to technologies that generally require significant
changes or an entirely new engine architecture. The words ``basic'' and
``advanced'' are not meant to confer any information about the level of
sophistication of the technology. Many advanced engine technology
definitions also include some basic engine technologies, and these
basic technologies are accounted for in the costs and effectiveness
values of the advance engine. Figure III-7 shows how the basic and
other engines are laid out on pathways evaluated in the compliance
simulation. Each engine technology is briefly described, below. It is
important to note the ``Basic Engine Path'' shows that every engine
starts with VVT and can add one, some, or all the technologies in the
dotted box, as discussed in Section III.D.1.a)(1).
[GRAPHIC] [TIFF OMITTED] TP03SE21.046

(1) Basic Engines
    In the CAFE Model, basic engine technologies may be applied
individually or in combination with other basic engine technologies.
The basic engine technologies include variable valve timing (VVT),
variable valve lift (VVL), stoichiometric gasoline direct injection
(SGDI), and cylinder deactivation. Cylinder deactivation includes a
basic level (DEAC) and an advanced level (ADEAC). DOT applies the basic
engine technologies across two engine architectures: dual over-head
camshaft (DOHC) engine architecture and single over-head camshaft
(SOHC) engine architecture.
    VVT: Variable valve timing is a family of valve-train designs that
dynamically adjusts the timing of the intake valves, exhaust valves, or
both, in relation to piston position. VVT can reduce pumping losses,
provide increased engine torque and horsepower over a broad engine
operating range, and allow unique operating modes, such as Atkinson
cycle operation, to further enhance efficiency.\109\ VVT is nearly
universally used in the MY 2020 fleet. VVT enables more control of in-
cylinder

air flow for exhaust scavenging and combustion relative to fixed valve
timing engines. Engine parameters such as volumetric efficiency,
effective compression ratio, and internal exhaust gas recirculation
(iEGR) can all be enabled and accurately controlled by a VVT system.
---------------------------------------------------------------------------

    \109\ 2015 NAS report, at 31.
---------------------------------------------------------------------------

    VVL: Variable valve lift dynamically adjusts the distance a valve
travels from the valve seat. The dynamic adjustment can optimize
airflow over a broad range of engine operating conditions. The
technology can increase effectiveness by reducing pumping losses and by
affecting the fuel and air mixture motion and combustion in-
cylinder.\110\ VVL is less common in the MY 2020 fleet than VVT, but
still prevalent. Some manufacturers have implemented a limited,
discrete approach to VVL. The discrete approach allows only limited
(e.g., two) valve lift profiles versus allowing a continuous range of
lift profiles.
---------------------------------------------------------------------------

    \110\ 2015 NAS report, at 32.
---------------------------------------------------------------------------

    SGDI: Stoichiometric gasoline direct injection sprays fuel at high
pressure directly into the combustion chamber, which provides cooling
of the in-cylinder charge via in-cylinder fuel vaporization to improve
spark knock tolerance and enable an increase in compression ratio and/
or more optimal spark timing for improved efficiency.\111\ SGDI is
common in the MY 2020 fleet, and the technology is used in many
advanced engines as well.
---------------------------------------------------------------------------

    \111\ 2015 NAS report, at 34.
---------------------------------------------------------------------------

    DEAC: Basic cylinder deactivation disables intake and exhaust
valves and turns off fuel injection for the deactivated cylinders
during light load operation. DEAC is characterized by a small number of
discrete operating configurations.\112\ The engine runs temporarily as
though it were a smaller engine, reducing pumping losses and improving
efficiency. DEAC is present in the MY 2020 baseline fleet.
---------------------------------------------------------------------------

    \112\ 2015 NAS report, at 33.
---------------------------------------------------------------------------

    ADEAC: Advanced cylinder deactivation systems, also known as
rolling or dynamic cylinder deactivation systems, allow a further
degree of cylinder deactivation than the base DEAC. ADEAC allows the
engine to vary the percentage of cylinders deactivated and the sequence
in which cylinders are deactivated, essentially providing
``displacement on demand'' for low load operations. A small number of
vehicles have ADEAC in the MY 2020 baseline fleet.
    Section III.D.1.d) contains additional information about each basic
engine technology used in this analysis, including information about
the engine map models used in the full vehicle technology effectiveness
modeling.
(2) Advanced Engines
    DOT defines advanced engine technologies in the analysis as
technologies that require significant changes in engine structure, or
an entirely new engine architecture.\113\ The advanced engine
technologies represent the application of alternate combustion cycles
or changes in the application of forced induction to the engine. Each
advanced engine technology has a discrete pathway for progression to
improved versions of the technology, as seen above in Figure III-7. The
advanced engine technology pathways include a turbocharged pathway, a
high compression ratio (Atkinson) engine pathway, a variable turbo
geometry (Miller Cycle) engine pathway, a variable compression ratio
pathway, and a diesel engine pathway. Although the CAFE Model includes
a compressed natural gas (CNG) pathway, that technology is a baseline-
only technology and was not included in the analysis; currently, there
are no dedicated CNG vehicles in the MY 2020 analysis fleet.
---------------------------------------------------------------------------

    \113\ Examples of this include but are not limited to changes in
cylinder count, block geometry or combustion cycle changes.
---------------------------------------------------------------------------

    TURBO: Forced induction engines, or turbocharged downsized engines,
are characterized by technology that can create greater-than-
atmospheric pressure in the engine intake manifold when higher output
is needed. The raised pressure results in an increased amount of
airflow into the cylinder supporting combustion, increasing the
specific power of the engine. Increased specific power means the engine
can generate more power per unit of cylinder volume. The higher power
per cylinder volume allows the overall engine volume to be reduced,
while maintaining performance. The overall engine volume decrease
results in an increase in fuel efficiency by reducing parasitic loads
associated with larger engine volumes.\114\
---------------------------------------------------------------------------

    \114\ 2015 NAS report, at 34.
---------------------------------------------------------------------------

    Cooled exhaust gas recirculation is also part of the advanced
forced induction technology path. The basic recycling of exhaust gases
using VVT is called internal EGR (iEGR) and is included as part of the
performance improvements provided by the VVT basic engine technology.
Cooled EGR (cEGR) is a second method for diluting the incoming air that
takes exhaust gases, passes them through a heat exchanger to reduce
their temperature, and then mixes them with incoming air in the intake
manifold.\115\ As discussed in Section III.D.1.d), many advanced engine
maps include EGR.
---------------------------------------------------------------------------

    \115\ 2015 NAS report, at 35.
---------------------------------------------------------------------------

    Five levels of turbocharged engine downsizing technologies are
considered in this analysis: A `basic' level of turbocharged downsized
technology (TURBO1), an advanced turbocharged downsized technology
(TURBO2), an advanced turbocharged downsized technology with cooled
exhaust gas recirculation applied (cEGR), a turbocharged downsized
technology with basic cylinder deactivation applied (TURBOD), and a
turbocharged downsized technology with advanced cylinder deactivation
applied (TURBOAD).
    HCR: Atkinson engines, or high compression ratio engines, represent
a class of engines that achieve a higher level of fuel efficiency by
implementing an alternate combustion cycle.\116\ Historically, the Otto
combustion cycle has been used by most gasoline-based spark ignition
engines. Increased research into improving fuel economy has resulted in
the development of alternate combustion cycles that allow for greater
levels of thermal efficiency. One such alternative combustion cycle is
the Atkinson cycle. Atkinson cycle operation is achieved by allowing
the expansion stroke of the engine to overextend allowing the
combustion products to achieve the lowest possible pressure before the
exhaust stroke.117 118 119
---------------------------------------------------------------------------

    \116\ See the 2015 NAS report, Appendix D, for a short
discussion on thermodynamic engine cycles.
    \117\ Otto cycle is a four-stroke cycle that has four piston
movements over two engine revolutions for each cycle. First stroke:
Intake or induction; seconds stroke: Compression; third stroke:
Expansion or power stroke; and finally, fourth stroke: Exhaust.
    \118\ Compression ratio is the ratio of the maximum to minimum
volume in the cylinder of an internal combustion engine.
    \119\ Expansion ratio is the ratio of maximum to minimum volume
in the cylinder of an IC engine when the valves are closed (i.e.,
the piston is traveling from top to bottom to produce work).
---------------------------------------------------------------------------

    Descriptions of Atkinson cycle engines and Atkinson mode or
Atkinson-enabled engine technologies have been used interchangeably in
association with high compression ratio (HCR) engines, for past
rulemaking analyses. Both technologies achieve a higher thermal
efficiency than traditional Otto cycle-only engines, however, the two
engine types operate differently. For purposes of this analysis,
Atkinson technologies can be categorized into two groups to reduce
confusion: (1) Atkinson-enabled engines and (2) Atkinson engines.
    Atkinson-enabled engines, or high compression ratio engines (HCR),

dynamically swing between operating closer to an Otto cycle or an
Atkinson cycle based on engine loads. During high loads the engine will
use the lower-efficiency, power-dense Otto cycle mode, while at low
loads the engine will use the higher-efficiency, lower power-dense
Atkinson cycle mode. The hybrid combustion cycle operation is used to
address the low power density issues that can limit the Atkinson-only
engine and allow for a wider application of the technology.
    The level of efficiency improvement experienced by a vehicle
employing Atkinson cycle operation is directly related to how much of
the engine's operation time is spent in Atkinson mode. Vehicles that
can experience operation at a high load for long portions of their
operating cycle will see little to no benefit from this technology.
This limitation to performance results in manufacturers typically
limiting the application of this technology to vehicles with a use
profile that can take advantage of the technology's behavior.
    Three HCR or Atkinson-enabled engines are available in the
analysis: (1) The baseline Atkinson-enabled engine (HCR0), (2) the
enhanced Atkinson enabled engine (HCR1), and finally, (3) the enhanced
Atkinson enabled engine with cylinder deactivation (HCR1D).
    In contrast, Atkinson engines in this analysis are defined as
engines that operate full-time in the Atkinson cycle. The most common
method of achieving Atkinson operation is the use of late intake valve
closing. This method allows backflow from the combustion chamber into
the intake manifold, reducing the dynamic compression ratio, and
providing a higher expansion ratio. The higher expansion ratio improves
thermal efficiency but reduces power density. The low power density
generally relegates these engines to hybrid vehicle (SHEVPS)
applications only in this analysis. Coupling the engines to electric
motors and significantly reducing road loads can compensate for the
lower power density and maintain desired performance levels for the
vehicle.\120\ The Toyota Prius is an example of a vehicle that uses an
Atkinson engine. The 2017 Toyota Prius achieved a peak thermal
efficiency of 40 percent.\121\
---------------------------------------------------------------------------

    \120\ Toyota. ``Under the Hood of the All-new Toyota Prius.''
Oct. 13, 2015. Available at https://global.toyota/en/detail/9827044.
Last accessed Nov. 22, 2019.
    \121\ Matsuo, S., Ikeda, E., Ito, Y., and Nishiura, H., ``The
New Toyota Inline 4 Cylinder 1.8L ESTEC 2ZR-FXE Gasoline Engine for
Hybrid Car,'' SAE Technical Paper 2016-01-0684, 2016, https://doi.org/10.4271/2016-01-0684.
---------------------------------------------------------------------------

    NHTSA seeks comment on whether and how to consider ``HCR2'' in the
analysis for the final rule.
    VTG: The Miller cycle is another type of overexpansion combustion
cycle, similar to the Atkinson cycle. The Miller cycle, however,
operates in combination with a forced induction system that helps
address the impacts of reduced power density during high load operating
conditions. Miller cycle-enabled engines use a similar technology
approach as seen in Atkinson-enabled engines to effectively create an
expanded expansion stroke of the combustion cycle.
    In the analysis, the baseline Miller cycle-enabled engine includes
the application of a variable turbo geometry technology (VTG). The
advanced Miller cycle enabled system includes the application of a 48V-
based electronic boost system (VTGE). VTG technology allows the system
to vary boost level based on engine operational needs. The use of a
variable geometry turbocharger also supports the use of cooled exhaust
gas recirculation.\122\ An electronic boost system has an electric
motor added to assist a turbocharger at low engine speeds. The motor
assist mitigates turbocharger lag and low boost pressure at low engine
speeds. The electronic assist system can provide extra boost needed to
overcome the torque deficits at low engine speeds.\123\
---------------------------------------------------------------------------

    \122\ 2015 NAS report, at 116.
    \123\ 2015 NAS report, at 62.
---------------------------------------------------------------------------

    VCR: Variable compression ratio (VCR) engines work by changing the
length of the piston stroke of the engine to optimize the compression
ratio and improve thermal efficiency over the full range of engine
operating conditions. Engines using VCR technology are currently in
production, but appear to be targeted primarily towards limited
production, high performance applications. Nissan is the only
manufacturer to use this technology in the MY 2020 baseline fleet. Few
manufacturers and suppliers provided information about VCR
technologies, and DOT reviewed several design concepts that could
achieve a similar functional outcome. In addition to design concept
differences, intellectual property ownership complicates the ability to
define a VCR hardware system that could be widely adopted across the
industry. Because of these issues, adoption of the VCR engine
technology is limited to Nissan only.
    ADSL: Diesel engines have several characteristics that result in
superior fuel efficiency over traditional gasoline engines. These
advantages include reduced pumping losses due to lack of (or greatly
reduced) throttling, high pressure direct injection of fuel, a more
efficient combustion cycle,\124\ and a very lean air/fuel mixture
relative to an equivalent-performance gasoline engine.\125\ However,
diesel technologies require additional enablers, such as a NOx
adsorption catalyst system or a urea/ammonia selective catalytic
reduction system, for control of NOx emissions.
---------------------------------------------------------------------------

    \124\ Diesel cycle is also a four-stroke cycle like the Otto
Cycle, except in the intake stroke no fuel is injected and fuel is
injected late in the compression stroke at higher pressure and
temperature.
    \125\ See the 2015 NAS report, Appendix D, for a short
discussion on thermodynamic engine cycles.
---------------------------------------------------------------------------

    DOT considered three levels of diesel engine technology: the
baseline diesel engine technology (ADSL) is based on a standard 2.2L
turbocharged diesel engine; the more advanced diesel engine (DSLI)
starts with the ADSL system and incorporates a combination of low
pressure and high pressure EGR, reduced parasitic loss, friction
reduction, a highly-integrated exhaust catalyst with low temp light off
temperatures, and closed loop combustion control; and finally the most
advanced diesel system (DSLIAD) is the DSLI system with advanced
cylinder deactivation technology added.
    EFR: Engine friction reduction technology is a general engine
improvement meant to represent future technologies that reduce the
internal friction of an engine. EFR technology is not available for
application until MY 2023. The future technologies do not significantly
change the function or operation of the engine but reduce the energy
loss due to the rotational or rubbing friction experienced in the
bearings or cylinder during normal operation. These technologies can
include improved surface coatings, lower-tension piston rings, roller
cam followers, optimal thermal management and piston surface
treatments, improved bearing design, reduced inertial loads, improved
materials, or improved geometry.
(b) Engine Analysis Fleet Assignments
    As a first step in assigning baseline levels of engine technologies
in the analysis fleet, DOT used data for each manufacturer to determine
which platforms shared engines. Within each manufacturer's fleet, DOT
assigned unique identification designations (engine codes) based on
configuration, technologies applied, displacement, compression ratio,
and power output. DOT used power output to distinguish between engines
that might have the same displacement and configuration

but significantly different horsepower ratings.
    The CAFE Model identifies leaders and followers for a
manufacturer's vehicles that use the same engine, indicated by sharing
the same engine code. The model automatically determines which engines
are leaders by using the highest sales volume row of the highest sales
volume nameplate that is assigned an engine code. This leader-follower
relationship allows the CAFE Model simulation to maintain engine
sharing as more technology is applied to engines.
    DOT accurately represents each engine using engine technologies and
engine technology classes. The first step is to assign engine
technologies to each engine code. Technology assignment is based on the
identified characteristics of the engine being modeled, and based on
technologies assigned, the engine will be aligned with an engine map
model that most closely corresponds.
    The engine technology classes are a second identifier used to
accurately account for engine costs. The engine technology class is
formatted as number of cylinders followed by the letter C, number of
banks followed by the letter B, and an engine head configuration
designator, which is _SOHC for single overhead cam, _ohv for overhead
valve, or blank for dual overhead cam. As an example, one variant of
the GMC Acadia has a naturally aspirated DOHC inline 4-cylinder engine,
so DOT assigned the vehicle to the `4C1B' engine technology class and
assigned the technology VVT and SGDI. Table III-7 shows examples of
observed engines with their corresponding assigned engine technologies
as well as engine technology classes.
[GRAPHIC] [TIFF OMITTED] TP03SE21.047

    The cost tables for a given engine class include downsizing (to an
engine architecture with fewer cylinders) when turbocharging technology
is applied, and therefore, the turbocharged engines observed in the
2020 fleet (that have already been downsized) often map to an engine
class with more cylinders. For instance, an observed TURBO1 V6 engine
would map to an 8C2B (V8) engine class, because the turbo costs on the
8C2B engine class worksheet assume a V6 (6C2B) engine architecture.
Diesel engines map to engine technology classes that match the observed
cylinder count since naturally aspirated diesel engines are not found
in new light duty vehicles in the U.S. market. Similarly, as indicated
above, the TURBO1 I3 in the Ford Escape maps to the 4C1B_L (I4) engine
class, because the turbo costs on the 4C1B_L engine class worksheet
assume a I3 (3C1B) engine architecture. Some instances can be more
complex, including low horsepower variants for 4-cylinder engines, and
are shown in Table III-8.
    For this analysis, we have allowed additional downsizing beyond
what has been previously modeled. We allow enhanced downsizing because
manufacturers have downsized low output naturally aspirated engines to
turbo engines with smaller architectures than traditionally
observed.126 127 128 To capture this new level of turbo
downsizing we created a new category of low output naturally aspirated
engines, which is only applied to 4-cylinder engines in the MY 2020
fleet. These engines use the costing tabs in the Technologies file with
the `L' designation and are assumed to downsize to turbocharged 3-
cylinder engines for costing purposes. We seek comment regarding the
expected further application of this technology to larger cylinder
count engines, such as 8-cylinder engines that may be turbo

downsized to 4-cylinder engines. We would also like comment on how to
define the characteristic of an engine that may be targeted for
enhanced downsizing.
---------------------------------------------------------------------------

    \126\ Richard Truett, ``GM Brining 3-Cylinder back to North
America.'' Automotive News, December 01, 2019. https://www.autonews.com/cars-concepts/gm-bringing-3-cylinder-back-na.
    \127\ Stoklosa, Alexander, ``2021 Mini Cooper Hardtop.'' Car and
Driver, December 2, 2014. https://www.caranddriver.com/reviews/a15109143/2014-mini-cooper-hardtop-manual-test-review/.
    \128\ Leanse, Alex ``2020 For Escape Options: Hybrid vs. 3-
Cylinder EcoBoost vs. 4-Cylinder EcoBoost.'' MotorTrend, Sept 24,
2019. https://www.motortrend.com/news/2020-ford-escape-engine-options-pros-and-cons-comparison/.
[GRAPHIC] [TIFF OMITTED] TP03SE21.048

    TSD Chapter 3.1.2 includes more details about baseline engine
technology assignment logic, and details about the levels of engine
technology penetration in the MY 2020 fleet.
(c) Engine Adoption Features
    Engine adoption features are defined through a combination of (1)
refresh and redesign cycles, (2) technology path logic, (3) phase-in
capacity limits, and (4) SKIP logic. Figure III-7 above shows the
technology paths available for engines in the CAFE Model. Engine
technology development and application typically results in an engine
design moving from the basic engine tree to one of the advanced engine
trees. Once an engine design moves to the advanced engine tree it is
not allowed to move to alternate advanced engine trees. Specific path
logic, phase-in caps, and SKIP logic applied to each engine technology
are discussed by engine technology, in turn.
    Refresh and redesign cycles dictate when engine technology can be
applied. Technologies applicable only during a platform redesign can be
applied during a platform refresh if another vehicle platform that
shares engine codes (uses the same engine) has already applied the
technology during a redesign. For example, models of the GMC Acadia and
the Cadillac XT4 use the same engine (assigned engine code 112011 in
the Market Data file); if the XT4 adds a new engine technology during a
redesign, then the Acadia may also add the same engine technology
during the next refresh or redesign. This allows the model to maintain
engine sharing relationships while also maintaining refresh and
redesign schedules.\129\ For engine technologies, DOHC, OHV, VVT, and
CNG engine technologies are baseline only, while all other engine
technologies can only be applied at a vehicle redesign.
---------------------------------------------------------------------------

    \129\ See Section III.C.2.a) for more discussion on platform
refresh and redesign cycles.
---------------------------------------------------------------------------

    Basic engine technologies in the CAFE Model are represented by four
technologies: VVT, VVL, SGDI, and DEAC. DOT assumes that 100% of basic
engine platforms use VVT as a baseline, based on wide proliferation of
the technology in the U.S. fleet. The remaining three technologies,
VVL, SGDI, and DEAC, can all be applied individually or in any
combination of the three. An engine can jump from the basic engines
path to any other engine path except the Alternative Fuel Engine Path.
    Turbo downsizing allows manufacturers to maintain vehicle
performance characteristics while reducing engine displacement and
cylinder count. Any basic engine can adopt one of the turbo engine
technologies (TURBO1, TURBO2 and CEGR1). Vehicles that have
turbocharged engines in the baseline fleet will stay on the turbo
engine path to prevent unrealistic engine technology change in the
short timeframe considered in the rulemaking analysis. Turbo technology
is a mutually exclusive technology in that it cannot be adopted for
HCR, diesel, ADEAC, or CNG engines.
    Non-HEV Atkinson mode engines are a collection of engines in the
HCR engine pathway (HCR0, HCR1, HCR1D and HCR2). Atkinson engines excel
in lower power applications for lower load conditions, such as driving
around a city or steady state highway driving without large payloads,
thus their adoption is more limited than some other technologies. DOT
expanded the availability of HCR technology compared to the 2020 final
rule because of new observed applications in the market.\130\ However,
there are three categories of adoption features specific to the HCR
engine pathway: \131\
---------------------------------------------------------------------------

    \130\ For example, the Hyundai Palisade and Kia Telluride have a
291 hp V6 HCR1 engine. The specification sheets for these vehicles
are located in the docket for this action.
    \131\ See Section III.D.1.d)(1) Engine Maps, for a discussion of
why HCR2 and P2HCR2 were not used in the central analysis. ``SKIP''
logic was used to remove this engine technology from application,
however as discussed below, we maintain HCR2 and P2HCR2 in the model
architecture for sensitivity analysis and for future engine map
model updates.
---------------------------------------------------------------------------

     DOT does not allow vehicles with 405 or more horsepower to
adopt HCR engines due to their prescribed duty cycle being more
demanding and likely not supported by the lower power density found in
HCR-based engines.\132\
---------------------------------------------------------------------------

    \132\ Heywood, John B. Internal Combustion Engine Fundamentals.
McGraw-Hill Education, 2018. Chapter 5.
---------------------------------------------------------------------------

     Pickup trucks and vehicles that share engines with pickup
trucks are

also excluded from receiving HCR engines; the duty cycle for these
heavy vehicles, particularly when hauling cargo or towing, are likely
unable to take full advantage of Atkinson cycle use, and would
ultimately spend the majority of operation as an Otto cycle engine,
negating the benefits of HCR technology.\133\
---------------------------------------------------------------------------

    \133\ This is based on CBI conversation with manufacturers that
currently employ HCR-based technology but saw no benefit when the
technology was applied to truck platforms in their fleet.
---------------------------------------------------------------------------

     HCR engine application is also restricted for some
manufacturers that are heavily performance-focused and have
demonstrated a significant commitment to power dense technologies such
as turbocharged downsizing.\134\
---------------------------------------------------------------------------

    \134\ There are three manufacturers that met the criteria (near
100% turbo downsized fleet, and future hybrid systems are based on
turbo-downsized engines) described and were excluded: BMW, Daimler,
and Jaguar Land Rover.
---------------------------------------------------------------------------

NHTSA seeks comment on the appropriateness of these restrictions for
the final rule.
    Advanced cylinder deactivation technology (ADEAC), or dynamic
cylinder deactivation (e.g., Dynamic Skip Fire), can be applied to any
engine with basic technology. This technology represents a naturally
aspirated engine with ADEAC. Additional technology can be applied to
these engines by moving to the Advanced Turbo Engine Path.
    Miller cycle (VTG and VTGE) engines can be applied to any basic and
turbocharged engine. VTGE technology is enabled by the use of a 48V
system that presents an improvement from traditional turbocharged
engines, and accordingly VTGE includes the application of a mild hybrid
(BISG) system.
    VCR engines can be applied to basic and turbocharged engines, but
the technology is limited to Nissan and Mitsubishi.\135\ VCR technology
requires a complete redesign of the engine, and in the analysis fleet,
only two of Nissan's models had incorporated this technology. The
agency does not believe any other manufacturers will invest to develop
and market this technology in their fleet in the rulemaking time frame.
---------------------------------------------------------------------------

    \135\ Nissan and Mitsubishi are strategic partners and members
of the Renault-Nissan-Mitsubishi Alliance.
---------------------------------------------------------------------------

    Advanced turbo engines are becoming more prevalent as the
technologies mature. TURBOD combines TURBO1 and DEAC technologies and
represents the first advanced turbo. TURBOAD combines TURBO1 and ADEAC
technologies and is the second and last level of advanced turbos.
Engines from either the Turbo Engine Path or the ADEAC Engine Path can
adopt these technologies.
    Any basic engine technologies (VVT, VVL, SGDI, and DEAC) can adopt
ADSL and DSLI engine technologies. Any basic engine and diesel engine
can adopt DSLIAD technology in this analysis; however, DOT applied a
phase in cap and year for this technology at 34 percent and MY 2023,
respectively. In DOT's engineering judgement, this is a rather complex
and costly technology to adopt and it would take significant investment
for a manufacturer to develop. For more than a decade, diesel engine
technologies have been used in less than one percent of the total
light-duty fleet production and have been found mostly on medium and
heavy-duty vehicles.
    Finally, DOT allows the CAFE Model to apply EFR to any engine
technology except for DSLI and DSLIAD. DSLI and DSLIAD inherently have
incorporated engine friction technologies from ADSL. In addition,
friction reduction technologies that apply to gasoline engines cannot
necessarily be applied to diesel engines due to the higher temperature
and pressure operation in diesel engines.
(d) Engine Effectiveness Modeling
    Effectiveness values used for engine technologies were simulated in
two ways. The value was either calculated based on the difference in
full vehicle simulation results created using the Autonomie modeling
tool, or effectiveness values were determined using an alternate
calculation method, including analogous improvement or fuel economy
improvement factors.
(1) Engine Maps
    Most effectiveness values used as inputs for the CAFE Model were
determined by comparing results of full vehicle simulations using the
Autonomie simulation tool. For a full discussion about how Autonomie
was used, see Section III.C.4 and TSD Chapter 2.4, in addition to the
Autonomie model documentation. Engine map models were the primary
inputs used to simulate the effects of different engine technologies in
the Autonomie full vehicle simulations.
    Engine maps provide a three-dimensional representation of engine
performance characteristics at each engine speed and load point across
the operating range of the engine. Engine maps have the appearance of
topographical maps, typically with engine speed on the horizontal axis
and engine torque, power, or brake mean effective pressure (BMEP) \136\
on the vertical axis. A third engine characteristic, such as brake-
specific fuel consumption (BSFC),\137\ is displayed using contours
overlaid across the speed and load map. The contours provide the values
for the third characteristic in the regions of operation covered on the
map. Other characteristics typically overlaid on an engine map include
engine emissions, engine efficiency, and engine power. The engine maps
developed to model the behavior of the engines used in this analysis
are referred to as engine map models.
---------------------------------------------------------------------------

    \136\ Brake mean effective pressure is an engineering measure,
independent of engine displacement, that indicates the actual work
an engine performs.
    \137\ Brake-specific fuel consumption is the rate of fuel
consumption divided by the power being produced.
---------------------------------------------------------------------------

    The engine map models used in this analysis are representative of
technologies that are currently in production or are expected to be
available in the rulemaking timeframe, MYs 2024-2026. The engine map
models were developed to be representative of the performance
achievable across industry for a given technology and are not intended
to represent the performance of a single manufacturer's specific
engine. The broadly representative performance level was targeted
because the same combination of technologies produced by different
manufacturers will have differences in performance, due to
manufacturer-specific designs for engine hardware, control software,
and emissions calibration.
    Accordingly, DOT expects that the engine maps developed for this
analysis will differ from engine maps for manufacturers' specific
engines. However, DOT intends and expects that the incremental changes
in performance modeled for this analysis, due to changes in
technologies or technology combinations, will be similar to the
incremental changes in performance observed in manufacturers' engines
for the same changes in technologies or technology combinations.
    The analysis never applies absolute BSFC levels from the engine
maps to any vehicle model or configuration for the rulemaking analysis.
The absolute fuel economy values from the full vehicle Autonomie
simulations are used only to determine incremental effectiveness for
switching from one technology to another technology. The incremental
effectiveness is applied to the absolute fuel economy of vehicles in
the analysis fleet, which are based on CAFE compliance data. For
subsequent

technology changes, incremental effectiveness is applied to the
absolute fuel economy level of the previous technology configuration.
Therefore, for a technically sound analysis, it is most important that
the differences in BSFC among the engine maps be accurate, and not the
absolute values of the individual engine maps. However, achieving this
can be challenging.
    For this analysis, DOT used a small number of baseline engine
configurations with well-defined BSFC maps, and then, in a very
systematic and controlled process, added specific well-defined
technologies to create a BSFC map for each unique technology
combination. This could theoretically be done through engine or vehicle
testing, but testing would need to be conducted on a single engine, and
each configuration would require physical parts and associated engine
calibrations to assess the impact of each technology configuration,
which is impractical for the rulemaking analysis because of the
extensive design, prototype part fabrication, development, and
laboratory resources that are required to evaluate each unique
configuration. Modeling is an approach used by industry to assess an
array of technologies with more limited testing. Modeling offers the
opportunity to isolate the effects of individual technologies by using
a single or small number of baseline engine configurations and
incrementally adding technologies to those baseline configurations.
This provides a consistent reference point for the BSFC maps for each
technology and for combinations of technologies that enables the
differences in effectiveness among technologies to be carefully
identified and quantified.
    The Autonomie model documentation provides a detailed discussion on
how the engine map models were used as inputs to the full vehicle
simulations performed using the Autonomie tool. The Autonomie model
documentation contains the engine map model topographic figures, and
additional engine map model data can be found in the Autonomie input
files.\138\
---------------------------------------------------------------------------

    \138\ See additional Autonomie supporting materials in docket
number NHTSA-2021-0053 for this proposal.
---------------------------------------------------------------------------

    Most of the engine map models used in this analysis were developed
by IAV GmbH (IAV) Engineering. IAV is one of the world's leading
automotive industry engineering service partners with an over 35-year
history of performing research and development for powertrain
components, electronics, and vehicle design.\139\ The primary outputs
of IAV's work for this analysis are engine maps that model the
operating characteristics of engines equipped with specific
technologies.
---------------------------------------------------------------------------

    \139\ IAV Automotive Engineering, https://www.iav.com/en/.
---------------------------------------------------------------------------

    The generated engine maps were validated against IAV's global
database of benchmarked data, engine test data, single cylinder test
data, prior modeling studies, technical studies, and information
presented at conferences.\140\ The effectiveness values from the
simulation results were also validated against detailed engine maps
produced from the Argonne engine benchmarking programs, as well as
published information from industry and academia, ensuring reasonable
representation of simulated engine technologies.\141\ The engine map
models used in this analysis and their specifications are shown in
Table III-9.
---------------------------------------------------------------------------

    \140\ Friedrich, I., Pucher, H., and Offer, T., ``Automatic
Model Calibration for Engine-Process Simulation with Heat-Release
Prediction,'' SAE Technical Paper 2006-01-0655, 2006, https://doi.org/10.4271/2006-01-0655. Rezaei, R., Eckert, P., Seebode, J.,
and Behnk, K., ``Zero-Dimensional Modeling of Combustion and Heat
Release Rate in DI Diesel Engines,'' SAE Int. J. Engines 5(3):874-
885, 2012, https://doi.org/10.4271/2012-01-1065. Multistage
Supercharging for Downsizing with Reduced Compression Ratio (2015).
MTZ Rene Berndt, Rene Pohlke, Christopher Severin and Matthias
Diezemann IAV GmbH. Symbiosis of Energy Recovery and Downsizing
(2014). September 2014 MTZ Publication Heiko Neukirchner, Torsten
Semper, Daniel Luederitz and Oliver Dingel IAV GmbH.
    \141\ Bottcher,. L, Grigoriadis, P. ``ANL--BSFC map prediction
Engines 22-26.'' IAV (April 30, 2019). 20190430_ANL_Eng 22-26
Updated_Docket.pdf.
---------------------------------------------------------------------------

BILLING CODE 4910-59-P

[GRAPHIC] [TIFF OMITTED] TP03SE21.049

BILLING CODE 4910-59-C
    Two engine map models shown in Table III-9, Eng24 and Eng25, were
not developed as part of the IAV modeling effort and only Eng24 is used
in this

analysis. The Eng24 and Eng25 engine maps are equivalent to the ATK and
ATK2 models developed for the 2016 Draft Technical Assessment Report
(TAR), EPA Proposed Determination, and Final Determination.\142\ The
ATK1 engine model is based directly on the 2.0L 2014 Mazda SkyActiv-G
(ATK) engine. The ATK2 represents an Atkinson engine concept based on
the Mazda engine, adding cEGR, cylinder deactivation, and an increased
compression ratio (14:1). In this analysis, Eng24 and Eng25 correspond
to the HCR1 and HCR2 technologies.
---------------------------------------------------------------------------

    \142\ Ellies, B., Schenk, C., and Dekraker, P., ``Benchmarking
and Hardware-in-the-Loop Operation of a 2014 MAZDA SkyActiv 2.0L
13:1 Compression Ratio Engine,'' SAE Technical Paper 2016-01-1007,
2016, doi:10.4271/2016-01-1007.
---------------------------------------------------------------------------

    The HCR2 engine map model application in this analysis follows the
approach of the 2020 final rule.\143\ The agency believes the use of
HCR0, HCR1, and the new addition of HCR1D reasonably represents the
application of Atkinson Cycle engine technologies within the current
light-duty fleet and the anticipated applications of Atkinson Cycle
technology in the MY 2024-2026 timeframe.
---------------------------------------------------------------------------

    \143\ 85 FR 24425-27 (April 30, 2020).
---------------------------------------------------------------------------

    We are currently developing an updated family of HCR engine map
models that will include cEGR, cylinder deactivation and a combination
thereof. The new engine map models will closely align with the baseline
assumptions used in the other IAV-based HCR engine map models used for
the agency's analysis. The updated engine map models will likely not be
available for the final rule associated with this proposal because of
engine map model testing and validation requirements but will be
available for future CAFE analyses. We believe the timing for including
the new engine map models is reasonable, because a manufacturer that
could apply this technology in response to CAFE standards is likely not
do so before MY 2026, as the application of this technology will
require an engine redesign. We also believe this is reasonable given
manufacturer's statements that there are diminishing returns to
additional conventional engine technology improvements considering
vehicle electrification commitments.
    NHTSA seeks comment on whether and how to change our engine maps
for HCR2 in the analysis for the final rule.
(2) Analogous Engine Effectiveness Improvements and Fuel Economy
Improvement Factors
    For some technologies, the effectiveness for applying an
incremental engine technology was determined by using the effectiveness
values for applying the same engine technology to a reasonably similar
base engine. An example of this can be seen in the determination of the
application of SGDI to the baseline SOHC engine. Currently there is no
engine map model for the SOHC+VVT+SGDI engine configuration. To create
the effectiveness data required as an input to the CAFE Model, first, a
pairwise comparison between technology configurations that included the
DOHC+VVT engine (Eng1) and the DOHC+VVT+SGDI (Eng18) engine was
conducted. Then, the results of that comparison were used to generate a
data set of emulated performance values for adding the SGDI technology
to the SOHC+VVT engine (Eng5b) systems.
    The pairwise comparison is performed by finding the difference in
fuel consumption performance between every technology configuration
using the analogous base technology (e.g., Eng1) and every technology
configuration that only changes to the analogous technology (e.g.,
Eng18). The individual changes in performance between all the
technology configurations are then added to the same technology
configurations that use the new base technology (e.g., Eng5b) to create
a new set of performance values for the new technology (e.g.,
SOHC+VVT+SGDI). Table III-10 shows the engine technologies where
analogous effectiveness values were used.
[GRAPHIC] [TIFF OMITTED] TP03SE21.050

    DOT also developed a static fuel efficiency improvement factor to
simulate applying an engine technology for some technologies where
there was either no appropriate analogous technology or there were not
enough data to create a full engine map model. The improvement factors
were generally developed based on literature review or confidential
business information (CBI) provided by stakeholders. Table III-11
provides a summary of the technology

effectiveness values simulated using improvement factors, and the value
and rules for how the improvement factors were applied. Advanced
cylinder deactivation (ADEAC, TURBOAD, DSLIAD), advanced diesel engines
(DSLIA) and engine friction reduction (EFR) are the three technologies
modeled using improvement factors.
    The application of the advanced cylinder deactivation is
responsible for three of the five technologies using an improvement
factor in this analysis. The initial review of the advanced cylinder
deactivation technology was based on a technical publication that used
a MY 2010 SOHC VVT basic engine.\144\ Additional information about the
technology effectiveness came from a benchmarking analysis of pre-
production 8-cylinder OHV prototype systems.\145\ However, at the time
of the analysis no studies of production versions of the technology
were available, and the only available technology effectiveness came
from existing studies, not operational information. Thus, only
estimates of effect could be developed and not a full model of
operation. No engine map model could be developed, and no other
technology pairs were analogous.
---------------------------------------------------------------------------

    \144\ Wilcutts, M., Switkes, J., Shost, M., and Tripathi, A.,
``Design and Benefits of Dynamic Skip Fire Strategies for Cylinder
Deactivated Engines,'' SAE Int. J. Engines 6(1):278-288, 2013,
available at https://doi.org/10.4271/2013-01-0359. Eisazadeh-Far, K.
and Younkins, M., ``Fuel Economy Gains through Dynamic-Skip-Fire in
Spark Ignition Engines,'' SAE Technical Paper 2016-01-0672, 2016,
available at https://doi.org/10.4271/2016-01-0672.
    \145\ EPA, 2018. ``Benchmarking and Characterization of a Full
Continuous Cylinder Deactivation System.'' Presented at the SAE
World Congress, April 10-12, 2018. Retrieved from https://www.regulations.gov/document?D=EPA-HQ-OAR-2018-0283-0029.
---------------------------------------------------------------------------

    To model the effects of advanced cylinder deactivation, an
improvement factor was determined based on the information referenced
above and applied across the engine technologies. The effectiveness
values for naturally aspirated engines were predicted by using full
vehicle simulations of a basic engine with DEAC, SGDI, VVL, and VVT,
and adding 3 percent or 6 percent improvement based on engine cylinder
count: 3 percent for engines with 4 cylinders or less and 6 percent for
all other engines. Effectiveness values for turbocharged engines were
predicted using full vehicle simulations of the TURBOD engine and
adding 1.5 percent or 3 percent improvement based on engine cylinder
count: 1.5 percent for engines with 4 cylinders or less and 3 percent
for all other engines. For diesel engines, effectiveness values were
predicted by using the DSLI effectiveness values and adding 4.5 percent
or 7.5 percent improvement based on vehicle technology class: 4.5
percent improvement was applied to small and medium non-performance
cars, small performance cars, and small non-performance SUVs. 7.5
percent improvement was applied to all other vehicle technology
classes.
    The analysis modeled advanced engine technology application to the
baseline diesel engine by applying an improvement factor to the ADSL
engine technology combinations. A 12.8 percent improvement factor was
applied to the ADSL technology combinations to create the DSLI
technology combinations. The improvement in performance was based on
the application of a combination of low pressure and high pressure EGR,
reduced parasitic loss, advanced friction reduction, incorporation of
highly-integrated exhaust catalyst with low temp light off
temperatures, and closed loop combustion
control.146 147 148 149
---------------------------------------------------------------------------

    \146\ 2015 NAS report, at 104.
    \147\ Hatano, J., Fukushima, H., Sasaki, Y., Nishimori, K.,
Tabuchi, T., Ishihara, Y. ``The New 1.6L 2-Stage Turbo Diesel Engine
for HONDA CR-V.'' 24th Aachen Colloquium--Automobile and Engine
Technology 2015.
    \148\ Steinparzer, F., Nefischer, P., Hiemesch, D., Kaufmann,
M., Steinmayr, T. ``The New Six-Cylinder Diesel Engines from the BMW
In-Line Engine Module.'' 24th Aachen Colloquium--Automobile and
Engine Technology 2015.
    \149\ Eder, T., Weller, R., Spengel, C., B[ouml]hm, J., Herwig,
H., Sass, H. Tiessen, J., Knauel, P. ``Launch of the New Engine
Family at Mercedes-Benz.'' 24th Aachen Colloquium--Automobile and
Engine Technology 2015.
---------------------------------------------------------------------------

    As discussed above, the application of the EFR technology does not
simulate the application of a specific technology, but the application
of an array of potential improvements to an engine. All reciprocating
and rotating components in the engine are potential candidates for
friction reduction, and minute improvements in several components can
add up to a measurable fuel economy
improvement.150 151 152 153 Because of the incremental
nature of this analysis, a range of 1-2 percent improvement was
identified initially, and narrowed further to a specific 1.39%
improvement. The final value is likely representative of a typical
value industry may be able to achieve in future years.
---------------------------------------------------------------------------

    \150\ ``Polyalkylene Glycol (PAG) Based Lubricant for Light- &
Medium-Duty Axles,'' 2017 DOE Annual Merit Review. Ford Motor
Company, Gangopadhyay, A., Ved, C., Jost, N. https://energy.gov/sites/prod/files/2017/06/f34/ft023_gangopadhyay_2017_o.pdf.
    \151\ ``Power-Cylinder Friction Reduction through Coatings,
Surface Finish, and Design,'' 2017 DOE Annual Merit Review. Ford
Motor Company. Gangopadhay, A. Erdemir, A. https://energy.gov/sites/prod/files/2017/06/f34/ft050_gangopadhyay_2017_o.pdf.
    \152\ ``Nissan licenses energy-efficient engine technology to
HELLER,'' https://newsroom.nissan-global.com/releases/170914-01-e?lang=en-US&rss&la=1&downloadUrl=%2Freleases%2F170914-01-e%2Fdownload. Last accessed April 2018.
    \153\ ``Infiniti's Brilliantly Downsized V-6 Turbo Shines,''
http://wardsauto.com/engines/infiniti-s-brilliantly-downsized-v-6-turbo-shines. Last Accessed April 2018.

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[GRAPHIC] [TIFF OMITTED] TP03SE21.051

(3) Engine Effectiveness Values
    The effectiveness values for the engine technologies, for all ten
vehicle technology classes, are shown in Figure III-8. Each of the
effectiveness values shown is representative of the improvements seen
for upgrading only the listed engine technology for a given combination
of other technologies. In other words, the range of effectiveness
values seen for each specific technology (e.g., TURBO1) represents the
addition of the TURBO1 technology to every technology combination that
could select the addition of TURBO1. See Table III-12 for several
specific examples. It must be emphasized, the change in fuel
consumption values between entire technology keys is used,\154\ and not
the individual technology effectiveness values. Using the change
between whole technology keys captures the complementary or non-
complementary interactions among technologies.
---------------------------------------------------------------------------

    \154\ Technology key is the unique collection of technologies
that constitutes a specific vehicle, see Section III.C.4.c).
[GRAPHIC] [TIFF OMITTED] TP03SE21.052

    Some of the advanced engine technologies have values that indicate
seemingly low effectiveness. Investigation of these values shows the
low effectiveness was a result of applying the advanced engines to
existing SHEVP2 architectures. This effect is expected and illustrates
the importance of using the full vehicle modeling to capture
interactions between technologies and capture instances of both
complimentary technologies and non-complimentary technologies. In this
instance, the SHEVP2 powertrain improves fuel economy, in part, by
allowing the engine to spend more time operating at efficient engine
speed and load conditions. This reduces the advantage of adding
advanced engine technologies, which also improve fuel economy, by
broadening the range of speed and load conditions for the engine to
operate at high efficiency. This redundancy in fuel savings mechanism
results in a lower effectiveness when the technologies are added to
each other.
---------------------------------------------------------------------------

    \155\ The full data set we used to generate this example can be
found in the FE_1 Improvements file.

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[GRAPHIC] [TIFF OMITTED] TP03SE21.053

(e) Engine Costs
    The CAFE Model considers both cost and effectiveness in selecting
any technology changes. We have allocated considerable resources to
sponsoring research to determine direct manufacturing costs (DMCs) for
fuel saving technologies. As discussed in detail in TSD Chapter 3.1.5,
the engine costs used in this analysis build on estimates from the 2015
NAS report, agency-funded teardown studies, and work performed by non-
government organizations.\157\
---------------------------------------------------------------------------

    \156\ The box shows the inner quartile range (IQR) of the
effectiveness values and whiskers extend out 1.5 x IQR. The dots
outside this range show effectiveness values outside those
thresholds. The data used to create this figure can be found in the
FE_1 Improvements file.
    \157\ FEV prepared several cost analysis studies for EPA on
subjects ranging from advanced 8-speed transmissions to belt
alternator starters or start/stop systems. NHTSA contracted
Electricore, EDAG, and Southwest Research for teardown studies
evaluating mass reduction and transmissions. The 2015 NAS report
also evaluated technology costs developed based on these teardown
studies.
---------------------------------------------------------------------------

    Absolute costs of the engine technology are used in this analysis
instead of relative costs, which were used prior to the 2020 final
rule. The absolute costs are used to ensure the full cost of the IC
engine is removed when electrification technologies are applied
specifically for the transition to BEVs. This analysis models the cost
of adoption of BEV technology by first removing the costs associated
with IC powertrain systems, then applying the BEV systems costs.
Relative costs can still be determined through comparison of the
absolute costs for the initial technology combination and the new
technology combination.
    As discussed in detail in TSD Chapter 3.1.5, engine costs are
assigned based on the number of cylinders in the engine and whether the
engine is naturally aspirated or turbocharged and downsized. Table III-
13 below shows an example of absolute costs for engine technologies in
2018$. The example costs are shown for a straight 4-cylinder DOHC
engine and V-6-cylinder DOHC engine. The table shows costs declining
across successive years due to the learning rate applied to each engine
technology. For a full list of all absolute engine costs used in the
analysis across all model years, see the Technologies file.

[GRAPHIC] [TIFF OMITTED] TP03SE21.054

2. Transmission Paths
    For this analysis, DOT classified all light duty vehicle
transmission technologies into discrete transmission technology paths.
These paths are used to model the most representative characteristics,
costs, and performance of the fuel-economy improving transmissions most
likely available during the rulemaking time frame, MYs 2024-2026.
    The following sections discuss how transmission technologies
considered in this analysis are defined, the general technology
categories used by the CAFE Model, and the transmission technologies'
relative effectiveness and costs. The following sections also provide
an overview of how the transmission technologies were assigned to the
MY 2020 fleet, as well as the adoption features applicable to the
transmission technologies.
(a) Transmission Modeling in the CAFE Model
    DOT modeled two major categories of transmissions for this
analysis: Automatic and manual. Automatic transmissions are
characterized by automatically selecting and shifting between
transmission gears for the driver during vehicle operation. Automatic
transmissions are further subdivided into four subcategories:
Traditional automatic transmissions (AT), dual clutch transmissions
(DCT), continuously variable transmissions (CVT), and direct drive
transmissions (DD).
    ATs and CVTs also employ different levels of high efficiency
gearbox (HEG) technology. HEG improvements for transmissions represent
incremental advancement in technology that improve efficiency, such as
reduced friction seals, bearings and clutches, super finishing of
gearbox parts, and improved lubrication. These advancements are all
aimed at reducing frictional and other parasitic loads in transmissions
to improve efficiency. DOT considered three levels of HEG improvements
in this analysis, based on 2015 recommendations by the National Academy
of Sciences and CBI data.\158\ HEG efficiency improvements are applied
to ATs and CVTs, as those transmissions inherently have higher friction
and parasitic loads related to hydraulic control systems and greater
component complexity, compared to MTs and DCTs. HEG technology
improvements are noted in the transmission technology pathways by
increasing ``levels'' of a transmission technology; for example, the
baseline 8-speed automatic transmission is termed ``AT8'', while an AT8
with level 2 HEG technology is ``AT8L2'' and an AT8 with level 3 HEG
technology is ``AT8L3.''
---------------------------------------------------------------------------

    \158\ 2015 NAS report, at 191.
---------------------------------------------------------------------------

    AT: Conventional planetary gear automatic transmissions are the
most

popular transmission.\159\ ATs typically contain three or four
planetary gear sets that provide the various gear ratios. Gear ratios
are selected by activating solenoids which engage or release multiple
clutches and brakes as needed. ATs are packaged with torque converters,
which provide a fluid coupling between the engine and the driveline and
provide a significant increase in launch torque. When transmitting
torque through this fluid coupling, energy is lost due to the churning
fluid. These losses can be eliminated by engaging the torque convertor
clutch to directly connect the engine and transmission (``lockup'').
For the Draft TAR and 2020 final rule, EPA and DOT surveyed automatic
transmissions in the market to assess trends in gear count and
purported fuel economy improvements.\160\ Based on that survey, and
also EPA's more recent 2019 and 2020 Automotive Trends Reports,\161\
DOT concluded that modeling ATs with a range of 5 to 10 gears, with
three levels of HEG technology for this analysis was reasonable.
---------------------------------------------------------------------------

    \159\ 2020 EPA Automotive Trends Report, at 57-61.
    \160\ Draft TAR at 5-50, 5-51; Final Regulatory Impact Analysis
accompanying the 2020 final rule, at 549.
    \161\ The 2019 EPA Automotive Trends Report, EPA-420-R-20-006,
at 59 (March 2020), https://nepis.epa.gov/Exe/ZyPDF.cgi?Dockey=P100YVFS.pdf [hereinafter 2019 EPA Automotive
Trends Report]; 2020 EPA Automotive Trends Report, at 57.
---------------------------------------------------------------------------

    CVT: Conventional continuously variable transmissions consist of
two cone-shaped pulleys, connected with a belt or chain. Moving the
pulley halves allows the belt to ride inward or outward radially on
each pulley, effectively changing the speed ratio between the pulleys.
This ratio change is smooth and continuous, unlike the step changes of
other transmission varieties.\162\ DOT modeled two types of CVT systems
in the analysis, the baseline CVT and a CVT with HEG technology
applied.
---------------------------------------------------------------------------

    \162\ 2015 NAS report, at 171.
---------------------------------------------------------------------------

    DCT: Dual clutch transmissions, like automatic transmissions,
automate shift and launch functions. DCTs use separate clutches for
even-numbered and odd-numbered gears, allowing the next gear needed to
be pre-selected, resulting in faster shifting. The use of multiple
clutches in place of a torque converter results in lower parasitic
losses than ATs.\163\ Because of a history of limited
appeal,164 165 DOT constrains application of additional DCT
technology to vehicles already using DCT technology, and only models
two types of DCTs in the analysis.
---------------------------------------------------------------------------

    \163\ 2015 NAS report, at 170.
    \164\ 2020 EPA Automotive Trends Report, at 57.
    \165\ National Academies of Sciences, Engineering, and Medicine
2021. Assessment of Technologies for Improving Light-Duty Vehicle
Fuel Economy 2025-2035. Washington, DC: The National Academies
Press. https://doi.org/10.17226/26092, at 4-56 [hereinafter 2021 NAS
report].
---------------------------------------------------------------------------

    MT: Manual transmissions are transmissions that require direct
control by the driver to operate the clutch and shift between gears. In
a manual transmission, gear pairs along an output shaft and parallel
layshaft are always engaged. Gears are selected via a shift lever,
operated by the driver. The lever operates synchronizers, which speed
match the output shaft and the selected gear before engaging the gear
with the shaft. During shifting operations (and during idle), a clutch
between the engine and transmission is disengaged to decouple engine
output from the transmission. Automakers today offer a minimal
selection of new vehicles with manual transmissions.\166\ As a result
of reduced market presence, DOT only included three variants of manual
transmissions in the analysis.
---------------------------------------------------------------------------

    \166\ 2020 EPA Automotive Trends Report, at 61.
---------------------------------------------------------------------------

    The transmission model paths used in this analysis are shown in
Figure III-9. Baseline-only technologies (MT5, AT5, AT7L2, AT9L2, and
CVT) are grayed and can only be assigned as initial vehicle
transmission configurations. Further details about transmission path
modeling can be found in TSD Chapter 3.2.
[GRAPHIC] [TIFF OMITTED] TP03SE21.055

(b) Transmission Analysis Fleet Assignments
    The wide variety of transmissions on the market are classified into
discrete transmission technology paths for this analysis. These paths
are used to model the most representative characteristics, costs, and
performance of the fuel economy-improving technologies most likely
available during the rulemaking time frame.
    For the 2020 analysis fleet, DOT gathered data on transmissions
from manufacturer mid-model year CAFE compliance submissions and
publicly available manufacturer specification sheets. These data were
used to assign transmissions in the analysis fleet and determine which
platforms shared transmissions.
    Transmission type, number of gears, and high-efficiency gearbox
(HEG) level are all specified for the baseline fleet assignment. The
number of gears in the assignments for automatic and manual
transmissions usually match the number of gears listed by the data
sources, with some exceptions. Four-speed transmissions were not
modeled in Autonomie for this analysis due to their rarity and low
likelihood of being used in the future, so DOT assigned 2020 vehicles
with an AT4 or MT4 to an AT5 or MT5 baseline, respectively. Some dual-
clutch transmissions were also an exception; dual-clutch transmissions
with seven gears were assigned to DCT6.
    For automatic and continuously variable transmissions, the
identification of the most appropriate transmission path model required
additional steps; this is because high-efficiency gearboxes are
considered in the analysis but identifying HEG level from specification
sheets alone was not always straightforward. DOT conducted a review of
the age of the transmission design, relative performance versus
previous designs, and technologies incorporated and used the
information obtained to assign an HEG level. No automatic transmissions
in the MY 2020 analysis fleet were determined to be at HEG Level 3. In
addition, no six-speed automatic transmissions were assigned HEG Level
2. However, DOT found all 7-speed, all 9-speed, all 10-speed, and some
8-speed automatic transmissions to be advanced transmissions operating
at HEG Level 2 equivalence. Eight-speed automatic transmissions
developed after MY 2017 are assigned HEG Level 2. All other
transmissions are assigned to their respective transmission's baseline
level. The baseline (HEG level 1) technologies available include AT6,
AT8, and CVT.
    DOT assigned any vehicle in the analysis fleet with a hybrid or
electric powertrain a direct drive (DD) transmission. This designation
is for informational purposes; if specified, the transmission will not
be replaced or updated by the model.
    In addition to technology type, gear count, and HEG level,
transmissions are characterized in the analysis fleet by drive type and
vehicle architecture. Drive types considered in the analysis include
front-, rear-, all-, and four-wheel drive. The definition of drive
types in the analysis does not always align with manufacturers' drive
type designations; see the end of this subsection for further
discussion. These characteristics, supplemented by information such as
gear ratios and production locations, showed that manufacturers use
transmissions that are the same or similar on multiple vehicle models.
Manufacturers have told the agency they do this to control component
complexity and associated costs for development, manufacturing,
assembly, and service. If multiple vehicle models share technology
type, gear count, drive configuration, internal gear rations, and
production location, the transmissions are treated as a single group
for the analysis. Vehicles in the analysis fleet with the same
transmission configuration adopt additional fuel-saving transmission
technology together, as described in Section III.C.2.a).
    Shared transmissions are designated and tracked in the CAFE Model
input files using transmission codes. Transmission codes are six-digit
numbers that are assigned to each transmission and encode information
about them. This information includes the manufacturer, drive
configuration, transmission type, and number of gears. TSD Chapter
3.2.2 includes more information on the transmission codes designated in
the MY 2020 analysis fleet.
    Different transmission codes are assigned to variants of a
transmission that may have appeared to be similar based on the
characteristics considered in the analysis but are not mechanically
identical. DOT analysts distinguish among transmission variants by
comparing their internal gear ratios and production locations. For
example, several Ford nameplates carry a rear-wheel drive, 10-speed
automatic transmission. These nameplates comprise a wide variety of
body styles and use cases, and so DOT assigned different transmission
codes to these different nameplates. Because they have different
transmission codes, they are not treated as ``shared'' for the purposes
of the analysis and have the opportunity to adopt transmission
technologies independently.
    Note that when determining the drive type of a transmission, the
assignment of all-wheel drive versus four-wheel drive is determined by
vehicle architecture. This assignment does not necessarily match the
drive type used by the manufacturer in specification sheets and
marketing materials. Vehicles with a powertrain capable of providing
power to all wheels and a transverse engine (front-wheel drive
architecture) are assigned all-wheel drive. Vehicles with power to all
four wheels and a longitudinal engine (rear-wheel drive architecture)
are assigned four-wheel drive.
(c) Transmission Adoption Features
    Transmission technology pathways are designed to prevent ``branch
hopping''--changes in transmission type that would correspond to
significant changes in transmission architecture--for vehicles that are
relatively advanced on a given pathway. For example, any automatic
transmission with more than five gears cannot move to a dual-clutch
transmission. For a more detailed discussion of path logic applied in
the analysis, including technology supersession logic and technology
mutual exclusivity logic, please see CAFE Model Documentation S4.5
Technology Constraints (Supersession and Mutual Exclusivity).
Additionally, the CAFE Model prevents ``branch hopping'' to prevent
stranded capital associated with moving from one transmission
architecture to another. Stranded capital is discussed in Section
III.C.6.
    Some technologies that are modeled in the analysis are not yet in
production, and therefore are not assigned in the baseline fleet.
Nonetheless, these technologies, which are projected to be available in
the analysis timeframe, are available for future adoption. For
instance, an AT10L3 is not observed in the baseline fleet, but it is
plausible that manufacturers that employ AT10L2 technology may improve
the efficiency of those AT10L2s in the rulemaking timeframe.
    The following sections discuss specific adoption features applied
to each type of transmission technology.
    When electrification technologies are adopted, the transmissions
associated with those technologies will supersede the existing
transmission on a vehicle. The transmission technology is superseded if
P2 hybrids, plug-in hybrids, or battery electric vehicle technologies
are applied. For more information, see Section III.D.3.c).

    The automatic transmission path precludes adoption of other
transmission types once a platform progresses past an AT6. This
restriction is used to avoid the significant level of stranded capital
loss that could result from adopting a completely different
transmission type shortly after adopting an advanced transmission,
which would occur if a different transmission type were adopted after
AT6 in the rulemaking timeframe.
    Vehicles that did not start out with AT7L2 or AT9L2 transmissions
cannot adopt those technologies in the model. The agency observed that
MY 2017 vehicles with those technologies were primarily luxury
performance vehicles and concluded that other vehicles would likely not
adopt those technologies. DOT concluded that this was also a reasonable
assumption for the MY 2020 analysis fleet because vehicles that have
moved to more advanced automatic transmissions have overwhelmingly
moved to 8-speed and 10-speed transmissions.\167\
---------------------------------------------------------------------------

    \167\ 2020 EPA Automotive Trends Report, at 64, figure 4.18.
---------------------------------------------------------------------------

    CVT adoption is limited by technology path logic. CVTs cannot be
adopted by vehicles that do not originate with a CVT or by vehicles
with multispeed transmissions beyond AT6 in the baseline fleet.
Vehicles with multispeed transmissions greater than AT6 demonstrate
increased ability to operate the engine at a highly efficient speed and
load. Once on the CVT path, the platform is only allowed to apply
improved CVT technologies. The analysis restricts the application of
CVT technology on larger vehicles because of the higher torque (load)
demands of those vehicles and CVT torque limitations based on
durability constraints. Additionally, this restriction is used to avoid
the significant level of stranded capital.
    The analysis allows vehicles in the baseline fleet that have DCTs
to apply an improved DCT and allows vehicles with an AT5 to consider
DCTs. Drivability and durability issues with some DCTs have resulted in
a low relative adoption rate over the last decade; this is also broadly
consistent with manufacturers' technology choices.\168\
---------------------------------------------------------------------------

    \168\ Ibid.
---------------------------------------------------------------------------

    Manual transmissions can only move to more advanced manual
transmissions for this analysis, because other transmission types do
not provide a similar driver experience (utility). Manual transmissions
cannot adopt AT, CVT, or DCT technologies under any circumstance. Other
transmissions cannot move to MT because manual transmissions lack
automatic shifting associated with the other transmission types
(utility) and in recognition of the low customer demand for manual
transmissions.\169\
---------------------------------------------------------------------------

    \169\ Ibid.
---------------------------------------------------------------------------

(d) Transmission Effectiveness Modeling
    For this analysis, DOT used the Autonomie full vehicle simulation
tool to model the interaction between transmissions and the full
vehicle system to improve fuel economy, and how changes to the
transmission subsystem influence the performance of the full vehicle
system. The full vehicle simulation approach clearly defines the
contribution of individual transmission technologies and separates
those contributions from other technologies in the full vehicle system.
The modeling approach follows the recommendations of the National
Academy of Sciences in its 2015 light duty vehicle fuel economy
technology report to use full vehicle modeling supported by application
of collected improvements at the sub-model level.\170\ See TSD Chapter
3.2.4 for more details on transmission modeling inputs and results.
---------------------------------------------------------------------------

    \170\ 2015 NAS report, at 292.
---------------------------------------------------------------------------

    The only technology effectiveness results that were not directly
calculated using the Autonomie simulation results were for the AT6L2.
DOT determined that the model for this specific technology was
inconsistent with the other transmission models and overpredicted
effectiveness results. Evaluation of the AT6L2 transmission model
revealed an overestimated efficiency map was developed for the AT6L2
model. The high level of efficiency assigned to the transmission
surpassed benchmarked advanced transmissions.\171\ To address the
issue, DOT replaced the effectiveness values of the AT6L2 model. DOT
replaced the effectiveness for the AT6L2 technology with analogous
effectiveness values from the AT7L2 transmission model. For additional
discussion on how analogous effectiveness values are determined please
see Section III.D.1.d)(2).
---------------------------------------------------------------------------

    \171\ Autonomie model documentation, Chapter 5.3.4. Transmission
Performance Data.
---------------------------------------------------------------------------

    The effectiveness values for the transmission technologies, for all
ten vehicle technology classes, are shown in Figure III-10. Each of the
effectiveness values shown is representative of the improvements seen
for upgrading only the listed transmission technology for a given
combination of other technologies. In other words, the range of
effectiveness values seen for each specific technology, e.g., AT10L3,
represents the addition of the AT10L3 technology to every technology
combination that could select the addition of AT10L3. It must be
emphasized that the graph shows the change in fuel consumption values
between entire technology keys,\172\ and not the individual technology
effectiveness values. Using the change between whole technology keys
captures the complementary or non-complementary interactions among
technologies. In the graph, the box shows the inner quartile range
(IQR) of the effectiveness values and whiskers extend out 1.5 x IQR.
The dots outside of the whiskers show values for effectiveness that are
outside these bounds.
---------------------------------------------------------------------------

    \172\ Technology key is the unique collection of technologies
that constitutes a specific vehicle, see Section III.C.4.c).

---------------------------------------------------------------------------

[GRAPHIC] [TIFF OMITTED] TP03SE21.056

    Note that the effectiveness for the MT5, AT5 and DD technologies
are not shown. The DD transmission does not have a standalone
effectiveness because it is only implemented as part of electrified
powertrains. The MT5 and AT5 also have no effectiveness values because
both technologies are baseline technologies against which all other
technologies are compared.
---------------------------------------------------------------------------

    \173\ The data used to create this figure can be found the FE_1
Improvements file.
---------------------------------------------------------------------------

(e) Transmission Costs
    This analysis uses transmission costs drawn from several sources,
including the 2015 NAS report and NAS-cited studies. TSD Chapter 3.2.5
provides a detailed description of the cost sources used for each
transmission technology. Table III-14 shows an example of absolute
costs for transmission technologies in 2018$ across select model years,
which demonstrates how cost learning is applied to the transmission
technologies over time. Note, because transmission hardware is often
shared across vehicle classes, transmission costs are the same for all
vehicle classes. For a full list of all absolute transmission costs
used in the analysis across all model years, see the Technologies file.

[GRAPHIC] [TIFF OMITTED] TP03SE21.057

3. Electrification Paths
    The electric paths include a large set of technologies that share
the common element of using electrical power for certain vehicle
functions that were traditionally powered mechanically by engine power.
Electrification technologies thus can range from electrification of
specific accessories (for example, electric power steering to reduce
engine loads by eliminating parasitic losses) to electrification of the
entire powertrain (as in the case of a battery electric vehicle).
    The following subsections discuss how each electrification
technology is defined in the CAFE Model and the electrification
pathways down which a vehicle can travel in the compliance simulation.
The subsections also discuss how the agency assigned electrified
vehicle technologies to vehicles in the MY 2020 analysis fleet, any
limitations on electrification technology adoption, and the specific
effectiveness and cost assumptions used in the Autonomie and CAFE Model
analysis.
(a) Electrification Modeling in the CAFE Model
    The CAFE Model defines the technology pathway for each type of
electrification grouping in a logical progression. Whenever the CAFE
Model converts a vehicle model to one of the available electrified
systems, both effectiveness and costs are updated according to the
specific components' modeling algorithms. Additionally, all
technologies on the different electrification paths are mutually
exclusive and are evaluated in parallel. For example, the model may
evaluate PHEV20 technology prior to having to apply 12-volt stop-start
(SS12V) or strong hybrid technology. The specific set of algorithms and
rules are discussed further in the sections below, and more detailed
discussions are included in the CAFE Model Documentation. The
specifications for each electrification technology used in the analysis
is discussed below.
    The technologies that are included on the three vehicle-level paths
pertaining to the electrification and electric improvements defined
within the modeling system are illustrated in Figure III-11. As shown
in the Electrification path, the baseline-only CONV technology is
grayed out. This technology is used to denote whether a vehicle comes
in with a conventional powertrain (i.e., a vehicle that does not
include any level of hybridization) and to allow the model to properly
map to the Autonomie vehicle simulation database results. If multiple
branches converge on a single technology, the subset of technologies
that will be disabled from further adoption is extended only up the
point of convergence.
BILLING CODE 4910-59-P

[GRAPHIC] [TIFF OMITTED] TP03SE21.058

BILLING CODE 4910-59-C
    SS12V: 12-volt stop-start (SS12V), sometimes referred to as start-
stop, idle-stop, or a 12-volt micro hybrid system, is the most basic
hybrid system that facilitates idle-stop capability. In this system,
the integrated starter generator is coupled to the internal combustion
(IC) engine. When the vehicle comes to an idle-stop the IC engine
completely shuts off, and, with the help of the 12-volt battery, the
engine cranks and starts again in response to throttle to move the
vehicle, application or release of the brake pedal to move the vehicle.
The 12-volt battery used for the start-stop system is an improved unit
compared to a traditional 12-volt battery, and is capable of higher
power, increased life cycle, and capable of minimizing voltage drop on
restart. This technology is beneficial to reduce fuel consumption and
emissions when the vehicle frequently stops, such as in city driving
conditions or in stop and go traffic. 12VSS can be applied to all
vehicle technology classes.
    BISG: The belt integrated starter generator, sometimes referred to
as a mild hybrid system or P0 hybrid, provides idle-stop capability and
uses a higher voltage battery with increased energy capacity over
conventional automotive batteries. These higher voltages allow the use
of a smaller, more powerful and efficient electric motor/generator
which replaces the standard alternator. In BISG systems, the motor/
generator is coupled to the engine via belt (similar to a standard
alternator). In addition, these motor/generators can assist vehicle
braking and recover braking energy while the vehicle slows down
(regenerative braking) and in turn can propel the vehicle at the
beginning of launch, allowing the engine to be restarted later. Some
limited electric assist is also provided during acceleration to improve
engine efficiency. Like the micro hybrids, BISG can be applied to all
vehicles in the analysis except for Engine 26a (VCR). We assume all
mild hybrids are 48-volt systems with engine belt-driven motor/
generators.
    SHEVP2/SHEVPS: A strong hybrid vehicle is a vehicle that combines
two or more propulsion systems, where one uses gasoline (or diesel),
and the other captures energy from the vehicle during deceleration or
braking, or from the engine and stores that energy for later used by
the vehicle. This analysis evaluated the following strong hybrid
systems: Hybrids with ``P2'' parallel

drivetrain architectures (SHEVP2),\174\ and hybrids with power-split
architectures (SHEVPS). Both types provide start-stop or idle-stop
functionality, regenerative braking capability, and vehicle launch
assist. A SHEVPS has a higher potential for fuel economy improvement
than a SHEVP2, although its cost is also higher and engine power
density is lower.\175\
---------------------------------------------------------------------------

    \174\ Depending on the location of electric machine (motor with
or without inverter), the parallel hybrid technologies are
classified as P0-motor located at the primary side of the engine,
P1-motor located at the flywheel side of the engine, P2-motor
located between engine and transmission, P3-motor located at the
transmission output, and P4-motor located on the axle.
    \175\ Kapadia, J., Kok, D., Jennings, M., Kuang, M. et al.,
``Powersplit or Parallel--Selecting the Right Hybrid Architecture,''
SAE Int. J. Alt. Power. 6(1):2017, doi:10.4271/2017-01-1154.
---------------------------------------------------------------------------

    P2 parallel hybrids (SHEVP2) are a type of hybrid vehicle that use
a transmission-integrated electric motor placed between the engine and
a gearbox or CVT, with a clutch that allows decoupling of the motor/
transmission from the engine. Although similar to the configuration of
the crank mounted integrated starter generator (CISG) system discussed
previously, a P2 hybrid is typically equipped with a larger electric
motor and battery in comparison to the CISG. Disengaging the clutch
allows all-electric operation and more efficient brake-energy recovery.
Engaging the clutch allows coupling of the engine and electric motor
and, when combined with a transmission, reduces gear-train losses
relative to power-split or 2-mode hybrid systems. P2 hybrid systems
typically rely on the internal combustion engine to deliver high,
sustained power levels. Electric-only mode is used when power demands
are low or moderate.
    An important feature of the SHEVP2 system is that it can be applied
in conjunction with most engine technologies. Accordingly, once a
vehicle is converted to a SHEVP2 powertrain in the compliance
simulation, the CAFE Model allows the vehicle to adopt the conventional
engine technology that is most cost effective, regardless of relative
location of the existing engine on the engine technology path. For
example, a vehicle in the MY 2020 analysis fleet that starts with a
TURBO2 engine could adopt a TURBO1 engine with the SHEVP2 system, if
that TURBO1 engine allows the vehicle to meet fuel economy standards
more cost effectively.
    The power-split hybrid (SHEVPS) is a hybrid electric drive system
that replaces the traditional transmission with a single planetary gear
set (the power-split device) and a motor/generator. This motor/
generator uses the engine either to charge the battery or to supply
additional power to the drive motor. A second, more powerful motor/
generator is connected to the vehicle's final drive and always turns
with the wheels. The planetary gear splits engine power between the
first motor/generator and the drive motor either to charge the battery
or to supply power to the wheels. During vehicle launch, or when the
battery state of charge (SOC) is high, the engine is turned off and the
electric motor propels the vehicle.\176\ During normal driving, the
engine output is used both to propel the vehicle and to generate
electricity. The electricity generated can be stored in the battery
and/or used to drive the electric motor. During heavy acceleration,
both the engine and electric motor (by consuming battery energy) work
together to propel the vehicle. When braking, the electric motor acts
as a generator to convert the kinetic energy of the vehicle into
electricity to charge the battery.
---------------------------------------------------------------------------

    \176\ Autonomie model documentation, Chapter 4.13.2.
---------------------------------------------------------------------------

    Table III-15 below shows the configuration of conventional engines
and transmissions used with strong hybrids for this analysis. The
SHEVPS powertrain configuration was paired with a planetary
transmission (eCVT) and Atkinson engine (Eng26). This configuration was
designed to maximize efficiency at the cost of reduced towing
capability and real-world acceleration performance.\177\ In contrast,
the SHEVP2 powertrains were paired with an advanced 8-speed automatic
transmissions (AT8L2) and could be paired with most conventional
engines.\178\
---------------------------------------------------------------------------

    \177\ Kapadia, J., D, Kok, M. Jennings, M. Kuang, B. Masterson,
R. Isaacs, A. Dona. 2017. Powersplit or Parallel--Selecting the
Right Hybrid Architecture. SAE International Journal of Alternative
Powertrains 6 (1): 68-76. https://doi.org/10.4271/2017-01-1154.
    \178\ We did not model SHEVP2s with VTGe (Eng23c) and VCR
(Eng26a).
[GRAPHIC] [TIFF OMITTED] TP03SE21.059

    PHEV: Plug-in hybrid electric vehicles are hybrid electric vehicles
with the means to charge their battery packs from an outside source of
electricity (usually the electric grid). These vehicles have larger
battery packs with more energy storage and a greater capability to be
discharged than other non-plug-in hybrid electric vehicles. PHEVs also
generally use a control system that allows the battery pack to be
substantially depleted under electric-only or blended mechanical/
electric operation and batteries that can be cycled in charge-
sustaining operation at a lower state of charge than non-plug-in hybrid
electric vehicles. These vehicles generally have a greater all-electric
range than typical strong HEVs. Depending on how these vehicles are
operated, they can use electricity exclusively, operate like a
conventional hybrid, or operate in some combination of these two modes.
---------------------------------------------------------------------------

    \179\ Engine 01, 02, 03, 04, 5b, 6a, 7a, 8a, 12, 12-DEAC, 13,
14, 17, 18, 19, 20, 21, 22b, 23b, 24, 24-Deac. See Section III.D.1
for these engine specifications.

---------------------------------------------------------------------------

    There are four PHEV architectures included in this analysis that
reflect combinations of two levels of all-electric range (AER) and two
engine types. DOT selected 20 miles AER and 50 miles AER to reasonably
span the various AER in the market, and their effectiveness and cost.
DOT selected an Atkinson engine and a turbocharged downsized engine to
span the variety of engines in the market.
    PHEV20/PHEV20H and PHEV50/PHEV50H are essentially a SHEVPS with a
larger battery and the ability to drive with the engine turned off. In
the CAFE Model, the designation for ``H'' in PHEVxH could represent
another type of engine configuration, but for this analysis DOT used
the same effectiveness values as PHEV20 and PHEV50 to represent PHEV20H
and PHEV50H, respectively. The PHEV20/PHEV20H represents a ``blended-
type'' plug-in hybrid, which can operate in all-electric (engine off)
mode only at light loads and low speeds, and must blend electric motor
and engine power together to propel the vehicle at medium or high loads
and speeds. The PHEV50/PHEV50H represents an extended range electric
vehicle (EREV), which can travel in all-electric mode even at higher
speeds and loads. Further discussion of engine sizing, batteries, and
motors for these PHEVs is discussed in Section III.D.3.d).
    PHEV20T and PHEV50T are 20 mile and 50 mile AER vehicles based on
the SHEVP2 engine architecture. The PHEV versions of these
architectures include larger batteries and motors to meet performance
in charge sustaining mode at higher speeds and loads as well as similar
performance and range in all electric mode in city driving, at higher
speeds and loads. For this analysis, the CAFE Model considers these
PHEVs to have an advanced 8-speed automatic transmission (AT8L2) and
TURBO1 (Eng12) in the powertrain configuration. Further discussion of
engine sizing, batteries, and motors for these PHEVs is discussed in
Section III.D.3.d).
    Table III-16 shows the different PHEV configurations used in this
analysis.
[GRAPHIC] [TIFF OMITTED] TP03SE21.060

    BEV: Battery electric vehicles are equipped with all-electric drive
systems powered by energy-optimized batteries charged primarily by
electricity from the grid. BEVs do not have a combustion engine or
traditional transmission. Instead, BEVs rely on all electric
powertrains, with an advanced transmission packaged with the
powertrain. The range of battery electric vehicles vary by vehicle and
battery pack size.
    DOT simulated BEVs with ranges of 200, 300, 400, and 500 miles in
the CAFE Model. BEV range is measured pursuant to EPA test procedures
and guidance.\180\ The CAFE Model assumes that BEVs transmissions are
unique to each vehicle (i.e., the transmissions are not shared by any
other vehicle) and that no further improvements are available.
---------------------------------------------------------------------------

    \180\ BEV electric ranges are determined per EPA guidance
Document. ``EPA Test Procedure for Electric Vehicles and Plug-in
Hybrids.'' https://fueleconomy.gov/feg/pdfs/EPA%20test%20procedure%20for%20EVs-PHEVs-11-14-2017.pdf. November
14, 2017. Last Accessed May 3, 2021.
---------------------------------------------------------------------------

    A key note about the BEVs offered in this analysis is that the CAFE
Model does not account for vehicle range when considering additional
BEV technology adoption. That is, the CAFE Model does not have an
incentive to build BEV300, 400, and 500s, because the BEV200 is just as
efficient as those vehicles and counts the same toward compliance, but
at a significantly lower cost because of the smaller battery. While
manufacturers have been building 200-mile range BEVs, those vehicles
have generally been passenger cars. Manufacturers have told DOT that
greater range is important for meeting the needs of broader range of
consumers and to increase consumer demand. More recently, there has
been a trend towards manufacturers building higher range BEVs in the
market, and manufacturers building CUV/SUV and pickup truck BEVs. To
simulate the potential relationship of BEV range to consumer demand,
DOT has included several adoption features for BEVs. These are
discussed further in Section III.D.3.c).
    Fuel cell electric vehicle (FCEV): Fuel cell electric vehicles are
equipped with an all-electric drivetrain, but unlike BEVs, FCEVs do not
solely rely on batteries; rather, electricity to run the FCEV electric
motor is mainly generated by an onboard fuel cell system. FCEV
architectures are similar to series hybrids,\181\ but with the engine
and generator replaced by a fuel cell. Commercially available FCEVs
consume hydrogen to generate electricity for the fuel cell system, with
most automakers using high pressure gaseous hydrogen storage tanks.
FCEVs are currently produced in limited numbers and are available in
limited geographic areas where hydrogen refueling stations are
accessible. For reference, in MY 2020, only four FCV models were
offered for

sale, and since 2014 only 9,975 FCVs have been sold.182 183
---------------------------------------------------------------------------

    \181\ Series hybrid architecture is a strong hybrid that has the
engine, electric motor and transmission in series. The engine in a
series hybrid drives a generator that charges the battery.
    \182\ Argonne National Laboratory, ``Light Duty Electric Drive
Vehicles Monthly Sales Update.'' Energy Systems Division, https://www.anl.gov/es/light-duty-electric-drive-vehicles-monthly-sales-updates. Last Accessed May 4, 2021.
    \183\ See the MY 2020 Market Data file. The four vehicles are
the Honda Clarity, Hyundai Nexo and Nexo Blue, and Toyota Mirai.
---------------------------------------------------------------------------

    For this analysis, the CAFE Model simulates a FCEV with a range of
320 miles. Any type of powertrain could adopt a FCEV powertrain;
however, to account for limited market penetration and unlikely
increased adoption in the rulemaking timeframe, technology phase in
caps were used to control how many FCEVs a manufacturer could build.
The details of this concept are further discussed in Section
III.D.3.c).
(b) Electrification Analysis Fleet Assignments
    DOT identified electrification technologies present in the baseline
fleet and used these as the starting point for the regulatory analysis.
These assignments were based on manufacturer-submitted CAFE compliance
information, publicly available technical specifications, marketing
brochures, articles from reputable media outlets, and data from Wards
Intelligence.\184\
---------------------------------------------------------------------------

    \184\ ``U.S. Car and Light Truck Specifications and Prices, '20
Model Year.'' Wards Intelligence, 3 Aug. 2020,
wardsintelligence.informa.com/WI964244/US-Car-and-Light-Truck-Specifications-and-Prices-20-Model-Year.
---------------------------------------------------------------------------

    Table III-17 gives the baseline fleet penetration rates of
electrification technologies eligible to be assigned in the baseline
fleet. Over half the fleet had some level of electrification, with the
vast majority of these being micro hybrids. BEVs represented less than
2% of MY 2020 baseline fleet; BEV300 was the most common BEV
technology, while no BEV500s were observed.
[GRAPHIC] [TIFF OMITTED] TP03SE21.061

    Micro and mild hybrids refer to the presence of SS12V and BISG,
respectively. The data sources discussed above were used to identify
the presence of these technologies on vehicles in the fleet. Vehicles
were assigned one of these technologies only if its presence could be
confirmed with manufacturer brochures or technical specifications.
    Strong hybrid technologies included SHEVPS and SHEVP2. Note that
P2HCR0, P2HCR1, P2HCR1D, and P2HCR2 are not assigned in the fleet and
are only available to be applied by the model. When possible,
manufacturer specifications were used to identify the strong hybrid
architecture type. In the absence of more sophisticated information,
hybrid architecture was determined by number of motors. Hybrids with
one electric motor were assigned P2, and those with two were assigned
power-split (PS). DOT seeks comment on additional ways the agency could
perform initial hybrid assignments based on publicly available
information.
    Plug-in hybrid technologies PHEV20/20T and PHEV50/50T are assigned
in the baseline fleet. PHEV20H and PHEV50H are not assigned in the
fleet and are only available to be applied by the model. Vehicles with
an electric-only range of 40 miles or less were assigned PHEV20; those
with a range above 40 miles were assigned PHEV50. They were
respectively assigned PHEV20T/50T if the engine was turbocharged (i.e.,
if it would qualify for one of technologies on the turbo engine
technology pathway). DOT also had to calculate baseline fuel economy
values for PHEV technologies as part of the PHEV analysis fleet
assignments; that process is described in detail in TSD Chapter 3.3.2.
    Fuel cell and battery electric vehicle technologies included
BEV200/300/400/500 and FCV. Vehicles with all-electric powertrains that
used hydrogen fuel were assigned FCV. The BEV technologies were
assigned to vehicles based on range thresholds that best account for
vehicles' existing range capabilities while allowing room for the model
to potentially apply more advanced electrification technologies.

    For more detail about the electrification analysis fleet assignment
process, see TSD Chapter 3.3.2.
(c) Electrification Adoption Features
    Multiple types of adoption features applied to the electrification
technologies. The hybrid/electric technology path logic dictated how
vehicles could adopt different levels of electrification technology.
Broadly speaking, more advanced levels of hybridization or
electrification superseded all prior levels, with certain technologies
within each level being mutually exclusive. The analysis modeled (from
least to most electrified) micro hybrids, mild hybrids, strong hybrids,
plug-in hybrids, and fully electric vehicles.
    As discussed further below, SKIP logic--restrictions on the
adoption of certain technologies--applied to plug-in (PHEV) and strong
hybrid vehicles (SHEV). Some technologies on these pathways were
``skipped'' if a vehicle was high performance, required high towing
capabilities as a pickup truck, or belonged to certain manufacturers
who have demonstrated that their future product plans will more than
likely not include the technology. The specific criteria for SKIP logic
for each applicable electrification technology will be expanded on
later in this section.
    This section also discusses the supersession of engines and
transmissions on vehicles that adopt SHEV or PHEV powertrains. To
manage the complexity of the analysis, these types of hybrid
powertrains were modeled with several specific engines and
transmissions, rather than in multiple configurations. Therefore, the
cost and effectiveness values SHEV and PHEV technologies take into
account these specific engines and transmissions.
    Finally, phase-in caps limited the adoption rates of battery
electric (BEV) and fuel cell vehicles (FCV). These phase-in caps were
set by DOT, taking into account current market share, scalability, and
reasonable consumer adoption rates of each technology. TSD Chapter
3.3.3 discusses the electrification phase-in caps and the reasoning
behind them in detail.
    The only adoption feature applicable to micro and mild hybrid
technologies was path logic. The pathway consists of a linear
progression starting with a conventional powertrain with no
electrification at all, which is superseded by SS12V, which in turn is
superseded by BISG. Vehicles could only adopt micro and mild hybrid
technology if the vehicle did not already have a more advanced level of
electrification.
    The adoption features applied to strong hybrid technologies
included path logic, powertrain substitution, and vehicle class
restrictions. Per the defined technology pathways, SHEVPS, SHEVP2, and
the P2HCR technologies were considered mutually exclusive. In other
words, when the model applies one of these technologies, the others are
immediately disabled from future application. However, all vehicles on
the strong hybrid pathways could still advance to one or more of the
plug-in hybrid technologies.
    When the model applied any strong hybrid technology to a vehicle,
the transmission technology on the vehicle was superseded. Regardless
of the transmission originally present, P2 hybrids adopt an 8-speed
automatic transmission (AT8L2), and PS hybrids adopt a continuously
variable transmission (eCVT).
    When the model applies the SHEVP2 technology, the model can
consider various engine options to pair with the SHEVP2 architecture
according to existing engine path constraints, taking into account
relative cost effectiveness. For SHEVPS technology, the existing engine
was replaced with Eng26, a full Atkinson cycle engine.
    SKIP logic was also used to constrain adoption for SHEVPS, P2HCR0,
P2HCR1, and P2HCR1D. No SKIP logic applied to SHEVP2; P2HCR2 was
restricted from all vehicles in the 2020 fleet, as discussed further in
Section III.D.1.d)(1). These technologies were ``skipped'' for vehicles
with engines \185\ that met one of the following conditions:
---------------------------------------------------------------------------

    \185\ This refers to the engine assigned to the vehicle in the
2020 baseline fleet.
---------------------------------------------------------------------------

     The engine belonged to an excluded manufacturer; \186\
---------------------------------------------------------------------------

    \186\ Excluded manufacturers included BMW, Daimler, and Jaguar
Land Rover.
---------------------------------------------------------------------------

     The engine belonged to a pickup truck (i.e., the engine
was on a vehicle assigned the ``pickup'' body style);
     The engine's peak horsepower was more than 405 HP; or if
     The engine was on a non-pickup vehicle but was shared with
a pickup.
    The reasons for these conditions are similar to those for the SKIP
logic applied to HCR engine technologies, discussed in more detail
above. In the real world, pickups and performance vehicles with certain
powertrain configurations cannot adopt the technologies listed above
and maintain vehicle performance without redesigning the entire
powertrain. SKIP logic was put in place to prevent the model from
pursuing compliance pathways that are ultimately unrealistic.
    PHEV technologies superseded the micro, mild, and strong hybrids,
and could only be replaced by full electric technologies. Plug-in
hybrid technology paths were also mutually exclusive, with the PHEV20
technologies able to progress to the PHEV50 technologies.
    The engine and transmission technologies on a vehicle were
superseded when PHEV technologies were applied to a vehicle. For all
plug-in technologies, the model applied an AT8L2 transmission. For
PHEV20/50 and PHEV20H/50H, the vehicle received a full Atkinson cycle
engine, Eng26. For PHEV20T/50T, the vehicle received a TURBO1 engine,
Eng12.
    SKIP logic applied to PHEV20/20H and PHEV50/50H under the same four
conditions listed for the strong hybrid technologies in the previous
section, for the same reasons previously discussed.
    For the analysis, the adoption of BEVs and FCEVs was limited by
both path logic and phase in caps. BEV200/300/400/500 and FCEV were
applied as end-of-path technologies that superseded previous levels of
electrification.
    The main adoption feature applicable to BEVs and FCEVs is phase-in
caps, which are defined in the CAFE Model input files as percentages
that represent the maximum rate of increase in penetration rate for a
given technology. They are accompanied by a phase-in start year, which
determines the first year the phase-in cap applies. Together, the
phase-in cap and start year determine the maximum penetration rate for
a given technology in a given year; the maximum penetration rate equals
the phase-in cap times the number of years elapsed since the phase-in
start year. Note that phase-in caps do not inherently dictate how much
a technology is applied by the model. Rather, they represent how much
of the fleet could have a given technology by a given year. Because
BEV200 costs less and has higher effectiveness values than other
advanced electrification technologies,\187\ the model will have
vehicles adopt it first, until it is restricted by the phase-in cap.
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    \187\ This is because BEV200 uses fewer batteries and weighs
less than BEVs with greater ranges.
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    Table III-18 shows the phase-in caps, phase-in year, and maximum
penetration rate through 2050 for BEV and FCEV technologies. For
comparison, the actual penetration rate of each technology in the 2020
baseline fleet is also listed in the fourth column from the left.

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    The BEV200 phase-in cap was informed by manufacturers' tendency to
move away from low-range vehicle offerings, in part because of consumer
hesitancy to adopt this technology. The advertised range on most
electric vehicles does not reflect extreme cold and hot real-world
driving conditions, affecting the utility of already low-range
vehicles.\188\ Many manufacturers have told DOT that the portion of
consumers willing to accept a vehicle with less than 300 miles of
electric range is extremely small, and many manufacturers do not plan
to offer vehicles with less than 300 miles of electric range. For
example, in February 2021, Tesla, the U.S.' highest-selling BEV
manufacturer, discontinued the Standard Range Model Y because its range
did not meet the company's ``standard of excellence.'' \189\ Tesla does
sell long-range versions of many of its vehicles.
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    \188\ AAA. ``AAA Electric Vehicle Range Testing.'' February
2019. https://www.aaa.com/AAA/common/AAR/files/AAA-Electric-Vehicle-Range-Testing-Report.pdf.
    \189\ Baldwin, Roberto. ``Tesla Model Y Standard Range
Discontinued; CEO Musk Tweets Explanation.'' Car and Driver, 30 Apr.
2021, www.caranddriver.com/news/a35602581/elon-musk-model-y-discontinued-explanation/. Accessed May 20, 2020.
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    Furthermore, the average BEV range has steadily increased over the
past decade,\190\ perhaps in part as batteries become more cost
effective. EPA observed in its 2020 Automotive Trends Report that ``the
average range of new EVs has climbed substantially. In model year 2019
the average new EV is projected to have a 252-mile range, or about
three and a half times the range of an average EV in 2011. This
difference is largely attributable to higher production of new EVs with
much longer ranges.'' \191\ The maximum growth rate for BEV200 in the
model was set accordingly low to less than 0.1% per year. While this
rate is significantly lower than that of the other BEV technologies,
the BEV200 phase-in cap allows the penetration rate of low-range BEVs
to grow by a multiple of what is currently observed in the market.
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    \190\ 2020 EPA Automotive Trends Report, at 53, figure 4.14.
    \191\ 2020 EPA Automotive Trends Report, at 53.
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    For BEV300, 400, and 500, phase-in caps are largely a reflection of
the challenges facing the scalability of BEV manufacturing, and
implementing BEV technology on many vehicle configurations, including
larger vehicles. In the short term, the penetration of BEVs is largely
limited by battery availability.\192\ For example, Tesla has struggled
to scale production of new cells for its vehicles, and it remains a
bottleneck in the company's production capability.\193\ The Director of
Energy and Environmental Research at Toyota acknowledged in March 2021
that BEV adoption faces many challenges beyond battery availability,
including ``the cost of batteries, the need for national
infrastructure, long recharging times, limited driving range and the
need for consumer behavioral change.'' \194\ Incorporating battery
packs that provide greater amounts of electric range into vehicles also
poses its own engineering challenges. Heavy batteries and large packs
may be difficult to integrate for many vehicle configurations. Pickup
trucks and large SUVs in particular require higher levels of energy as
the number of passengers and/or payload increases, for towing and other
high-torque applications. DOT selected the BEV400 and 500 phase-in caps
to reflect these concerns.
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    \192\ See, e.g., Cohen, Ariel. ``Manufacturers Are Struggling To
Supply Electric Vehicles With Batteries.'' Forbes, Forbes Magazine,
25 March 2020, www.forbes.com/sites/arielcohen/2020/03/25/manufacturers-are-struggling-to-supply-electric-vehicles-with-batteries. Accessed May 20, 2021.
    \193\ Hyatt, Kyle. ``Tesla Will Build an Electric Van
Eventually, Elon Musk Says.'' Roadshow, CNET, 28 Jan. 2021,
www.cnet.com/roadshow/news/tesla-electric-van-elon-musk/. Accessed
May 20, 2021.
    \194\ https://www.energy.senate.gov/services/files/E2EA0E4F-BAD9-452D-99CC-35BC204DE6F0.
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    The phase-in cap for FCEVs was assigned based on existing market
share as well as historical trends in FCEV production. FCEV production
share in the past five years has been extremely low, and DOT set the
phase-in cap accordingly.\195\ As with BEV200, however, the phase-in
cap still allows for the market share of FCVs to grow several times
over.
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    \195\ 2020 EPA Automotive Trends Report, at 52, figure 4.13.
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(d) Electrification Effectiveness Modeling
    For this analysis, DOT considers a range of electrification
technologies which, when modeled, result in varying levels of
effectiveness at reducing fuel consumption. As discussed above, the
modeled electrification technologies include micro hybrids, mild
hybrids, two different strong hybrids, two different plug-in hybrids
with two separate all electric ranges, full electric vehicles and
FCEVs. Each electrification technology consists of many complex sub-
systems with unique component

characteristics and operational modes. As discussed further below, the
systems that contribute to the effectiveness of an electrified
powertrain in the analysis include the vehicle's battery, electric
motors, power electronics, and accessory loads. Procedures for modeling
each of these sub-systems are broadly discussed below, in Section
III.C.4, and the Autonomie model documentation.
    Argonne used data from their Advanced Mobility Technology
Laboratory (AMTL) to develop Autonomie's electrified powertrain models.
The modeled powertrains are not intended to represent any specific
manufacturer's architecture but are intended to act as surrogates
predicting representative levels of effectiveness for each
electrification technology.
    Autonomie determines the effectiveness of each electrified
powertrain type by modeling the basic components, or building blocks,
for each powertrain, and then combining the components modularly to
determine the overall efficiency of the entire powertrain. The basic
building blocks that comprise an electrified powertrain in the analysis
include the battery, electric motors, power electronics, and accessory
loads. Autonomie identifies components for each electrified powertrain
type, and then interlinks those components to create a powertrain
architecture. Autonomie then models each electrified powertrain
architecture and provides an effectiveness value for each architecture.
For example, Autonomie determines a BEV's overall efficiency by
considering the efficiencies of the battery, the electric traction
drive system (the electric machine and power electronics) and
mechanical power transmission devices. Or, for a SHEVP2, Autonomie
combines a very similar set of components to model the electric portion
of the hybrid powertrain, and then also includes the combustion engine
and related power for transmission components. See TSD Chapter 3.3.4
for a complete discussion of electrification component modeling.
    As discussed earlier in Section III.C.4, Autonomie applies
different powertrain sizing algorithms depending on the type of vehicle
considered because different types of vehicles not only contain
different powertrain components to be optimized, but they must also
operate in different driving modes. While the conventional powertrain
sizing algorithm must consider only the power of the engine, the more
complex algorithm for electrified powertrains must simultaneously
consider multiple factors, which could include the engine power,
electric machine power, battery power, and battery capacity. Also,
while the resizing algorithm for all vehicles must satisfy the same
performance criteria, the algorithm for some electric powertrains must
also allow those electrified vehicles to operate in certain driving
cycles, like the US06 cycle, without assistance of the combustion
engine, and ensure the electric motor/generator and battery can handle
the vehicle's regenerative braking power, all-electric mode operation,
and intended range of travel.
    To establish the effectiveness of the technology packages,
Autonomie simulates the vehicles' performance on compliance test
cycles, as discussed in Section III.C.4.196 197 198 The
range of effectiveness for the electrification technologies in this
analysis is a result of the interactions between the components listed
above and how the modeled vehicle operates on its respective test
cycle. This range of values will result in some modeled effectiveness
values being close to real-world measured values, and some modeled
values that will depart from measured values, depending on the level of
similarity between the modeled hardware configuration and the real-
world hardware and software configurations. This modeling approach
comports with the National Academy of Science 2015 recommendation to
use full vehicle modeling supported by application of lumped
improvements at the sub-model level.\199\ The approach allows the
isolation of technology effects in the analysis supporting an accurate
assessment.
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    \196\ See U.S. EPA, ``How Vehicles are Tested.'' https://www.fueleconomy.gov/feg/how_tested.shtml. Last accessed May 6, 2021.
    \197\ See Autonomie model documentation, Chapter 6: Test
Procedures and Energy Consumption Calculations.
    \198\ EPA Guidance Letter. ``EPA Test Procedures for Electric
Vehicles and Plug-in Hybrids.'' Nov. 14, 2017. https://www.fueleconomy.gov/feg/pdfs/EPA%20test%20procedure%20for%20EVs-PHEVs-11-14-2017.pdf. Last accessed May 6, 2021.
    \199\ 2015 NAS report, at 292.
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    The range of effectiveness values for the electrification
technologies, for all ten vehicle technology classes, is shown in
Figure III-12. In the graph, the box shows the inner quartile range
(IQR) of the effectiveness values and whiskers extend out 1.5 x IQR.
The dots outside of the whiskers show values outside these bounds.
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BILLING CODE 4910-59-C
(e) Electrification Costs
    The total cost to electrify a vehicle in this analysis is based on
the battery the vehicle requires, the non-battery electrification
component costs the vehicle requires, and the traditional powertrain
components that must be added or removed from the vehicle to build the
electrified powertrain.
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    \200\ The data used to create this figure can be found in the
FE_1 Adjustments file.
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    We worked collaboratively with the experts at Argonne National
Laboratory to generate battery costs using BatPaC, which is a model
designed to calculate the cost of a vehicle battery for a specified
battery power, energy, and type. Argonne used BatPaC v4.0 (October 2020
release) to create lookup tables for battery cost and mass that the
Autonomie simulations referenced when a vehicle received an electrified
powertrain. The BatPaC battery cost estimates are generated for a base
year, in this case for MY 2020. Accordingly, our BatPaC inputs
characterized the state of the market in MY 2020 and employed a widely
utilized cell chemistry (NMC622),\201\ average estimated battery pack
production volume per plant (25,000), and a plant efficiency or plant
cell yield value of 95%.
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    \201\ Autonomie model documentation, Chapter 5.9. Argonne
surveyed A2Mac1 and TBS teardown reports for electrified vehicle
batteries and of the five fully electrified vehicles surveyed, four
of those vehicles used NMC622 and one used NMC532. See also Georg
Bieker, A Global Comparison of the Life-Cycle Greenhouse Gas
Emissions of Combustion Engine and Electric Passenger Cars,
International Council on Clean Transportation (July 2021), https://theicct.org/sites/default/files/publications/Global-LCA-passenger-cars-jul2021_0.pdf (``For cars registered in 2021, the GHG emission
factors of the battery production are based on the most common
battery chemistry, NMC622-graphite batteries. . . .''); 2021 NAS
report, at 5-92 (``. . . NMC622 is the most common cathode chemistry
in 2019. . . .'').
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    For two specific electrified vehicle applications, BEV400 and
BEV500, we did not use BatPaC to generate battery pack costs. Rather,
we scaled the BatPaC-generated BEV300 costs to match the range of
BEV400 and BEV500 vehicles to compute a direct manufacturing cost for
those vehicles' batteries. We initially examined using BatPaC to model
the cost and weight of BEV400 and BEV500 packs, however, initial values
from the model could not be validated and were based on assumptions for
smaller sized battery packs. The initial results provided cost and
weight estimates for BEV400 battery packs out of alignment with current
examples of BEV400s in the market, and there are currently no examples
of BEV500 battery packs in the market against which to validate the
pack results.
    Finally, to reflect how we expect batteries could fall in cost over
the timeframe considered in the analysis, we applied a learning rate to
the direct manufacturing cost. Broadly, the learning rate applied in
this analysis reflects middle-of-the-road year-over-year improvements
until MY 2032, and then the learning rates incrementally become
shallower as battery technology is expected to mature in MY 2033 and
beyond. Applying learning curves to the battery pack DMC in subsequent
analysis years lowers the cost such that the cost of a battery pack in
any future model year could be representative of the cost to
manufacture a battery pack, regardless of potentially diverse
parameters such as cell chemistry, cell format, or production volume.

    TSD Chapter <IP_ADDRESS> includes more detail about the process we used
to develop battery costs for this analysis. In addition, all BatPaC-
generated direct manufacturing costs for all technology keys can be
found in the CAFE Model's Battery Costs file, and the Argonne BatPaC
Assumptions file includes the assumptions used to generate the costs,
and pack costs, pack mass, cell capacity, $/kW at the pack level, and
W/kg at the pack level for all vehicle classes.
    Table III-19 and Table III-20 show an example of our battery pack
direct manufacturing costs per kilowatt hour for BEV300s for all
vehicle classes for the base year, MY 2020. The tables shown here
demonstrate how the cost per kWh varies with the size of the battery
pack. While the overall cost of a battery pack will go up for larger
kWh battery packs, the cost per kWh goes down. The amortization of
costs for components required in all battery packs across a larger
number of cells results in this reduced cost per kWh.
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    A range of parameters can ultimately influence battery pack
manufacturing costs, including other vehicle improvements (e.g., mass
reduction technology, aerodynamic improvements, or tire rolling
resistance improvements all affect the size and energy of a battery
required to propel a vehicle where all else is equal), and the
availability of materials required to manufacture the
battery.202 203 Or, if manufacturers adopt more
electrification technology than projected in this analysis, increases
in battery pack production volume will likely lower actual battery pack
costs.
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    \202\ The cost of raw material also has a meaningful influence
on the future cost of the battery pack. As the production volume
goes up, the demand for battery critical raw materials also goes up,
which has an offsetting impact on the efficiency gains achieved
through economies of scale, improved plant efficiency, and advanced
battery cell chemistries. We do not consider future battery raw
material price fluctuations for this analysis, however that may be
an area for further exploration in future analyses.
    \203\ See, e.g., Jacky Wong, EV Batteries: The Next Victim of
High Commodity Prices?, The Wall Street Journal (July 22, 2021),
https://www.wsj.com/articles/ev-batteries-the-next-victim-of-high-commodity-prices-11626950276.
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    Like the 2020 final rule, we compared our battery pack costs in
future years to battery pack costs from other sources that may or may
not account for some of these additional parameters, including varying
potential future battery chemistry and learning rates. As discussed in
TSD Chapter <IP_ADDRESS>.4, our battery pack costs in 2025 and 2030 fell
fairly well in the middle of other sources' cost projections, with
Bloomberg New Energy Finance (BNEF) projections presenting the highest
year-over-year cost reductions,\204\ and MIT's Insights into Future
Mobility report providing an upper bound of potential future
costs.\205\ ICCT presented a similar comparison of costs from several
sources in its 2019 working paper, Update on Electric Vehicle Costs in
the United States through 2030, and predicted battery pack costs in
2025 and 2030 would drop to approximately $104/kWh and $72/kWh,