along with higher GCWR. While these heavy Class 8 tractor standards
will be optional for tractors sold into the U.S. market, we expect that
Canada will consider adopting these as mandatory requirements as part
of their regulatory development and consultation process. Given the
unique circumstances in the Canadian fleet, we believe that there is a
reasonable basis for considering such an approach for Canadian
tractors. As such, the agencies have coordinated these requirements
with ECCC. The agencies are only adopting optional heavy Class 8
standards for MY 2021 at this time. The expectation is that ECCC will
develop their own heavy-duty GHG regulations to harmonize with this
Phase 2 rulemaking through its own domestic regulatory process. We
expect that ECCC will include a mandate that heavy Class 8 tractors be
certified to the MY 2021 heavy Class 8 tractor standards, but could
also specify more stringent standards for later years for these
vehicles. We plan to coordinate with ECCC to incorporate any needed
future changes in a timely manner. Details of these optional standards
are included in Section III.D.1.
(b) Special Purpose Tractors
    During the development of Phase 1, the agencies received 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 off-road
or 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.
Therefore, we adopted provisions to allow these special purpose
tractors to certify as vocational vehicles (or vocational tractors).
Consistent with our approach in Phase 1, the agencies still believe
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.\221\ As adopted in Phase 1, a Phase 2 vehicle determined by the
manufacturer to be a HHD vocational tractor will 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 will be regulated as MHD vocational
vehicles. Specifically, the agencies adopted in Phase 1 provisions in
EPA's 40 CFR 1037.630 and NHTSA's regulation at 49 CFR 523.2 to only
allow the following three types of vocational tractors to be eligible
for reclassification by the manufacturer: Low-roof tractors intended
for intra-city pickup and delivery, such as those that deliver bottled
beverages to retail stores; tractors intended for off-road operation
(including mixed service operation), such as those with reinforced
frames and increased ground clearance; and tractors with a GCWR over
120,000 pounds.\222\
---------------------------------------------------------------------------

    \221\ 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.
    \222\ See existing 40 CFR 1037.630 (a)(1)(i) through (iii).
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    In the Phase 2 proposal, the agencies proposed to remove the third
type of vocational tractors, heavy-haul tractors with a GCWR over
120,000 pounds, from the Phase 2 Special Purpose Tractor category and
set unique standard for heavy-haul tractors. 80 FR 40214. The agencies
requested comment on the Special Purpose Tractor criteria and received
comments from the manufacturers. EMA and PACCAR commented there is a
group of special purpose tractors with a gross combination weight
rating over 120,000 pounds that fall in between the proposed regulatory
categories for heavy-haul tractors and Class 8 tractors that need to be
accounted for in a separate and distinct manner. They stated that such
vehicles are still appropriately categorized as Special Purpose
Tractors and should be included at the manufacturer's option in the
vocational tractor family, even though they may not meet the proposed
total gear reduction requirement or the frame rail requirements. PACCAR
and Volvo also requested a modification to the definition to include
``equal to 120,000 GCWR.''
    Volvo provided a list of recommended Special Purpose Tractor
criteria. Volvo stated that these characteristics differentiate these
vehicles from line haul operation, especially in terms of fuel economy
as well as the significant added costs for these features. Volvo's

recommended criteria included GCWR greater than 120,000 pounds or any
three of the following vehicles specifications: Configuration other
than 4x2, 6x2, or 6x4; greater than 14,600 pounds front axle load
rating; greater than 46,000 pounds rear axle load rating; greater than
or equal to 3.00:1 overall axle reduction in transmission high range;
greater than 57.00:1 overall axle reduction in transmission low range;
frame rails with a resistance bending moment greater than or equal to
2,000,000 in-lbs., greater than or equal to 20 degree approach angle;
or greater than or equal to 14 inch ground clearance.
    The heavy-haul tractor standards that the agencies are adopting in
Phase 2 apply to tractors with a GCWR greater than or equal to 120,000
pounds. As stated above, the agencies are adopting heavy-haul tractor
criteria based only on GCWR, and are not adopting the proposed criteria
of RBM or total gear reduction. With these Phase 2 changes to the
proposed heavy-haul tractor definition, all tractors that would have
been considered as Special Purpose Tractors in Phase 1 due to the GCWR
criteria listed in EPA's 40 CFR 1037.630 and NHTSA's regulation at 49
CFR 523.2 will now qualify as heavy-haul tractors in Phase 2.
Therefore, we no longer believe that it is necessary for heavy-haul
tractors to be treated as Special Purpose Tractors. The agencies also
reviewed Volvo's suggested criteria and concluded that the Phase 1
approach and Special Purpose Tractor criteria are working well;
therefore, we do not see the need to adopt more restrictive criteria.
Consequently, the agencies are adopting in Phase 2 provisions in EPA's
40 CFR 1037.630 and NHTSA's regulation at 49 CFR 523.2 to only allow
the following two types of vocational tractors to be eligible for
reclassification to Special Purpose Tractors by the manufacturer:
    (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.
    These provisions apply only for purposes of Phase 2. The agencies
are not amending the Phase 1 provisions for special purposes tractors.
    Volvo also requested that the agencies add a Vocational Heavy-Haul
Tractor subcategory that allows for a heavy-haul tractor which benefits
from the utilization of a powertrain optimized to meet the vocational
operational requirements of this segment, a technology package
corresponding to those operational characteristics, and with a
corresponding duty cycle and, most importantly, a payload
representative of heavy-haul operation. The agencies considered this
request and analyzed the expected technology package differences
between the vocational and tractor program. As described in Section
III.D.1, the agencies are only adopting technologies in the heavy-haul
tractor category that would be applicable to the operation of these
vehicles. For example, we are not adopting standards that are premised
on any improvements to aerodynamics or extended idle reduction.
Therefore, we concluded that there is no need to develop another
vocational subcategory to account for heavy-haul tractors.
    Because the difference between some vocational tractors and line-
haul tractors is potentially somewhat subjective, and because of
concerns about relative stringency, we also adopted in Phase 1 and
proposed to continue in Phase 2 a rolling three year sales limit of
21,000 vocational tractors per manufacturer consistent with past
production volumes of such vehicles to limit the use of this provision.
We proposed in Phase 2 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
volume 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 requested comment on whether
the proposed sales volume limit is set at an appropriate level looking
into the future. 80 FR 40214.
    Several of the manufacturers commented that it would be reasonable
to remove the sales cap limit. Allison stated that this limitation may
have been reasonable in the initial years of the program as a
precaution against unreasonably assigning too many tractors to the
vocational vehicle category. However in Phase 2, Allison recommended
that the agencies should remove the cap for three reasons: (1) Vehicle
configurations change over time; (2) the Phase 2 vocational program
drives technology improvements of powertrains; and (3) Phase 2 better
represents the diversity of vocational vehicle uses that would allow
for better alignment of vehicles with duty cycles that most represent
their real world operation. Daimler stated that they think that with
the addition of heavy-haul tractor standards, there will be less need
for a sales volume limit on special purpose tractors. In Volvo Group's
opinion, the proposed volume limit is overly constraining and
burdensome and should be removed. Volvo stated that given the recent
product lineup overhauls across the industry they do not believe that
there are many models still on the market that are sold in large
numbers into both highway tractor and vocational tractor segments, nor
is there sufficient reason that any OEM cannot identify specific
vehicle attributes in order to classify a tractor as suitable solely
for highway use, or for on/off-road use. Volvo Group suggested that the
agencies remove the vocational tractor volume restrictions and employ a
guideline based on specific vehicle characteristics.
    The agencies evaluated the sales cap limit proposed for special
purpose tractors and the comments addressing the issue of a sales cap.
EPA calculated the number of vocational tractors certified in MY 2014
and MY 2015. The number of tractors ranged between approximately 2,600
and 6,200 per year per manufacturer that certified special purpose
tractors, but one manufacturer did not use this provision at all.\223\
It is apparent that none of the manufacturers are utilizing this
provision near the maximum allowable level in Phase 1 (a rolling three
year sales limit of 21,000). We also believe that there is more
incentive for manufacturers to use the special purpose tractor
provisions in Phase 1 because the relative difference in stringency
between the tractor and vocational programs is much greater in Phase 1
than it will be in Phase 2. Upon further consideration, we concluded
that there is significantly less incentive for the manufacturers to
reclassify tractors that are not truly special purpose tractors as
vocational vehicles as a pathway to a less stringent standard in Phase
2 primarily since the Phase 2 vocational vehicle program stringency is
similar to the stringency of the tractor program. In addition, the
Phase 2 vocational vehicle compliance program and standards better
represent the duty cycles expected of these vehicles and are predicated
on performance of similar sets of vehicle technologies, except for
aerodynamic technologies, as the primary tractor program. Therefore, we
are adopting Phase 2 special purpose tractor provisions without a sales
cap, but will continue to monitor during the Phase 2 implementation.
---------------------------------------------------------------------------

    \223\ U.S. EPA. Memo to Docket: Special Purpose Tractor
Production Volumes. Docket EPA-HQ-OAR-2014-0827.

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

(5) Small Tractor Manufacturer Provisions
    In Phase 1, EPA determined that manufacturers that met the small
business criteria specified in 13 CFR 121.201 for ``Heavy Duty Truck
Manufacturing'' should not be subject to the initial phase of
greenhouse gas emissions standards in 40 CFR 1037.106.\224\ The
regulations required that qualifying manufacturers notify the
Designated Compliance Officer each model year before introducing the
exempted vehicles into commerce. The manufacturers are also required to
label the vehicles to identify them as excluded vehicles. EPA and NHTSA
proposed to eliminate this small business provision for tractor
manufacturers in the Phase 2 program. As stated in the NPRM, the
agencies are aware of two second stage manufacturers building custom
sleeper cab tractors. In the proposal we stated that 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.\225\ 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. 80 FR 40214.
---------------------------------------------------------------------------

    \224\ See 40 CFR 1037.150(c).
    \225\ 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.
---------------------------------------------------------------------------

    The agencies received comments on the second stage manufacturer
options for small manufacturers discussed in the proposal. American
Reliance Industries (ARI) raised concerns related to the proposed
alternative methods for excluding or exempting second stage
manufacturers performing cab sleeper modifications. ARI is concerned
that treating these vehicles as vocational vehicles may mean that other
regulations related to vocational vehicles would become applicable and
have unanticipated adverse results and that the vehicles would not be
certified as vocational vehicles when originally certified by an OEM.
ARI commented that if EPA and NHTSA adopt a frontal area approach for
second stage manufacturers making cab sleeper modifications, that the
section be revised to ensure greater clarity as to the intention and
effect of this section. In building a custom sleeper cab, ARI stated
that they may use wind fairings, fuel tank fairings, roof fairings, and
side extenders that can modify the frontal area of the tractor in
height and width as compared to the frontal area of the vehicle used to
obtain the original certification. ARI also commented that depending on
the custom cab sleeper modification, ARI may replace an aerodynamic
fairing from the tractor in order to provide better aerodynamic results
in light of the cab sleeper modification. ARI does not want to be
precluded from continuing to provide these benefits to clients. ARI
encourages the agencies to take a similar approach to small business
exemption under the Phase 1 regulation in the Phase 2 regulation.
    Daimler commented on the agencies' two proposed approaches for
second stage manufacturers that build custom sleepers. Daimler's main
concern is to clarify that where the primary manufacturer has certified
a vehicle as a day cab, the second stage manufacturer's actions do not
draw the primary manufacturer into noncompliance. Daimler stated that
in many cases, they do not know that a vehicle will be altered by a
second stage manufacturer. Daimler did not have a preference on the way
that the agencies proposed to regulate these secondary vehicle
manufacturers, as long as the primary vehicle manufacturers could
continue to sell vehicles with the expectation that anyone changing
them from the compliant state in which it was built would certify those
changes.
    In response to these comments, EPA is clarifying in 40 CFR 1037.622
that small businesses may modify tractors as long as they do not modify
the front of the vehicle and so long as the sleeper compartment is no
more than 102 inches wide or 162 inches in height. As an interim
provision, to allow for a better transition to Phase 2, EPA is
finalizing a more flexible compliance path in 40 CFR 1037.150(r). This
option allows small manufacturers to convert a low or mid roof tractor
to a high roof configuration without recertification, provided it is
for the purpose of building a custom sleeper tractor or for conversion
to a natural gas tractor. Although this more flexible allowance to
convert low and mid roof tractors to high roof tractors is being
adopted as an interim provision, we have not established an end date at
this time. We expect to reevaluate as manufacturers begin to make use
of and may decide to revise it in the future, potentially deciding to
make it a permanent allowance. To be eligible for this option, the
secondary manufacturer must be a small manufacturer and the original
low or mid roof tractor must be covered by a valid certificate of
conformity. The modifications may not increase the frontal area of the
tractor beyond the frontal area of the equivalent high roof tractor
paired with a standard box van. With respect to Daimler's comment, 40
CFR 1037.130 only applies to vehicles sold in an uncertified condition
and does not apply to vehicles sold in a certified condition.
(6) Glider Vehicles
    As described in Section XIII.B, EPA is adopting new provisions
related to glider vehicles, including glider tractors.\226\ NHTSA did
not propose such changes. Glider vehicles and glider kits were also
treated differently under NHTSA and EPA regulations prior to this
rulemaking. They are exempt from NHTSA's Phase 1 fuel consumption
standards. For EPA purposes, the CO2 provisions of Phase 1
exempted glider vehicles and glider kits produced by small businesses
but did not include such a blanket exemption for other glider kits.
Thus, some gliders and glider kits are already subject to the Phase 1
requirement to obtain a vehicle certificate prior to introduction into
commerce as a new vehicle. 80 FR 40528.
---------------------------------------------------------------------------

    \226\ See section I.E. 1 for descriptions of glider vehicles and
glider kits.
---------------------------------------------------------------------------

    In the NPRM, EPA proposed to revise the provisions applicable to
glider vehicles so that the engines used in these vehicles would need
to meet the standards for the year of the new glider vehicle. EPA's
resolution of issues relating to glider vehicles, including glider
tractors, and glider kits, is discussed fully in Section XIII.B and RTC
Section 14.2.
    Similarly, NHTSA considered including glider vehicles under its
Phase 2 program. After assessing the impact glider vehicles have on the
tractor segment, NHTSA has elected not to include glider vehicles in
its Phase 2 program. NHTSA may reconsider fuel efficiency regulations
for glider vehicles in a future rulemaking.
    As discussed in the NPRM, NHTSA would like to reiterate its safety
authority over gliders--notably, that it has become increasingly aware
of potential noncompliance with its regulations applicable to gliders.
While there are instances in which NHTSA regulations allow gliders to
use a ``donor VIN'' from a ``donor tractor,'' NHTSA has learned of
manufacturers that 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.
    We believe that the agencies having different policies for glider
kits and glider vehicles under the Phase 2 program will not result in
problematic disharmony between the NHTSA and EPA programs, because of
the small number of vehicles that will be involved. EPA believes that
its changes will result in the glider market returning to the pre-2007
levels, in which fewer than 1,000 glider vehicles will be produced in
most years. Only non-exempt glider vehicles will 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 will be few enough not to result in any meaningful
disharmony between the two agencies.
(7) Useful Life and Deterioration Factors
    Section 202(a)(1) of the CAA specifies that EPA is to adopt
emissions standards that are applicable for the useful life of the
vehicle. The in-use Phase 2 standards that EPA is adopting will apply
to individual vehicles and engines, just as EPA adopted for Phase 1.
NHTSA is also adopting the same useful life mileage and years as EPA
for Phase 2.
    EPA is also not adopting any changes to the existing provisions
that require 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-5. 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 did not adopt any changes to the regulations describing compliance
with GHG pollutants with regards to deterioration. See 40 CFR 1037.241.

                Table III-5--Tractor Useful Life Periods
------------------------------------------------------------------------
                                                        Years     Miles
------------------------------------------------------------------------
Class 7 Tractors....................................        10   185,000
Class 8 Tractors....................................        10   435,000
------------------------------------------------------------------------

D. Feasibility of the Final Phase 2 Tractor Standards

    This section describes the agencies' technical feasibility and cost
analysis. Further detail on all of these technologies can be found in
the 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 continuing the
Phase 1 provisions that treat vocational tractors as vocational
vehicles instead of as combination tractors, as noted in Section
III.C.4. The focus of this section is on the feasibility of final
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, including new information collected since the
NPRM was promulgated. The primary sources of pre-proposal information
were the Southwest Research Institute evaluation of heavy-duty vehicle
fuel efficiency and costs for NHTSA,\227\ the Department of Energy's
SuperTruck Program,\228\ 2010 National Academy of Sciences report of
Technologies and Approaches to Reducing the Fuel Consumption of Medium-
and Heavy-Duty Vehicles,\229\ TIAX's assessment of technologies to
support the NAS panel report,\230\ 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),\231\ and the technology cost analysis
conducted by ICF for EPA.\232\ Some additional information and data
were also provided in comments.
---------------------------------------------------------------------------

    \227\ 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.
    \228\ U.S. Department of Energy. SuperTruck Initiative.
Information available at http://energy.gov/eere/vehicles/vehicle-technologies-office.
    \229\ 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.
    \230\ TIAX, LLC. ``Assessment of Fuel Economy Technologies for
Medium- and Heavy-Duty Vehicles,'' Final Report to National Academy
of Sciences, November 19, 2009.
    \231\ NESCCAF, ICCT, Southwest Research Institute, and TIAX.
Reducing Heavy-Duty Long Haul Combination Truck Fuel Consumption and
CO2 Emissions. October 2009.
    \232\ 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.
---------------------------------------------------------------------------

    Commenters generally supported the agencies' projection that
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 final HD Phase 2 standards is based on our updated projection of
the use of these technologies and an updated 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 final standards on their use for the model years covered
by this rule, for various reasons discussed below.
(1) 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 these standards.
    Based on information available at the time of the NPRM, the
agencies proposed Phase 2 standards that projected 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. At
proposal, the agencies assumed the 2027 MY engines would achieve an
additional 4 percent improvement over Phase 1 engines and we projected
15 percent adoption of waste heat recovery (WHR) and many other
advanced engine technologies. In addition, we proposed standards that
projected 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.
    The agencies also discussed several other alternatives in the
proposal. When considering alternatives, it is necessary to evaluate
the impact of a regulation in terms of CO2 emission
reductions, fuel consumption reductions, and technology costs. However,
it is also necessary to consider other aspects, such as manufacturers'
research and development resources, the impact on purchase price, and
the impact on purchasers. Manufacturers are limited in their ability to
develop and implement new technologies due to their human resources and
budget constraints. This has a direct impact on the amount of lead time
that is required to meet any new standards. From the owner/operator
perspective, heavy-duty vehicles are a capital investment for firms and
individuals so large increases in the upfront cost could impact buying
patterns. Though the dollar value of the lifetime fuel savings will far
exceed the upfront technology costs, purchasers often discount future
fuel savings for a number of reasons, as discussed in more detail in
Section IX.A. Tractor purchasers are often uncertain regarding the
amount of fuel savings that can be expected for their specific
operation due to the diversity of the heavy-duty tractor market.
Although a nationwide perspective that averages out this uncertainty is
appropriate for rulemaking analysis, individual operators must consider
their potentially narrow operation. In addition, purchasers often put a
premium on reliability (because downtime is costly in terms of towing,
repair, late deliveries, and lost revenue) and may perceive any new
technology as a potential risk with respect to reliability. Another
factor that purchasers consider is the impact of a new technology on
the resale market, which can also be impacted by uncertainty.
    The agencies solicited comment on all of these issues and again
noted the possibility of adopting, in a final action, standards that
are more accelerated than those in Alternative 3, notably what we
termed at proposal, Alternative 4 which would have involved a three
year pull ahead of the proposed 2027 standards. 80 FR 40211. The
agencies also assumed in the NPRM that both the proposed standards and
Alternative 4 could be accomplished with all changes being made during
manufacturers' normal product design cycles. However, we noted that
doing so would be more challenging for Alternative 4 and may require
accelerated research and development outside of design cycles with
attendant increased costs. Commenters were encouraged in the NPRM to
address all aspects of feasibility analysis, including costs, the
likelihood of developing the technology to achieve sufficient
relaibility within the lead time, and the extent to which the market
could utilize the technology.
    The agencies received several general comments on the overall
stringency of the proposed Phase 2 standards. Several entities
encouraged the agencies to adopt more stringent tractor standards,
including adoption of Alternative 4. They pointed out that DOE's
SuperTruck program demonstrated over 40 percent improvement over 2010
levels, including 10.7 mpg by Cummins-Peterbuilt and 12.2 mpg by
Daimler. CBD stated that the technology forcing nature of Clean Air Act
section 202(a)(2) \233\ and EPCA/EISA requires more aggressive
assumptions regarding technology adoption. UCS commented that the
tractor standards could be strengthened by another six percent in 2024
and seven percent in 2027 to reflect the full range of improvements to
the powertrain and engine. ICCT stated that its analysis indicates that
the technology potential is higher and costs are lower than the
agencies' assessments in the NPRM. CARB stated that Alternative 4 is
technologically feasible and will result in more emission and fuel
consumption reductions. CARB continued to state that the increased cost
due to accelerated implementation is minimal, about $1,000 per vehicle
purportedly according to the NPRM.
---------------------------------------------------------------------------

    \233\ CBD is mistaken that section 202(a)(2) mandates
technology-forcing standards, although it allows them. See generally
74 FR 49464-465 (Sept. 28, 2009).
---------------------------------------------------------------------------

    In contrast to the commenters that called for more stringent
standards than those proposed, several other commenters cautioned the
agencies from adopting final standards that are more stringent than
those proposed. Diesel Technology Forum commented that the agencies
should proceed with caution on technologies that are not in wide use
that have not demonstrated reliability or commercial availability. The
International Foodservice Distributors Association is concerned about
Alternative 4 in terms of reliability, commenting that it would require
their members to purchase unproven and unreliable equipment in order
for OEMs to meet the requirements. OOIDA commented if owners fear a
reduction in reliability, increased operating costs, reduced residual
value, or large increases in purchase prices, they will adjust their
purchase plans.
    PACCAR commented about the importance of lead time because their
customers need time to determine if a technology meets their specific
needs in their specific application and need assurance that a
technology will be reliable in use. PACCAR also stated that the timing
provided in the NPRM Alternative 3 provides the ``greatest likelihood
for a successful program.'' Volvo commented that SuperTruck
demonstration vehicles serve only the purpose of demonstration but are
not proven with respect to cost, reliability, and durability. Volvo
stated that the purpose of SuperTruck was narrow in applicability of
matched tractor-trailers and that it did not result in a cost effective
tractor because each project cost between $40 and $80 million to
produce a single vehicle. Volvo also commented that not all SuperTruck
technologies should be forced into all applications and duty cycles and
if they are a pre-buy (or no-buy) could result.
    The agencies considered all of the general comments associated with
the proposed Alternative 3 and Alternative 4 tractor standards. We
believe there is merit in many of the detailed comments received
regarding technologies. These are discussed in detail in the following
sections. Instead of merely choosing from among the proposed
alternatives, the agencies have developed a set of final tractor
standards that reflect our reevaluation of the ability to pull ahead
certain technologies, the limitations in adoption rates and/or
effectiveness of other technologies, and consideration of additional
technologies. In general, the final Phase 2 tractor standards are
similar in overall stringency as the levels proposed in Alternative 3,
but have been determined using new technology packages that reflect
consideration of all of the technology comments, and in some respects
reflect greater stringency than the proposed Alternative 3.
    As can be seen from the comments, there is uncertainty and a wide
range of opinions regarding the extent to which these technologies can
be applied to heavy-duty tractors. Vehicle manufacturers tended to take
the conservative position for each technology and argue that the
agencies should not project effectiveness or adoption rates beyond that
which is certain. Many other commenters took a more optimistic view and
argued for the agencies to assume that each potential technology will
be highly effective in most applications. However the agencies believe
the most likely outcome will be that some technologies

will work out better than expected while others will be slightly more
challenging than projected. Thus, the agencies have tended to make
balanced projections for the various technologies, although some may be
slightly optimistic while others are somewhat conservative. We believe
the overall effect of this approach will be standards that achieve
large reductions with minimal risks to the industry.
(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.
    As noted earlier, the Phase 1 2017 model year tractor standards
(based on Phase 1 GEM and test procedures) and the baseline 2017 model
year tractor results (using Phase 2 GEM and test procedures) 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 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 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.
    The agencies used the same adoption rates of tire rolling
resistance for the Phase 2 baseline as we used to set the Phase 1 2017
MY standards. See 76 FR 57211. 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 pre-Phase 1 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 pre-Phase 1 baseline level, 60 percent Level 1 and
10 percent Level 2. Finally, the low and mid roof day cab 2017 MY
standards were premised on a weighted average rolling resistance
consisting of 40 percent baseline, 50 percent Level 1, and 10 percent
Level 2. The agencies did not receive comments on the tire packages
used to develop the Phase 2 baseline in the NPRM.
    The agencies sought comment on the baseline vehicle attributes
described in the NPRM. The agencies received comments related to the
baseline adoption rate of automatic engine shutdown systems (AESS) and
the baseline aerodynamics assessment. In the proposal, the agencies
noted that the manufacturers were not using tamper-proof AESS to comply
with the Phase 1 standards so the agencies reverted back to the
baseline APU adoption rate of 30 percent used in the Phase 1 baseline.
EMA and TRALA commented that the agencies confused the use of an APU
with the use of tamper-proof idle technologies in assessing the
baseline for the proposed Phase 2 standards. They stated that a 30
percent penetration rate of APUs is not the same as a 30 percent
penetration rate of tamper-proof idle systems. ATA and Volvo also
commented that the assumption that 30 percent of 2017 sleeper tractors
will utilize the tamper-proof automatic engine shutdown is too high.
EMA and PACCAR commented that virtually all tractors in the field have
an automatic shutdown programmed in their engine; however, less than
one percent of vehicles sold in recent years have tamper-proof AESS
that are triggered in less than five minutes and cannot be reprogrammed
for 1.259 million miles. In response to these comments, the agencies
reassessed the baseline idle reduction adoption rates. The latest NACFE
confidence report found that 9 percent of tractors had auxiliary power
units and 96 percent of vehicles are equipped with adjustable automatic
engine shutdown systems.\234\ Therefore, the agencies are projecting
that 9 percent of sleeper cabs will contain an adjustable AESS and APU,
while the other 87 percent will only have an adjustable AESS.
Additional discussion on adjustable AESS is included in Section
III.D.1.b.
---------------------------------------------------------------------------

    \234\ North American Council for Freight Efficiency. Confidence
Report:Idle Reduction Solutions. 2014. Page 13.
---------------------------------------------------------------------------

    The Phase 2 baseline in the NPRM was determined based on the
aerodynamic bin adoption rates used to determine the Phase 1 MY 2017
tractor standards. Volvo, EMA, and other manufacturers also commented
that the aerodynamic drag baseline for 2017 tractors included in the
NPRM was too aerodynamically efficient. EMA commented that some of the
best aerodynamic tractors available were tested by the agencies and
then declared to be the baseline. According to the manufacturers, the
average tractor--the true baseline--is a full bin worse than these best
tractors. While the agencies agree with the commenters that it is
important to develop an accurate baseline so that the appropriate
aerodynamic technology package effectiveness and costs can be evaluated
in determining the final Phase 2 standards, there appears to be some
confusion regarding the NPRM baseline aerodynamic assessment. The Phase
2 baseline in the NPRM was determined based on the aerodynamic bin
adoption rates used to determine the Phase 1 MY 2017 tractor standards
(see 76 FR 57211). The baseline was not determined by or declared to be
the average results of the vehicles tested, as some commenters
maintained. The vehicles that were tested prior to the NPRM were used
to develop the proposed aerodynamic bin structure for Phase 2. In both
the NPRM and this final rulemaking, we developed the Phase 2 bins such
that there is an alignment between the Phase 1 and Phase 2 aerodynamic
bins after taking into consideration the changes in aerodynamic test
procedures and reference trailers required in Phase 2. The Phase 2 bins
were developed so that tractors that performed as a Bin III in Phase 1
would also perform as Bin III tractors in Phase 2. Additional details
regarding how the agencies refined the aerodynamic bin values for Phase
2 for the final rule can be found in Section III.E.2.a. The baseline
aerodynamic value for the Phase 2 final rulemaking was determined in
the same manner as the NPRM, using the adoption rates of the bins used
to determine the Phase 1 standards, but reflect the final Phase 2 bin
CdA values.
    In the NPRM, we used a transmission top gear ratio of 0.73 and
drive axle ratio of 3.70 in the baseline 2017 MY tractor. UCS commented
that the baseline axle ratio is too high. The agencies determined the
rear axle ratio and final drive ratio in the baseline tractor based on
axle market information shared by Meritor,\235\ one of the primary
suppliers of heavy-duty axles, and confidential business information
provided by Daimler. Our assessment of this information found that a
rear axle ratio

of 3.70 and a top gear ratio of 0.73 (equivalent to a final drive ratio
of 2.70) is a commonly spec'd tractor. Meritor's white paper on
downspeeding stated that final drive ratios of less than 2.64 are
considered to be ``downsped.'' \236\ The agencies recognize that there
is a significant range in final drive ratios that will be utilized by
tractors built in 2017 MY, we do not believe that the average (i.e.,
baseline) tractor in 2017 MY will downsped (i.e., have a final drive
ratio of less than 2.64). Therefore, the agencies are maintaining the
proposed top gear ratio and drive axle ratio for the assessment of the
baseline tractor performance.
---------------------------------------------------------------------------

    \235\ NACFE. Confidence Report: Programmable Engine Parameters.
February 2015. Page 23.
    \236\ Ostrander, Robert, et.al. (Meritor). Understanding the
Effects of Engine Downspeeding on Drivetrain Components. 2014. Page
2.
---------------------------------------------------------------------------

    The agencies are using the specific attributes of each tractor
subcategory as are listed below in Table III-6 for the Phase 2
baselines. Using these values, the agencies assessed the CO2
emissions and fuel consumption performance of the baseline tractors
using the Phase 2 GEM. The results of these simulations are shown below
in Table III-7.

                                             Table III-6--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 15L      2017 MY 15L      2017 MY 15L
   Engine 350     Engine 350 HP      Engine 350       Engine 455       Engine 455       Engine 455       Engine 455       Engine 455       Engine 455
           HP                                HP               HP               HP               HP               HP               HP               HP
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                Aerodynamics (CdA in m2)
--------------------------------------------------------------------------------------------------------------------------------------------------------
         5.41             6.48             6.38             5.41             6.48             6.38             5.41             6.48             5.90
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                           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--Adjustable AESS with no Idle Red Tech Adoption Rate @1% Effectiveness
--------------------------------------------------------------------------------------------------------------------------------------------------------
          N/A              N/A              N/A              N/A              N/A              N/A              87%              87%              87%
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                Extended Idle Reduction--Adjustable AESS with Diesel APU Adoption Rate @3% Effectiveness
--------------------------------------------------------------------------------------------------------------------------------------------------------
          N/A              N/A              N/A              N/A              N/A              N/A               9%               9%               9%
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                       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 Configuration = 4 x 2           Drive Axle Configuration = 6 x 4
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                  Tire Revs/Mile = 512
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                 Drive Axle Ratio = 3.70
--------------------------------------------------------------------------------------------------------------------------------------------------------

                                  Table III-7--Class 7 and 8 Tractor Baseline CO[ihel2] 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
--------------------------------------------------------------------------------------------------------------------------------------------------------
CO[ihel2] (grams CO[ihel2]/ton-mile).................      119.1      127.2      129.7       91.3       96.6       98.2       84.0       90.2       87.8
Fuel Consumption (gal/1,000 ton-mile)................   11.69941   12.49509   12.74067    8.96857    9.48919    9.64637    8.25147    8.86051    8.62475
--------------------------------------------------------------------------------------------------------------------------------------------------------

    The agencies also received comments related to the baseline heavy-
haul tractor parameters. Volvo did not agree that certain segments of
the heavy-haul population are appropriately represented by the baseline
in the NPRM. Volvo stated that these types of vehicles typically
utilize an 18-speed transmission, since they require the very close
gear ratios and nearly all heavy-haul tractors have deeper drive axle
ratios than the agencies have assumed

(3.55). PACCAR commented the 14.4 first gear of the 18-speed
transmission coupled with the 3.73 rear axle ratio is an example of a
significant sales volume combination that meets their recommended 53:1
Total Reduction ratio. Upon further consideration, the agencies find
the suggestion that the baseline heavy-haul tractor is better
represented by an 18-speed manual transmission to be persuasive. We
therefore revised the baseline heavy-haul tractor configuration, as
shown in Table III-8.
    The baseline 2017 MY heavy-haul tractor will emit 56.9 grams of
CO2 per ton-mile and consume 5.59 gallons of fuel per 1,000
ton-mile.

         Table III-8--Heavy-Haul Tractor Baseline Configuration
------------------------------------------------------------------------
                Baseline heavy-haul tractor configuration
-------------------------------------------------------------------------
Engine = 2017 MY 15L Engine with 600 HP.
------------------------------------------------------------------------
Aerodynamics (CdA in m\2\) = 5.00.
------------------------------------------------------------------------
Steer Tires (CRR in kg/metric ton) = 7.0.
------------------------------------------------------------------------
Drive Tires (CRR in kg/metric ton) = 7.4.
------------------------------------------------------------------------
Transmission = 18 speed Manual Transmission
Gear ratio = 14.4, 12.29, 8.51, 7.26, 6.05, 5.16, 4.38, 3.74, 3.2, 2.73,
 2.28, 1.94, 1.62, 1.38, 1.17, 1.00, 0.86, 0.73.
------------------------------------------------------------------------
Drive axle Ratio = 3.73.
------------------------------------------------------------------------
All Technology Improvement Factors = 0%.
------------------------------------------------------------------------

    The fuel consumption and CO2 emissions in this ``flat''
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 ``dynamic''
baseline, was developed to estimate the potential effect of market
pressures and non-regulatory government initiatives to improve tractor
fuel consumption. The 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
in 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 \237\ 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 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-7. 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-6 is 5.90 m\2\ in 2017. In 2028, the CdA of a high
roof sleeper cab would be assumed to still be 5.90 m\2\ in the flat
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 RIA Chapter 11.
---------------------------------------------------------------------------

    \237\ U.S. Department of Energy. See SuperTruck Report to
Congress. http://energy.gov/eere/vehicles/downloads/vehicle-technologies-office-report-adoption-new-fuel-efficient-technologies.
---------------------------------------------------------------------------

(b) Tractor Technology Effectiveness
    The agencies' assessment of the technology effectiveness was
developed through the use of the GEM in coordination with modeling
conducted by Southwest Research Institute. The agencies developed these
standards through a three-step process, similar to the approach used in
Phase 1. First, the agencies developed estimates of technology
performance characteristics and effectiveness in terms of reducing
CO2 emissions and fuel consumption for each technology, as
described below. Each technology is associated with an input parameter
which in turn is used as an input to the Phase 2 GEM simulation tool.
There are two types of GEM input parameters. The first type requires a
manufacturer to measure aspects of the technology. These aspects are
used as inputs to GEM which then models the technology's effectiveness
(i.e. the effectiveness for that technology is the GEM output).
Aerodynamics, tire rolling resistance, engine fuel maps, axle ratio,
the optional axle efficiency, and optional transmission efficiencies
are examples of this first type of GEM input. The second type of GEM
input only requires a manufacturer to install the technology onto the
vehicle and does not require any testing to determine the GEM input.
The agencies determined and specify in the regulations (see 40 CFR
1037.520) the effectiveness of this second type of GEM input. The
agencies also define the technologies that qualify to be eligible for
these GEM technology inputs in the regulations (see 40 CFR 1037.660 and
1037.801). Examples of these technology inputs include transmission
type, idle reduction technologies, tire pressure systems, vehicle speed
limiters, weight reduction, intelligent controls, and other
accessories. The performance levels for the range of Class 7 and 8
tractor aerodynamic packages and vehicle technologies are described
below in Table III-10.\238\ All percentage improvements noted below are
relative to the 2017 MY baseline tractor.
---------------------------------------------------------------------------

    \238\ These GEM default values could be superseded on a case-by-
case basis based on an appropriate off-cycle credit demonstration.
---------------------------------------------------------------------------

    As discussed in Section I.C.1.a, we assume manufacturers will
incorporate appropriate compliance margins for all measured GEM inputs.
In other words, they will declare values slightly higher than their
measured values. As discussed in Section II.D.5, compliance margins
associated with fuel maps are likely to be approximately one percent.
For aerodynamic inputs, we believe the bin structure will eliminate the
need for CdA compliance margins for most vehicles. However,
for vehicles with measured CdA values very near the upper
bin boundary, manufacturers will likely choose to certify some of them
to the next higher bin values (as a number of commenters noted). For
tire rolling resistance, our feasibility rests on the Phase 1
standards, consistent with our expectation that manufacturers will to
continue to incorporate the compliance margins they considered
necessary for Phase 1. With respect to optional axle and/or
transmission power loss maps, we believe manufacturers will need very
small compliance margins. These power loss procedures require high
precision so measurement uncertainty will likely be on the order of 0.1
percent of the transmitted power. All of these margins are reflected in
our projections of the emission levels that will be technologically
feasible.
    The agencies then determined the adoption rates feasible for each

technology in each model year, as described in Section III.D.1.c. Then
as described in Section III.D.1.f, the agencies combined the technology
performance levels with a projected technology adoption rate to
determine the GEM inputs used to set the stringency of these standards.
The agencies input these parameters into Phase 2 GEM and used the
output to determine the final CO2 emissions and fuel
consumption levels.
(i) Engine Improvements
    There are several technologies that could be used to improve the
efficiency of diesel engines used in tractors. These technologies
include friction reduction, combustion system optimization, and waste
heat recovery using the Rankine cycle. Details of the engine
technologies, adoption rates, and overall fuel consumption and
CO2 emission reductions are included in Section II.D. The
Phase 2 engine standards will lead each manufacturer to achieve
reductions of 1.8 percent in 2021 MY, 4.2 percent in 2024 MY, and 5.1
percent in 2027 MY. For the final Phase 2 rule, we recognize that it
could be possible to achieve greater reductions than those included in
the engine standard by designing entirely new engine platforms. See
Section II.D.2.e. Unlike existing platforms, which are limited with
respect to peak cylinder pressures (precluding certain efficiency
improvements), new platforms can be designed to have higher cylinder
pressure than today's engines. New designs are also better able to
incorporate recent improvements in materials and manufacturing, as well
as other technological developments. Considered together, it is likely
that a new engine platform could be about 2 percent better than engines
using older platforms. Moreover, the agencies have seen CBI data that
suggests improvement of more than 3 percent are possible. As discussed
in Section II.D.2.e above, how far the various manufacturers are into
their design cycles suggests that one or more manufacturers will
probably introduce a new engine platform during the Phase 2 time frame.
Thus, we project that 50 percent of tractor engines produced in 2027 MY
will be redesigned engines (i.e. engines reflecting redesigned engine
platforms, again based on existing engine platform redesign schedules
within the industry). This means the average 2027 MY tractor engine
would be 5.4 and 6.4 percent better than Phase 1 for day and sleeper
cabs respectively.\239\ This reflects an average 0.8 percent
improvement beyond what is required to meet the engine standards.
---------------------------------------------------------------------------

    \239\ See RIA Chapter <IP_ADDRESS> for the analysis of the engine
technologies and the associated fuel maps.
---------------------------------------------------------------------------

    As noted in Section II.D.2.e, it is import to note that these new
platforms will be developed based on normal market forces rather than
as a result of this rulemaking. Some engine manufacturers have
developed new platforms with the last ten years, and we do not expect
these engines to be replaced within the Phase 2 time frame. However,
other engines have not been fundamentally redesigned recently and will
be due for replacement by 2027. Because these new platforms will occur
because of market forces rather than this rulemaking, these reductions
are in some ways windfalls for vehicle manufacturers. Thus, we have not
included the cost of these new platforms as part of our rulemaking
analysis.
    We have factored these levels into our analysis of the vehicle
efficiency levels that will be achievable in MY 2027. These additional
engine improvements will result in vehicles having lower GEM results.
Thus, they make more stringent vehicle standards feasible, and the
final standards are structured so that these improved engines are not
able to generate windfall credits against the engine standards, but
rather that their projected performance is reflected in the stringency
of the final tractor vehicle standard. It is important to also note
that manufacturers that do not achieve this level of engine reduction
would be able to make up the difference by applying one of the many
other available and cost-effective tractor technologies to a greater
extent or more effectively, so that there are multiple technology paths
for meeting the final standards. In other words, a manufacturer that
does not invest in updating engine platforms in the Phase 2 time frame
is likely to be able to invest in improving other vehicle technologies.
(Note that these same reductions cannot be assumed as part of the
engine standards because engine manufacturers will not have this same
flexibility). These reductions from the engine will show up in the fuel
maps used in GEM to set the Phase 2 tractor stringencies.
(ii) Aerodynamics
    There are opportunities to reduce aerodynamic drag from the tractor
by further optimization of body components, 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 high roof sleeper cab tractor
and box trailer combinations that achieve a 50 percent improvement in
freight efficiency evaluated as a 65,000 pound vehicle operating on the
highway under somewhat controlled circumstances. However, these
demonstration vehicles developed in SuperTruck are not necessarily
designed to handle the rigors of daily use over actual in-use roads.
For example, they generally have very limited ground clearance that
would likely preclude operation in snow, and would be very susceptible
to damage from potholes or other road hazards. Nevertheless, this
SuperTruck program has led to significant advancements in the
aerodynamics of combination tractor-trailers. While the agencies cannot
simply apply the SuperTruck program achievements directly into the
Phase 2 program because of the significant differences in the limited
purpose of SuperTruck and the plenary applicability of a regulation to
all operating conditions and duty cycles, it is helpful to assess the
achievements and evaluate how the technologies could be applied into
mass production into a variety of real world applications while
maintaining performance throughout the full useful life of the vehicle.
A manufacturer's SuperTruck demonstration vehicle achieved
approximately a seven percent freight efficiency improvement over a
2009 MY baseline vehicle due to improvements in tractor aerodynamics
and approximately 16 percent overall for the tractor-trailer
combination.\240\ The seven percent freight efficiency improvement due
to tractor aerodynamics equates to roughly a 14 percent reduction in
CdA from a 2010 MY baseline vehicle. The 2010 NAS Report on
heavy-duty trucks found that there are achievable aerodynamic

improvements which yield 3 to 4 percent fuel consumption reduction or
six to eight percent reduction in Cd values, beyond a baseline
reflecting performance of technologies used in today's SmartWay
trucks.\241\
---------------------------------------------------------------------------

    \240\ Daimler Truck North America. SuperTruck Program Vehicle
Project Review. June 19, 2014.
    \241\ See TIAX, Note 230, Page 4-40.
---------------------------------------------------------------------------

    The Phase 2 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. Bin I represents the least aerodynamic tractors,
while Bins V-VII would be more aerodynamic than any tractor on the road
today. A more complete description of these aerodynamic packages is
included in Chapter <IP_ADDRESS> of the RIA. In general, the 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.
    The agencies received comments on our aerodynamic technology
assessment. A de F Limited commented that wheel covers improve the
aerodynamics of tractors and trailers, though the results may be lost
in the noise when evaluated on tractors and trailers separately.
Daimler commented that they found in their SuperTruck work that there
are diminishing opportunities for tractor aerodynamics improvements and
there may be impediments to some due to the need to access the back of
cab and reliability concerns. AIR CTI commented that they have built a
truck with aerodynamic technologies such as a front spoiler that
automatically deploys at vehicle speeds over 30 mph, aerodynamic
mirrors, and wheel covers over the rear wheels. ICCT found in their
workshop that opportunities exist for high roof line haul tractor
aerodynamic improvements that could lead to a three to nine percent
improvement in fuel consumption over a 2010 baseline.\242\ The HD
manufacturers and EMA raised significant concerns with regard to the
proposed aerodynamic assessment for Phase 2. They stated that even the
best anticipated future-technology SuperTruck tractor configurations
with a Phase 2 reference trailer likely would only qualify for the
proposed Phase 2 Bin IV or possibly Bin V, leaving Bins V, VI and VII
largely infeasible and unachievable.
---------------------------------------------------------------------------

    \242\ Delgado, Oscar. N. Lutsey. Advanced Tractor-Trailer
Efficiency Technology Potential in the 2020-2030 Timeframe. April
2015. Docket EPA-HQ-OAR-2014-0827.
---------------------------------------------------------------------------

    The agencies' assessment is that the most aerodynamic tractor
tested by EPA in 2015 achieved Bin IV performance. See RIA Chapter
<IP_ADDRESS>. This vehicle did not include all of the possible aerodynamic
technologies, such as wheel covers or active aerodynamics like a grill
shutter or front air dam. Upon further analysis of simulation modeling
of a SuperTruck tractor with a Phase 2 reference trailer with skirts,
we agree with the manufacturers that a SuperTruck tractor technology
package would only achieve the Bin V level of CdA, as
discussed above and in RIA Chapter <IP_ADDRESS>. Therefore, the agencies'
assessment is that Bin V is achievable with known aerodynamic
technologies, as discussed in RIA Chapter <IP_ADDRESS> and <IP_ADDRESS>, but
agree with the manufacturers that Bins VI and VII have less known
technology paths. The agencies are including definitions of Bins VI and
VII performance in the Phase 2 regulations with the understanding that
aerodynamics will continue to improve over the next ten years until the
full phase-in of the Phase 2 program and to provide a value to be input
to GEM should they do so. However, we considered the comments and
discuss the adoption rates of the more aerodynamic bins in Section
III.D.1.c.i, which ultimately concludes that the standards should be
predicated only on performance of aerodynamic technologies reflecting
up to Bin V.
    As discussed in Section III.E.2, the agencies are increasing the
number of aerodynamic bins for low and mid roof tractors from the two
levels adopted in Phase 1 to seven levels in Phase 2. The agencies
adopted an increase in 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.
(iii) Tire Rolling Resistance
    A tire's rolling resistance is a function of 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
6.5 kg/metric ton for the steer tire and less than 6.6 kg/metric ton
for the drive tire.\243\ 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
rolling resistance coefficient target for the Phase 2 NPRM was
developed from SmartWay's tire testing to develop the SmartWay
certification and testing a selection of tractor tires as part of the
Phase 1 and Phase 2 programs. 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 in the
Phase 2 proposal included 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 for Phase 1. The Level 3 values in the NPRM represented 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.
---------------------------------------------------------------------------

    \243\ U.S. EPA. ``US EPA Low Rolling Resistance Tire Testing
Activities'' presentation to SAE Government-Industry Meeting.
January 22, 2016. Values represent the ISO 28580 2 meter drum
results because these align with the test method used to certify
tractors to the GHG and fuel consumption standards.
---------------------------------------------------------------------------

    ICCT found in their workshop that opportunities exist for
improvements in rolling resistance for tractor tires that could lead to
a two to six percent improvement in fuel consumption when compared to a
2010 baseline tractor.\244\ A fuel consumption improvement in this
range would require a six to 18 percent improvement in the tractor tire
rolling resistance levels. Michelin commented that the proposed values
for the drive tires seem reasonable, though the 4.5 kg/ton level would
require significantly higher adoption rate of

new generation wide base single tires. Michelin also stated that the
value of 4.3 kg/ton target for steer tires is highly unlikely based on
current evolution and that research shows that 5.0 kg/ton would be more
likely.
---------------------------------------------------------------------------

    \244\ Delgado, Oscar. N. Lutsey. Advanced Tractor-Trailer
Efficiency Technology Potential in the 2020-2030 Timeframe. April
2015. Docket EPA-HQ-OAR-2014-0827.
---------------------------------------------------------------------------

    The agencies have evaluated this comment and find it persuasive.
The agencies analyzed the 2014MY certification data for tractors
between the NPRM and final rulemaking. We found that the lowest rolling
resistance value submitted for 2014 MY GHG and fuel efficiency
certification for tractors was 4.9 and 5.1 kg/metric ton for the steer
and drive tires respectively, while the highest rolling resistance tire
had a CRR of 9.8 kg/metric ton.\245\ We have accordingly increased the
coefficient of rolling resistance for Level 3 tires in the final rule
based on the comments and the certification data.
---------------------------------------------------------------------------

    \245\ U.S. EPA. Memo to Docket. Coefficient of Rolling
Resistance and Coefficient of Drag Certification Data for Tractors.
See Docket EPA-HQ-OAR-2014-0827.
---------------------------------------------------------------------------

(iv) Tire Pressure Monitoring and 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 low 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.\246\ Generally, a 10 psi reduction in overall tire inflation
results in about a one percent reduction in fuel economy.\247\ To
achieve the intended fuel efficiency benefits of low rolling resistance
tires, it is critical that tires are maintained at the proper inflation
pressure.
---------------------------------------------------------------------------

    \246\ Bridgestone Tires. Real Questions, Real Answers. http://www.bridgestonetrucktires.com/us_eng/real/magazines/ra_special-edit_4/ra_special4_fuel-tires.asp
    \247\ ``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.\248\ A 2011 FMCSA study estimated
under inflation 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 under
inflation.\249\ A recent study by The North American Council on Freight
Efficiency, found that openness to the use 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.\250\ These automatic tire
inflation systems (ATIS) monitor tire pressure and also automatically
keep tires inflated to a specific level. The agencies proposed to
provide a one percent CO2 and fuel consumption reduction
value for tractors with automatic tire inflation systems installed.
---------------------------------------------------------------------------

    \248\ 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.
    \249\ TMC Future Truck Committee Presentation ``FMCSA Tire
Pressure Monitoring Field Operational Test Results,'' February 8,
2011.
    \250\ North American Council for Freight Efficiency, ``Tire
Pressure Systems,'' 2013.
---------------------------------------------------------------------------

    Tire pressure monitoring systems (TPMS) 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 did not propose an emission reduction value for tire
pressure monitoring systems. Instead, we requested comment on this
approach and sought data from those that support a reduction value be
assigned to tire pressure monitoring systems. 80 FR 40218.
    Many commenters including OOIDA, ATA, the truck manufacturers, RMA,
UPS, Bendix, Doran, First Industries, NADA, and others suggested that
the agencies should recognize TPMS as a technology in GEM, with the
effectiveness value set at an equal level as ATIS. On the other hand,
ARB generally supported the use of ATIS but not TPMS because it
requires action from the driver. Many stakeholders stated that TPMS
offers similar benefit, but at a lower cost, so is more acceptable in
the market. UPS commented that they prefer TPMS because TPMS gives the
truck owner an affirmative indication that there is a tire pressure
problem, so it can be fixed, whereas the ATIS does not and they are
concerned that ATIS simply keeps adding tire pressure automatically,
wasting energy, and the truck owner may never know it. Bendix believes
that both ATIS and TPMS should be available in the market in the Phase
2 timeframe for tractors. RMA cited a NHTSA study of LD vehicles of
model years 2004-2007 and found that the presence of a TPMS system led
to a 55.6 percent reduction in the likelihood that a vehicle would have
one tire that is significantly underinflated (25 percent or
greater).\251\ RMA also stated that NHTSA found TPMS to be effective in
reducing moderate under inflation (at least 10 percent, but under 25
percent), which was reduced by 35.3 percent.\252\ RMA's comments also
stated for light trucks and vans, the effectiveness rates were even
higher, with TPMS reducing severe under inflation by 61.2 percent and
moderate under inflation by 37.7 percent. RMA commented that NHTSA
found that in 2011, the TPMS systems save $511 million in fuel costs
across the vehicle fleet.\253\ Navistar said the driver alert with TPMS
is simpler and sufficient to ensure tire inflation in commercial
applications. Navistar also commented that in heavy duty, a
professional driver has both the incentive and the knowledge to keep
tires adequately inflated, neither of which may necessarily be the case
with light duty. Doran Manufacturing cited FMCSA studies on TPMS in
2006 that found TPMS were accurate at assessing tire pressure, in 2007
found acceptable durability of TPMS, and in 2011 found that TPMS or
ATIS in fleet studies showed a 1.4 percent improvement in fuel economy.
ARB's technology assessment found ATIS benefit at one percent.\254\
ICCT found in their workshop that opportunities exist for ATIS that
could lead to a 0.5 to two percent improvement in fuel
consumption.\255\ AIR CTI discussed the consequences of improper
inflation pressures on tire life, safety, stopping distance, vehicle
vibration, and damage to the roads. AIR CTI commented that their
Central Tire Inflation system controls tire pressure from controls on
the dash and is commonly used in logging and other off-road
transportation.
---------------------------------------------------------------------------

    \251\ 80 FR at 40173.
    \252\ 80 FR 40278.
    \253\ 80 FR at 40258.
    \254\ California Air Resources Board. Draft Technology
Assessment: Engine/Powerplant and Drivetrain Optimization and
Vehicle Efficiency. June 2015. Page III-3. Report is available at
www.arb.ca.gov.
    \255\ Delgado, Oscar. N. Lutsey. Advanced Tractor-Trailer
Efficiency Technology Potential in the 2020-2030 Timeframe. April
2015. Docket EPA-HQ-OAR-2014-0827.
---------------------------------------------------------------------------

    After consideration of the comments, the agencies found them
persuasive and are adopting provisions in Phase 2 GEM that allow
manufacturers flexibility to

show compliance with the CO2 and fuel consumption standards
using various technologies, including the flexibility to adopt ATIS or
TPMS (see 40 CFR 1037.520). This reflects a change from the Phase 2
NPRM, where only ATIS (not TPMS) was a GEM input. The agencies believe
that sufficient incentive exists for truck operators to address low
tire pressure conditions if they are notified that they exist through a
TPMS.
    The agencies also considered the comments to determine the
effectiveness of TPMS and ATIS. The agencies conducted a further review
of the FCMSA study cited by commenters and we interpret the results of
the study to indicate that overall a combination of TPMS and ATIS in
the field achieved 1.4 percent reduction. However, it did not separate
the results from each technology, and therefore did not indicate that
TPMS and ATIS achieved the same levels of reduction. Therefore, we set
the effectiveness of TPMS slightly lower than ATIS to reflect that
operators will be required to take some action to insure that the
proper inflation pressure is maintained. The input values to the Phase
2 GEM are set to 1.2 percent reduction in CO2 emissions and
fuel consumption for ATIS and 1.0 percent reduction for TPMS. In other
words, if a manufacturer installs an ATIS onto a vehicle, then they
will enter 1.2 percent into the Tire Pressure System value in their GEM
input file. If a manufacturer installs a TPMS, then they will input 1.0
percent into the Tire Pressure System value in GEM.
    EPA proposed a definition of ATIS in 40 CFR 1037.801 to qualify it
as a technology input to GEM. The proposed definition stated that
``Automatic tire inflation system means a system installed on a vehicle
to keep each tire inflated to within 10 percent of the target value
with no operator input.'' The agencies received comment about this
definition. Meritor suggested adopting the historical industry
definition of ATIS as ``Automatic Tire Inflation Systems maintain tire
pressure at a single preset level and are pneumatically or
electronically activated. These systems eliminate the need to manually
inflate tires.'' Meritor is concerned with the proposed definition of
ATIS that required the system must ``keep each tire inflated to within
10 percent'' to qualify as a technology input to GEM. Meritor commented
that the proposed definition is not consistent with the manner in which
these systems are used in practice. Meritor stated that an ATIS assures
that tires will always be running at the recommended cold tire
inflation pressure. The agencies are adopting changes to reflect the
appropriate definition of ATIS in the final rule (see 40 CFR 1037.801).
(v) Idle Reduction
    Auxiliary power units (APU), fuel operated heaters (FOH), battery
supplied air conditioning, and thermal storage systems are among the
technologies available today to reduce fuel consumption and
CO2 emissions from extended idling (or hoteling). Each of
these technologies reduces fuel consumption during idling relative to a
truck without this equipment. In Phase 1 and in the Phase 2 NPRM, the
agencies took an approach whereby tractor manufacturers could input an
idle reduction value into GEM only if a vehicle included a tamper-proof
automatic engine shutdown system (AESS) programmed to shut down the
engine after five minutes or less. This approach allows the
manufacturers to use AESS as one of the technologies (in combination
with other technologies such as aerodynamics or low rolling resistance
tires) to demonstrate compliance with the CO2 emission and
fuel consumption standards. The agencies also included several override
provisions for the AESS and a discounted GEM input value for an
expiring AESS or a system that allowed a specified number of hours of
idling per year (see 40 CFR 1037.660).
    The agencies did not differentiate between the various idle
reduction technologies in terms of effectiveness because we adopted in
Phase 1 and proposed in Phase 2 a conservative effectiveness level to
recognize that some vehicles may be sold with only an AESS but may then
install an idle reduction technology after it leaves the factory (76 FR
57207). The effectiveness for AESS in Phase 1 and proposed in Phase 2
was determined by comparing the idle fuel consumption of the main
engine at approximately 0.8 gallons per hour to the fuel consumption of
a diesel powered APU that consumes approximately 0.2 gallons per hour.
This difference equates to a five percent reduction in overall
CO2 emissions and fuel consumption of a Class 8 sleeper cab.
A diesel powered APU was selected for determining the effectiveness and
cost because it was a conservative estimate. Diesel powered APUs have
the highest fuel consumption and cost of the idle reduction
technologies considered.\256\ The agencies proposed that a tamper-proof
AESS would receive a five percent CO2 emissions and fuel
consumption reduction in GEM for vehicles that included this
technology. This value is in line with the TIAX assessment which found
a five percent reduction in overall fuel consumption to be
achievable.\257\ The agencies requested comments on the proposed
approach.
---------------------------------------------------------------------------

    \256\ See the draft RIA Chapter 2.4.8 for details.
    \257\ See the 2010 NAS Report at 128.
---------------------------------------------------------------------------

    The agencies received a number of comments regarding ``mandating
APU'' or ``mandating AESS.'' There is a misconception of the proposed
Phase 2 program where stakeholders thought that the agencies were
mandating use of APUs. This is incorrect. The tractor standards are
performance standards. The agencies merely projected an adoption rate
of up to 90 percent for tamper-proof AESS in our analysis for
determining the stringency level of the proposed standard. As stated
above, we did not propose to differentiate between the various idle
reduction technologies in terms of effectiveness and only used the
diesel powered APU in terms of determining the cost and effectiveness
of a potential standard. Also, because the standards are performance
standards, the agencies are not mandating any specific fuel consumption
or GHG emission reducing technology. For each standard, we developed
one potential technology pathway to demonstrate the feasibility of the
standards, but manufacturers will be free to choose other paths.\258\
---------------------------------------------------------------------------

    \258\ The one exception being the design standards for certain
non-aero trailers. See Section IV below.
---------------------------------------------------------------------------

    The agencies received a significant number of comments about idle
reduction for sleeper cabs, including recommendations to the agencies
to assess the emission reduction for a variety of idle reduction
technologies instead of just a tamper-proof AESS. ATA, NADA, and others
commented that fleets have a variety of choices available in providing
the driver power and comfort in-lieu of idling including use of APUs,
FOHs, stop-start (main engine turns on only to recharge the battery
after several hours), shore power, battery stand-by, stand-alone anti-
idling infrastructure establishments, slip-seat operations, and hotel
accommodations. Convoy Solutions stated that IdleAir's electrified
parking spaces are an important bridge technology to more electrified
solutions. IdleAir commented it may be possible to recognize off board
behavior at the OEM level as a buyer of a new truck could enter into a
contract with an EPS provider prior to accepting delivery. ATA and
First Industries support efficiency credits for idling reduction
options installed by fleets either at the OEM point-of-sale or
installed in the after-market.

    The agencies also received comments regarding the level of
effectiveness of idle reduction technologies. ICCT found in their
workshop that opportunities exist for line haul tractor idle reduction
improvements that could lead to a four to seven percent improvement in
fuel consumption.\259\ MEMA recommended that the agencies modify the
projected effectiveness level based on the merit of the individual idle
control technology. MEMA's recommendation for effectiveness levels
based on the fuel consumption and GHG emissions of each technology
ranged from 7.7 g/ton-mile for fuel cell APU, 6 g/ton-mile for diesel
APU, and 9 g/ton-mile for batter air conditioning systems, fuel
operated heater, and combinations of technologies. MEMA supports the
agencies' proposal that, in order to qualify for the use of an idle
reduction technology in GEM, it is mandatory that the truck be equipped
with an AESS. MEMA also commented that in the Phase 1 RIA, the agencies
assumed a Class 8 sleeper cab spends 1,800 hours in extended idle per
year and travels about 250 days per year. MEMA recommends that the
agencies use 2,500 annual hours for APUs and 1,250 annual hours for
FOHs to better reflect real-world application and experiences.
Additionally, MEMA recommends that 0.87 gallon/hour fuel consumed by
the main engine during idle be used in the calculations for credit.
---------------------------------------------------------------------------

    \259\ Delgado, Oscar. N. Lutsey. Advanced Tractor-Trailer
Efficiency Technology Potential in the 2020-2030 Timeframe. April
2015. Docket EPA-HQ-OAR-2014-0827.
---------------------------------------------------------------------------

    The agencies also received a significant number of comments about
idle reduction encouraging the agencies to consider recognizing
adjustable AESS instead of only a tamper-proof AESS. ATA commented that
most fleets already purchase ``programmable'' idle shutdown timers to
limit idling due to the national patchwork of anti-idling laws
currently in place. ATA continued to say that these timers are
typically set for a given period of time throughout the initial fleet's
ownership period. ATA also stated as witnessed under Phase I, fleets
are unwilling to purchase hard-programmed, tamper-proof AESS given
their need for flexibility regarding their resale of used equipment on
the secondary market. Caterpillar also noted that fleets do not
purchase tamper-resistant automatic engine shutdown systems; therefore,
AESS should not be part of the stringency setting, unless the agencies
also consider programmable versions of AESS. PACCAR, Volvo and EMA
request the agencies to consider partial credit for AESS that are
programmed to a 5-minute or sooner shutdown but are not tamper-
resistant to changes by an owner. Daimler and Navistar also commented
that the agencies should consider adjustable AESS as a technology input
to GEM. Daimler found that less than one percent of the adjustable AESS
systems set at or below 5 minutes that were installed in customer
tractors were deactivated or reprogrammed to a value longer than 5
minutes. PACCAR viewed the proposed tamper-proof AESS for 1.259 million
miles as unrealistic and not reflecting current market conditions.
    While the agencies do not necessarily believe that customer
reluctance in the initial years of Phase 1 should be considered
insurmountable, we do agree with commenters that the agencies should
allow adjustable AESS to be a technology input to GEM and should
differentiate effectiveness based on the idle reduction technology
installed by the tractor manufacturer. We will still apply the Phase 1
requirement that the AESS be programmed to 5 minutes or less at the
factory to qualify as a technology input in GEM (see 40 CFR 1037.660),
but for Phase 2 will allow a variety of both tamper-proof and
adjustable systems to qualify for some reduction (i.e. to be recognized
by GEM). Any changes made subsequent to the factory but prior to
delivery to the purchaser, must be accounted for in the manufacturer's
end of year reports.
    The agencies developed effectiveness levels for the extended idle
technologies from literature, SmartWay work, and the 2010 NAS report.
The agencies also reviewed the NACFE report on programmable engine
parameters which included a fleet survey on how often the fleets change
programmable parameters, such as automatic engine shutdown timers.\260\
The survey found that approximately 70 percent of these fleets never
changed the setting. The agencies developed the effectiveness levels to
reflect that there is some greater uncertainty of adjustable AESS
systems, therefore the effectiveness values are discounted from the
values determined for tamper-proof AESS. A detailed discussion
regarding the comments and the associated calculations to determine the
effectiveness of each of the idle reduction technologies are included
in RIA Chapter <IP_ADDRESS>.1. In summary, the effectiveness for each type
of idle reduction technology is included in Table III-9.
---------------------------------------------------------------------------

    \260\ North American Council for Freight Efficiency. Confidence
Report: Programmable Engine Parameters. February 2015. Page 48.

          Table III-9--Idle Reduction Technology Effectiveness
------------------------------------------------------------------------
                                                          Idle reduction
                Idle Reduction Technology                  value in GEM
                                                                (%)
------------------------------------------------------------------------
Tamper-Proof AESS.......................................               4
Tamper-Proof AESS w/Diesel APU..........................               4
Tamper-Proof AESS w/Battery APU.........................               6
Tamper-Proof AESS w/Automatic Stop-Start................               3
Tamper-Proof AESS w/FOH Cold, Main Engine Warm..........               3
Adjustable AESS w/Diesel APU............................               3
Adjustable AESS w/Battery APU...........................               5
Adjustable AESS w/Automatic Stop-Start..................               3
Adjustable AESS w/FOH Cold, Main Engine Warm............               2
Adjustable AESS programmed to 5 minutes.................               1
------------------------------------------------------------------------

    In addition to extended idling (or hoteling) by sleeper cabs, the
agencies discussed work day idle by day cabs in the Phase 2 NPRM. 80 FR
40217. 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. Prior to issuing the
Phase 2 NPRM, 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.\261\ 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. At the time of the Phase 2 NPRM, the agencies were
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 AESS. We welcomed comment and data on quantifying
the effectiveness of AESS on day cabs. We further requested comment on
the possibility of adapting the idle-only duty cycle for vocational
vehicles to certain day cab tractors, and also considered the
possibility of neutral idle technology for tractors using torque-
converter automatic

transmissions and stop-start for any tractor. Id.
---------------------------------------------------------------------------

    \261\ Gaines, L., A. Vyas, J. Anderson. Estimation of Fuel Use
by Idling Commercial Trucks. January 2006.
---------------------------------------------------------------------------

    The agencies received a significant number of comments regarding
day cab idle reduction. CARB commented that the agencies should include
idle reduction technologies for day cabs, similar to the proposed
vocational vehicle approach. CARB stated that even if the first owners
do not see significant emission reductions, many of the day cab
tractors are used in port and drayage applications in their second life
where they would see significant reductions. CARB suggested that the
GEM composite weighting factor for idle should be between 5 and 10
percent. Bendix would like to see the vocational vehicle idle reduction
approach extended to day cab tractors based on their data which found
that there are many applications of day cab tractors that spend a
significant portion of their day's drive time at idle, especially pick-
up and delivery type applications and a growing number of fleets that
run hub and spoke type operations. MEMA supported extending neutral
idle and stop-start technologies to day cab tractors. MEMA recommends
that the agencies set the effectiveness of day cabs idle reduction
technologies at a value equal to 35 percent of the effectiveness
associated with a comparable technology in a Class 8 sleeper cab.
Allison stated that agencies should include automatic neutral in all
tractors. Allison stated that automatic neutral is standard with the
Allison TC10 and is available with the Allison 3000 and 4000 Series
transmissions.
    Daimler commented that they have not validated that stop-start
strategies are viable for Class 7 and 8 applications and considers it
premature for the agencies to project that stop-start strategies are
viable for this class of engines. Daimler stated that lubrication of
critical bearing surfaces is lacking or severely compromised during
engine start up due to the lack of lubricating oil pressure and this
lack of lubrication leads to metal to metal contact, wear, and
ultimately failure. In addition, Daimler commented that firing
pressures inherent to compression ignition engines further exacerbate
wear as compared to, for example, spark ignition engines where stop-
start technology is being increasingly applied. Daimler also stated
that these known problems, coupled with the extremely long million mile
plus service life expectations for this heavier class of heavy-duty
engines, together pose a development challenge that is significantly
more challenging than that posed to spark ignition engines in passenger
cars. Daimler further stated that heat soak of temperature critical
parts and temporary disruption of their lubrication/cooling systems
will have to be understood and possible degradations handled through
modifications at either component or system basis, the extent of which
is not yet fully quantified. Daimler also stated that similarly, on the
turbocharger side, the larger speed swings will shorten turbocharger
wheel life, which is increasingly challenged in vocational applications
that are characteristically more transient as compared to the
relatively steady operation nature of line haul.
    The agencies considered the comments, both supporting and raising
concerns over idle reduction in day cabs. The agencies determined that
neutral idle for automatic transmissions is an appropriate technology
for use in tractors. Therefore, the agencies are adopting provisions in
Phase 2 to recognize neutral-idle in automatic transmissions as an
input to GEM. Our analysis shows that neutral idle effectiveness is
approximately 0.8 to one percent over the composite day cab tractor
cycles, as shown in RIA Chapter <IP_ADDRESS>.2. The agencies will also
include neutral idle as a GEM input for sleeper cabs, though the
effectiveness is very low. The agencies are predicating the standards
for day cabs based on a technology package that includes neutral idle.
    In terms of stop-start technologies in tractors, the agencies are
not including it as a technology input to GEM because we believe the
technology, as applied to tractors, needs further development. If this
technology is developed in the future for tractors, then manufacturers
may consider applying for off-cycle technology credits. Since the
agencies are not predicating the Phase 2 standards on adoption of
start-stop technologies, the agencies are also not including this
technology as a GEM input.
(vi) Transmissions
    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.\262\ 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 zero to eight percent.\263\
Well-trained drivers would be expected to perform as well or even
better than an automated 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, less well-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, dual clutch
transmissions (DCTs) are now being used in the European heavy-duty
vehicle market. DCTs operate similar to AMTs, but with two clutches so
that the transmission can maintain engine speed during a shift which
improves fuel efficiency.
---------------------------------------------------------------------------

    \262\ 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.
    \263\ See TIAX, Note 230, above at 4-70.
---------------------------------------------------------------------------

    The benefits for automated manual, automatic, and dual clutch
transmissions were developed from literature, from simulation modeling
conducted by Southwest Research Institute, and powertrain testing
conducted at Oak Ridge National Laboratory. The proposed Phase 2
benefit of these transmissions in GEM was set at a two percent
improvement over a manual transmission due to the automation of the
gear shifting. 80 FR 40217.
    Allison Transmission commented that their real world studies
indicate that automatic transmissions perform as well or better than
AMTs or DCTs in terms of GHG and fuel efficiency impact. Allison
commented that their ATs can exceed the 2 percent level estimated at
proposal, but believe it is a reasonable level to apply this level of
effectiveness for ATs and AMTs. Allison stated that automatic
transmissions in tractors have neutral at stop capability, first gear
lockup operation, load-based and grade-based shift algorithms and
acceleration rate management that contribute to the overall fuel
efficiency of ATs in tractors. Allison also commented that although
DCTs should logically perform better than the MT baseline, there was no
record information to support that assumption. Volvo commented that
fuel consumption with their I-Shift DCT is the same as the I-Shift AMT.
PACCAR recommends that the agencies take a more detailed approach to
assessing transmission advances and revise the

agencies' estimate to reflect technologies that are already under true
consideration for use in production powertrains.
    UCS commented that as much as 1.3 to 2.0 percent savings from
tractor-trailers could be added to the proposed stringency to reflect
the true potential from tractor-trailers from powertrain optimization,
particularly since every major manufacturer already offers at least one
``integrated powertrain'' option in its long-haul fleet. ICCT referred
to two studies related to tractor-trailer technologies in their
comments.264 265 In their stakeholder workshop, they found
that the effectiveness of automated manual transmissions ranged between
two and three percent. They also cited another finding that highlighted
opportunities to improve transmission efficiency, including direct
drive, which would provide about two percent fuel consumption
reduction.\266\
---------------------------------------------------------------------------

    \264\ Lutsey, Nic. T. Langer, S. Khan. Stakeholder Workshop on
Tractor-Trailer Efficiency Technology in the 2015-2030 Timeframe.
August 2014. Docket EPA-HQ-OAR-2014-0827.
    \265\ Delgado, Oscar. N. Lutsey. Advanced Tractor-Trailer
Efficiency Technology Potential in the 2020-2030 Timeframe. April
2015. Docket EPA-HQ-OAR-2014-0827.
    \266\ Stoltz, T. and Dorobantu, M. Transmission Potential to
Contribute to CO2 Reduction: 2020 and Beyond Line Haul
Perspective. ACEEE/ICCT Workshop on Emerging Technologies for Heavy-
Duty Fuel Efficiency. July 2014.
---------------------------------------------------------------------------

    The agencies' assessment of the comments is that Allison, ICCT, and
Volvo support the proposed two percent effectiveness for AT and AMT
transmission types. In addition, the agencies reviewed the NACFE report
on electronically controlled transmissions (AT, AMT, and DCT).\267\
This report had similar findings as those noted above in the NAS 2010
report. Electronically controlled transmissions were found to be more
fuel efficient than manual transmissions, though the amount varied
significantly. The report also stated that fleets found that
electronically controlled transmissions also reduced the fuel
efficiency variability between drivers. Therefore after considering the
comments related to effectiveness and additional reports, the agencies
are adopting as proposed a two percent effectiveness for AMT. As
discussed in RIA <IP_ADDRESS>, the agencies conducted powertrain testing at
Oak Ridge National Laboratory to compare the fuel efficiency of an AMT
to an AT. Based on the results, the agencies expect that automatic
transmissions designed for long haul operation and automated manual
transmissions will perform similarly and have similar effectiveness
when compared to a manual transmission.
---------------------------------------------------------------------------

    \267\ North American Council for Freight Efficiency. Confidence
Report: Electronically Controlled Transmissions. December 2014.
---------------------------------------------------------------------------

    The benefit of the AMT's automatic shifting compared to a manual
transmission is recognized in Phase 2 GEM by simulating the MT as an
AMT and increasing the emission results from the simulation by two
percent. For ATs, the agencies developed the default automatic
transmission inputs to GEM to represent a typical heavy-duty automatic
transmission, which is less efficient than the TC10 (the transmission
tested at Oak Ridge National Lab). The agencies selected more
conservative default transmission losses in GEM so that we would not
provide a false efficiency improvement for the less efficient automatic
transmissions that exist in the market today. Under the regulations in
this rulemaking, manufacturers that certify using the TC10 transmission
would need to either conduct the optional transmission gear efficiency
testing or powertrain testing to recognize the effectiveness of this
type of automatic transmission in GEM. In our technology packages
developed to set the Phase 2 standard stringencies, the agencies used a
two percent effectiveness for automatic transmissions with neutral idle
under the assumption that either powertrain or transmission gear
efficiency tests would be conducted. The compliance costs for this type
of testing (which crosses over both the vocational and tractor
programs) are included as noted in RIA Chapter <IP_ADDRESS>.
    The agencies agree with PACCAR that we should consider future
transmission advances. There are three certification pathways for
manufacturers to assess benefits of future transmissions; that is, to
generate a value reflecting greater improvement than the two percent
GEM input. The first is an optional powertrain test (40 CFR 1037.550),
the second is an optional transmission efficiency test (40 CFR
1037.565), and the third is off-cycle credits (40 CFR 1037.610).
    The agencies acknowledge UCS's comment about increasing the
stringency of the tractor program due to the opportunity to further
improve powertrain optimization through powertrain testing. For the
Phase 2 final rule, we have made several changes that capture much of
the improvement potential highlighted by UCS. First, the required use
of a cycle average fuel map in lieu of a steady state fuel map for
evaluating the transient cycle in GEM will recognize improvements to
transient fuel control of the engine. The agencies are including the
impact of improved transient fuel control in the engine fuel maps used
to derive the final standards. Second, the optional transmission
efficiency test will recognize the benefits of improved gear
efficiencies. The agencies have built some improvements in transmission
gear efficiency into the technology package used to derive the final
standards. This leaves only the optimization of the transmission shift
strategy, which would need to be captured on a powertrain test. The
agencies believe that the opportunity of shift strategy optimization is
less for tractors than for other types of vocational vehicles because a
significant portion of the tractor drive cycles are at highway speeds
with limited transmission shifting. Therefore, we have not included the
powertrain optimization portion only recognized through powertrain
testing into the standard setting for the final rule.
    The agencies also proposed standards that considered the efficiency
benefit of transmissions that operate with top gear direct drive
instead of overdrive. In the proposal, we estimated that direct drive
had two percent higher gear efficiency than an overdrive gear. 80 FR
40229. The benefit of direct drive was recognized through the
transmission gear ratio inputs to GEM. Direct drive leads to greater
reductions of CO2 emissions and fuel consumption during
highway operation, but virtually none in transient operation. The
agencies did not receive any negative comments regarding the efficiency
difference between direct drive and overdrive; therefore, we continued
to include the default transmission gear efficiency advantage of two
percent for a gear with a direct drive ratio in the version of GEM
adopted for the final Phase 2 rules.
    The agencies are also adopting in Phase 2 an optional transmission
efficiency test (40 CFR 1037.565) for generating an input to GEM that
overrides the default efficiency of each gear based on the results of
the test. Although optional, the transmission efficiency test will
allow manufacturers to reduce the CO2 emissions and fuel
consumption by designing better transmissions with lower friction due
to better gear design and/or mandatory use of better lubricants. The
agencies project that transmission efficiency could improve one percent
over the 2017 baseline transmission in Phase 2. Our assessment was
based on comments received and discussions with transmission
manufacturers.\268\
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    \268\ Memorandum to the Docket ``Effectiveness of Technology to
Increase Transmission Efficiency.'' July 2016.

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(vii) Drivetrain and Engine Downspeeding
    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 brake mean effective pressure 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, and 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 in
combination with the vehicle's transmission gear ratios, drive axle
ratio, and tire diameter. The agencies evaluated the impact of
downspeeding in setting the stringencies by modeling different rear
axle ratios in GEM. As shown in RIA Chapter <IP_ADDRESS>, a decrease in
final drive ratio from 2.6 to 2.3 will lead to a 2.5 percent reduction
in tractor CO2 emissions and fuel consumption. The reshaping
of the torque curve of an engine to increase the low speed torque and
reduce the speed at which maximum torque occurs, will impact the
CO2 emissions and fuel consumption on the engine test
cycles, but will also have a small impact on the vehicle fuel
consumption. Higher torque at lower engine speeds will allow the
transmission to operate in top gear for a longer period of the time
which will reduce the number of downshifts over a cycle and in turn
means that the engine speed is lower on average. This benefit will show
up in GEM. Additional information on engine downspeeding can be found
in RIA Chapter 2.3.8.
    Low Friction Axle and Wheel Bearing Lubricants: The 2010 NAS report
assessed low friction lubricants for the drivetrain as providing a one
percent improvement in fuel consumption based on fleet testing.\269\ 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.\270\ 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 zero and one percent compared to
traditional lubricants. In the Phase 2 proposal, the agencies proposed
the reduction in friction due to low viscosity axle lubricants of 0.5
percent. 80 FR 40217.
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    \269\ See the 2010 NAS Report, Note 229, page 67.
    \270\ 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.
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    Lubrizol commented that high performing lubricants should play a
role in Phase 2. Lubrizol also supports the axle test procedures to
further recognize axle efficiency improvements. PACCAR recommended
eliminating the rear axle efficiency test and provide credits based on
calculated values.
    The agencies' assessment of axle improvements found that axles
built in the Phase 2 timeline could be 2 percent more efficient than a
2017 baseline axle.\271\ In lieu of a fixed value for low friction axle
lubricants (i.e. in lieu of a specified GEM input), the agencies are
adopting an axle efficiency test procedure (40 CFR 1037.560), as
discussed in the NPRM. 80 FR 40185. The axle efficiency test will be
optional, but will allow manufacturers to recognize in GEM reductions
in CO2 emissions and fuel consumption through improved axle
gear designs and/or mandatory use of low friction lubricants. The
agencies are not providing an alternate path to recognize better
lubricants without axle testing.
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    \271\ Memorandum to the Docket ``Effectiveness of Technology to
Increase Axle Efficiency.'' July 2016.
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    Axle Configuration: 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.\272\
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 one and three percent.273 274 The NACFE report found
in OEM evaluations of 6x2 axles that the effectiveness ranged between
1.6 and 2.2 percent. NACFE also evaluated 6x2 axle tests conducted by
several fleets and found the effectiveness in the range of 2.2 to 4.6
percent. 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. The agencies proposed to apply a 2.5 percent
improvement in vehicle efficiency to 6x4 and 4x2 axle configurations.
80 FR 40217-218.
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    \272\ North American Council for Freight Efficiency.
``Confidence Findings on the Potential of 6x2 Axles.'' 2014. Page
16.
    \273\ Ibid.
    \274\ 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.
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    Meritor stated in their comments that their internal testing and
real world testing supported the 2.5 percent efficiency proposed by the
agencies for 6x2 axles. Meritor suggested the need to better define a
``disengageable tandem'' when the agencies discussed what we called
axle disconnect in the NPRM. Meritor recommends that a fuel efficiency
benefit of 2.0 percent be assigned to the disengageable tandem for the
55 mph and 65 mph drive cycles to account for the more limited use.
    ICCT referred to two studies related to tractor-trailer
technologies in their comments.275 276 In their stakeholder
workshop, they found that the effectiveness of 6x2 axles ranged between
one and 2.5 percent.
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    \275\ Lutsey, Nic. T. Langer, S. Khan. Stakeholder Workshop on
Tractor-Trailer Efficiency Technology in the 2015-2030 Timeframe.
August 2014. Docket EPA-HQ-OAR-2014-0827.
    \276\ Delgado, Oscar. N. Lutsey. Advanced Tractor-Trailer
Efficiency Technology Potential in the 2020-2030 Timeframe. April
2015. Docket EPA-HQ-OAR-2014-0827.
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    The agencies' assessments of these technologies show that the
reductions are in the range of two to three percent. For the final
rule, the agencies are simulating 6x2, 4x2, and disengageable axles
within GEM based on the manufacturer input of the axle configuration
instead of providing a fixed value for the reduction. This approach is
more technically sound because it will take into account future changes
in axle efficiency. See RIA

Chapter 4 for additional details regarding GEM.
(viii) Accessories and Other Technologies
    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