duty engine (over 33,000 lbs GVWR) would be subject to all the emission
standards and other requirements that apply to compression-ignition
engines.
    Table II-17 describes the provisions that would apply differently
for compression-ignition and spark-ignition engines:

 Table II-17--Regulatory Provisions That Are Different for Compression-
                   Ignition and Spark-Ignition Engines
------------------------------------------------------------------------
           Provision             Compression-ignition    Spark-ignition
------------------------------------------------------------------------
Transient duty cycle..........  40 CFR part 86,         40 CFR part 86,
                                 Appendix I, paragraph   Appendix I,
                                 (f)(2) cycle; divide    paragraph
                                 by 1.12 to de-          (f)(1) cycle.
                                 normalize.
Ramped-modal test (SET).......  yes...................  no.
NTE standards.................  yes...................  no.
Smoke standard................  yes...................  no.
Manufacturer-run in-use         yes...................  no.
 testing.
ABT--pollutants...............  NOX, PM...............  NOX, NMHC.
ABT-- transient conversion      6.5...................  6.3.
 factor.
ABT--averaging set............  Separate averaging      One averaging
                                 sets for light,         set for all SI
                                 medium, and heavy       engines.
                                 HDDE.
Useful life...................  110,000 miles for       110,000 miles
                                 light HDDE.
                                185,000 miles for
                                 medium HDDE..
                                435,000 miles for
                                 heavy HDDE..
Warranty......................  50,000 miles for light  50,000 miles.
                                 HDDE.
                                100,000 miles for
                                 medium HDDE..
                                100,000 miles for
                                 heavy HDDE..
Detailed AECD description.....  yes...................  no.
Test engine selection.........  highest injected fuel   most likely to
                                 volume.                 exceed emission
                                                         standards.
------------------------------------------------------------------------

    The onboard diagnostic requirements already differentiate
requirements by fuel type, so there is no need for those provisions to
change based on the considerations of this section.
    We are not aware of any currently certified engines that would
change from compression-ignition to spark-ignition under the proposed
clarified approach. Nonetheless, because these proposed standards
implicate rules for criteria pollutants (as well as GHGs), the
provisions of CAA section 202(a)(3)(C) apply (for the criteria
pollutants), notably the requirement of four years lead time. We are
therefore proposing to continue to apply the existing interim provision
through model year 2020.\110\

Starting in model year 2021, all the provisions would apply as
described above. Manufacturers would not be permitted to certify any
engine families using carryover emission data if a particular engine
model switched from compression-ignition to spark-ignition, or vice
versa. However, as noted above, in practice these vehicles are already
being certified as CI engines, so we view these changes as
clarifications ratifying the current status quo.
---------------------------------------------------------------------------

    \110\ Section 202(a)(2), applicable to emissions of greenhouse
gases, does not mandate a specific period of lead time, but EPA sees
no reason for a different compliance date here for GHGs and criteria
pollutants. This is also true with respect to the closed crankcase
emission discussed in the following subsection.
---------------------------------------------------------------------------

    We are also proposing that these provisions would apply equally to
engines fueled by any fuel other than gasoline or ethanol, should such
engines be produced in the future. Given the current and historic
market for vehicles above 19,500 lbs GVWR, EPA believes any
alternative-fueled vehicles in this weight range would be competing
primarily with diesel vehicles and should be subject to the same
requirements as them. We request comment on all aspects of classifying
natural-gas and other engines for purposes of applying emission
standards. See Sections XI and XII for additional discussion of natural
gas fueled engines.
(f) Crankcase Emissions From Natural Gas Engines
    EPA is proposing one fuel-specific provision for natural gas
engines, likewise applicable to all pollutant emissions, both GHGs and
criteria pollutant emissions. Note that we are also proposing other
vehicle-level emissions controls for the natural gas storage tanks and
refueling connections. These are presented in Section XIII.
    EPA is proposing to require that all natural gas-fueled engines
have closed crankcases, rather than continuing the provision that
allows venting to the atmosphere all crankcase emissions from all
compression-ignition engines. This has been allowed as long as these
vented crankcase emissions are measured and accounted for as part of an
engine's tailpipe emissions. This allowance has historically been in
place to address the technical limitations related to recirculating
diesel-fueled engines' crankcase emissions, which have high PM
emissions, back into the engine's air intake. High PM emissions vented
into the intake of an engine can foul turbocharger compressors and
aftercooler heat exchangers. In contrast, historically EPA has mandated
closed crankcase technology on all gasoline fueled engines and all
natural gas spark-ignition engines.\111\ The inherently low PM
emissions from these engines posed no technical barrier to a closed
crankcase mandate. Because natural gas-fueled compression ignition
engines also have inherently low PM emissions, there is no
technological limitation that would prevent manufacturers from closing
the crankcase and recirculating all crankcase gases into a natural gas-
fueled compression ignition engine's air intake. We are requesting
comment on the costs and effectiveness of technologies that we have
identified to comply with these provisions. In addition, EPA is
proposing that this revised standard not take effect until the 2021
model year, consistent with the requirement of section 202(a)(3)(C) to
provide four years lead time.

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

    \111\ See 40 CFR 86.008-10(c).
---------------------------------------------------------------------------

III. Class 7 and 8 Combination Tractors

    Class 7 and 8 combination tractors-trailers contribute the largest
portion of the total GHG emissions and fuel consumption of the heavy-
duty sector, approximately two-thirds, due to their large payloads,
their high annual miles traveled, and their major role in national
freight transport.\112\ These vehicles consist of a cab and engine
(tractor or combination tractor) and a trailer.\113\ In general,
reducing GHG emissions and fuel consumption for these vehicles would
involve improvements to all aspects of the vehicle.
---------------------------------------------------------------------------

    \112\ The on-highway Class 7 and 8 combination tractor-trailers
constitute the vast majority of this regulatory category. A small
fraction of combination tractors are used in off-road applications
and are regulated differently, as described in Section III.C.
    \113\ ``Tractor'' is defined in 49 CFR 571.3 to mean ``a truck
designed primarily for drawing other motor vehicles and not so
constructed as to carry a load other than a part of the weight of
the vehicle and the load so drawn.''
---------------------------------------------------------------------------

    As we found during the development in Phase 1 and as continues to
be true in the industry today, the heavy-duty combination tractor-
trailer industry consists of separate tractor manufacturers and trailer
manufacturers. We are not aware of any manufacturer that typically
assembles both the finished truck and the trailer and introduces the
combination into commerce for sale to a buyer. There are also large
differences in the kinds of manufacturers involved with producing
tractors and trailers. For HD highway tractors and their engines, a
relatively limited number of manufacturers produce the vast majority of
these products. The trailer manufacturing industry is quite different,
and includes a large number of companies, many of which are relatively
small in size and production volume. Setting standards for the products
involved--tractors and trailers--requires recognition of the large
differences between these manufacturing industries, which can then
warrant consideration of different regulatory approaches. Thus,
although tractor-trailers operate essentially as a unit from both a
commercial standpoint and for purposes of fuel efficiency and
CO2 emissions, the agencies have developed separate proposed
standards for each.
    Based on these industry characteristics, EPA and NHTSA believe that
the most appropriate regulatory approach for combination tractors and
trailers is to establish standards for tractors separately from
trailers. As discussed below in Section IV, the agencies are also
proposing standards for certain types of trailers.

A. Summary of the Phase 1 Tractor Program

    The design of each tractor's cab and drivetrain determines the
amount of power that the engine must produce in moving the truck and
its payload down the road. As illustrated in Figure III-1, the loads
that require additional power from the engine include air resistance
(aerodynamics), tire rolling resistance, and parasitic losses
(including accessory loads and friction in the drivetrain). The
importance of the engine design is that it determines the basic GHG
emissions and fuel consumption performance for the variety of demands
placed on the vehicle, regardless of the characteristics of the cab in
which it is installed.

[GRAPHIC] [TIFF OMITTED] TP13JY15.002

    Accordingly, for Class 7 and 8 combination tractors, the agencies
adopted two sets of Phase 1 tractor standards for fuel consumption and
CO2 emissions. The CO2 emission and fuel
consumption reductions related to engine technologies are recognized in
the engine standards. For vehicle-related emissions and fuel
consumption, tractor manufacturers are required to meet vehicle-based
standards. Compliance with the vehicle standard must be determined
using the GEM vehicle simulation tool.
---------------------------------------------------------------------------

    \114\ Adapted from Figure 4.1. Class 8 Truck Energy Audit,
Technology Roadmap for the 21st Century Truck Program: A Government-
Industry Research Partnership, 21CT-001, December 2000.
---------------------------------------------------------------------------

    The Phase 1 tractor standards were based on several key attributes
related to GHG emissions and fuel consumption that reasonably represent
the many differences in utility and performance among these vehicles.
Attribute-based standards in general recognize the variety of functions
performed by vehicles and engines, which in turn can affect the kind of
technology that is available to control emissions and reduce fuel
consumption, or its effectiveness. Attributes that characterize
differences in the design of vehicles, as well as differences in how
the vehicles will be employed in-use, can be key factors in evaluating
technological improvements for reducing CO2 emissions and
fuel consumption. Developing an appropriate attribute-based standard
can also avoid interfering with the ability of the market to offer a
variety of products to meet the customer's demand. The Phase 1 tractor
standards differ depending on GVWR (i.e., whether the truck is Class 7
or Class 8), the height of the roof of the cab, and whether it is a
``day cab'' or a ``sleeper cab.'' These later two attributes are
important because the height of the roof, designed to correspond to the
height of the trailer, significantly affects air resistance, and a
sleeper cab generally corresponds to the opportunity for extended
duration idle emission and fuel consumption improvements. Based on
these attributes, the agencies created nine subcategories within the
Class 7 and 8 combination tractor category. The Phase 1 rules set
standards for each of them. Phase 1 standards began with the 2014 model
year and were followed with more stringent standards following in model
year 2017.\115\ The standards represent an overall fuel consumption and
CO2 emissions reduction up to 23 percent from the tractors
and the engines installed in them when compared to a baseline 2010
model year tractor and engine without idle shutdown technology.
Although the EPA and NHTSA standards are expressed differently (grams
of CO2 per ton-mile and gallons per 1,000 ton-mile
respectively), the standards are equivalent.
---------------------------------------------------------------------------

    \115\ Manufacturers may voluntarily opt-in to the NHTSA fuel
consumption standards in model years 2014 or 2015. Once a
manufacturer opts into the NHTSA program it must stay in the program
for all optional MYs.
---------------------------------------------------------------------------

    In Phase 1, the agencies allowed manufacturers to certify certain
types of combination tractors as vocational vehicles. These are
tractors that do not typically operate at highway speeds, or would
otherwise not benefit from efficiency improvements designed for line-
haul tractors (although standards would still apply to the engines
installed in these vehicles). The agencies created a subcategory of
``vocational tractors,'' or referred to as ``special purpose tractors''
in 40 CFR part 1037, because real world operation of these tractors is
better represented by our Phase 1 vocational vehicle duty cycle than
the tractor duty cycles. Vocational tractors are subject to the
standards for vocational vehicles rather than the combination tractor
standards. In addition, specific vocational tractors and heavy-duty
vocational vehicles primarily designed to perform work off-road or
having tires installed with a maximum speed rating at or below 55 mph
are exempted from the Phase 1 standards.
    In Phase 1, the agencies also established separate performance
standards for the engines manufactured for use in these tractors. EPA's
engine-based CO2 standards and NHTSA's engine-based fuel
consumption standards are being implemented using EPA's existing test
procedures and regulatory structure for criteria pollutant emissions
from medium- and heavy-duty engines. These engine standards vary
depending on engine size linked to intended vehicle service class
(which are the same service classes used for many years for EPA's
criteria pollutant standards).
    Manufacturers demonstrate compliance with the Phase 1 tractor
standards using the GEM simulation tool. As explained in Section II
above, GEM is a customized vehicle simulation model which is the
preferred approach to demonstrating compliance testing for combination
tractors rather than chassis dynamometer testing used in light-duty
vehicle compliance. As discussed in the development of HD Phase 1 and
recommended by the NAS 2010 study,

a simulation tool is the preferred approach for HD tractor compliance
because of the extremely large number of vehicle configurations.\116\
The GEM compliance tool was developed by EPA and is an accurate and
cost-effective alternative to measuring emissions and fuel consumption
while operating the vehicle on a chassis dynamometer. Instead of using
a chassis dynamometer as an indirect way to evaluate real world
operation and performance, various characteristics of the vehicle are
measured and these measurements are used as inputs to the model. For HD
Phase 1, these characteristics relate to key technologies appropriate
for this category of truck including aerodynamic features, weight
reductions, tire rolling resistance, the presence of idle-reducing
technology, and vehicle speed limiters. The model also assumes the use
of a representative typical engine in compliance with the separate,
applicable Phase 1 engine standard. Using these inputs, the model is
used to quantify the overall performance of the vehicle in terms of
CO2 emissions and fuel consumption. CO2 emission
reduction and fuel consumption technologies not measured by the model
must be evaluated separately, and the HD Phase 1 rules establish
mechanisms allowing credit for such ``off-cycle'' technologies.
---------------------------------------------------------------------------

    \116\ National Academy of Science. ``Technologies and Approaches
to Reducing the Fuel Consumption of Medium- and Heavy-Duty
Vehicles.'' 2010. Recommendation 8-4 stated ``Simulation modeling
should be used with component test data and additional tested inputs
from powertrain tests, which could lower the cost and administrative
burden yet achieve the needed accuracy of results.''
---------------------------------------------------------------------------

    In addition to the final Phase 1 tractor-based standards for
CO2, EPA adopted a separate standard to reduce leakage of
HFC refrigerant from cabin air conditioning (A/C) systems from
combination tractors, to apply to the tractor manufacturer. This HFC
leakage standard is independent of the CO2 tractor standard.
Manufacturers can choose technologies from a menu of leak-reducing
technologies sufficient to comply with the standard, as opposed to
using a test to measure performance.
    The Phase 1 program also provided several flexibilities to advance
the goals of the overall program while providing alternative pathways
to achieve compliance. The primary flexibility is the averaging,
banking, and trading program which allows emissions and fuel
consumption credits to be averaged within an averaging set, banked for
up to five years, or traded among manufacturers. Manufacturers with
credit deficits were allowed to carry-forward credit deficits for up to
three model years, similar to the LD GHG and CAFE carry-back credits.
Phase 1 also included several interim provisions, such as incentives
for advanced technologies and provisions to obtain credits for
innovative technologies (called off-cycle in the Phase 2 program) not
accounted for by the HD Phase 1 version of GEM or for certifying early.

B. Overview of the Proposed Phase 2 Tractor Program

    The proposed HD Phase 2 program is similar in many respects to the
Phase 1 approach. The agencies are proposing to maintain the Phase 1
attribute-based regulatory structure in terms of dividing the tractor
category into the same nine subcategories based on the tractor's GVWR,
cab configuration, and roof height. This structure is working well in
the implementation of Phase 1. The one area where the agencies are
proposing to change the regulatory structure is related to heavy-haul
tractors. As noted above, the Phase 1 regulations include a set of
provisions that allow vocational tractors to be treated as vocational
vehicles. However, because the agencies propose to include the
powertrain as part of the technology basis for the tractor and
vocational vehicle standards in Phase 2, we are proposing to classify a
certain set of these vocational tractors as heavy-haul tractors and
subject them to a separate tractor standard that reflects their unique
powertrain requirements and limitations in application of technologies
to reduce fuel consumption and CO2 emissions.\117\
---------------------------------------------------------------------------

    \117\ See 76 FR 57138 for Phase 1 discussion. See 40 CFR
1037.801 for proposed Phase 2 heavy-haul tractor regulatory
definition.
---------------------------------------------------------------------------

    The agencies propose to also retain much of the certification and
compliance structure developed in Phase 1 but to simplify end of the
year reporting. The agencies propose that the Phase 2 tractor
CO2 emissions and fuel consumption standards, as in Phase 1,
be aligned.\118\ The agencies also propose to continue to have separate
engine and vehicle standards to drive technology improvements in both
areas. The reasoning behind the proposal to maintain separate standards
is discussed above in Section II.B.2. As in Phase 1, the agencies
propose to certify tractors using the GEM simulation tool and to
require manufacturers to evaluate the performance of subsystems through
testing (the results of this testing to be used as inputs to the GEM
simulation tool). Other aspects of the proposed HD Phase 2
certification and compliance program also mirror the Phase 1 program,
such as maintaining a single reporting structure to satisfy both
agencies, requiring limited data at the beginning of the model year for
certification, and determining compliance based on end of year reports.
In the Phase 1 program, manufacturers participating in the ABT program
provided 90 day and 270 day reports after the end of the model year.
The agencies required two reports for the initial program to help
manufacturers become familiar with the reporting process. For the Phase
2 program, the agencies propose that manufacturers would only be
required to submit one end of the year report, which would simplify
reporting.
---------------------------------------------------------------------------

    \118\ Fuel consumption is calculated from CO2 using
the conversion factor of 10,180 grams of CO2 per gallon
for diesel fuel.
---------------------------------------------------------------------------

    Even though many aspects of the proposed HD Phase 2 program are
similar to Phase 1, there are some key differences. While Phase 1
focused on reducing CO2 emissions and fuel consumption in
tractors through the application of existing (``off-the-shelf'')
technologies, the proposed HD Phase 2 standards seek additional
reductions through increased use of existing technologies and the
development and deployment of more advanced technologies. To evaluate
the effectiveness of a more comprehensive set of technologies, the
agencies propose several additional inputs to GEM. The proposed set of
inputs includes the Phase 1 inputs plus parameters to assess the
performance of the engine, transmission, and driveline. Specific inputs
for, among others, predictive cruise control, automatic tire inflation
systems, and 6x2 axles would now be required. Manufacturers would
conduct component testing to obtain the values for these technologies
(should they choose to use them), which testing values would then be
input into the GEM simulation tool. See Section III.D.2 below. To
effectively assess performance of the technologies, the agencies also
propose to change some aspects of the drive cycle used in certification
through the addition of road grade. To reflect the existing trailer
market, the agencies are proposing to refine the aerodynamic test
procedure for high roof cabs by adding some aerodynamic improving
devices to the reference trailer (used for determining the relative
aerodynamic performance of the tractor). The agencies also propose to
change the aerodynamic certification test procedure to capture
aerodynamic improvement of trailers and the impact of wind on tractor
aerodynamic performance. The agencies are also proposing to change some
of the interim provisions developed in Phase 1 to reflect the maturity
of the program and

reduced need and justification for some of the Phase 1 flexibilities.
Further discussions on all of these matters are covered in the
following sections.

C. Proposed Phase 2 Tractor Standards

    EPA is proposing CO2 standards and NHTSA is proposing
fuel consumption standards for new Class 7 and 8 combination tractors.
In addition, EPA is proposing to maintain the HFC standards for the air
conditioning systems that were adopted in Phase 1. EPA is also seeking
comment on new standards to further control emissions of particulate
matter (PM) from auxiliary power units (APU) installed in tractors that
would prevent an unintended consequence of increasing PM emissions from
tractors during long duration idling.
    This section describes in detail the proposed standards. In
addition to describing the proposed alternative (``Alternative 3''), in
Section III.D.2.f we also detail another alternative (``Alternative
4''). Alternative 4 provides less lead time than the proposed set of
standards but may provide more net benefits in the form of greater
emission and fuel consumption reductions (with somewhat higher costs)
in the early years of the program. The agencies believe Alternative 4
has the potential to be maximum feasible and appropriate as discussed
later in this section.
    The agencies welcome comment on all aspects of the proposed
standards and the alternative standards described in Section III.D.2.f.
Commenters are encouraged to address all aspects of feasibility
analysis, including costs, the likelihood of developing the technology
to achieve sufficient relaibility within the proposed and alternative
lead-times, and the extent to which the market could utilize the
technology. It would be helpful if comments addressed these issues
separately for each type of technology.
(1) Proposed Fuel Consumption and CO2 Standards
    The proposed fuel consumption and CO2 standards for the
tractor cab are shown below in Table III-1. These proposed standards
would achieve reductions of up to 24 percent compared to the 2017 model
year baseline level when fully phased in beginning in the 2027 MY.\119\
The proposed standards for Class 7 are described as ``Day Cabs''
because we are not aware of any Class 7 sleeper cabs in the market
today; however, the agencies propose to require any Class 7 tractor,
regardless of cab configuration, meet the standards described as
``Class 7 Day Cab.'' We welcome comment on this proposed approach.
---------------------------------------------------------------------------

    \119\ Since the HD Phase 1 tractor standards fully phase-in by
the MY 2017, this is the logical baseline year.
---------------------------------------------------------------------------

    The agencies' analyses, as discussed briefly below and in more
detail later in this preamble and in the draft RIA Chapter 2, indicate
that these proposed standards, if finalized, would be maximum feasible
(within the meaning of 49 U.S.C. Section 32902 (k)) and would be
appropriate under each agency's respective statutory authorities. The
agencies solicit comment on all aspects of these analyses.

 Table III-1--Proposed Phase 2 Heavy-Duty Combination Tractor EPA Emissions Standards (g CO2/ton-mile) and NHTSA
                                 Fuel Consumption Standards (gal/1,000 ton-mile)
----------------------------------------------------------------------------------------------------------------
                                                                              Day cab               Sleeper cab
                                                                 -----------------------------------------------
                                                                      Class 7         Class 8         Class 8
----------------------------------------------------------------------------------------------------------------
2021 Model Year CO2 Grams per Ton-Mile..........................................................................
----------------------------------------------------------------------------------------------------------------
Low Roof........................................................              97              78              70
Mid Roof........................................................             107              84              78
High Roof.......................................................             109              86              77
----------------------------------------------------------------------------------------------------------------
2021 Model Year Gallons of Fuel per 1,000 Ton-Mile..............................................................
----------------------------------------------------------------------------------------------------------------
Low Roof........................................................          9.5285          7.6621          6.8762
Mid Roof........................................................         10.5108          8.2515          7.6621
High Roof.......................................................         10.7073          8.4479          7.5639
----------------------------------------------------------------------------------------------------------------
2024 Model Year CO2 Grams per Ton-Mile..........................................................................
----------------------------------------------------------------------------------------------------------------
Low Roof........................................................              90              72              64
Mid Roof........................................................             100              78              71
High Roof.......................................................             101              79              70
----------------------------------------------------------------------------------------------------------------
2024 Model Year and Later Gallons of Fuel per 1,000 Ton-Mile....................................................
----------------------------------------------------------------------------------------------------------------
Low Roof........................................................          8.8409          7.0727          6.2868
Mid Roof........................................................          9.8232          7.6621          6.9745
High Roof.......................................................          9.9214          7.7603          6.8762
----------------------------------------------------------------------------------------------------------------
2027 Model Year CO2 Grams per Ton-Mile..........................................................................
----------------------------------------------------------------------------------------------------------------
Low Roof........................................................              87              70              62
Mid Roof........................................................              96              76              69
High Roof.......................................................              96              76              67
----------------------------------------------------------------------------------------------------------------
2027 Model Year and Later Gallons of Fuel per 1,000 Ton-Mile....................................................
----------------------------------------------------------------------------------------------------------------
Low Roof........................................................          8.5462          6.8762          6.0904
Mid Roof........................................................          9.4303          7.4656          6.7780

High Roof.......................................................          9.4303          7.4656          6.5815
----------------------------------------------------------------------------------------------------------------

    It should be noted that the proposed HD Phase 2 CO2 and
fuel consumptions standards are not directly comparable to the Phase 1
standards. This is because the agencies are proposing several test
procedure changes to more accurately reflect real world operation of
tractors. These changes will result in the following differences.
First, the same vehicle evaluated using the proposed HD Phase 2 version
of GEM will obtain higher (i.e. less favorable) CO2 and fuel
consumption values because the Phase 2 drive cycles include road grade.
Road grade, which (of course) exists in the real-world, requires the
engine to operate at higher horsepower levels to maintain speed while
climbing a hill. Even though the engine saves fuel on a downhill
section, the overall impact increases CO2 emissions and fuel
consumption. The second of the key differences between the
CO2 and fuel consumption values in Phase 1 and Phase 2 is
due to proposed changes in the evaluation of aerodynamics. In the real
world, vehicles are exposed to wind which increases the drag of the
vehicle and in turn increases the power required to move the vehicle
down the road. To more appropriately reflect the in-use aerodynamic
performance of tractor-trailers, the agencies are proposing to input
into Phase 2 GEM the wind averaged coefficient of drag instead of the
no-wind (zero yaw) value used in Phase 1. The final key difference
between Phase 1 and the proposed Phase 2 program includes a more
realistic and improved simulation of the transmission in GEM, which
could increase CO2 and fuel consumption relative to Phase 1.
    The agencies are proposing Phase 2 CO2 emissions and
fuel consumption standards for the combination tractors that reflect
reductions that can be achieved through improvements in the tractor's
powertrain, aerodynamics, tires, and other vehicle systems. The
agencies have analyzed the feasibility of achieving the proposed
CO2 and fuel consumption standards, and have identified
means of achieving the proposed standards that are technically feasible
in the lead time afforded, economically practicable and cost-effective.
EPA and NHTSA present the estimated costs and benefits of the proposed
standards in Section III.D.2. In developing the proposed standards for
Class 7 and 8 tractors, the agencies have evaluated the following:

 the current levels of emissions and fuel consumption
 the kinds of technologies that could be utilized by tractor
and engine manufacturers to reduce emissions and fuel consumption from
tractors and associated engines
 the necessary lead time
 the associated costs for the industry
 fuel savings for the consumer
 the magnitude of the CO2 and fuel savings that may
be achieved

    The technologies on whose performance the proposed tractor
standards are predicated include: Improvements in the engine,
transmission, driveline, aerodynamic design, tire rolling resistance,
other accessories of the tractor, and extended idle reduction
technologies. These technologies, and other accessories of the tractor,
are described in draft RIA Chapter 2.4. The agencies' evaluation shows
that some of these technologies are available today, but have very low
adoption rates on current vehicles, while others will require some lead
time for development. EPA and NHTSA also present the estimated costs
and benefits of the proposed Class 7 and 8 combination tractor
standards in draft RIA Chapter 2.8 and 2.12, explaining as well the
basis for the agencies' proposed stringency level.
    As explained below in Section III.D, EPA and NHTSA have determined
that there would be sufficient lead time to introduce various tractor
and engine technologies into the fleet starting in the 2021 model year
and fully phasing in by the 2027 model year. This is consistent with
NHTSA's statutory requirement to provide four full model years of
regulatory lead time for standards. As was adopted in Phase 1, the
agencies are proposing for Phase 2 that manufacturers may generate and
use credits from Class 7 and 8 combination tractors to show compliance
with the standards. This is discussed further in Section III.F.
    Based on our analysis, the 2027 model year standards for
combination tractors and engines represent up to a 24 percent reduction
in CO2 emissions and fuel consumption over a 2017 model year
baseline tractor, as detailed in Section III.D.2. In considering the
feasibility of vehicles to comply with the proposed standards over
their useful lives, EPA also considered the potential for
CO2 emissions to increase during the regulatory useful life
of the product. As we discuss in Phase 1 and separately in the context
of deterioration factor (DF) testing, we have concluded that
CO2 emissions are likely to stay the same or actually
decrease in-use compared to new certified configurations. In general,
engine and vehicle friction decreases as products wear, leading to
reduced parasitic losses and consequent lower CO2 emissions.
Similarly, tire rolling resistance falls as tires wear due to the
reduction in tread height. In the case of aerodynamic components, we
project no change in performance through the regulatory life of the
vehicle since there is essentially no change in their physical form as
vehicles age. Similarly, weight reduction elements such as aluminum
wheels are (evidently) not projected to increase in mass through time,
and hence, we can conclude will not deteriorate with regard to
CO2 performance in-use. Given all of these considerations,
the agencies are confident in projecting that the tractor standards
being proposed today would be technically feasible throughout the
regulatory useful life of the program.
(2) Proposed Non-CO2 GHG Standards for Tractors
    EPA is also proposing standards to control non-CO2 GHG
emissions from Class 7 and 8 combination tractors.
(a) N2O and CH4 Emissions
    The proposed heavy-duty engine standards for both N2O
and CH4 as well as details of the proposed standards are
included in the discussion in Section II.D.3 and II.D.4. No additional
controls for N2O or CH4 emissions beyond those in
the proposed HD Phase 2 engine standards are being considered for the
tractor category.
(b) HFC Emissions
    Manufacturers can reduce hydrofluorocarbon (HFC) emissions from air
conditioning (A/C) leakage emissions in two ways. First, they can

utilize leak-tight A/C system components. Second, manufacturers can
largely eliminate the global warming impact of leakage emissions by
adopting systems that use an alternative, low-Global Warming Potential
(GWP) refrigerant, to replace the commonly used R-134a refrigerant. EPA
proposes to address HFC emissions by maintaining the A/C leakage
standards adopted in HD Phase 1 (see 40 CFR 1037.115). EPA believes the
Phase 1 use of leak-tight components is at an appropriate level of
stringency while maintaining the flexibility to produce the wide
variety of A/C system configurations required in the tractor category.
In addition, there currently are not any low GWP refrigerants approved
for the heavy-duty vehicle sector. Without an alternative refrigerant
approved for this sector, it is challenging to demonstrate feasibility
to reduce the amount of leakage allowed under the HFC leakage standard.
Please see Section I.F(1)(b) for a discussion related to alternative
refrigerants.
(3) PM Emissions From APUs
    Auxiliary power units (APUs) can be used in lieu of operating the
main engine during extended idle operations to provide climate control
and power to the driver. APUs can reduce fuel consumption,
NOX, HC, CH4, and CO2 emissions when
compared to main engine idling.\120\ However, a potential unintended
consequence of reducing CO2 emissions from combination
tractors through the use of APUs during extended idle operation is an
increase in PM emissions. Therefore, EPA is seeking comment on the need
and appropriateness to further reduce PM emissions from APUs.
---------------------------------------------------------------------------

    \120\ U.S. EPA. Development of Emission Rates for Heavy-Duty
Vehicles in the Motor Vehicle Emissions Simulator MOVES 2010. EPA-
420-B-12-049. August 2012.
---------------------------------------------------------------------------

    EPA conducted an analysis evaluating the potential impact on PM
emissions due to an increase in APU adoption rates using MOVES. In this
analysis, EPA assumed that these APUs emit criteria pollutants at the
level of the EPA standard for this type of non-road diesel engines.
Under this assumption, an APU would emit 1.8 grams PM per hour,
assuming an extended idle load demand of 4.5 kW (6 hp).\121\ However, a
2010 model year or newer tractor that uses its main engine to idle
emits approximately 0.35 grams PM per hour.\122\ The results from these
MOVES runs are shown below in Table III-2. These results show that an
increase in use of APUs could lead to an overall increase in PM
emissions if left uncontrolled. Column three labeled ``Proposed Program
PM2.5 Emission Impact without Further PM Control (tons)''
shows the incremental increase in PM2.5 without further
regulation of APU PM2.5 emissions.
---------------------------------------------------------------------------

    \121\ Tier 4, less-than-8 kW nonroad compression-ignition engine
exhaust emissions standards assumed for APUs: http://www.epa.gov/otaq/standards/nonroad/nonroadci.htm.
    \122\ U.S. EPA. MOVES2014 Reports. Last accessed on May 1, 2015
at http://www.epa.gov/otaq/models/moves/moves-reports.htm.

     Table III-2--Projected Impact of Increased Adoption of APUs in
                                 Phase 2
------------------------------------------------------------------------
                                                       Proposed program
                                Baseline HD vehicle   PM2.5\a\ emission
              CY                  PM2.5 emissions       impact without
                                       (tons)         further PM control
                                                            (tons)
------------------------------------------------------------------------
2035..........................               21,452                1,631
2050..........................               24,675                2,257
------------------------------------------------------------------------
Note:
\a\ Positive numbers mean emissions would increase from baseline to
  control case. PM2.5 from tire wear and brake wear are included.

    Since January 1, 2008, California ARB has prohibited the idling of
sleeper cab tractors during periods of sleep and rest.\123\ The
regulations apply additional requirements to diesel-fueled APUs on
tractors equipped with 2007 model year or newer engines. Truck owners
in California must either: (1) Fit the APU with an ARB verified Level 3
particulate control device that achieves 85 percent reduction in
particulate matter; or (2) have the APU exhaust plumbed into the
vehicle's exhaust system upstream of the particulate matter
aftertreatment device.\124\ Currently ARB includes four control devices
that have been verified to meet the Level 3 p.m. requirements. These
devices include HUSS Umwelttechnik GmbH's FS-MK Series Diesel
Particulate filters, Impco Ecotrans Technologies' ClearSky Diesel
Particulate Filter, Thermo King's Electric Regenerative Diesel
Particulate Filter, and Proventia's Electronically Heated Diesel
Particulate Filter. In addition, ARB has approved a Cummins integrated
diesel-fueled APU and several fuel-fired heaters produced by Espar and
Webasto.
---------------------------------------------------------------------------

    \123\ California Air Resources Board. Idle Reduction
Technologies for Sleeper Berth Trucks. Last viewed on September 19,
2014 at http://www.arb.ca.gov/msprog/cabcomfort/cabcomfort.htm.
    \124\ California Air Resources Board. Sec.  2485(c)(3)(A)(1).
---------------------------------------------------------------------------

    EPA conducted an evaluation of the impact of potentially requiring
further PM control from APUs nationwide. As shown in Table III-2, EPA
projects that the HD Phase 2 program as proposed (without additional PM
controls) would increase PM2.5 emissions by 1,631 tons in
2035 and 2,257 tons in 2050. The annual impact of a program to further
control PM could lead to a reduction of PM2.5 emissions
nationwide by 3,084 tons in 2035 and by 4,344 tons in 2050, as shown in
Table III-3 the column labeled ``Net Impact on National
PM2.5 Emission with Further PM Control of APUs (tons).''

                     Table III-3--Projected Impact of Further Control on PM2.5 Emissions \a\
----------------------------------------------------------------------------------------------------------------
                                                   Proposed HD phase 2  Proposed HD Phase 2     Net impact on
                               Baseline national     program national     Program National      national PM2.5
             CY                heavy-duty vehicle    PM2.5 Emissions      PM2.5 emissions       emission with
                                PM2.5 emissions     without Further PM    with further pm     further PM control
                                     (tons)           Control (tons)       control (tons)       of APUs (tons)
----------------------------------------------------------------------------------------------------------------
2035........................               21,452               23,083               19,999               -3,084
2050........................               24,675               26,932               22,588               -4,344
----------------------------------------------------------------------------------------------------------------
Note:
\a\ PM2.5 from tire wear and brake wear are included.

    EPA developed long-term cost projections for catalyzed diesel
particulate filters (DPF) as part of the Nonroad Diesel Tier 4
rulemaking. In that rulemaking, EPA estimated the DPF costs would add
$580 to the cost of 150 horsepower engines (69 FR 39126, June 29,
2004). On the other hand, ARB estimated the cost of retrofitting a
diesel powered APU with a PM trap to be $2,000 in 2005.\125\ The costs
of a DPF for an APU that provides less than 25 horsepower would be less
than the projected cost of a 150 HP engine because the filter volume is
in general proportional to the engine-out emissions and exhaust flow
rate. Proventia is charging customers $2,240 for electronically heated
DPF.\126\ EPA welcomes comments on cost estimates associated with DPF
systems for APUs.
---------------------------------------------------------------------------

    \125\ California Air Resources Board. Staff Report: Initial
Statement of Reasons; Notice of Public Hearing to Consider
Requirements to Reduce Idling Emissions From New and In-Use Trucks,
Beginning in 2008. September 1, 2005. Page 38. Last viewed on
October 20, 2014 at http://www.arb.ca.gov/regact/hdvidle/isor.pdf.
    \126\ Proventia. Tripac Filter Kits. Last accessed on October
21, 2014 at http://www.proventiafilters.com/purchase.html.
---------------------------------------------------------------------------

    EPA requests comments on the technical feasibility of diesel
particulate filters ability to reduce PM emissions by 85 percent from
non-road engines used to power APUs. EPA also requests comments on
whether the technology costs outlined above are accurate, and if so, if
projected reductions are appropriate taking into account cost, noise,
safety, and energy factors. See CAA section 213(a)(4).
(4) Proposed Exclusions From the Phase 2 Tractor Standards
    As noted above, in Phase 1, the agencies adopted provisions to
allow tractor manufacturers to reclassify certain tractors as
vocational vehicles.\127\ The agencies propose in Phase 2 to continue
to allow manufacturers to exclude certain vocational-types of tractors
from the combination tractor standards and instead be subject to the
vocational vehicle standards. However, the agencies propose to set
unique standards for tractors used in heavy haul applications in Phase
2. Details regarding the proposed heavy-haul standards are included
below in Section II.D.3.
---------------------------------------------------------------------------

    \127\ See 40 CFR 1037.630.
---------------------------------------------------------------------------

    During the development of Phase 1, the agencies received multiple
comments from several stakeholders supporting an approach for an
alternative treatment of a subset of tractors because they were
designed to operate at lower speeds, in stop and go traffic, and
sometimes operate at higher weights than the typical line-haul tractor.
These types of applications have limited potential for improvements in
aerodynamic performance to reduce CO2 emissions and fuel
consumption. Consistent with the agencies' approach in Phase 1, the
agencies agree that these vocational tractors are operated differently
than line-haul tractors and therefore fit more appropriately into the
vocational vehicle category. However, we need to continue to ensure
that only tractors that are truly vocational tractors are classified as
such.\128\ A vehicle determined by the manufacturer to be a HHD
vocational tractor would fall into one of the HHD vocational vehicle
subcategories and be regulated as a vocational vehicle. Similarly, MHD
tractors which the manufacturer chooses to reclassify as vocational
tractors would be regulated as a MHD vocational vehicle. Specifically,
the agencies are proposing to change the provisions in EPA's 40 CFR
1037.630 and NHTSA's regulation at 49 CFR 523.2 and only allow the
following two types of vocational tractors to be eligible for
reclassification by the manufacturer:
---------------------------------------------------------------------------

    \128\ As a part of the end of the year compliance process, EPA
and NHTSA verify manufacturer's production reports to avoid any
abuse of the vocational tractor allowance.
---------------------------------------------------------------------------

    (1) Low-roof tractors intended for intra-city pickup and delivery,
such as those that deliver bottled beverages to retail stores.
    (2) Tractors intended for off-road operation (including mixed
service operation), such as those with reinforced frames and increased
ground clearance.\129\
---------------------------------------------------------------------------

    \129\ See existing 40 CFR 1037.630(a)(1)(i) through (iii).
---------------------------------------------------------------------------

    Because the difference between some vocational tractors and line-
haul tractors is potentially somewhat subjective, we are also proposing
to continue to limit the use of this provision to a rolling three year
sales limit of 21,000 vocational tractors per manufacturer consistent
with past production volumes of such vehicles. We propose to carry-over
the existing three year sales limit with the recognition that heavy-
haul tractors would no longer be permitted to be treated as vocational
vehicles (suggesting a lower volumetric cap could be appropriate) but
that the heavy-duty market has improved since the development of the HD
Phase 1 rule (suggesting the need for a higher sales cap). The agencies
welcome comment on whether the proposed sales volume limit is set at an
appropriate level looking into the future.
    Also in Phase 1, EPA determined that manufacturers that met the
small business criteria specified in 13 CFR 121.201 for ``Heavy Duty
Truck Manufacturing'' were not subject to the greenhouse gas emissions
standards of 40 CFR 1037.106.\130\ The regulations required that
qualifying manufacturers must notify the Designated Compliance Officer
each model year before introducing the vehicles into commerce. The
manufacturers are also required to label the vehicles to identify them
as excluded vehicles. EPA and NHTSA are seeking comments on eliminating
this provision for tractor manufacturers in the Phase 2 program. The
agencies are aware of two second stage manufacturers building custom
sleeper cab tractors. We could treat these vehicles in one of two ways.
First, the vehicles may be considered as dromedary vehicles and
therefore treated as vocational vehicles.\131\ Or the

agencies could provide provisions that stated if a manufacturer changed
the cab, but not the frontal area of the vehicle, then it could retain
the aerodynamic bin of the original tractor. We welcome comments on
these considerations.
---------------------------------------------------------------------------

    \130\ See 40 CFR 1037.150(c).
    \131\ A dromedary is a box, deck, or plate mounted behind the
tractor cab and forward of the fifth wheel on the frame of the power
unit of a tractor-trailer combination to carry freight.
---------------------------------------------------------------------------

    EPA is proposing to not exempt glider kits from the Phase 2 GHG
emission standards.\132\ Gliders and glider kits are exempt from
NHTSA's Phase 1 fuel consumption standards. For EPA purposes, the
CO2 provisions of Phase 1 exempted gliders and glider kits
produced by small businesses but did not include such a blanket
exemption for other glider kits.\133\ Thus, some gliders and glider
kits are already subject to the requirement to obtain a vehicle
certificate prior to introduction into commerce as a new vehicle.
However, the agencies believe glider manufacturers may not understand
how these regulations apply to them, resulting in a number of
uncertified vehicles.
---------------------------------------------------------------------------

    \132\ Glider vehicles are new vehicles produced to accept
rebuilt engines (or other used engines) along with used axles and/or
transmissions. The common commercial term ``glider kit'' is used
here primarily to refer to an assemblage of parts into which the
used/rebuilt engine is installed.
    \133\ Rebuilt engines used in glider vehicles are subject to EPA
criteria pollutant emission standards applicable for the model year
of the engine. See 40 CFR 86.004-40 for requirements that apply for
engine rebuilding. Under existing regulations, engines that remain
in their certified configuration after rebuilding may continue to be
used.
---------------------------------------------------------------------------

    EPA is concerned about adverse economic impacts on small businesses
that assemble glider kits and glider vehicles. Therefore, EPA is
proposing an option that would grandfather existing small businesses,
but cap annual production based on their recent sales. EPA requests
comment on whether any special provisions would be needed to
accommodate glider kits. See Section XIV for additional discussion of
the proposed requirements for glider vehicles.
    Similarly, NHTSA is considering including glider vehicles under its
Phase 2 program. The agencies request comment on their respective
considerations.
    We believe that the agencies potentially having different policies
for glider kits and glider vehicles under the Phase 2 program would not
result in problematic disharmony between the NHTSA and EPA programs,
because of the small number of vehicles that would be involved. EPA
believes that its proposed changes would result in the glider market
returning to the pre-2007 levels, in which fewer than 1,000 glider
vehicles would be produced in most years. Only non-exempt glider
vehicles would be subject to different requirements under the NHTSA and
EPA regulations. However, we believe that this is unlikely to exceed a
few hundred vehicles in any year, which would be few enough not to
result in any meaningful disharmony between the two agencies.
    With regard to NHTSA's safety authority over gliders, the agency
notes that it has become increasingly aware of potential noncompliance
with its regulations applicable to gliders. NHTSA has learned of
manufacturers who are creating glider vehicles that are new vehicles
under 49 CFR 571.7(e); however, the manufacturers are not certifying
them and obtaining a new VIN as required. NHTSA plans to pursue
enforcement actions as applicable against noncompliant manufacturers.
In addition to enforcement actions, NHTSA may consider amending 49 CFR
571.7(e) and related regulations as necessary. NHTSA believes
manufacturers may not be using this regulation as originally intended.
(5) In-Use Standards
    Section 202(a)(1) of the CAA specifies that EPA is to propose
emissions standards that are applicable for the useful life of the
vehicle. The in-use Phase 2 standards that EPA is proposing would apply
to individual vehicles and engines, just as EPA adopted for Phase 1.
NHTSA is also proposing to use the same useful life mileage and years
as EPA for Phase 2.
    EPA is also not proposing any changes to provisions requiring that
the useful life for tractors with respect to CO2 emissions
be equal to the respective useful life periods for criteria pollutants,
as shown below in Table III-4. See 40 CFR 1037.106(e). EPA does not
expect degradation of the technologies evaluated for Phase 2 in terms
of CO2 emissions, therefore we propose no changes to the
regulations describing compliance with GHG pollutants with regards to
deterioration. See 40 CFR 1037.241. We welcome comments that highlight
a need to change this approach.

                Table III-4--Tractor Useful Life Periods
------------------------------------------------------------------------
                                                      Years      Miles
------------------------------------------------------------------------
Class 7 Tractors..................................         10    185,000
Class 8 Tractors..................................         10    435,000
------------------------------------------------------------------------

D. Feasibility of the Proposed Tractor Standards

    This section describes the agencies' technical feasibility and cost
analysis in greater detail. Further detail on all of these technologies
can be found in the draft RIA Chapter 2.
    Class 7 and 8 tractors are used in combination with trailers to
transport freight. The variation in the design of these tractors and
their typical uses drive different technology solutions for each
regulatory subcategory. As noted above, the agencies are proposing to
continue the Phase 1 provisions that treat vocational tractors as
vocational vehicles instead of as combination tractors, as noted in
Section III.C. The focus of this section is on the feasibility of the
proposed standards for combination tractors including the heavy-haul
tractors, but not the vocational tractors.
    EPA and NHTSA collected information on the cost and effectiveness
of fuel consumption and CO2 emission reducing technologies
from several sources. The primary sources of information were the
Southwest Research Institute evaluation of heavy-duty vehicle fuel
efficiency and costs for NHTSA,\134\ the Department of Energy's
SuperTruck Program,\135\ 2010 National Academy of Sciences report of
Technologies and Approaches to Reducing the Fuel Consumption of Medium-
and Heavy-Duty Vehicles,\136\ TIAX's assessment of technologies to
support the NAS panel report,\137\ the analysis conducted by the
Northeast States Center for a Clean Air Future, International Council
on Clean Transportation, Southwest Research Institute and TIAX for
reducing fuel consumption of heavy-duty long haul combination tractors
(the NESCCAF/ICCT study),\138\ and the technology cost analysis
conducted by ICF for EPA.\139\

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

    \134\ Reinhart, T.E. (June 2015). Commercial Medium- and Heavy-
Duty Truck Fuel Efficiency Technology Study--Report #1. (Report No.
DOT HS 812 146). Washington, DC: National Highway Traffic Safety
Administration.
    \135\ U.S. Department of Energy. SuperTruck Initiative.
Information available at http://energy.gov/eere/vehicles/vehicle-technologies-office.
    \136\ Committee to Assess Fuel Economy Technologies for Medium-
and Heavy-Duty Vehicles; National Research Council; Transportation
Research Board (2010). Technologies and Approaches to Reducing the
Fuel Consumption of Medium- and Heavy-Duty Vehicles. (``The 2010 NAS
Report'') Washington, DC, The National Academies Press.
    \137\ TIAX, LLC. ``Assessment of Fuel Economy Technologies for
Medium- and Heavy-Duty Vehicles,'' Final Report to National Academy
of Sciences, November 19, 2009.
    \138\ NESCCAF, ICCT, Southwest Research Institute, and TIAX.
Reducing Heavy-Duty Long Haul Combination Truck Fuel Consumption and
CO2 Emissions. October 2009.
    \139\ ICF International. ``Investigation of Costs for Strategies
to Reduce Greenhouse Gas Emissions for Heavy-Duty On-Road
Vehicles.'' July 2010. Docket Number EPA-HQ-OAR-2010-0162-0283.
---------------------------------------------------------------------------

(1) What technologies did the agencies consider to reduce the
CO2 emissions and fuel consumption of combination tractors?
    Manufacturers can reduce CO2 emissions and fuel
consumption of combination tractors through use of many technologies,
including engine, drivetrain, aerodynamic, tire, extended idle, and
weight reduction technologies. The agencies' determination of the
feasibility of the proposed HD Phase 2 standards is based on our
projection of the use of these technologies and an assessment of their
effectiveness. We will also discuss other technologies that could
potentially be used, such as vehicle speed limiters, although we are
not basing the proposed standards on their use for the model years
covered by this proposal, for various reasons discussed below.
    In this section we discuss generally the tractor and engine
technologies that the agencies considered to improve performance of
heavy-duty tractors, while Section III.D.2 discusses the baseline
tractor definition and technology packages the agencies used to
determine the proposed standard levels.
    Engine technologies: As discussed in Section II.D above, there are
several engine technologies that can reduce fuel consumption of heavy-
duty tractors. These technologies include friction reduction,
combustion system optimization, and Rankine cycle. These engine
technologies would impact the Phase 2 vehicle results because the
agencies propose that the manufacturers enter a fuel map into GEM.
    Aerodynamic technologies: There are opportunities to reduce
aerodynamic drag from the tractor, but it is sometimes difficult to
assess the benefit of individual aerodynamic features. Therefore,
reducing aerodynamic drag requires optimizing of the entire system. The
potential areas to reduce drag include all sides of the truck--front,
sides, top, rear and bottom. The grill, bumper, and hood can be
designed to minimize the pressure created by the front of the truck.
Technologies such as aerodynamic mirrors and fuel tank fairings can
reduce the surface area perpendicular to the wind and provide a smooth
surface to minimize disruptions of the air flow. Roof fairings provide
a transition to move the air smoothly over the tractor and trailer.
Side extenders can minimize the air entrapped in the gap between the
tractor and trailer. Lastly, underbelly treatments can manage the flow
of air underneath the tractor. DOE has partnered with the heavy-duty
industry to demonstrate vehicles that achieve a 50 percent improvement
in freight efficiency. This SuperTruck program has led to significant
advancements in the aerodynamics of combination tractor-trailers. The
manufacturers' SuperTruck demonstration vehicles are achieving
approximately 7 percent freight efficiency improvements over a 2010 MY
baseline vehicle due to improvements in tractor aerodynamics.\140\ The
2010 NAS Report on heavy-duty trucks found that aerodynamic
improvements which yield 3 to 4 percent fuel consumption reduction or 6
to 8 percent reduction in Cd values, beyond technologies used in
today's SmartWay trucks are achievable.\141\
---------------------------------------------------------------------------

    \140\ Daimler Truck North America. SuperTruck Program Vehicle
Project Review. June 19, 2014.
    \141\ See TIAX, Note 137, Page 4-40.
---------------------------------------------------------------------------

    Lower Rolling Resistance Tires: A tire's rolling resistance results
from the tread compound material, the architecture and materials of the
casing, tread design, the tire manufacturing process, and its operating
conditions (surface, inflation pressure, speed, temperature, etc.).
Differences in rolling resistance of up to 50 percent have been
identified for tires designed to equip the same vehicle. Since 2007,
SmartWay designated tractors have had steer tires with rolling
resistance coefficients of less than 6.6 kg/metric ton for the steer
tire and less than 7.0 kg/metric ton for the drive tire.\142\ Low
rolling resistance (LRR) drive tires are currently offered in both dual
assembly and wide-based single configurations. Wide based single tires
can offer rolling resistance reduction along with improved aerodynamics
and weight reduction. The lowest rolling resistance value submitted for
2014MY GHG and fuel efficiency certification was 4.3 and 5.0 kg/metric
ton for the steer and drive tires respectively.\143\
---------------------------------------------------------------------------

    \142\ Ibid.
    \143\ Memo to Docket. Coefficient of Rolling Resistance
Certification Data. See Docket EPA-HQ-OAR-2014-0827.
---------------------------------------------------------------------------

    Weight Reduction: Reductions in vehicle mass lower fuel consumption
and GHG emissions by decreasing the overall vehicle mass that is moved
down the road. Weight reductions also increase vehicle payload
capability which can allow additional tons to be carried by fewer
trucks consuming less fuel and producing lower emissions on a ton-mile
basis. We treated such weight reduction in two ways in Phase 1 to
account for the fact that combination tractor-trailers weigh-out
approximately one-third of the time and cube-out approximately two-
thirds of the time. Therefore in Phase 1 and also as proposed for Phase
2, one-third of the weight reduction would be added payload in the
denominator while two-thirds of the weight reduction is subtracted from
the overall weight of the vehicle in GEM. See 76 FR 57153.
    In Phase 1, we reflected mass reductions for specific technology
substitutions (e.g., installing aluminum wheels instead of steel
wheels). These substitutions were included where we could with
confidence verify the mass reduction information provided by the
manufacturer. The agencies propose to expand the list of weight
reduction components which can be input into GEM in order to provide
the manufacturers with additional means to comply via GEM with the
combination tractor standards and to further encourage reductions in
vehicle weight. As in Phase 1, we recognize that there may be
additional potential for weight reduction in new high strength steel
components which combine the reduction due to the material substitution
along with improvements in redesign, as evidenced by the studies done
for light-duty vehicles.\144\ In the development of the high strength
steel component weights, we are only assuming a reduction from material
substitution and no weight reduction from redesign, since we do not
have any data specific to redesign of heavy-duty components nor do we
have a regulatory mechanism to differentiate between material
substitution and improved design. Additional weight reduction would be
evaluated as a potential off-cycle credit.
---------------------------------------------------------------------------

    \144\ American Iron and Steel Institute. ``A Cost Benefit
Analysis Report to the North American Steel Industry on Improved
Material and Powertrain Architectures for 21st Century Trucks.''
---------------------------------------------------------------------------

    Extended Idle Reduction: Auxiliary power units (APU), fuel operated
heaters, battery supplied air conditioning, and thermal storage systems
are among the technologies available today to reduce main engine
extended idling from sleeper cabs. Each of these technologies reduces
fuel consumption during idling from a truck without this equipment (the
baseline) from approximately 0.8 gallons per hour (main engine idling
fuel consumption rate) to approximately 0.2 gallons per hour for an
APU.\145\ EPA and NHTSA agree with the TIAX assessment that a 5 percent
reduction in overall fuel consumption reduction is achievable.\146\
---------------------------------------------------------------------------

    \145\ See the draft RIA Chapter 2.4.8 for details.
    \146\ See the 2010 NAS Report, Note 136, above, at 128.

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

    Idle Reduction: Day cab tractors often idle while cargo is loaded
or unloaded, as well as during the frequent stops that are inherent
with driving in urban traffic conditions near cargo destinations. To
recognize idle reduction technologies that reduce workday idling, the
agencies have developed a new idle-only duty cycle that is proposed to
be used in GEM. As discussed above in Section II.D, this new proposed
certification test cycle would measure the amount of fuel saved and
CO2 emissions reduced by two primary types of technologies:
Neutral idle and stop-start. The proposed rules apply this test cycle
only to vocational vehicles because these types of vehicles spend more
time at idle than tractors. However, the agencies request comment on
whether we should extend this vocational vehicle idle reduction
approach to day cab tractors. Neutral idle would only be available for
tractors using torque-converter automatic transmissions, and stop-start
would be available for any tractor. Unlike the fixed numerical value in
GEM for automatic engine shutdown systems to reduce overnight idling of
combination tractors, this new idle reduction approach would result in
different numerical values depending on user inputs. The required
inputs and other details about this cycle, as it would apply to
vocational vehicles, are described in the draft RIA Chapter 3. If we
extended this approach to day cab tractors, we could set a fixed GEM
composite cycle weighting factor at a value representative of the time
spent at idle for a typical day cab tractor, possibly five percent.
Under this approach, tractor manufacturers would be able to select GEM
inputs that identify the presence of workday idle reduction
technologies, and GEM would calculate the associated benefit due to
these technologies, using this new idle-only cycle as described in the
draft RIA Chapter 3.
    The agencies have also received a letter from the California Air
Resources Board requesting consideration of credits for reducing solar
loads. Solar reflective paints and solar control glazing technologies
are briefly discussed in draft RIA Chapter <IP_ADDRESS>. The agencies
request comment on the Air Resources Board's letter and
recommendations.\147\
---------------------------------------------------------------------------

    \147\ California Air Resources Board. Letter from Michael Carter
to Matthew Spears dated December 3, 2014. Solar Control: Heavy-Duty
Vehicles White Paper. Docket EPA-HA-OAR-2014-0827.
---------------------------------------------------------------------------

    Vehicle Speed Limiters: Fuel consumption and GHG emissions increase
proportional to the square of vehicle speed. Therefore, lowering
vehicle speeds can significantly reduce fuel consumption and GHG
emissions. A vehicle speed limiter (VSL), which limits the vehicle's
maximum speed, is another technology option for compliance that is
already utilized today by some fleets (though the typical maximum speed
setting is often higher than 65 mph).
    Downsized Engines and Downspeeding: As tractor manufacturers
continue to reduce the losses due to vehicle loads, such as aerodynamic
drag and rolling resistance, the amount of power required to move the
vehicle decreases. In addition, engine manufacturers continue to
improve the power density of heavy-duty engines through means such as
reducing the engine friction due to smaller surface area. These two
changes lead to the ability for truck purchasers to select lower
displacement engines while maintaining the previous level of
performance. Engine downsizing could be more effective if it is
combined with the downspeeding assuming increased BMEP does not affect
durability. The increased efficiency of the vehicle moves the operating
points down to a lower load zone on a fuel map, which often moves the
engine away from its sweet spot to a less efficient zone. In order to
compensate for this loss, downspeeding allows the engine to run at a
lower engine speed and move back to higher load zones, thus can
slightly improve fuel efficiency. Reducing the engine size allows the
vehicle operating points to move back to the sweet spot, thus further
improving fuel efficiency. Engine downsizing can be accounted for as a
vehicle technology through the use of the engine's fuel map in GEM.
    Transmission: As discussed in the 2010 NAS report, automatic (AT)
and automated manual transmissions (AMT) may offer the ability to
improve vehicle fuel consumption by optimizing gear selection compared
to an average driver.\148\ However, as also noted in the report and in
the supporting TIAX report, the improvement is very dependent on the
driver of the truck, such that reductions ranged from 0 to 8
percent.\149\ Well-trained drivers would be expected to perform as well
or even better than an automatic transmission since the driver can see
the road ahead and anticipate a changing stoplight or other road
condition that neither an automatic nor automated manual transmission
can anticipate. However, poorly-trained drivers that shift too
frequently or not frequently enough to maintain optimum engine
operating conditions could be expected to realize improved in-use fuel
consumption by switching from a manual transmission to an automatic or
automated manual transmission. As transmissions continue to evolve, we
are now seeing in the European heavy-duty vehicle market the addition
of dual clutch transmissions (DCT). DCTs operate similar to AMTs, but
with two clutches so that the transmission can maintain engine speed
during a shift which improves fuel efficiency. We believe there may be
real benefits in reduced fuel consumption and GHG emissions through the
adoption of dual clutch, automatic or automated manual transmission
technology.
---------------------------------------------------------------------------

    \148\ Manual transmissions require the driver to shift the gears
and manually engage and disengage the clutch. Automatic
transmissions shift gears through computer controls and typically
include a torque converter. An AMT operates similar to a manual
transmission, except that an automated clutch actuator disengages
and engages the drivetrain instead of a human driver. An AMT does
not include a clutch pedal controllable by the driver or a torque
converter.
    \149\ See TIAX, Note 137, above at 4-70.
---------------------------------------------------------------------------

    Low Friction Transmission, Axle, and Wheel Bearing Lubricants: The
2010 NAS report assessed low friction lubricants for the drivetrain as
providing a 1 percent improvement in fuel consumption based on fleet
testing.\150\ A field trial of European medium-duty trucks found an
average fuel consumption improvement of 1.8 percent using SAE 5W-30
engine oil, SAE 75W90 axle oil and SAE 75W80 transmission oil when
compared to SAE 15W40 engine oil and SAE 90W axle oil, and SAE 80W
transmission oil.\151\ The light-duty 2012-16 MY vehicle rule and the
pickup truck portion of this program estimate that low friction
lubricants can have an effectiveness value between 0 and 1 percent
compared to traditional lubricants.
---------------------------------------------------------------------------

    \150\ See the 2010 NAS Report, Note 136, page 67.
    \151\ Green, D.A., et al. ``The Effect of Engine, Axle, and
Transmission Lubricant, and Operating Conditions on Heavy Duty
Diesel Fuel Economy. Part 1: Measurements.'' SAE 2011-01-2129. SAE
International Journal of Fuels and Lubricants. January 2012.
---------------------------------------------------------------------------

    Drivetrain: Most tractors today have three axles--a steer axle and
two rear drive axles, and are commonly referred to as 6x4 tractors.
Manufacturers offer 6x2 tractors that include one rear drive axle and
one rear non-driving axle. The 6x2 tractors offer three distinct
benefits. First, the non-driving rear axle does not have internal
friction and therefore reduces the overall parasitic losses in the
drivetrain. In addition, the 6x2 configuration typically weighs
approximately 300 to 400 lbs less than

a 6x4 configuration.\152\ Finally, the 6x2 typically costs less or is
cost neutral when compared to a 6x4 tractor. Sources cite the
effectiveness of 6x2 axles at between 1 and 3 percent.\153\ Similarly,
with the increased use of double and triple trailers, which reduce the
weight on the tractor axles when compared to a single trailer,
manufacturers offer 4x2 axle configurations. The 4x2 axle configuration
would have as good as or better fuel efficiency performance than a 6x2.
---------------------------------------------------------------------------

    \152\ North American Council for Freight Efficiency.
''Confidence Findings on the Potential of 6x2 Axles.'' 2014. Page
16.
    \153\ Reinhart, T.E. (June 2015). Commercial Medium- and Heavy-
Duty Truck Fuel Efficiency Technology Study--Report #1. (Report No.
DOT HS 812 146). Washington, DC: National Highway Traffic Safety
Administration.
---------------------------------------------------------------------------

    Accessory Improvements: Parasitic losses from the engine come from
many systems, including the water pump, oil pump, and power steering
pump. Reductions in parasitic losses are one of the areas being
developed under the DOE SuperTruck program. As presented in the DOE
Merit reviews, Navistar stated that they demonstrated a 0.45 percent
reduction in fuel consumption through water pump improvements and 0.3
percent through oil pump improvements compared to a current engine. In
addition, Navistar showed a 0.9 percent benefit for a variable speed
water pump and variable displacement oil pump. Detroit Diesel reports a
0.5 percent coming from improved water pump efficiency.\154\ It should
be noted that water pump improvements include both pump efficiency
improvement and variable speed or on/off controls. Lube pump
improvements are primarily achieved using variable displacement pumps
and may also include efficiency improvement. All of these results shown
in this paragraph are demonstrated through the DOE SuperTruck program
at single operating point on the engine map, and therefore the overall
expected reduction of these technologies is less than the single point
result.
---------------------------------------------------------------------------

    \154\ See the draft RIA Chapter 2.4 for details.
---------------------------------------------------------------------------

    Intelligent Controls: Skilled drivers know how to control a vehicle
to obtain maximum fuel efficiency by, among other things, considering
road terrain. For example, the driver may allow the vehicle to slow
down below the target speed on an uphill and allow it to go over the
target speed when going downhill, to essentially smooth out the engine
demand. Electronic controls can be developed to essentially mimic this
activity. The agencies propose to provide a 2 percent reduction in fuel
consumption and CO2 emissions for vehicles configured with
intelligent controls, such as predictive cruise control.
    Automatic Tire Inflation Systems: Proper tire inflation is critical
to maintaining proper stress distribution in the tire, which reduces
heat loss and rolling resistance. Tires with reduced inflation pressure
exhibit a larger footprint on the road, more sidewall flexing and tread
shearing, and therefore, have greater rolling resistance than a tire
operating at its optimal inflation pressure. Bridgestone tested the
effect of inflation pressure and found a 2 percent variation in fuel
consumption over a 40 psi range.\155\ Generally, a 10 psi reduction in
overall tire inflation results in about a 1 percent reduction in fuel
economy.\156\ To achieve the intended fuel efficiency benefits of low
rolling resistance tires, it is critical that tires are maintained at
the proper inflation pressure.
---------------------------------------------------------------------------

    \155\ Bridgestone Tires. Real Questions, Real Answers. http://www.bridgestonetrucktires.com/us_eng/real/magazines/ra_special-edit_4/ra_special4_fuel-tires.asp.
    \156\ ``Factors Affecting Truck Fuel Economy,'' Goodyear, Radial
Truck and Retread Service Manual. Accessed February 16, 2010 at
http://www.goodyear.com/truck/pdf/radialretserv/Retread_S9_V.pdf.
---------------------------------------------------------------------------

    Proper tire inflation pressure can be maintained with a rigorous
tire inspection and maintenance program or with the use of tire
pressure and inflation systems. According to a study conducted by FMCSA
in 2003, about 1 in 5 tractors/trucks is operating with 1 or more tires
underinflated by at least 20 psi.\157\ A 2011 FMCSA study estimated
underinflation accounts for one service call per year and increases
tire procurement costs 10 to 13 percent. The study found that total
operating costs can increase by $600 to $800 per year due to
underinflation.\158\ A recent study by The North American Council on
Freight Efficiency, found that adoption of tire pressure monitoring
systems is increasing. It also found that reliability and durability of
commercially available tire pressure systems are good and early issues
with the systems have been addressed.\159\ These automatic tire
inflation systems monitor tire pressure and also automatically keep
tires inflated to a specific level. The agencies propose to provide a 1
percent CO2 and fuel consumption reduction value for
tractors with automatic tire inflation systems installed.
---------------------------------------------------------------------------

    \157\ American Trucking Association. Tire Pressure Monitoring
and Inflation Maintenance. June 2010. Page 3. Last accessed on
December 15, 2014 at http://www.trucking.org/ATA%20Docs/About/Organization/TMC/Documents/Position%20Papers/Study%20Group%20Information%20Reports/Tire%20Pressure%20Monitoring%20and%20Inflation%20Maintenance%E2%80%94TMC%20I.R.%202010-2.pdf.
    \158\ TMC Future Truck Committee Presentation ``FMCSA Tire
Pressure Monitoring Field Operational Test Results,'' February 8,
2011.
    \159\ North American Council for Freight Efficiency, ``Tire
Pressure Systems,'' 2013.
---------------------------------------------------------------------------

    Tire pressure monitoring systems notify the operator of tire
pressure, but require the operator to manually inflate the tires to the
optimum pressure. Because of the dependence on the operator's action,
the agencies are not proposing to provide a reduction value for tire
pressure monitoring systems. We request comment on this approach and
seek data from those that support a reduction value be assigned to tire
pressure monitoring systems.
    Hybrid: Hybrid powertrain development in Class 7 and 8 tractors has
been limited to a few manufacturer demonstration vehicles to date. One
of the key benefit opportunities for fuel consumption reduction with
hybrids is less fuel consumption when a vehicle is idling, but the
standard is already premised on use of extended idle reduction so use
of hybrid technology would duplicate many of the same emission
reductions attributable to extended idle reduction. NAS estimated that
hybrid systems would cost approximately $25,000 per tractor in the 2015
through the 2020 time frame and provide a potential fuel consumption
reduction of 10 percent, of which 6 percent is idle reduction which can
be achieved (less expensively) through the use of other idle reduction
technologies.\160\ The limited reduction potential outside of idle
reduction for Class 8 sleeper cab tractors is due to the mostly highway
operation and limited start-stop operation. Due to the high cost and
limited benefit during the model years at issue in this action (as well
as issues regarding sufficiency of lead time (see Section III.D.2
below), the agencies are not including hybrids in assessing standard
stringency (or as an input to GEM).
---------------------------------------------------------------------------

    \160\ See the 2010 NAS Report, Note 136, page 128.
---------------------------------------------------------------------------

    Management: The 2010 NAS report noted many operational
opportunities to reduce fuel consumption, such as driver training and
route optimization. The agencies have included discussion of several of
these strategies in draft RIA Chapter 2, but are not using these
approaches or technologies in the standard setting process. The
agencies are looking to other resources, such as EPA's SmartWay
Transport Partnership and regulations that could potentially be
promulgated by the Federal Highway Administration and the Federal Motor
Carrier Safety Administration, to continue to encourage the development
and utilization of these approaches.

(2) Projected Technology Effectiveness and Cost
    EPA and NHTSA project that CO2 emissions and fuel
consumption reductions can be feasibly and cost-effectively met through
technological improvements in several areas. The agencies evaluated
each technology and estimated the most appropriate adoption rate of
technology into each tractor subcategory. The next sections describe
the baseline vehicle configuration, the effectiveness of the individual
technologies, the costs of the technologies, the projected adoption
rates of the technologies into the regulatory subcategories, and
finally the derivation of the proposed standards.
    The agencies propose Phase 2 standards that project by 2027, all
high-roof tractors would have aerodynamic performance equal to or
better today's SmartWay performance--which represents the best of
today's technology. This would equate to having 40 percent of new high
roof sleeper cabs in 2027 complying with the current best practices and
60 percent of the new high-roof sleeper cab tractors sold in 2027
having better aerodynamic performance than the best tractors available
today. For tire rolling resistance, we premised the proposed standards
on the assumption that nearly all tires in 2027 would have rolling
resistance equal to or superior to tires meeting today's SmartWay
designation. As discussed in Section II.D, the agencies assume the
proposed 2027 MY engines would achieve an additional 4 percent
improvement over Phase 1 engines and we project would include 15
percent of waste heat recovery (WHR) and many other advanced engine
technologies. In addition, we are proposing standards that project
improvements to nearly all of today's transmissions, incorporation of
extended idle reduction technologies on 90 percent of sleeper cabs, and
significant adoption of other types of technologies such as predictive
cruise control and automatic tire inflation systems.
    In addition to the high cost and limited utility of hybrids for
many tractor drive cycles noted above, the agencies believe that hybrid
powertrains systems for tractors may not be sufficiently developed and
the necessary manufacturing capacity put in place to base a standard on
any significant volume of hybrid tractors. Unlike hybrids for
vocational vehicles and light-duty vehicles, the agencies are not aware
of any full hybrid systems currently developed for long haul tractor
applications. To date, hybrid systems for tractors have been primarily
focused on idle shutdown technologies and not on the broader energy
storage and recovery systems necessary to achieve reductions over
typical vehicle drive cycles. The proposed standards reflect the
potential for idle shutdown technologies through GEM. Further as
highlighted by the 2010 NAS report, the agencies do believe that full
hybrid powertrains may have the potential in the longer term to provide
significant improvements in tractor fuel efficiency and to greenhouse
gas emission reductions. However, due to the high cost, limited benefit
during highway driving, and lacking any existing systems or
manufacturing base, we cannot conclude with certainty, absent
additional information, that such technology would be available for
tractors in the 2021-2027 timeframe. However the agencies welcome
comment from industry and others on their projected timeline for
deployment of hybrid powertrains for tractor applications.
(a) Tractor Baselines for Costs and Effectiveness
    The fuel efficiency and CO2 emissions of combination
tractors vary depending on the configuration of the tractor. Many
aspects of the tractor impact its performance, including the engine,
transmission, drive axle, aerodynamics, and rolling resistance. For
each subcategory, the agencies selected a theoretical tractor to
represent the average 2017 model year tractor that meets the Phase 1
standards (see 76 FR 57212, September 15, 2011). These tractors are
used as baselines from which to evaluate costs and effectiveness of
additional technologies and standards. The specific attributes of each
tractor subcategory are listed below in Table III-5. Using these
values, the agencies assessed the CO2 emissions and fuel
consumption performance of the proposed baseline tractors using the
proposed version of Phase 2 GEM. The results of these simulations are
shown below in Table III-6.
    As noted earlier, the Phase 1 2017 model year tractor standards and
the baseline 2017 model year tractor results are not directly
comparable. The same set of aerodynamic and tire rolling resistance
technologies were used in both setting the Phase 1 standards and
determining the baseline of the Phase 2 tractors. However, there are
several aspects that differ. First, a new version of GEM was developed
and validated to provide additional capabilities, including more
refined modeling of transmissions and engines. Second, the
determination of the proposed HD Phase 2 CdA value takes into account a
revised test procedure, a new standard reference trailer, and wind
averaged drag as discussed below in Section III.E. In addition, the
proposed HD Phase 2 version of GEM includes road grade in the 55 mph
and 65 mph highway cycles, as discussed below in Section III.E.
Finally, the agencies assessed the current level of automatic engine
shutdown and idle reduction technologies used by the tractor
manufacturers to comply with the 2014 model year CO2 and
fuel consumption standards. To date, the manufacturers are meeting the
2014 model year standards without the use of this technology.
Therefore, in this proposal the agencies reverted back to the baseline
APU adoption rate of 30 percent, the value used in the Phase 1
baseline.

                         Table III-5--GEM Inputs for the Baseline Class 7 and 8 Tractor
----------------------------------------------------------------------------------------------------------------
               Class 7                                                  Class 8
----------------------------------------------------------------------------------------------------------------
               Day cab                                Day cab                             Sleeper cab
----------------------------------------------------------------------------------------------------------------
  Low roof     Mid roof    High roof     Low roof     Mid roof    High roof    Low roof    Mid roof    High roof
----------------------------------------------------------------------------------------------------------------
                                                     Engine
----------------------------------------------------------------------------------------------------------------
2017 MY 11L  2017 MY 11L  2017 MY 11L  2017 MY 15L  2017 MY 15L  2017 MY 15L    2017 MY     2017 MY     2017 MY
 Engine 350  Engine 350   Engine 350   Engine 455   Engine 455   Engine 455   15L Engine  15L Engine  15L Engine
     HP              HP           HP           HP           HP           HP      455 HP      455 HP      455 HP
----------------------------------------------------------------------------------------------------------------
                                           Aerodynamics (CdA in m\2\)
----------------------------------------------------------------------------------------------------------------
      5.00         6.40         6.42         5.00         6.40         6.42        4.95        6.35        6.22
----------------------------------------------------------------------------------------------------------------
                                       Steer Tires (CRR in kg/metric ton)
----------------------------------------------------------------------------------------------------------------
      6.99         6.99         6.87         6.99         6.99         6.87        6.87        6.87        6.54
----------------------------------------------------------------------------------------------------------------
                                       Drive Tires (CRR in kg/metric ton)
----------------------------------------------------------------------------------------------------------------
      7.38         7.38         7.26         7.38         7.38         7.26        7.26        7.26        6.92
----------------------------------------------------------------------------------------------------------------
                                      Extended Idle Reduction Adoption Rate
----------------------------------------------------------------------------------------------------------------
       N/A          N/A          N/A          N/A          N/A          N/A         30%         30%         30%
----------------------------------------------------------------------------------------------------------------
                                   Transmission = 10 Speed Manual Transmission
----------------------------------------------------------------------------------------------------------------
                    Gear Ratios = 12.8, 9.25, 6.76, 4.90, 3.58, 2.61, 1.89, 1.38, 1.00, 0.73
----------------------------------------------------------------------------------------------------------------
                                             Drive Axle Ratio = 3.70
----------------------------------------------------------------------------------------------------------------

                                     Table III-6--Class 7 and 8 Tractor Baseline CO2 Emissions and Fuel Consumption
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                   Class 7                                           Class 8
                                                      --------------------------------------------------------------------------------------------------
                                                                   Day cab                          Day cab                        Sleeper cab
                                                      --------------------------------------------------------------------------------------------------
                                                        Low roof   Mid roof  High roof   Low roof   Mid roof  High roof   Low roof   Mid roof  High roof
--------------------------------------------------------------------------------------------------------------------------------------------------------
CO2 (grams CO2/ton-mile).............................     107        118        121         86         93         95         79         87         88
Fuel Consumption (gal/1,000 ton-mile)................      10.5       11.6       11.9        8.4        9.1        9.3        7.8        8.5        8.6
--------------------------------------------------------------------------------------------------------------------------------------------------------

    The fuel consumption and CO2 emissions in the baseline
described above remains the same over time with no assumed improvements
after 2017, absent a Phase 2 regulation. An alternative baseline was
also evaluated by the agencies in which there is a continuing uptake of
technologies in the tractor market that reduce fuel consumption and
CO2 emissions absent a Phase 2 regulation. This alternative
baseline, referred to as the more dynamic baseline, was developed to
estimate the effect of market pressures and non-regulatory government
initiatives to improve tractor fuel consumption. The more dynamic
baseline assumes that the significant level of research funded and
conducted by the Federal government, industry, academia and other
organizations will, in the future, result the adoption of some
technologies beyond the levels required to comply with Phase 1
standards. One example of such research is the Department of Energy
Super Truck program \161\ which has a goal of demonstrating cost-
effective measures to improve the efficiency of Class 8 long-haul
freight trucks by 50 percent by 2015. The more dynamic baseline also
assumes that manufacturers will not cease offering fuel efficiency
improving technologies that currently have significant market
penetration, such as automated manual transmissions. The baselines (one
for each of the nine tractor types) are characterized by fuel
consumption and CO2 emissions that gradually decrease
between 2019 and 2028. In 2028, the fuel consumption for the
alternative tractor baselines is approximately 4.0 percent lower than
those shown in Table III-6. This results from the assumed introduction
of aerodynamic technologies such as down exhaust, underbody airflow
treatment in addition to tires with lower rolling resistance. The
assumed introduction of these technologies reduces the CdA of the
baseline tractors and CRR of the tractor tires. To take one example,
the CdA for baseline high roof sleeper cabs in Table III-5 is 6.22
(m\2\) in 2018. In 2028, the CdA of a high roof sleeper cab would be
assumed to still be 6.22 m\2\ in the baseline case outlined above.
Alternatively, in the dynamic baseline, the CdA for high roof sleeper
cabs is 5.61 (m\2\) in 2028 due to assumed market penetration of
technologies absent the Phase 2 regulation. The dynamic baseline
analysis is discussed in more detail in draft RIA Chapter 11.
---------------------------------------------------------------------------

    \161\ U.S. Department of Energy. ``SuperTruck Making Leaps in
Fuel Efficiency.'' 2014. Last accessed on May 10, 2015 at http://energy.gov/eere/articles/supertruck-making-leaps-fuel-efficiency.

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

(b) Tractor Technology Packages
    The agencies' assessment of the proposed technology effectiveness
was developed through the use of the GEM in coordination with modeling
conducted by Southwest Research Institute. The agencies developed the
proposed standards through a three-step process, similar to the
approach used in Phase 1. First, the agencies developed technology
performance characteristics for each technology, as described below.
Each technology is associated with an input parameter which in turn
would be used as an input to the Phase 2 GEM simulation tool and its
effectiveness thereby modeled. The performance levels for the range of
Class 7 and 8 tractor aerodynamic packages and vehicle technologies are
described below in Table III-7. Second, the agencies combined the
technology performance levels with a projected technology adoption rate
to determine the GEM inputs used to set the stringency of the proposed
standards. Third, the agencies input these parameters into Phase 2 GEM
and used the output to determine the proposed CO2 emissions
and fuel consumption levels. All percentage improvements noted below
are over the 2017 baseline tractor.
(i) Engine Improvements
    There are several technologies that could be used to improve the
efficiency of diesel engines used in tractors. Details of the engine
technologies, adoption rates, and overall fuel consumption and
CO2 emission reductions are included in Section II.D. The
proposed heavy-duty tractor engine standards would lead to a 1.5
percent reduction in 2021MY, a 3.5 percent reduction in 2024MY, and a 4
percent reduction in 2027MY. These reductions would show up in the fuel
map used in GEM.
(ii) Aerodynamics
    The aerodynamic packages are categorized as Bin I, Bin II, Bin III,
Bin IV, Bin V, Bin VI, or Bin VII based on the wind averaged drag
aerodynamic performance determined through testing conducted by the
manufacturer. A more complete description of these aerodynamic packages
is included in Chapter 2 of the draft RIA. In general, the proposed CdA
values for each package and tractor subcategory were developed through
EPA's coastdown testing of tractor-trailer combinations, the 2010 NAS
report, and SAE papers.
(iii) Tire Rolling Resistance
    The proposed rolling resistance coefficient target for Phase 2 was
developed from SmartWay's tire testing to develop the SmartWay
certification, testing a selection of tractor tires as part of the
Phase 1 and Phase 2 programs, and from 2014 MY certification data. Even
though the coefficient of tire rolling resistance comes in a range of
values, to analyze this range, the tire performance was evaluated at
four levels for both steer and drive tires, as determined by the
agencies. The four levels are the baseline (average) from 2010, Level I
and Level 2 from Phase 1, and Level 3 that achieves an additional 25
percent improvement over Level 2. The Level 1 rolling resistance
performance represents the threshold used to develop SmartWay
designated tires for long haul tractors. The Level 2 threshold
represents an incremental step for improvements beyond today's SmartWay
level and represents the best in class rolling resistance of the tires
we tested. The Level 3 values represent the long-term rolling
resistance value that the agencies predicts could be achieved in the
2025 timeframe. Given the multiple year phase-in of the standards, the
agencies expect that tire manufacturers will continue to respond to
demand for more efficient tires and will offer increasing numbers of
tire models with rolling resistance values significantly better than
today's typical low rolling resistance tires. The tire rolling
resistance level assumed to meet the 2017 MY Phase 1 standard high roof
sleeper cab is considered to be a weighted average of 10 percent
baseline rolling resistance, 70 percent Level 1, and 20 percent Level
2. The tire rolling resistance to meet the 2017MY Phase 1 standards for
the high roof day cab, low roof sleeper cab, and mid roof sleeper cab
includes 30 percent baseline, 60 percent Level 1 and 10 percent Level
2. Finally, the low roof day cab 2017MY standard can be met with a
weighted average rolling resistance consisting of 40 percent baseline,
50 percent Level 1, and 10 percent Level 2.
(iv) Idle Reduction
    The benefits for the extended idle reductions were developed from
literature, SmartWay work, and the 2010 NAS report. Additional details
regarding the comments and calculations are included in draft RIA
Section 2.4.
(v) Transmission
    The benefits for automated manual, automatic, and dual clutch
transmissions were developed from literature and from simulation
modeling conducted by Southwest Research Institute. The benefit of
these transmissions is proposed to be set to a two percent improvement
over a manual transmission due to the automation of the gear shifting.
(vi) Drivetrain
    The reduction in friction due to low viscosity axle lubricants is
set to 0.5 percent. 6x4 and 4x2 axle configurations lead to a 2.5
percent improvement in vehicle efficiency. Downspeeding would be as
demonstrated through the Phase 2 GEM inputs of transmission gear ratio,
drive axle ratio, and tire diameter. Downspeeding is projected to
improve the fuel consumption by 1.8 percent.
(vii) Accessories and Other Technologies
    Compared to 2017MY air conditioners, air conditioners with improved
efficiency compressors will reduce CO2 emissions by 0.5
percent. Improvements in accessories, such as power steering, can lead
to an efficiency improvement of 1 percent over the 2017MY baseline.
Based on literature information, intelligent controls such as
predictive cruise control will reduce CO2 emissions by 2
percent while automatic tire inflation systems improve fuel consumption
by 1 percent by keeping tire rolling resistance to its optimum based on
inflation pressure.
(viii) Weight Reduction
    The weight reductions were developed from tire manufacturer
information, the Aluminum Association, the Department of Energy, SABIC
and TIAX, as discussed above in Section II.B.3.e.
(ix) Vehicle Speed Limiter
    The agencies did not consider the availability of vehicle speed
limiter technology in setting the Phase 1 stringency levels, and again
did not consider the availability of the technology in developing
regulatory alternatives for Phase 2. However, as described in more
detail above, speed limiters could be an effective means for achieving
compliance, if employed on a voluntary basis.
(x) Summary of Technology Performance
    Table III-7 describes the performance levels for the range of Class
7 and 8 tractor vehicle technologies.

                                                     Table III-7--Proposed Phase 2 Technology Inputs
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                   Class 7                                           Class 8
                                                      --------------------------------------------------------------------------------------------------
                                                                   Day cab                          Day cab                        Sleeper cab
                                                      --------------------------------------------------------------------------------------------------
                                                        Low roof   Mid roof  High roof   Low roof   Mid roof  High roof   Low roof   Mid roof  High roof
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                         Engine
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                         2021MY     2021MY     2021MY     2021MY     2021MY     2021MY     2021MY     2021MY     2021MY
                                                          11L        11L        11L        15L        15L        15L        15L        15L        15L
                                                         Engine     Engine     Engine     Engine     Engine     Engine     Engine     Engine     Engine
                                                         350 HP     350 HP     350 HP     455 HP     455 HP     455 HP     455 HP     455 HP     455 HP
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                               Aerodynamics (CdA in m\2\)
--------------------------------------------------------------------------------------------------------------------------------------------------------
Bin I................................................        5.3        6.7        7.6        5.3        6.7        7.6        5.3        6.7        7.4
Bin II...............................................        4.8        6.2        7.1        4.8        6.2        7.1        4.8        6.2        6.9
Bin III..............................................        4.3        5.7        6.5        4.3        5.7        6.5        4.3        5.7        6.3
Bin IV...............................................        4.0        5.4        5.8        4.0        5.4        5.8        4.0        5.4        5.6
Bin V................................................        N/A        N/A        5.3        N/A        N/A        5.3        N/A        N/A        5.1
Bin VI...............................................        N/A        N/A        4.9        N/A        N/A        4.9        N/A        N/A        4.7
Bin VII..............................................        N/A        N/A        4.5        N/A        N/A        4.5        N/A        N/A        4.3
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                           Steer Tires (CRR in kg/metric ton)
--------------------------------------------------------------------------------------------------------------------------------------------------------
Base.................................................        7.8        7.8        7.8        7.8        7.8        7.8        7.8        7.8        7.8
Level 1..............................................        6.6        6.6        6.6        6.6        6.6        6.6        6.6        6.6        6.6
Level 2..............................................        5.7        5.7        5.7        5.7        5.7        5.7        5.7        5.7        5.7
Level 3..............................................        4.3        4.3        4.3        4.3        4.3        4.3        4.3        4.3        4.3
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                           Drive Tires (CRR in kg/metric ton)
--------------------------------------------------------------------------------------------------------------------------------------------------------
Base.................................................        8.2        8.2        8.2        8.2        8.2        8.2        8.2        8.2        8.2
Level 1..............................................        7.0        7.0        7.0        7.0        7.0        7.0        7.0        7.0        7.0
Level 2..............................................        6.0        6.0        6.0        6.0        6.0        6.0        6.0        6.0        6.0
Level 3..............................................        4.5        4.5        4.5        4.5        4.5        4.5        4.5        4.5        4.5
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                              Idle Reduction (% reduction)
--------------------------------------------------------------------------------------------------------------------------------------------------------
APU..................................................        N/A        N/A        N/A        N/A        N/A        N/A         5%         5%         5%
Other................................................        N/A        N/A        N/A        N/A        N/A        N/A         7%         7%         7%
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                             Transmission Type (% reduction)
--------------------------------------------------------------------------------------------------------------------------------------------------------
Manual...............................................         0%         0%         0%         0%         0%         0%         0%         0%         0%
AMT..................................................          2          2          2          2          2          2          2          2          2
Auto.................................................          2          2          2          2          2          2          2          2          2
Dual Clutch..........................................          2          2          2          2          2          2          2          2          2
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                 Driveline (% reduction)
--------------------------------------------------------------------------------------------------------------------------------------------------------
Axle Lubricant.......................................       0.5%       0.5%       0.5%       0.5%       0.5%       0.5%       0.5%       0.5%       0.5%
6x2 or 4x2 Axle......................................        2.5        2.5        2.5        2.5        2.5        2.5        2.5        2.5        2.5
Downspeed............................................        1.8        1.8        1.8        1.8        1.8        1.8        1.8        1.8        1.8
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                          Accessory Improvements (% reduction)
--------------------------------------------------------------------------------------------------------------------------------------------------------
A/C..................................................       0.5%       0.5%       0.5%       0.5%       0.5%       0.5%       0.5%       0.5%       0.5%
Electric Access......................................          1          1          1          1          1          1          1          1          1
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                            Other Technologies (% reduction)
--------------------------------------------------------------------------------------------------------------------------------------------------------
Predictive Cruise Control............................         2%         2%         2%         2%         2%         2%         2%         2%         2%
Automated Tire Inflation System......................          1          1          1          1          1          1          1          1          1
--------------------------------------------------------------------------------------------------------------------------------------------------------

(c) Tractor Technology Adoption Rates
    As explained above, tractor manufacturers often introduce major
product changes together, as a package. In this manner the
manufacturers can optimize their available resources, including
engineering, development, manufacturing and marketing activities to
create a product with multiple new features. In addition, manufacturers
recognize that a truck design will need to remain competitive over the
intended life of the design and meet future regulatory requirements. In
some limited cases, manufacturers may implement an individual
technology outside of a vehicle's redesign cycle.
    With respect to the levels of technology adoption used to develop
the proposed HD Phase 2 standards, NHTSA and EPA established technology

adoption constraints. The first type of constraint was established
based on the application of fuel consumption and CO2
emission reduction technologies into the different types of tractors.
For example, extended idle reduction technologies are limited to Class
8 sleeper cabs using the reasonable assumption that day cabs are not
used for overnight hoteling. A second type of constraint was applied to
most other technologies and limited their adoption based on factors
reflecting the real world operating conditions that some combination
tractors encounter. This second type of constraint was applied to the
aerodynamic, tire, powertrain, and vehicle speed limiter technologies.
    Table III-8 and Table III-10, specify the adoption rates that EPA
and NHTSA used to develop the proposed standards. The agencies welcome
comments on these adoption rates.
    NHTSA and EPA believe that within each of these individual vehicle
categories there are particular applications where the use of the
identified technologies would be either ineffective or not technically
feasible. For example, the agencies are not predicating the proposed
standards on the use of full aerodynamic vehicle treatments on 100
percent of tractors because we know that in many applications (for
example gravel truck engaged in local aggregate delivery) the added
weight of the aerodynamic technologies will increase fuel consumption
and hence CO2 emissions to a greater degree than the
reduction that would be accomplished from the more aerodynamic nature
of the tractor.
(i) Aerodynamics Adoption Rate
    The impact of aerodynamics on a tractor-trailer's efficiency
increases with vehicle speed. Therefore, the usage pattern of the
vehicle will determine the benefit of various aerodynamic technologies.
Sleeper cabs are often used in line haul applications and drive the
majority of their miles on the highway travelling at speeds greater
than 55 mph. The industry has focused aerodynamic technology
development, including SmartWay tractors, on these types of trucks.
Therefore the agencies are proposing the most aggressive aerodynamic
technology application to this regulatory subcategory. All of the major
manufacturers today offer at least one SmartWay sleeper cab tractor
model, which is represented as Bin III aerodynamic performance. The
proposed aerodynamic adoption rate for Class 8 high roof sleeper cabs
in 2027 (i.e., the degree of technology adoption on which the
stringency of the proposed standard is premised) consists of 20 percent
of Bin IV, 35 percent Bin V, 20 percent Bin VI, and 5 percent Bin VII
reflecting our assessment of the fraction of tractors in this segment
that could successfully apply these aerodynamic packages with this
amount of lead time. We believe that there is sufficient lead time to
develop aerodynamic tractors that can move the entire high roof sleeper
cab aerodynamic performance to be as good as or better than today's
SmartWay designated tractors. The changes required for Bin IV and
better performance reflect the kinds of improvements projected in the
Department of Energy's SuperTruck program. That program assumes that
such systems can be demonstrated on vehicles by 2017. In this case, the
agencies are projecting that truck manufacturers would be able to begin
implementing these aerodynamic technologies as early as 2021 MY on a
limited scale. Importantly, our averaging, banking and trading
provisions provide manufacturers with the flexibility (and incentive)
to implement these technologies over time even though the standard
changes in a single step.
    The aerodynamic adoption rates used to develop the proposed
standards for the other tractor regulatory categories are less
aggressive than for the Class 8 sleeper cab high roof. Aerodynamic
improvements through new tractor designs and the development of new
aerodynamic components is an inherently slow and iterative process. The
agencies recognize that there are tractor applications which require
on/off-road capability and other truck functions which restrict the
type of aerodynamic equipment applicable. We also recognize that these
types of trucks spend less time at highway speeds where aerodynamic
technologies have the greatest benefit. The 2002 VIUS data ranks trucks
by major use.\162\ The heavy trucks usage indicates that up to 35
percent of the trucks may be used in on/off-road applications or
heavier applications. The uses include construction (16 percent),
agriculture (12 percent), waste management (5 percent), and mining (2
percent). Therefore, the agencies analyzed the technologies to evaluate
the potential restrictions that would prevent 100 percent adoption of
more advanced aerodynamic technologies for all of the tractor
regulatory subcategories.
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    \162\ U.S. Department of Energy. Transportation Energy Data
Book, Edition 28-2009. Table 5.7.
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    As discussed in Section III.C.2, the agencies propose to increase
the number of aerodynamic bins for low and mid roof tractors from the
two levels adopted in Phase 1 to four levels in Phase 2. The agencies
propose to increase the number of bins for these tractors to reflect
the actual range of aerodynamic technologies effective in low and mid
roof tractor applications. The aerodynamic improvements to the bumper,
hood, windshield, mirrors, and doors are developed for the high roof
tractor application and then carried over into the low and mid roof
applications.
(ii) Low Rolling Resistance Tire Adoption Rate
    For the tire manufacturers to further reduce tire rolling
resistance, the manufacturers must consider several performance
criteria that affect tire selection. The characteristics of a tire also
influence durability, traction control, vehicle handling, comfort, and
retreadability. A single performance parameter can easily be enhanced,
but an optimal balance of all the criteria will require improvements in
materials and tread design at a higher cost, as estimated by the
agencies. Tire design requires balancing performance, since changes in
design may change different performance characteristics in opposing
directions. Similar to the discussion regarding lesser aerodynamic
technology application in tractor segments other than sleeper cab high
roof, the agencies believe that the proposed standards should not be
premised on 100 percent application of Level 3 tires in all tractor
segments given the potential interference with vehicle utility that
could result.
(iii) Weight Reduction Technology Adoption Rate
    Unlike in HD Phase 1, the agencies propose setting the 2021 through
2027 model year tractor standards without using weight reduction as a
technology to demonstrate the feasibility. However, as described in
Section III.C.2 below, the agencies are proposing an expanded list of
weight reduction options which could be input into the GEM by the
manufacturers to reduce their certified CO2 emission and
fuel consumption levels. The agencies view weight reduction as a
technology with a high cost that offers a small benefit in the tractor
sector. For example, our estimate of a 400 pound weight reduction would
cost $2,050 (2012$) in 2021MY, but offers a 0.3 percent reduction in
fuel consumption and CO2 emissions.
(iv) Idle Reduction Technology Adoption Rate
    Idle reduction technologies provide significant reductions in fuel
consumption and CO2 emissions for Class 8 sleeper cabs and
are available on

the market today. There are several different technologies available to
reduce idling. These include APUs, diesel fired heaters, and battery
powered units. Our discussions with manufacturers indicate that idle
technologies are sometimes installed in the factory, but it is also a
common practice to have the units installed after the sale of the
truck. We would like to continue to incentivize this practice and to do
so in a manner that the emission reductions associated with idle
reduction technology occur in use. Therefore, as adopted in Phase 1, we
are allowing only idle emission reduction technologies which include an
automatic engine shutoff (AES) with some override provisions.\163\
However, we welcome comment on other approaches that would
appropriately quantify the reductions that would be experienced in the
real world.
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    \163\ The agencies are proposing to continue the HD Phase 1 AES
override provisions included in 40 CFR 1037.660(b) for driver
safety.
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    We propose an overall 90 percent adoption rate for this technology
for Class 8 sleeper cabs. The agencies are unaware of reasons why AES
with extended idle reduction technologies could not be applied to this
high fraction of tractors with a sleeper cab, except those deemed a
vocational tractor, in the available lead time.
    The agencies are interested in extending the idle reduction
benefits beyond Class 8 sleepers, to day cabs. The agencies reviewed
literature to quantify the amount of idling which is conducted outside
of hoteling operations. One study, conducted by Argonne National
Laboratory, identified several different types of trucks which might
idle for extended amounts of time during the work day.\164\ Idling may
occur during the delivery process, queuing at loading docks or border
crossings, during power take off operations, or to provide comfort
during the work day. However, the study provided only ``rough
estimates'' of the idle time and energy use for these vehicles. The
agencies are not able to appropriately develop a baseline of workday
idling for day cabs and identify the percent of this idling which could
be reduced through the use of AES. We welcome comment and data on
quantifying the effectiveness of AES on day cabs.
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    \164\ Gaines, L., A. Vyas, J. Anderson. Estimation of Fuel Use
by Idling Commercial Trucks. January 2006.
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(v) Vehicle Speed Limiter Adoption Rate