Air conditioning.............................................           90           90           90           90           90           90           90
Other vehicle technologies...................................          261          261          261          261          261          261          261
                                                              ------------------------------------------------------------------------------------------
    Total....................................................        8,946        8,769        8,999        8,816       11,397       11,397       11,318
--------------------------------------------------------------------------------------------------------------------------------------------------------
Notes:
\a\ Costs shown are for the 2021 model year and are incremental to the costs of a tractor meeting the Phase 1 standards. These costs include indirect
  costs via markups along with learning impacts. For a description of the markups and learning impacts considered in this analysis and how it impacts
  technology costs for other years, refer to Chapter 2 of the draft RIA (see draft RIA 2.12).
\b\ Note that values in this table include adoption rates. Therefore, the technology costs shown reflect the average cost expected for each of the
  indicated tractor classes. To see the actual estimated technology costs exclusive of adoption rates, refer to Chapter 2 of the draft RIA (see draft
  RIA 2.12 in particular).
\c\ Engine costs are for a heavy HD diesel engine meant for a combination tractor. The engine costs in this table are equal to the engine costs
  associated with the separate engine standard because both include the same set of engine technologies (see Section II.D.2.e).

       Table III-29-Class 7 and 8 Tractor Technology Incremental Costs in the 2024 Model Year Alternative 4 vs. the Less Dynamic Baseline \a\ \b\
                                                                   (2012$ per vehicle)
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                        Class 7                                      Class 8
                                                              ------------------------------------------------------------------------------------------
                                                                        Day cab                   Day cab                       Sleeper cab
                                                              ------------------------------------------------------------------------------------------
                                                                 Low/mid                   Low/mid
                                                                   roof      High roof       roof      High roof     Low roof     Mid roof    High roof
--------------------------------------------------------------------------------------------------------------------------------------------------------
Engine \c\...................................................       $1,885       $1,885       $1,885       $1,885       $1,885       $1,885       $1,885
Aerodynamics.................................................          805          935          805          935          773          773          997
Tires........................................................           50           14           83           23           63           63           23
Tire inflation system........................................          330          330          330          330          330          330          330
Transmission.................................................        7,143        7,143        7,143        7,143        7,143        7,143        7,143
Axle & axle lubes............................................          102          102          138          210          138          138          210
Idle reduction with APU......................................            0            0            0            0        2,687        2,687        2,687
Air conditioning.............................................          123          123          123          123          123          123          123
Other vehicle technologies...................................          318          318          318          318          318          318          318
                                                              ------------------------------------------------------------------------------------------
    Total....................................................       10,757       10,851       10,826       10,968       13,461       13,461       13,717
--------------------------------------------------------------------------------------------------------------------------------------------------------
Notes:
\a\ Costs shown are for the 2024 model year and are incremental to the costs of a tractor meeting the Phase 1 standards. These costs include indirect
  costs via markups along with learning impacts. For a description of the markups and learning impacts considered in this analysis and how it impacts
  technology costs for other years, refer to Chapter 2 of the draft RIA (see draft RIA 2.12).
\b\ Note that values in this table include adoption rates. Therefore, the technology costs shown reflect the average cost expected for each of the
  indicated tractor classes. To see the actual estimated technology costs exclusive of adoption rates, refer to Chapter 2 of the draft RIA (see draft
  RIA 2.12 in particular).
\c\ Engine costs are for a heavy HD diesel engine meant for a combination tractor. The engine costs in this table are equal to the engine costs
  associated with the separate engine standard because both include the same set of engine technologies (see Section II.D.2.e).

E. Proposed Compliance Provisions for Tractors

    In HD Phase 1, the agencies developed an entirely new program to
assess the CO2 emissions and fuel consumption of tractors.
The agencies propose to carry over many aspects of the Phase 1
compliance approach, but are proposing to enhance several aspects of
the compliance program. The sections below highlight the key areas that
are the same and those that are different.
(1) HD Phase 2 Compliance Provisions That Remain the Same
    The regulatory structure considerations for Phase 2 are discussed
in more detail above in Section II. We welcome comment on all aspects
of the

compliance program including where we are not proposing any changes.
(a) Application and Certification Process
    For the Phase 2 proposed rule, the agencies are proposing to keep
many aspects of the HD Phase 1 tractor compliance program. For example,
the agencies propose to continue to use GEM (as revised for Phase 2),
in coordination with additional component testing by manufacturers to
determine the inputs, to determine compliance with the proposed fuel
efficiency and CO2 standards. Another aspect that we propose
to carry over is the overall compliance approach.
    In Phase 1 and as proposed in Phase 2, the general compliance
process in terms of the pre-model year, during the model year, and post
model year activities remain unchanged. The manufacturers would
continue to be required to apply for certification through a single
source, EPA, with limited sets of data and GEM results (see 40 CFR
1037.205). EPA would issue certificates upon approval based on
information submitted through the VERIFY database (see 40 CFR
1037.255). In Phase 1, EPA and NHTSA jointly review and approve
innovative technology requests, i.e. performance of any technology
whose performance is not measured by the GEM simulation tool and is not
in widespread use in the 2010 MY. For Phase 2, the agencies are
proposing a similar process for allowing credits for off-cycle
technologies that are not measured by the GEM simulation tool (see
Section I.B.v. for a more detailed discussion of off-cycle requests).
During the model year, the manufacturers would continue to generate
certification data and conduct GEM runs on each of the vehicle
configurations it builds. After the model year ends, the manufacturers
would submit end of year reports to EPA that include the GEM results
for all of the configurations it builds, along with credit/deficit
balances if applicable (see 40 CFR 1037.250 and 1037.730). EPA and
NHTSA would jointly coordinate on any enforcement action required.
(b) Compliance Requirements
    The agencies are also proposing not to change the following
provisions:

 Useful life of tractors (40 CFR 1037.105(e) and 1037.106(e))
although added for NHTSA in Phase 2 (40 CFR 535.5)
 Emission-related warranty requirements (40 CFR 1037.120)
 Maintenance instructions, allowable maintenance, and amending
maintenance instructions (40 CFR 1037.125 and 137.220)
 Deterioration factors (40 CFR 1037.205(l) and 1037.241(c))
 Vehicle family, subfamily, and configurations (40 CFR
1037.230)
(c) Drive Cycles and Weightings
    In Phase 1, the agencies adopted three drive cycles used in GEM to
evaluate the fuel consumption and CO2 emissions from various
vehicle configurations. One of the cycles is the Transient mode of the
California ARB Heavy Heavy-Duty Truck 5 Mode cycle. It is intended to
broadly cover urban driving. The other two cycles represent highway
driving at 55 mph and 65 mph.
    The agencies propose to maintain the existing drive cycles and
weighting. For sleeper cabs, the weightings would remain 5 percent of
the Transient cycle, 9 percent of the 55 mph cycle, and 86 percent of
the 65 mph cycle. The day cab results would be weighted based on 19
percent of the transient cycle, 17 percent of the 55 mph cycle, and 64
percent of the 65 mph cycle (see 40 CFR 1037.510(c)). One key
difference in the proposed drive cycles is the addition of grade,
discussed below in Section III.E.2.
    The 55 mph and 65 mph drive cycles used in GEM assume constant
speed operation at nominal vehicle speeds with downshifting occurring
if road incline causes a predetermined drop in vehicle speed. In real-
world vehicle operation, traffic conditions and other factors may cause
periodic operation at lower (e.g. creep) or variable vehicle speeds.
The agencies therefore request comment on the need to include segments
of lower or variable speed operation in the nominally 55 mph and 65 mph
drive cycles used in GEM and how this may or may not impact the
strategies manufacturers would develop. We also request data from fleet
operators or others that may track vehicle speed operation of heavy-
duty tractors.
(d) Empty Weight and Payload
    The total weight of the tractor-trailer combination is the sum of
the tractor curb weight, the trailer curb weight, and the payload. The
total weight of a vehicle is important because it in part determines
the impact of technologies, such as rolling resistance, on GHG
emissions and fuel consumption. In Phase 2, we are proposing to carry
over the total weight of the tractor-trailer combination used in GEM
for Phase 1. The agencies developed the proposed tractor curb weight
inputs for Phase 2 from actual tractor weights measured in two of EPA's
Phase 1 test programs. The proposed trailer curb weight inputs were
derived from actual trailer weight measurements conducted by EPA and
from weight data provided to ICF International by the trailer
manufacturers.\174\
---------------------------------------------------------------------------

    \174\ ICF International. Investigation of Costs for Strategies
to Reduce Greenhouse Gas Emissions for Heavy-Duty On-road Vehicles.
July 2010. Pages 4-15. Docket Number EPA-HQ-OAR-2010-0162-0044.
---------------------------------------------------------------------------

    There is a further issue of what payload weight to assign during
compliance testing. In use, trucks operate at different weights at
different times during their operations. The greatest freight transport
efficiency (the amount of fuel required to move a ton of payload) would
be achieved by operating trucks at the maximum load for which they are
designed all of the time. However, this may not always be practicable.
Delivery logistics may dictate partial loading. Some payloads, such as
potato chips, may fill the trailer before it reaches the vehicle's
maximum weight limit. Or full loads simply may not be available
commercially. M.J. Bradley analyzed the Truck Inventory and Use Survey
and found that approximately 9 percent of combination tractor miles
travelled empty, 61 percent are ``cubed-out'' (the trailer is full
before the weight limit is reached), and 30 percent are ``weighed out''
(operating weight equal 80,000 lbs which is the gross vehicle weight
limit on the Federal Interstate Highway System or greater than 80,000
lbs for vehicles traveling on roads outside of the interstate
system).\175\
---------------------------------------------------------------------------

    \175\ M.J. Bradley & Associates. Setting the Stage for
Regulation of Heavy-Duty Vehicle Fuel Economy and GHG Emissions:
Issues and Opportunities. February 2009. Page 35. Analysis based on
1992 Truck Inventory and Use Survey data, where the survey data
allowed developing the distribution of loads instead of merely the
average loads.
---------------------------------------------------------------------------

    The amount of payload that a tractor can carry depends on the
category (or GVWR and GCWR) of the vehicle. For example, a typical
Class 7 tractor can carry less payload than a Class 8 tractor. For
Phase 1, the agencies used the Federal Highway Administration Truck
Payload Equivalent Factors using Vehicle Inventory and Use Survey
(VIUS) and Vehicle Travel Information System data to determine the
payloads. FHWA's results indicated that the average payload of a Class
8 vehicle ranged from 36,247 to 40,089 lbs, depending on the average
distance travelled per day.\176\ The same study shows that Class 7
vehicles carried between 18,674 and 34,210 lbs of payload also
depending on average distance travelled per day. Based on

these data, the agencies are proposing to continue to prescribe a fixed
payload of 25,000 lbs for Class 7 tractors and 38,000 lbs for Class 8
tractors for certification testing. The agencies propose to continue to
use a common payload for Class 8 day cabs and sleeper cabs as a
predefined GEM input because the data available do not distinguish
among Class 8 tractor types. These proposed payload values represent a
heavily loaded trailer, but not maximum GVWR, since as described above
the majority of tractors ``cube-out'' rather than ``weigh-out.''
---------------------------------------------------------------------------

    \176\ The U.S. Federal Highway Administration. Development of
Truck Payload Equivalent Factor. Table 11. Last viewed on March 9,
2010 at http://ops.fhwa.dot.gov/freight/freight_analysis/faf/faf2_reports/reports9/s510_11_12_tables.htm.
---------------------------------------------------------------------------

    Details of the proposed individual weight inputs by regulatory
category, as shown in Table III-30, are included in draft RIA Chapter
3. We welcome comment or new data to support changes to the tractor
weights, or refinements to the heavy-haul tractor, trailer, and payload
weights.

                            Table III-30--Proposed Combination Tractor Weight Inputs
----------------------------------------------------------------------------------------------------------------
                                  Regulatory     Tractor tare    Trailer weight                    Total weight
          Model type             subcategory     weight  (lbs)        (lbs)       Payload  (lbs)       (lbs)
----------------------------------------------------------------------------------------------------------------
Class 8......................  Sleeper Cab              19,000            13,500          38,000          70,500
                                High Roof.
Class 8......................  Sleeper Cab Mid          18,750            10,000          38,000          66,750
                                Roof.
Class 8......................  Sleeper Cab Low          18,500            10,500          38,000          67,000
                                Roof.
Class 8......................  Day Cab High             17,500            13,500          38,000          69,000
                                Roof.
Class 8......................  Day Cab Mid              17,100            10,000          38,000          65,100
                                Roof.
Class 8......................  Day Cab Low              17,000            10,500          38,000          65,500
                                Roof.
Class 7......................  Day Cab High             11,500            13,500          25,000          50,000
                                Roof.
Class 7......................  Day Cab Mid              11,100            10,000          25,000          46,100
                                Roof.
Class 7......................  Day Cab Low              11,000            10,500          25,000          46,500
                                Roof.
Class 8......................  Heavy-Haul.....          19,000            13,500          86,000         118,500
----------------------------------------------------------------------------------------------------------------

(e) Tire Testing
    In Phase 1, the manufacturers are required to input their tire
rolling resistance coefficient into GEM. Also in Phase 1, the agencies
adopted the provisions in ISO 28580 to determine the rolling resistance
of tires. As described in 40 CFR 1037.520(c), the agencies require that
at least three tires for each tire design are to be tested at least one
time. Our assessment of the Phase 1 program to date indicates that
these requirements reasonably balance the need for precision,
repeatability, and testing burden. Therefore we propose to carry over
the Phase 1 testing provisions for tire rolling resistance into Phase
2. We welcome comments regarding the proposed tire testing provisions.
    In Phase 1, the agencies received comments from stakeholders
highlighting a need to develop a reference lab and alignment tires for
the HD sector. The agencies discussed the lab-to-lab comparison
conducted in the Phase 1 EPA tire test program (76 FR 57184). The
agencies reviewed the rolling resistance data from the tires that were
tested at both the STL and Smithers laboratories to assess inter-
laboratory and test machine variability. The agencies conducted
statistical analysis of the data to gain better understanding of lab-
to-lab correlation and developed an adjustment factor for data measured
at each of the test labs. Based on these results, the agencies believe
the lab-to-lab variation for the STL and Smithers laboratories would
have very small effect on measured rolling resistance values. Based on
the test data, the agencies judge for the HD Phase 2 program to
continue to use the current levels of variability, and the agencies
therefore propose to allow the use of either Smithers or STL
laboratories for determining the tire rolling resistance value.
However, we welcome comment on the need to establish a reference
machine for the HD sector and whether tire testing facilities are
interested in and willing to commit to developing a reference machine.
(2) Key Differences in HD Phase 2 Compliance Provisions
    We welcome comment on all aspects of the compliance program for
which we are proposing changes.
(a) Aerodynamic Assessment
    In Phase 1, the manufacturers conduct aerodynamic testing to
establish the appropriate bin and GEM input for determining compliance
with the CO2 and fuel consumption standards. The agencies
propose to continue this general approach in HD Phase 2, but make
several enhancements to the aerodynamic assessment of tractors. As
discussed below in this section, we propose some modifications to the
aerodynamic test procedures--the addition of wind averaged yaw in the
aerodynamic assessment, the addition of trailer skirts to the standard
trailer used to determine aerodynamic performance of tractors and
revisions to the aerodynamic bins.
(i) Aerodynamic Test Procedures
    The aerodynamic drag of a vehicle is determined by the vehicle's
coefficient of drag (Cd), frontal area, air density and speed.
Quantifying tractor aerodynamics as an input to the GEM presents
technical challenges because of the proliferation of tractor
configurations, and subtle variations in measured aerodynamic values
among various test procedures. In Phase 1, Class 7 and 8 tractor
aerodynamic results are developed by manufacturers using a range of
techniques, including wind tunnel testing, computational fluid
dynamics, and constant speed tests.
    We continue to believe a broad approach allowing manufacturers to
use these multiple test procedures to demonstrate aerodynamic
performance of its tractor fleet is appropriate given that no single
test procedure is superior in all aspects to other approaches. However,
we also recognize the need for consistency and a level playing field in
evaluating aerodynamic performance. To address the consistency and
level playing field concerns, NHTSA and EPA adopted in Phase 1, while
working with industry, an approach that identified a reference
aerodynamic test method and a procedure to align results from other
aerodynamic test procedures with the reference method.
    The agencies adopted in Phase 1 an enhanced coastdown procedure as
the reference method (see 40 CFR 1066.310) and defined a process for
manufacturers to align drag results from each of their own test methods
to the reference method results using Falt-aero (see 40 CFR 1037.525).
Manufacturers are able to use any aerodynamic evaluation method in
demonstrating a vehicle's aerodynamic performance as long as the method
is aligned to the reference method. The agencies propose to continue to
use this alignment method

approach to maintain the testing flexibility that manufacturers have
today. However, the agencies propose to increase the rigor in
determining the Falt-aero for Phase 2. Beginning in 2021 MY, we propose
that the manufacturers would be required to determine a new Falt-aero
for each of their tractor models for each aerodynamic test method. In
Phase 1, manufacturers are required to determine their Falt-aero using
only a high roof sleeper cab with a full aerodynamics package (see 40
CFR 1037.521(a)(2) and proposed 40 CFR 1037.525(b)(2)). In Phase 2, we
propose that manufacturers would be required to determine a unique
Falt-aero value for each major model of their high roof day cabs and
high roof sleeper cabs. In Phase 2, we propose that manufacturers may
carry over the Falt-aero value until a model changeover or based on the
agencies' discretion to require up to six new Falt-aero determinations
each year. We welcome comment on the burden associated with this
proposed change to conduct up to six coastdown tests per year per
manufacturer.
    Based on feedback received during the development of Phase 1, we
understand that there is interest from some manufacturers to change the
reference method in Phase 2 from coastdown to constant speed testing.
EPA has conducted an aerodynamic test program at Southwest Research
Institute to evaluate both methods in terms of cost of testing, testing
time, testing facility requirements, and repeatability of results.
Details of the analysis and results are included in draft RIA Chapter
3.2. The results showed that the enhanced coastdown test procedures and
analysis produced results with acceptable repeatability and at a lower
cost than the constant speed testing. Based on the results of this
testing, the agencies propose to continue to use the enhanced coastdown
procedure for the reference method in Phase 2.\177\ However, we welcome
comment on the need to change the reference method for the Phase 2
final rule to constant speed testing, including comparisons of
aerodynamic test results using both the coastdown and constant speed
test procedures. In addition, we welcome comments on and suggested
revisions to the constant speed test procedure specifications set forth
in Chapter <IP_ADDRESS> of the draft RIA and 40 CFR 1037.533. If we
determine that it is appropriate to make the change, then the
aerodynamic bins in the final rule would be adjusted to take into
account the difference in absolute CdA values due to the change in
method.
---------------------------------------------------------------------------

    \177\ Southwest Research Institute. ``Heavy Duty Class 8 Truck
Coastdown and Constant Speed Testing.'' April 2015.
---------------------------------------------------------------------------

    The agencies are also considering refinements to the computational
fluid dynamics modeling method to determine the aerodynamic performance
of tractors. Specifically, we are considering whether the conditions
for performing the analysis require greater specificity (e.g., wind
speed and direction inclusion, turbulence intensity criteria value) or
if turbulence model and mesh deformation should be required, rather
than ``if applicable,'' for all CFD analysis.\178\ The agencies welcome
comment on the proposed revisions.
---------------------------------------------------------------------------

    \178\ 40 CFR 1037.531 ``Computational fluid dynamics (CFD)''.
---------------------------------------------------------------------------

    In Phase 1, we adopted interim provisions in 40 CFR 1037.150(k)
that accounted for coastdown measurement variability by allowing a
compliance demonstration based on in-use test results if the drag area
was at or below the maximum drag area allowed for the bin above the bin
to which the vehicle was certified. Since adoption of Phase 1, EPA has
conducted in-use aerodynamic testing and found that uncertainty
associated with coastdown testing is less than anticipated.\179\ In
addition, we are proposing additional enhancements in the Phase 2
coastdown procedures to continue to reduce the variability of coastdown
results, including the impact of environmental conditions. Therefore,
we are proposing to sunset the provision in 40 CFR 1037.150(k) at the
end of the Phase 1 program (after the 2020 model year). We request
comment on whether or not we should factor in a test variability
compliance margin into the aerodynamic test procedure, and therefore
request data on aerodynamic test variability.
---------------------------------------------------------------------------

    \179\ Southwest Research Institute. ``Heavy Duty Class 8 Truck
Coastdown and Constant Speed Testing.'' April 2015.
---------------------------------------------------------------------------

(ii) Wind Averaged Drag
    In Phase 1, EPA and NHTSA recognized that wind conditions, most
notably wind direction, have a greater impact on real world
CO2 emissions and fuel consumption of heavy-duty trucks than
of light-duty vehicles.\180\ As noted in the NAS report, the wind
average drag coefficient is about 15 percent higher than the zero
degree coefficient of drag.\181\ In addition, the agencies received
comments in Phase 1 that supported the use of wind averaged drag
results for the aerodynamic determination. The agencies considered
adopting the use of a wind averaged drag coefficient in the Phase 1
regulatory program, but ultimately decided to finalize drag values
which represent zero yaw (i.e., representing wind from directly in
front of the vehicle, not from the side) instead. We took this approach
recognizing that the reference method is coastdown testing and it is
not capable of determining wind averaged yaw.\182\ Wind tunnels and CFD
are currently the only tools to accurately assess the influence of wind
speed and direction on a truck's aerodynamic performance. The agencies
recognized, as NAS did, that the results of using the zero yaw approach
may result in fuel consumption predictions that are offset slightly
from real world performance levels, not unlike the offset we see today
between fuel economy test results in the CAFE program and actual fuel
economy performance observed in-use.
---------------------------------------------------------------------------

    \180\ See 2010 NAS Report, page 95
    \181\ See 2010 NAS Report, Finding 2-4 on page 39. Also see 2014
NAS Report, Recommendation 3.5.
    \182\ See 2010 NAS Report. Page 95.
---------------------------------------------------------------------------

    As the tractor manufacturers continue to refine the aerodynamics of
tractors, we believe that continuing the zero yaw approach into Phase 2
could potentially impact the overall technology effectiveness or change
the kinds of technology decisions made by the tractor manufacturers in
developing equipment to meet our proposed HD Phase 2 standards.
Therefore, we are proposing aerodynamic test procedures that take into
account the wind averaged drag performance of tractors. The agencies
propose to account for this change in aerodynamic test procedure by
appropriately adjusting the aerodynamic bins to reflect a wind averaged
drag result instead of a zero yaw result.
    The agencies propose that beginning in 2021 MY, the manufacturers
would be required to adjust their CdA values to represent a zero yaw
value from coastdown and add the CdA impact of the wind averaged drag.
The impact of wind averaged drag relative to a zero yaw condition can
only be measured in a wind tunnel or with CFD. We welcome data
evaluating the consistency of wind averaged drag measurements between
wind tunnel, CFD, and other potential methods such as constant speed or
coastdown. The agencies propose that manufacturers would use the
following equation to make the necessary adjustments to a coastdown
result to obtain the CdAwad value:

CdAwad = CdAzero,coastdown +
(CdAwad,wind tunnel-CdAzero,wind tunnel) *
Falt-aero

    If the manufacturer has a wind averaged CdA value from either a
wind tunnel or CFD, then we propose they

would use the following equation to obtain the CdAwad value:

CdAwad = CdAwad,wind tunnel or CFD *
Falt-aero

    We welcome comment on whether the wind averaged drag should be
determined using a full yaw sweep as specified in Appendix A of the
Society of Automotive Engineers (SAE) recommended practice number J1252
``SAE Wind Tunnel Test Procedure for Trucks and Buses'' (e.g., zero
degree yaw and a six other yaw angles at increments of 3 degrees or
greater) or a subset of specific angles as currently allowed in the
Phase 1 regulations.\183\
---------------------------------------------------------------------------

    \183\ Proposed 40 CFR 1037.525(d)(2); ``Yaw Sweep Corrections''.
---------------------------------------------------------------------------

    To reduce the testing burden the agencies propose that
manufacturers have the option of determining the offset between zero
yaw and wind averaged yaw either through testing or by using the EPA-
defined default offset. Details regarding the determination of the
offset are included in the draft RIA Chapter 3.2. We propose the
manufacturers would use the following equation if they had a zero yaw
coastdown value and choose not to conduct wind averaged measurements.

CdAwad = CdAzero,coastdown + 0.80

    In addition, we propose the manufacturers would use the following
equation if they had a zero yaw wind tunnel or CFD value and choose not
to conduct wind averaged measurements.

CdAwad = (CdAzero,wind tunnel or CFD *
Falt-aero)+0.80
    We welcome comments on all aspects of the proposed wind averaged
drag provisions.
(iii) Standard Trailer Definition
    Similar to the approach the agencies adopted in Phase 1, NHTSA and
EPA are proposing provisions such that the tractor performance in GEM
is judged assuming the tractor is pulling a standardized trailer.\184\
The agencies believe that an assessment of the tractor fuel consumption
and CO2 emissions should be conducted using a tractor-
trailer combination, as tractors are invariably used in combination
with trailers and this is their essential commercial purpose. Trailers,
of course, also influence the extent of carbon emissions from the
tractor (and vice-versa). We believe that using a standardized trailer
best reflects the impact of the overall weight of the tractor-trailer
and the aerodynamic technologies in actual use, and consequent real-
world performance, where tractors are designed and used with a trailer.
EPA research confirms what one would intuit: tractor-trailer pairings
are almost always optimized. EPA conducted an evaluation of over 4,000
tractor-trailer combinations using live traffic cameras in 2010.\185\
The results showed that approximately 95 percent of the tractors were
matched with the standard trailer specified (high roof tractor with box
trailer, mid roof tractor with tanker trailer, and low roof with
flatbed trailer). Therefore, the agencies propose that Phase 2 GEM
continue to use a predefined typical trailer defined in Phase 1 in
assessing overall performance for test purposes. As such, the high roof
tractors would be paired with a standard box trailer; the mid roof
tractors would be paired with a tanker trailer; and the low roof
tractors would be paired with a flatbed trailer.
---------------------------------------------------------------------------

    \184\ See 40 CFR 1037.501(g).
    \185\ See Memo to Docket, Amy Kopin. ``Truck and Trailer Roof
Match Analysis.'' August 2010.
---------------------------------------------------------------------------

    However, the agencies are proposing to change the definition of the
standard box trailer used by tractor manufacturers to determine the
aerodynamic performance of high roof tractors in Phase 2. We believe
this is necessary to reflect the aerodynamic improvements experienced
by the trailer fleet over the last several years due to influences from
the California Air Resources Board mandate \186\ and EPA's SmartWay
Transport Partnership. The standard box trailer used in Phase 1 to
assess the aerodynamic performance of high roof tractors is a 53 foot
box trailer without any aerodynamic devices. In the development of
Phase 2, the agencies evaluated the increase in adoption rates of
trailer side skirts and boat tails in the market over the last several
years and have seen a marked increase. We estimate that approximately
50 percent of the new trailers sold in 2018 will have trailer side
skirts.187 188 As the agencies look towards the proposed
standards in the 2021 and beyond timeframe, we believe that it is
appropriate to update the standard box trailer definition. In 2021-
2027, we believe the trailer fleet will be a mix of trailers with no
aerodynamics, trailers with skirts, and trailers with advanced aero;
with the advanced aero being a very limited subset of the new trailers
sold each year. Consequently, overall, we believe a trailer with a
skirt will be the most representative of the trailer fleet for the
duration of the regulation timeframe, and plausibly beyond. Therefore,
we are proposing that the standard box trailer in Phase 2--the trailer
assumed during the certification process to be paired with a high roof
tractor--be updated to include a trailer skirt starting in 2021 model
year. Even though the agencies are proposing new box trailer standards
beginning in 2018 MY, we are not proposing to update the standard
trailer in the tractor certification process until 2021 MY, to align
with the new tractor standards. If we were to revise the standardized
trailer definition for Phase 1, then we would need to revise the Phase
1 tractor standards. The details of the trailer skirt definition are
included in 40 CFR 1037.501(g)(1).
---------------------------------------------------------------------------

    \186\ California Air Resources Board. Tractor-Trailer Greenhouse
Gas regulation. Last viewed on September 4, 2014 at http://www.arb.ca.gov/msprog/truckstop/trailers/trailers.htm.
    \187\ Ben Sharpe (ICCT) and Mike Roeth (North American Council
for Freight Efficiency), ``Costs and Adoption Rates of Fuel-Saving
Technologies for Trailer in the North American On-Road Freight
Sector'', Feb 2014.
    \188\ Frost & Sullivan, ``Strategic Analysis of North American
Semi-trailer Advanced Technology Market'', Feb 2013.
---------------------------------------------------------------------------

    EPA has conducted extensive aerodynamic testing to quantify the
impact on the coefficient of drag of a high roof tractor due to the
addition of a trailer skirt. Details of the test program and the
results can be found in the draft RIA Chapter 3.2. The results of the
test program indicate that on average, the impact of a trailer skirt
matching the definition of the skirt specified in 40 CFR 1037.501(g)(1)
is approximately 8 percent improvement in coefficient of drag area.
This off-set was used during the development of the Phase 2 aerodynamic
bins.
    We seek comment on our proposed HD Phase 2 standard trailer
configuration. We also welcome comments on suggestions on alternative
ways to define the standard trailer, such as developing a certified
computer aided drawing (CAD) model.
(iv) Aerodynamic Bins
    The agencies are proposing to continue the approach where the
manufacturer would determine a tractor's aerodynamic drag force through
testing, determine the appropriate predefined aerodynamic bin, and then
input the predefined CdA value for that bin into the GEM. The agencies
proposed Phase 2 aerodynamic bins reflect three changes to the Phase 1
bins--the incorporation of wind averaged drag, the addition of trailer
skirts to the standard box trailer used to determine the aerodynamic
performance of high roof tractors, and the addition of bins to reflect
the continued improvement of tractor aerodynamics in the future.
Because of each of these changes, the aerodynamic bins proposed for
Phase 2 are not directly comparable to the Phase 1 bins.
    HD Phase 1 included five aerodynamic bins to cover the spectrum of
aerodynamic performance of high

roof tractors. Since the development of the Phase 1 rules, the
manufacturers have continued to invest in aerodynamic improvements for
tractors. This continued evolution of aerodynamic performance, both in
production and in the research stage as part of the SuperTruck program,
has consequently led the agencies to propose two additional aerodynamic
technology bins (Bins VI and VII) for high roof tractors. These two new
bins would further segment the Phase 1 aerodynamic Bin V to recognize
the difference in advanced aerodynamic technologies and designs.
    In both HD Phase 1 and as proposed by the agencies in Phase 2,
aerodynamic Bin I through Bin V represent tractors sharing similar
levels of technology. The first high roof aerodynamic category, Bin I,
is designed to represent tractor bodies which prioritize appearance or
special duty capabilities over aerodynamics. These Bin I tractors
incorporate few, if any, aerodynamic features and may have several
features that detract from aerodynamics, such as bug deflectors, custom
sunshades, B-pillar exhaust stacks, and others. The second high roof
aerodynamics category is Bin II which roughly represents the
aerodynamic performance of the average new tractor sold in 2010. The
agencies developed this bin to incorporate conventional tractors which
capitalize on a generally aerodynamic shape and avoid classic features
which increase drag. High roof tractors within Bin III build on the
basic aerodynamics of Bin II tractors with added components to reduce
drag in the most significant areas on the tractor, such as integral
roof fairings, side extending gap reducers, fuel tank fairings, and
streamlined grill/hood/mirrors/bumpers, similar to 2013 model year
SmartWay tractors. The Bin IV aerodynamic category for high roof
tractors builds upon the Bin III tractor body with additional
aerodynamic treatments such as underbody airflow treatment, down
exhaust, and lowered ride height, among other technologies. HD Phase 1
Bin V tractors incorporate advanced technologies which are currently in
the prototype stage of development, such as advanced gap reduction,
rearview cameras to replace mirrors, wheel system streamlining, and
advanced body designs. For HD Phase 2, the agencies propose to segment
the aerodynamic performance of these advanced technologies into Bins V
through VII.
    In Phase 1, the agencies adopted only two aerodynamic bins for low
and mid roof tractors. The agencies limited the number of bins to
reflect the actual range of aerodynamic technologies effective in low
and mid roof tractor applications. High roof tractors are consistently
paired with box trailer designs, and therefore manufacturers can design
the tractor aerodynamics as a tractor-trailer unit and target specific
areas like the gap between the tractor and trailer. In addition, the
high roof tractors tend to spend more time at high speed operation
which increases the impact of aerodynamics on fuel consumption and GHG
emissions. On the other hand, low and mid roof tractors are designed to
pull variable trailer loads and shapes. They may pull trailers such as
flat bed, low boy, tankers, or bulk carriers. The loads on flat bed
trailers can range from rectangular cartons with tarps, to a single
roll of steel, to a front loader. Due to these variables, manufacturers
do not design unique low and mid roof tractor aerodynamics but instead
use derivatives from their high roof tractor designs. 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. As mentioned above, the types
of designs that would move high roof tractors from a Bin III to Bins IV
through VII include features such as gap reducers and integral roof
fairings which would not be appropriate on low and mid roof tractors.
    As Phase 2 looks to further improve the aerodynamics for high roof
sleeper cabs, we believe it is also appropriate to expand the number of
bins for low and mid roof tractors too. For Phase 2, the agencies are
proposing to differentiate the aerodynamic performance for low and mid
roof applications with four bins, instead of two, in response to
feedback received from manufacturers of low and mid roof tractors
related to the limited opportunity to incorporate aerodynamic
technologies in their compliance plan. We propose that low and mid roof
tractors may determine the aerodynamic bin based on the aerodynamic bin
of an equivalent high roof tractor, as shown below in Table III-31.

    Table III-31--Proposed Phase 2 Revisions to 40 CFR 1037.520(b)(3)
------------------------------------------------------------------------
            High roof bin                    Low and mid roof bin
------------------------------------------------------------------------
Bin I                                 Bin I
Bin II                                Bin I
Bin III                               Bin II
Bin IV                                Bin II
Bin V                                 Bin III
Bin VI                                Bin III
Bin VII                               Bin IV
------------------------------------------------------------------------

    The agencies developed new high roof tractor aerodynamic bins for
Phase 2 that reflect the change from zero yaw to wind averaged drag,
the more aerodynamic reference trailer, and the addition of two bins.
Details regarding the derivation of the proposed high roof bins are
included in Draft RIA Chapter 3.2.8. The proposed high roof tractor
bins are defined in Table III-32. The proposed revisions to the low and
mid roof tractor bins reflect the addition of two new aerodynamic bins
and are listed in Table III-33.

 Table III-32--Proposed Phase 2 Aerodynamic Input Definitions to GEM for
                           High Roof Tractors
------------------------------------------------------------------------
                                     Class 7             Class 8
                                  --------------------------------------
                                     Day cab      Day cab    Sleeper cab
                                  --------------------------------------
                                    High roof    High roof    High roof
------------------------------------------------------------------------
                Aerodynamic Test Results (CdAwad in m\2\)
------------------------------------------------------------------------
Bin I............................        >=7.5        >=7.5        >=7.3
Bin II...........................      6.8-7.4      6.8-7.4      6.6-7.2
Bin III..........................      6.2-6.7      6.2-6.7      6.0-6.5
Bin IV...........................      5.6-6.1      5.6-6.1      5.4-5.9
Bin V............................      5.1-5.5      5.1-5.5      4.9-5.3
Bin VI...........................      4.7-5.0      4.7-5.0      4.5-4.8
Bin VII..........................        <=4.6        <=4.6        <=4.4
------------------------------------------------------------------------

                Aerodynamic Input to GEM (CdAwad in m\2\)
------------------------------------------------------------------------
Bin I............................          7.6          7.6          7.4
Bin II...........................          7.1          7.1          6.9
Bin III..........................          6.5          6.5          6.3
Bin IV...........................          5.8          5.8          5.6
Bin V............................          5.3          5.3          5.1
Bin VI...........................          4.9          4.9          4.7
Bin VII..........................          4.5          4.5          4.3
------------------------------------------------------------------------

        Table III-33--Proposed Phase 2 Aerodynamic Input Definitions to GEM for Low and Mid Roof Tractors
----------------------------------------------------------------------------------------------------------------
                                             Class 7                                Class 8
                                   -----------------------------------------------------------------------------
                                             Day cab                   Day cab                 Sleeper cab
                                   -----------------------------------------------------------------------------
                                      Low roof     Mid roof     Low roof     Mid roof     Low roof     Mid roof
----------------------------------------------------------------------------------------------------------------
                                     Aerodynamic Test Results (CdA in m\2\)
----------------------------------------------------------------------------------------------------------------
Bin I.............................        >=5.1        >=6.5        >=5.1        >=6.5        >=5.1        >=6.5
Bin II............................      4.6-5.0      6.0-6.4      4.6-5.0      6.0-6.4      4.6-5.0      6.0-6.4
Bin III...........................      4.2-4.5      5.6-5.9      4.2-4.5      5.6-5.9      4.2-4.5      5.6-5.9
Bin IV............................        <=4.1        <=5.5        <=4.1        <=5.5        <=4.1        <=5.5
----------------------------------------------------------------------------------------------------------------
                                     Aerodynamic Input to GEM (CdA in m\2\)
----------------------------------------------------------------------------------------------------------------
Bin I.............................          5.3          6.7          5.3          6.7          5.3          6.7
Bin II............................          4.8          6.2          4.8          6.2          4.8          6.2
Bin III...........................          4.3          5.7          4.3          5.7          4.3          5.7
Bin IV............................          4.0          5.4          4.0          5.4          4.0          5.4
----------------------------------------------------------------------------------------------------------------

(b) Road Grade in the Drive Cycles
    Road grade can have a significant impact on the overall fuel
economy of a heavy-duty vehicle. Table III-34 shows the results from a
real world evaluation of heavy-duty tractor-trailers conducted by Oak
Ridge National Lab.\189\ The study found that the impact of a mild
upslope of one to four percent led to a decrease in average fuel
economy from 7.33 mpg to 4.35 mpg. These results are as expected
because vehicles consume more fuel while driving on an upslope than
driving on a flat road because the vehicle needs to exert additional
power to overcome the grade resistance force.\190\ The amount of extra
fuel increases with increases in road gradient. On downgrades, vehicles
consume less fuel than on a flat road. However, as shown in the fuel
consumption results in Table III-34, the amount of increase in fuel
consumption on an upslope is greater than the amount of decrease in
fuel consumption on a downslope which leads to a net increase in fuel
consumption. As an example, the data shows that a vehicle would use 0.3
gallons per mile more fuel in a severe upslope than on flat terrain,
but only save 0.1 gallons of fuel per mile on a severe downslope. In
another study, Southwest Research Institute modeling found that the
addition of road grade to a drive cycle has an 8 to 10 percent negative
impact on fuel economy.\191\
---------------------------------------------------------------------------

    \189\ Oakridge National Laboratory. Transportation Energy Book,
Edition 33. Table 5.10 Effect of Terrain on Class 8 Truck Fuel
Economy. 2014. Last accessed on September 19, 2014 at http://cta.ornl.gov/data/Chapter5.shtml.
    \190\ Ibid.
    \191\ Reinhart, T. (2015). Commercial Medium- and Heavy-Duty
(MD/HD) Truck Fuel Efficiency Technology Study--Report #2.
Washington, DC: National Highway Traffic Safety Administration.

          Table III-34--Fuel Consumption Relative to Road Grade
------------------------------------------------------------------------
                                  Average fuel          Average fuel
       Type of terrain         economy  (miles per       consumption
                                     gallon)         (gallons per mile)
------------------------------------------------------------------------
Severe upslope (>4%)........                  2.90                  0.34
Mild upslope (1% to 4%).....                  4.35                  0.23
Flat terrain (1% to 1%).....                  7.33                  0.14
Mild downslope (-4% to -1%).                 15.11                  0.07
Severe downslope (<-4%).....                 23.50                  0.04
------------------------------------------------------------------------

    In Phase 1, the agencies did not include road grade. However, we
believe it is important to propose including road grade in Phase 2 to
properly assess the value of technologies, such as downspeeding and the
integration of the engine and transmission, which were not technologies
included in the technology basis for Phase 1 and are not directly
assessed by GEM in its Phase 1 iteration. The addition of road grade to
the drive cycles would be consistent with the NAS recommendation in the
2014 Phase 2 First Report.\192\
---------------------------------------------------------------------------

    \192\ National Academy of Science. ``Reducing the Fuel
Consumption and GHG Emissions of Medium- and Heavy-Duty Vehicles,
Phase Two, First Report.'' 2014. Recommendation S.3 (3.6).
---------------------------------------------------------------------------

    The U.S. Department of Energy and EPA have partnered to support a
project aimed at evaluating, refining and/or developing the appropriate
road grade profiles for the 55 mph and 65 mph highway cruise duty
cycles that would be used in the certification of heavy-duty vehicles
to the Phase 2 GHG emission and fuel efficiency standards. The National
Renewable Energy Laboratory (NREL) was contracted to do this work and
has since developed two pairs of candidate, activity-weighted road
grade profiles representative of U.S. limited-access highways. To this
end, NREL used high-accuracy road grade data and county-specific
vehicle miles traveled data. One pair of the profiles is representative
of the nation's limited-access highways with 55 and 60 mph speed
limits, and another is representative of such highways with speed
limits of 65 to 75 mph. The profiles are distance-based and cover a
maximum distance of 12 and 15 miles, respectively. A report documenting
this NREL work is in the public docket for these proposed rules, and
comments are requested on the recommendations therein.\193\ In addition
to NREL work, the agencies have independently developed yet another
candidate road grade profile for use in the 55 mph and 65 mph highway
cruise duty cycles. While based on the same road grade database
generated by NREL for U.S. restricted-access highways, its design is
predicated on a different approach. The development of this profile is
documented in the memorandum to the docket.\194\ The agencies have
evaluated all of the candidate road grade profiles and have prepared
possible alternative tractor standards based on these profiles. The
agencies request comment on this analysis, which is available in a
memorandum to the docket.\195\
---------------------------------------------------------------------------

    \193\ See NREL Report ``EPA Road Grade profiles'' for DOE-EPA
Interagency Agreement to Refine Drive Cycles for GHG Certification
of Medium- and Heavy-Duty Vehicles, IA Number DW-89-92402501.
    \194\ Memorandum dated April 2015 on Possible Tractor, Trailer,
and Vocational Vehicle Standards Derived from Alternative Road Grade
Profiles.
    \195\ Ibid.
---------------------------------------------------------------------------

    For the proposal, the agencies developed an interim road grade
profile for development of the proposed standards. The agencies are
proposing the inclusion of an interim road grade profile, as shown
below in Figure III-2, in both the 55 mph and 65 mph cycles. The grade
profile was developed by Southwest Research Institute on a 12.5 mile
stretch of restricted-access highway during on-road tests conducted for
EPA's validation of the Phase 2 version of GEM.\196\ The minimum grade
in the interim cycle is -2.1 percent and the maximum grade is 2.4
percent. The cycle spends 30 percent of the distance in grades of +/-
0.5 percent. Overall, the cycle spends approximately 50 percent of the
time in relatively flat terrain with road gradients of less than 1
percent.
---------------------------------------------------------------------------

    \196\ Southwest Research Institute. ``GEM Validation'',
Technical Research Workshop supporting EPA and NHTSA Phase 2
Standards for MD/HD Greenhouse Gas and Fuel Efficiency--December 10
and 11, 2014. Can be accessed at http://www.epa.gov/otaq/climate/regs-heavy-duty.htm.
---------------------------------------------------------------------------

    The agencies believe the interim cycle has sufficient
representativeness based on a comparison to data from the Department of
Transportation used in the development of the light-duty Federal Test
Procedure cycle (FTP), which found approximately 55 percent of the
vehicle miles traveled were on road gradients of less than 1
percent.\197\ Consequently, we expect that road grade profiles
developed by NREL and by the agencies will not differ significantly
from the interim profile proposed here. The agencies request data from
fleet operators or others that have real world grade profile data.
---------------------------------------------------------------------------

    \197\ U.S. EPA. FTP Preliminary Report. May 14, 1993. Table 5-1,
page 76. EPA-420-R-93-007.
[GRAPHIC] [TIFF OMITTED] TP13JY15.003

(c) Weight Reduction
    In Phase 1, the agencies adopted regulations that provided
manufacturers with the ability to use GEM to measure emission reduction
and reductions in fuel consumption resulting from use of high strength
steel and aluminum components for weight reduction,, and to do so
without the burden of entering the curb weight of every tractor
produced. We treated such weight reduction in two ways in Phase 1 to
account for the fact that combination tractor-trailers weigh-out
approximately one-third of the time and cube-out approximately two-
thirds of the time. Therefore, one-third of the weight reduction is
added payload in the denominator while two-thirds of the weight
reduction is subtracted from the overall weight of the vehicle in GEM.
See 76 FR 57153. The agencies also allowed manufacturers to petition
for off-cycle credits for components not measured in GEM.
    NHTSA and EPA propose carrying the Phase 1 treatment of weight
reduction into Phase 2. That is, these types of weight reduction,
although not part of the agencies' technology packages for

the proposed (or alternative) standards, can still be recognized in GEM
up to a point. In addition, the agencies propose to add additional
thermoplastic components to the weight reduction table, as shown below
in Table III-35. The thermoplastic component weight reduction values
were developed in coordination with SABIC, a thermoplastic component
supplier. Also, in Phase 2, we are proposing to recognize the potential
weight reduction opportunities in the powertrain and drivetrain systems
as part of the vehicle inputs into GEM. Therefore, we believe it is
appropriate to also recognize the weight reduction associated with both
smaller engines and 6x2 axles.\198\ We propose including the values
listed in Table III-36 and make them available upon promulgation of the
final Phase 2 rules (i.e., available even under Phase 1). We welcome
comments on all aspects of weight reduction.
---------------------------------------------------------------------------

    \198\ North American Council for Freight Efficiency.
``Confidence Findings on the Potential of 6x2 Axles.'' 2014. Page
16.

                    Table III-35--Proposed Phase 2 Weight Reduction Technologies for Tractors
----------------------------------------------------------------------------------------------------------------

----------------------------------------------------------------------------------------------------------------
                               Weight reduction technology                                    Weight reduction
                                                                                (lb per tire/wheel)
----------------------------------------------------------------------------------------------------------------
Single Wide Drive Tire with.....................  Steel Wheel............................                     84
                                                  Aluminum Wheel.........................                    139
                                                  Light Weight Aluminum Wheel............                    147
Steer Tire or Dual Wide Drive Tire with.........  High Strength Steel Wheel..............                      8
                                                  Aluminum Wheel.........................                     21
                                                  Light Weight Aluminum Wheel............                     30
----------------------------------------------------------------------------------------------------------------

                                                                   Aluminum      High strength    Thermoplastic
                                                                    weight        steel weight        weight
                Weight reduction technologies                     reduction        reduction        reduction
                                                                    (lb.)            (lb.)            (lb.)
----------------------------------------------------------------------------------------------------------------
Door (per door)..............................................               20                6  ...............
Roof (per vehicle)...........................................               60               18  ...............
Cab rear wall (per vehicle)..................................               49               16  ...............
Cab floor (per vehicle)......................................               56               18  ...............
Hood (per vehicle)...........................................               55               17  ...............
Hood Support Structure (per vehicle).........................               15                3  ...............
Hood and Front Fender (per vehicle)..........................  ...............  ...............               65
Day Cab Roof Fairing (per vehicle)...........................  ...............  ...............               18
Sleeper Cab Roof Fairing (per vehicle).......................               75               20               40
Aerodynamic Side Extender (per vehicle)......................  ...............  ...............               10
Fairing Support Structure (per vehicle)......................               35                6  ...............
Instrument Panel Support Structure (per vehicle).............                5                1  ...............
Brake Drums--Drive (per 4)...................................              140               11  ...............
Brake Drums--Non Drive (per 2)...............................               60                8  ...............
Frame Rails (per vehicle)....................................              440               87  ...............
Crossmember--Cab (per vehicle)...............................               15                5  ...............
Crossmember--Suspension (per vehicle)........................               25                6  ...............
Crossmember--Non Suspension ( per 3).........................               15                5  ...............
Fifth Wheel (per vehicle)....................................              100               25  ...............
Radiator Support (per vehicle)...............................               20                6  ...............
Fuel Tank Support Structure (per vehicle)....................               40               12  ...............
Steps (per vehicle)..........................................               35                6  ...............
Bumper (per vehicle).........................................               33               10  ...............
Shackles (per vehicle).......................................               10                3  ...............
Front Axle (per vehicle).....................................               60               15  ...............
Suspension Brackets, Hangers (per vehicle)...................              100               30  ...............
Transmission Case (per vehicle)..............................               50               12  ...............
Clutch Housing (per vehicle).................................               40               10  ...............
Drive Axle Hubs (per 4)......................................               80               20  ...............
Non Drive Front Hubs (per 2).................................               40                5  ...............
Driveshaft (per vehicle).....................................               20                5  ...............
Transmission/Clutch Shift Levers (per vehicle)...............               20                4  ...............
----------------------------------------------------------------------------------------------------------------

    Table III-36--Proposed Phase 2 Weight Reduction Values for Other
                               Components
------------------------------------------------------------------------
                                                      Weight reduction
            Weight reduction technology                     (lb)
------------------------------------------------------------------------
6x2 axle configuration in tractors................                   300
4x2 axle configuration in Class 8 tractors........                   300
Tractor engine with displacement less than 14.0L..              \199\300
CI Liquified Natural Gas tractor..................       \200\ \201\-600
SI Compressed Natural Gas tractor.................                  -525

CI Compressed Natural Gas tractor.................                  -900
------------------------------------------------------------------------

(d) GEM Inputs
---------------------------------------------------------------------------

    \199\ Kenworth. ``Kenworth T680 with PACCAR MX-13 Engine Lowers
Costs for Oregon Open-Deck Carrier.'' Last viewed on December 16,
2014 at http://www.kenworth.com/news/news-releases/2013/december/t680-cotc.aspx.
    \200\ National Energy Policy Institute. ``What Set of Conditions
Would Make the Business Case to Convert Heavy Trucks to Natural
Gas?--A Case Study.'' May 1, 2012. Last accessed on December 15,
2014 at http://www.tagnaturalgasinfo.com/uploads/1/2/2/3/12232668/natural_gas_for_heavy_trucks.pdf.
    \201\ Westport presentation (2013). Last accessed on December
15, 2014 at http://www.westport.com/file_library/files/webinar/2013-06-19_CNGandLNG.pdf.
---------------------------------------------------------------------------

    The agencies propose to continue to require the Phase 1 GEM inputs
for tractors in Phase 2. These inputs include the following:
     Steer tire rolling resistance,
     Drive tire rolling resistance,
     Coefficient of Drag Area,
     Idle Reduction, and
     Vehicle Speed Limiter.
    As discussed above in Section II.C and III.D, there are several
additional inputs that are proposed for Phase 2. The new GEM inputs
proposed for Phase 2 include the following:
     Engine information including manufacturer, model,
combustion type, fuel type, family name, and calibration identification
     Engine fuel map,
     Engine full-load torque curve,
     Engine motoring curve,
     Transmission information including manufacturer and model
     Transmission type,
     Transmission gear ratios,
     Drive axle ratio,
     Loaded tire radius for drive tires, and
     Other technology inputs.
    The agencies welcome comments on the inclusion of these proposed
technologies into GEM in Phase 2.
(e) Vehicle Speed Limiters and Extended Idle Provisions
    The agencies received comments during the development of Phase 1
that the Clean Air Act provisions to prevent tampering (CAA section
203(a)(3)(A); 42 U.S.C. 7522(a)(3)(A)) of vehicle speed limiters and
extended idle reduction technologies would prohibit their use for
demonstrating compliance with the Phase 1 standards. In Phase 1, the
agencies adopted provisions to allow for discounted credits for idle
reduction technologies that allowed for override conditions and
expiring engine shutdown systems (see 40 CFR 1037.660). Similarly, the
agencies adopted provisions to allow for ``soft top'' speeds and
expiring vehicle speed limiters, and we are not proposing to change
those provisions (see 40 CFR 1037.640). However, as we develop Phase 2,
we understand that the concerns still exist that the ability for a
tractor manufacturer to reflect the use of a VSL in its compliance
determination may be constrained by the demand for flexibility in the
use of VSLs by the customers. . The agencies welcome suggestions on how
to close the gap between the provisions that would be acceptable to the
industry while maintaining our need to ensure that modifications do not
violate 42 U.S.C. 7522(a)(3)(A). We request comment on potential
approaches which would enable feedback mechanism between the vehicle
owner/fleet that would provide the agencies the assurance that the
benefits of the VSLs will be seen in use but which also provides the
vehicle owner/fleet the flexibility they many need during in-use
operation. More generally in our discussions with several trucking
fleets and with the American Trucking Associations an interest was
expressed by the fleets if there was a means by which they could
participate in the emissions credit transactions which is currently
limited to the directly regulated truck manufacturers. VSLs and
extended idle systems were two example technologies that fleets and
individual owners can order for a new build truck, and that from the
fleet's perspective the truck manufacturers receive emission credits
for. The agencies do not have a specific proposal or a position on the
request from the American Trucking Association and its members, but we
request comment on whether or not it is appropriate to allow owners to
participate in the overall compliance process for the directly
regulated parties, if such a thing is allowed under the two agencies'
respective statutes, and what regulatory provisions would be needed to
incorporate such an approach.
(f) Emission Control Labels
    The agencies consider it crucial that authorized compliance
inspectors are able to identify whether a vehicle is certified, and if
so whether it is in its certified condition. To facilitate this
identification in Phase 1, EPA adopted labeling provisions for tractors
that included several items. The Phase 1 tractor label must include the
manufacturer, vehicle identifier such as the Vehicle Identification
Number (VIN), vehicle family, regulatory subcategory, date of
manufacture, compliance statements, and emission control system
identifiers (see 40 CFR 1037.135). In Phase 1, the emission control
system identifiers are limited to vehicle speed limiters, idle
reduction technology, tire rolling resistance, some aerodynamic
components, and other innovative and advanced technologies.
    The number of proposed emission control systems for greenhouse gas
emissions in Phase 2 has increased significantly. For example, the
engine, transmission, drive axle ratio, accessories, tire radius, wind
averaged drag, predictive cruise control, and automatic tire inflation
system are controls which can be evaluated on-cycle in Phase 2 (i.e.
these technologies' performance can now be input to GEM), but could not
be in Phase 1. Due to the complexity in determining greenhouse gas
emissions as proposed in Phase 2, the agencies do not believe that we
can unambiguously determine whether or not a vehicle is in a certified
condition through simply comparing information that could be made
available on an emission control label with the components installed on
a vehicle. Therefore, EPA proposes to remove the requirement to include
the emission control system identifiers required in 40 CFR
1037.135(c)(6) and in Appendix III to 40 CFR part 1037 from the
emission control labels for vehicles certified to the Phase 2
standards. However, the agencies may finalize requirements to maintain
some label content to facilitate a limited visual inspection of key
vehicle parameters that can be readily observed. Such requirements may
be very similar to the labeling requirements from the Phase 1
rulemaking, though we would want to more carefully consider the list of
technologies that would allow for the most effective inspection. We
request comment on an appropriate list of candidate technologies that
would properly balance the need to limit label content with the
interest in providing the most useful information for inspectors to
confirm that vehicles have been properly built. We are not proposing to
modify the existing emission control labels for tractors certified for
MYs 2014-2020 (Phase 1) CO2 standards.
    Under the agencies' existing authorities, manufacturers must
provide detailed build information for a specific vehicle upon our
request. Our expectation is that this information should be available
to us via email or other similar electronic communication

on a same-day basis, or within 24 hours of a request at most. We
request comment on any practical limitations in promptly providing this
information. We also request comment on approaches that would minimize
burden for manufacturers to respond to requests for vehicle build
information and would expedite an authorized compliance inspector's
visual inspection. For example, the agencies have started to explore
ideas that would provide inspectors with an electronic method to
identify vehicles and access on-line databases that would list all of
the engine-specific and vehicle-specific emissions control system
information. We believe that electronic and Internet technology exists
today for using scan tools to read a bar code or radio frequency
identification tag affixed to a vehicle that would then lead to secure
on-line access to a database of manufacturers' detailed vehicle and
engine build information. Our exploratory work on these ideas has
raised questions about the level of effort that would be required to
develop, implement and maintain an information technology system to
provide inspectors real-time access to this information. We have also
considered questions about privacy and data security. We request
comment on the concept of electronic labels and database access,
including any available information on similar systems that exist today
and on burden estimates and approaches that could address concerns
about privacy and data security. Based on new information that we
receive, we may consider initiating a separate rulemaking effort to
propose and request comment on implementing such an approach.
(g) End of Year Reports
    In the Phase 1 program, manufacturers participating in the ABT
program provided 90 day and 270 day reports to EPA and NHTSA after the
end of the model year. The agencies adopted two reports for the initial
program to help manufacturers become familiar with the reporting
process. For the HD Phase 2 program, the agencies propose to simplify
reporting such that manufacturers would only be required to submit the
final report 90 days after the end of the model year with the potential
to obtain approval for a delay up to 30 days. We are accordingly
proposing to eliminate the end of year report, which represents a
preliminary set of ABT figures for the preceding year. We welcome
comment on this proposed revision.
(h) Special Compliance Provisions
    In Phase 2, the agencies propose to consider the performance of the
engine, transmission, and drivetrain in determining compliance with the
Phase 2 tractor standards. With the inclusion of the engine's
performance in the vehicle compliance, EPA proposes to modify the
prohibition to introducing into U.S. commerce a tractor containing an
engine not certified for use in tractor (see proposed 40 CFR
1037.601(a)(1)). In Phase 2, we no longer see the need to prohibit the
use of vocational engines in tractors because the performance of the
engine would be appropriately reflected in GEM. We welcome comment on
removing this prohibition.
    The agencies also propose to change the compliance process for
manufacturers seeking to use the off-road exclusion. During the Phase 1
program, manufacturers realized that contacting the agencies in advance
of the model year was necessary to determine whether vehicles would
qualify for exemption and need approved certificates of conformity. The
agencies found that the petition process allowed at the end of the
model year was not necessary and that an informal approval during the
precertification period was more effective. Therefore, NHTSA is
proposing to remove its off-road petitioning process in 49 CFR 535.8
and EPA is proposing to add requirements for informal approvals in 40
CFR 1037.610.
(i) Chassis Dynamometer Testing Requirement
    The agencies foresee the need to continue to track the progress of
the Phase 2 program throughout its implementation. As discussed in
Section II, the agencies expect to evaluate the overall performance of
tractors with the GEM results provided by manufacturers through the end
of year reports. However, we also need to continue to have confidence
in our simulation tool, GEM, as the vehicle technologies continue to
evolve. Therefore, EPA proposes that the manufacturers conduct annual
chassis dynamometer testing of three sleeper cabs tractor and two day
cab tractor and provide the data and the GEM result from each of these
two tractor configurations to EPA (see 40 CFR 1037.665). We request
comment on the costs and efficacy of this data submission requirement.
We emphasize that this program would not be used for compliance or
enforcement purposes.

F. Flexibility Provisions

    EPA and NHTSA are proposing two flexibility provisions specifically
for heavy-duty tractor manufacturers in Phase 2. These are an
averaging, banking and trading program for CO2 emissions and
fuel consumption credits, as well as provisions for credits for off-
cycle technologies which are not included as inputs to the GEM. Credits
generated under these provisions can only be used within the same
averaging set which generated the credit.
    The agencies are also proposing to remove or modify several Phase 1
interim provisions, as described below.
(1) Averaging, Banking, and Trading (ABT) Program
    Averaging, banking, and trading of emission credits have been an
important part of many EPA mobile source programs under CAA Title II,
and the NHTSA light-duty CAFE program. The agencies also included this
flexibility in the HD Phase 1 program. ABT provisions are useful
because they can help to address many potential issues of technological
feasibility and lead-time, as well as considerations of cost. They
provide manufacturers flexibilities that assist in the efficient
development and implementation of new technologies and therefore enable
new technologies to be implemented at a more aggressive pace than
without ABT. A well-designed ABT program can also provide important
environmental and energy security benefits by increasing the speed at
which new technologies can be implemented. Between MYs 2013 and 2014
all four tractor manufacturers are taking advantage of the ABT
provisions in the Phase 1 program. NHTSA and EPA propose to carry-over
the Phase 1 ABT provisions for tractors into Phase 2.
    The agencies propose to continue the five year credit life and
three year deficit carry-over provisions from Phase 1 (40 CFR
1037.740(c) and 1037.745). Please see additional discussion in Section
I.C.1.b. Although we are not proposing any additional restrictions on
the use of Phase 1 credits, we are requesting comment on this issue.
Early indications suggest that positive market reception to the Phase 1
technologies could lead to manufacturers accumulating credits surpluses
that could be quite large at the beginning of the proposed Phase 2
program. This appears especially likely for tractors. The agencies are
specifically requesting comment on the likelihood of this happening,
and whether any regulatory changes would be appropriate. For example,
should the agencies limit the amount of credits than could be carried

over from Phase 1 or limit them to the first year or two of the Phase 2
program? Also, if we determine that large surpluses are likely, how
should that factor into our decision on the feasibility of more
stringent standards in MY 2021?
    We welcome comments on these proposed flexibilities and are
interested in information that may indicate doing as proposed could
distort the heavy-duty vehicle market.
(2) Off-Cycle Technology Credits
    In Phase 1, the agencies adopted an emissions and fuel consumption
credit generating opportunity that applied to innovative technologies
that reduce fuel consumption and CO2 emissions. These
technologies were required to not be in common use with heavy-duty
vehicles before the 2010MY and not reflected in the GEM simulation tool
(i.e., the benefits are ``off-cycle''). See 76 FR 57253. The agencies
propose to largely continue, but redesignate the Phase 1 innovative
technology program as part of the off-cycle program for Phase 2. In
other words, beginning in 2021 MY all technologies that are not fully
accounted for in the GEM simulation tool, or by compliance dynamometer
testing could be considered off-cycle, including those technologies
that may have been considered innovative technologies in Phase 1 of the
program. The agencies propose to maintain the requirement that, in
order for a manufacturer to receive credits for Phase 2, the off-cycle
technology would still need to meet the requirement that it was not in
common use prior to MY 2010. For additional information on the
treatment of off-cycle technologies see Section I.C.1.c.
    The agencies are proposing a split process for handling off-cycle
technologies in Phase 2. First, there is a set of predefined off-cycle
technologies that are entering the market today, but could be fully-
recognized in our proposed HD Phase 2 certification procedures.
Examples of such technologies include predictive cruise control, 6x2
axles, axle lubricants, automated tire inflation systems, and air
conditioning efficiency improvements. For these technologies, the
agencies propose to define the effectiveness value of these
technologies similar to the approach taken in the MY2017-2025 light-
duty rule (see 77 FR 62832-62840 (October 15, 2012)). These default
effectiveness values could be used as valid inputs to Phase 2 GEM. The
proposed effectiveness value of each technology is discussed above in
Section III.D.2.
    The agencies also recognize that there are emerging technologies
today that are being developed, but would not be accounted for in the
GEM inputs, therefore would be considered off-cycle. These technologies
could include systems such as efficient steering systems, cooling fan
optimization, and further tractor-trailer integration. These off-cycle
technologies could include known, commercialized technologies if they
are not yet widely utilized in a particular heavy-duty sector
subcategory. Any credits for these technologies would need to be based
on real-world fuel consumption and GHG reductions that can be measured
with verifiable test methods using representative driving conditions
typical of the engine or vehicle application.
    The agencies propose that the approval for Phase 1 innovative
technology credits (approved prior to 2021 MY) would be carried into
the Phase 2 program on a limited basis for those technologies where the
benefit is not accounted for in the Phase 2 test procedure. Therefore,
the manufacturers would not be required to request new approval for any
innovative credits carried into the off-cycle program, but would have
to demonstrate the new cycle does not account for these improvements
beginning in the 2021 MY. The agencies believe this is appropriate
because technologies, such as those related to the transmission or
driveline, may no longer be ``off-cycle'' because of the addition of
these technologies into the Phase 2 version of GEM. The agencies also
seek comments on whether off-cycle technologies in the Phase 2 program
should be limited by infrequent common use and by what model years, if
any. We also seek comments on an appropriate penetration rate for a
technology not to be considered in common use.
    As in Phase 1, the agencies are proposing to continue to provide
two paths for approval of the test procedure to measure the
CO2 emissions and fuel consumption reductions of an off-
cycle technology used in the HD tractor. See proposed 40 CFR 1037.610
and 49 CFR 535.7. The first path would not require a public approval
process of the test method. A manufacturer could use ``pre-approved''
test methods for HD vehicles including the A-to-B chassis testing,
powerpack testing or on-road testing. A manufacturer may also use any
developed test procedure that has known quantifiable benefits. A test
plan detailing the testing methodology would be required to be approved
prior to collecting any test data. The agencies are also proposing to
continue the second path, which includes a public approval process of
any testing method that could have questionable benefits (i.e., an
unknown usage rate for a technology). Furthermore, the agencies are
proposing to modify their provisions to clarify what documentation must
be submitted for approval, which would align them with provisions in 40
CFR 86.1869-12. NHTSA and EPA are also proposing to prohibit credits
from technologies addressed by any of NHTSA's crash avoidance safety
rulemakings (i.e., congestion management systems). See 77 FR 62733
(discussing similar issues in the context of the light-duty fuel
economy and greenhouse gas reduction standards). We welcome
recommendations on how to improve or streamline the off-cycle
technology approval process.
(3) Post Useful Life Modifications
    Under 40 CFR part 1037, it is generally prohibited for any person
to remove or render inoperative any emission control device installed
to comply with the requirements of part 1037. However, in 40 CFR
1037.655 EPA clarifies that certain vehicle modifications are allowed
after a vehicle reaches the end of its regulatory useful life. This
section applies for all vehicles subject to 40 CFR part 1037 and would
thus apply for trailers regulated in Phase 2. EPA is proposing to
continue this provision and requests comment on it.
    This section states (as examples) that it is generally allowable to
remove tractor roof fairings after the end of the vehicle's useful life
if the vehicle will no longer be used primarily to pull box trailers,
or to remove other fairings if the vehicle will no longer be used
significantly on highways with vehicle speed of 55 miles per hour or
higher. More generally, this section clarifies that owners may modify a
vehicle for the purpose of reducing emissions, provided they have a
reasonable technical basis for knowing that such modification will not
increase emissions of any other pollutant. This essentially requires
the owner to have information that would lead an engineer or other
person familiar with engine and vehicle design and function to
reasonably believe that the modifications will not increase emissions
of any regulated pollutant. Thus, this provision does not provide a
blanket allowance for modifications after the useful life.
    This section also makes clear that no person may ever disable a
vehicle speed limiter prior to its expiration point, or remove
aerodynamic fairings from tractors that are used primarily to pull box
trailers on highways. It is also clear that this allowance does not
apply with

respect to engine modifications or recalibrations.
    This section does not apply with respect to modifications that
occur within the useful life period, other than to note that many such
modifications to the vehicle during the useful life and to the engine
at any time are presumed to violate 42 U.S.C. 7522(a)(3)(A). EPA notes,
however, that this is merely a presumption, and would not prohibit
modifications during the useful life where the owner clearly has a
reasonable technical basis for knowing that the modifications would not
cause the vehicle to exceed any applicable standard.
(4) Other Interim Provisions
    In HD Phase 1, EPA adopted provisions to delay the onboard
diagnostics (OBD) requirements for heavy-duty hybrid powertrains (see
40 CFR 86.010-18(q)). This provision delayed full OBD requirements for
hybrids until 2016 and 2017 model years. In discussion with
manufacturers during the development of Phase 2, the agencies have
learned that meeting the on-board diagnostic requirements for criteria
pollutant engine certification continues to be a potential impediment
to adoption of hybrid systems. See Section XIV.A.1 for a discussion of
regulatory changes proposed to reduce the non-GHG certification burden
for engines paired with hybrid powertrain systems.
(5) Phase 1 Flexibilities Not Proposed for Phase 2
    The Phase 1 advanced technology credits were adopted to promote the
implementation of advanced technologies, such as hybrid powertrains,
Rankine cycle engines, all-electric vehicles, and fuel cell vehicles
(see 40 CFR 1037.150(i)). As the agencies stated in the Phase 1 final
rule, the Phase 1 standards were not premised on the use of advanced
technologies but we expected these advanced technologies to be an
important part of the Phase 2 rulemaking (76 FR 57133, September 15,
2011). The proposed HD Phase 2 heavy-duty engine and tractor standards
are premised on the use of Rankine-cycle engines, therefore the
agencies believe it is no longer appropriate to provide extra credit
for this technology. While the agencies have not premised the proposed
HD Phase 2 tractor standards on hybrid powertrains, fuel cells, or
electric vehicles, we also foresee some limited use of these
technologies in 2021 and beyond. Therefore, we propose to not provide
advanced technology credits in Phase 2 for any technology, but we
welcome comments on the need for such incentive.
    Also in Phase 1, the agencies adopted early credits to create
incentives for manufacturers to introduce more efficient engines and
vehicles earlier than they otherwise would have planned to do (see 40
CFR 1037.150(a)). The agencies are not proposing to extend this
flexibility to Phase 2 because the ABT program from Phase 1 will be
available to manufacturers in 2020 model year and this would displace
the need for early credits.

IV. Trailers

    As mentioned in Section III, trailers pulled by Class 7 and 8
tractors (together considered ``tractor-trailers'') account for
approximately two-thirds of the heavy-duty sector's total
CO2 emissions and fuel consumption. Because neither trailers
nor the tractors that pull them are useful by themselves, it is the
combination of the tractor and the trailer that forms the useful
vehicle. Although trailers do not directly generate exhaust emissions
or consume fuels (except for the refrigeration units on refrigerated
trailers), their designs and operation nevertheless contribute
substantially to the CO2 emissions and diesel fuel
consumption of the tractors pulling them. See also Section I.E (1) and
(2) above.
    The agencies are proposing standards for trailers specifically
designed to be drawn by Class 7 and 8 tractors when coupled to the
tractor's fifth wheel. The agencies are not proposing standards for
trailers designed to be drawn by vehicles other than tractors, and
those that are coupled to vehicles with pintle hooks or hitches instead
of a fifth wheel. These proposed standards are expressed as
CO2 and fuel consumption standards, and would apply to each
trailer with respect to the emissions and fuel consumption that would
be expected for a specific standard type of tractor pulling such a
trailer. Note that this approach is discussed in more detail later.
Nevertheless, EPA and NHTSA believe it is appropriate to establish
standards for trailers separately from tractors because they are
separately manufactured by distinct companies; the agencies are not
aware of any manufacturers that currently assemble both the finished
tractor and the trailer.

A. Summary of Trailer Consideration in Phase 1

    In the Phase 1 program, the agencies did not regulate trailers, but
discussed how we might do so in the future (see 76 FR 57362). We chose
not to regulate trailers at that time, primarily because of the lack of
a proposed test procedure, as well as the technical and policy issues
at that time. The agencies also noted the large number of small
businesses in this industry, the possibility that regulations would
substantially impact these small businesses, and the agencies'
consequent obligations under the Small Business Regulatory Enforcement
Fairness Act.\202\ However, the agencies did indicate the potential
CO2 and fuel consumption benefits of including trailers in
the program and we committed to consider establishing standards for
trailers in future rulemakings.
---------------------------------------------------------------------------

    \202\ The Regulatory Flexibility Act (RFA), as amended by the
Small Business Regulatory Enforcement Fairness Act (SBREFA),
requires agencies to account for economic impacts of all rules that
may have a significant impact on a substantial number of small
businesses and in addition contains provisions specially applicable
to EPA requiring a multi-agency pre-proposal process involving
outreach and consultation with representatives of potentially
affected small businesses. See http://www.epa.gov/rfa/ for more
information. Note that for this Phase 2 proposal, EPA has completed
a Small Business Advocacy Review panel process that included small
trailer manufacturers, as discussed in XIV.C below.
---------------------------------------------------------------------------

    In the Phase 1 proposal, the agencies solicited general comments on
controlling CO2 emissions and fuel consumption through
future trailer regulations (see 75 FR 74345-74351). Although we neither
proposed nor finalized trailer regulations at that time, the agencies
have considered those comments in developing this proposal. This notice
proposes the first EPA regulations covering trailer manufacturers for
CO2 emissions (or any other emissions), and the first fuel
consumption regulations by NHTSA for these manufacturers. The agencies
intend for this program to be a unified national program so that when a
trailer model complies with EPA's standards it will also comply with
NHTSA's standards.

B. The Trailer Industry

(1) Industry Characterization
    The trailer industry encompasses a wide variety of trailer
applications and designs. Among these are box trailers (dry vans and
refrigerated vans of all sizes) and ``non-box'' trailers, including
platform (sometimes called ``flatbed''), tanker, container chassis,
bulk, dump, grain, and many specialized types of trailers, such as car
carriers, pole trailers, and logging trailers. Most trailers are
designed for predominant use on paved streets, roads, and highways
(called ``highway trailers'' for purposes of this proposed rule). A
relatively small number of trailers are designed for dedicated use in
logging and mining operations or for use in

applications that we expect would involve little or no time on paved
roadways. A more detailed description of the characteristics that
distinguish these trailers is included in Section IV.C.(5).
    The trailer manufacturing industry is very competitive, and
manufacturers are highly responsive to their customers' diverse
demands. The wide range of trailer designs and features reflects the
broad variety of customer needs, chief among them typically being the
ability to maximize the amount of freight the trailer can transport.
Other design goals reflect the numerous, more specialized customer
needs.
    Box trailers are the most common type of trailer and are made in
many different lengths, generally ranging from 28 feet to 53 feet.
While all have a rectangular shape, they can vary widely in basic
construction design (internal volume and weight), materials (steel,
fiberglass composites, aluminum, and wood) and the number and
configuration of axles (usually two axles closely spaced, but number
and spacing of axles can be greater). Box trailer designs may also
include additional features, such as one or more side doors, out-
swinging or roll-up rear doors, side or rear lift gates, and numerous
types of undercarriage accessories.
    Non-box trailers are uniquely designed to transport a specific type
of freight. Platform trailers carry cargo that may not be easily
contained within or loaded and unloaded into a box trailer, such as
large, nonuniform equipment or machine components. Tank trailers are
often pressure-tight enclosures designed to carry liquids, gases or
bulk, dry solids and semi-solids. There are also a number of other
specialized trailers such as grain, dump, automobile hauler, livestock
trailers, construction and heavy-hauling trailers.
    Chapter 1 of the Draft RIA includes a more thorough
characterization of the trailer industry. The agencies have considered
the variety of trailer designs and applications in developing the
proposed CO2 emissions and fuel consumption standards for
trailers.
(2) Historical Context for Proposed Trailer Provisions
(a) SmartWay Program
    EPA's voluntary SmartWay Transport Partnership program encourages
businesses to take actions that reduce fuel consumption and
CO2 emissions while cutting costs. See Section I.A.2.f
above. SmartWay staff work with the shipping, logistics, and carrier
communities to identify low carbon strategies and technologies across
their transportation supply chains. It is a voluntary, fleet-targeted
program that provides an objective ranking of a fleet's freight
efficiency relative to its competitors. SmartWay Partners commit to
adopting fuel-saving practices and technologies relative to a baseline
year as well as tracking their progress.
    EPA's SmartWay program has accelerated the availability and market
penetration of advanced, fuel efficient technologies and operational
practices. In conjunction with the SmartWay Partners Program, EPA
established a testing, verification, and designation program, the
SmartWay Technology Program, to help freight companies identify the
equipment, technologies, and strategies that save fuel and lower
emissions. SmartWay verifies the performance of aerodynamic equipment
and low rolling resistance tires and maintains a list of verified
technologies on its Web site. The trailer aerodynamic technologies
verified are grouped in bins that represent one percent, four percent,
or five percent fuel savings relative to a typical long-haul tractor-
trailer at 65-mph cruise conditions. Historically, use of verified
aerodynamic devices totaling at least five percent fuel savings, along
with verified tires, qualifies a 53-foot dry van trailer for the
``SmartWay Trailer'' designation. In 2014, EPA expanded the program to
qualify trailers as ``SmartWay Elite'' if they use verified tires and
aerodynamic equipment providing nine percent or greater fuel savings.
The 2014 updates also expanded the SmartWay-designated trailer
eligibility to include 53-foot refrigerated van trailers in addition to
53-foot dry van trailers.
    The SmartWay Technology Program continues to improve the technical
quality of data that EPA and stakeholders need for verification. EPA
bases its SmartWay verifications on common industry test methods using
SmartWay-specified testing protocols. Historically, SmartWay's
aerodynamic equipment verification was performed using the SAE J1321
test procedure, which measures fuel consumption as the test vehicle
drives laps around a test track. Under SmartWay's 2014 updates, EPA
expanded its trailer designation and equipment verification programs to
allow additional testing options. The updates included a new, more
stringent 2014 track test protocol based on SAE's 2012 update to its
SAE J1321 test method,\203\ as well as protocols for wind tunnel,
coastdown, and possibly computational fluid dynamics (CFD) approaches.
These new protocols are based on stakeholder input, the latest industry
standards (i.e., 2012 versions of the SAE fuel consumption and wind
tunnel test \204\ methods), EPA's own testing and research, and lessons
learned from years of implementing technology verification programs.
Wind tunnel, coastdown, and CFD testing produce values for aerodynamic
drag improvements in terms of coefficient of drag (CD),
which is then related to projected fuel savings using a mathematical
curve.\205\
---------------------------------------------------------------------------

    \203\ SAE International, Fuel Consumption Test Procedure--Type
II. SAE Standard J1321. Revised 2012-02-06. Available at: http://standards.sae.org/j1321_201202/.
    \204\ SAE International. Wind Tunnel Test Procedure for Trucks
and Buses. SAE Standard J1252. Revised 2012-07-16. Available at:
http://standards.sae.org/j1252_201207/.
    \205\ McCallen, R., et al. Progress in Reducing Aerodynamic Drag
for Higher Efficiency of Heavy Duty Trucks (Class 7-8). SAE
Technical Paper. 1999-01-2238.
---------------------------------------------------------------------------

    SmartWay verifies tires based on test data submitted by tire
manufacturers demonstrating the coefficient of rolling resistance
(CRR) of their tires using either the SAE J1269 or ISO 28580
test methods. These verified tires have rolling resistance targets for
each axle position on the tractor-trailer. SmartWay-verified trailer
tires achieve a CRR of 5.1 kg/metric ton or less on the
ISO28580 test method. An operator who replaces the trailer tires with
SmartWay-verified tires can expect fuel consumption savings of one
percent or more at a 65-mph cruise. Operators who apply SmartWay-
verified tires on both the trailer and tractor can achieve three
percent fuel consumption savings at 65-mph.
    Over the last decade, SmartWay partners have demonstrated
measureable fuel consumption benefits by adding aerodynamic features
and low rolling resistance tires to their 53-foot dry van trailers. To
date, SmartWay has verified over 70 technologies, including nine
packages from five manufacturers that have received the Elite
designation. The SmartWay Transport program has worked with over 3,000
partners, the majority of which are trucking fleets, and broadly
throughout the supply-chain industry, since 2004. These relationships,
combined with the Technology Program's extensive involvement in the HD
vehicle technology industry, have provided EPA with significant
experience in freight fuel efficiency. Furthermore, the more than 10-
year duration of the voluntary SmartWay Transport Partnership has
resulted in significant fleet and manufacturer experience with
innovating and deploying technologies

that reduce CO2 emissions and fuel consumption.
(b) California Tractor-Trailer Greenhouse Gas Regulation
    The state of California passed the Global Warming Solutions Act of
2006 (Assembly Bill 32, or AB32), enacting the state's 2020 greenhouse
gas emissions reduction goal into law. Pursuant to this Act, the
California Air Resource Board (CARB) was required to begin developing
early actions to reduce GHG emissions. As a part of a larger effort to
comply with AB32, the California Air Resource Board issued a regulation
entitled ``Heavy-Duty Greenhouse Gas Emission Reduction Regulation'' in
December 2008.
    This regulation reduces GHG emissions by requiring improvement in
the efficiency of heavy-duty tractors and 53 foot or longer dry and
refrigerated box trailers that operate in California.\206\ The program
is being phased in between 2010 and 2020. Small fleets have been
allowed special compliance opportunities to phase in the retrofits of
their existing trailer fleets through 2017. The regulation requires
affected trailer fleet owners to either use SmartWay-verified trailers
or to retrofit trailers with SmartWay-verified technologies. The
efficiency improvements are achieved through the use of aerodynamic
equipment and low rolling resistance tires on both the tractor and
trailer. EPA has granted a waiver for this California program.\207\
---------------------------------------------------------------------------

    \206\ Recently, in December 2013, ARB adopted regulations that
establish its own parallel Phase 1 program with standards consistent
with the EPA Phase 1 tractor standards. On December 5, 2014
California's Office of Administrative Law approved ARB's adoption of
the Phase 1 standards, with an effective date of December 5, 2014.
    \207\ See EPA's waiver of CARB's heavy-duty tractor-trailer
greenhouse gas regulation applicable to new 2011 through 2013 model
year Class 8 tractors equipped with integrated sleeper berths
(sleeper-cab tractors) and 2011 and subsequent model year dry-can
and refrigerated-van trailers that are pulled by such tractors on
California highways at 79 FR 46256 (August 7, 2014).
---------------------------------------------------------------------------

(c) NHTSA Safety-Related Regulations for Trailers and Tires
    NHTSA regulates new trailer safety through regulations. Table IV-1
lists the current regulations in place related to trailers. Trailer
manufacturers will continue to be required to meet current safety
regulations for the trailers they produce. We welcome any comments on
additional regulations that are not included and particularly those
that may be incompatible with the regulations outlined in this
proposal.
    FMVSS Nos. 223 and 224 \208\ require installation of rear guard
protection on trailers. The definition of rear extremity of the trailer
in 223 limits installation of rear fairings to a specified zone behind
the trailer. The agencies request comment on any issues associated with
installing potential boat tails or other rear aerodynamic fairings that
would be more effective than current designs, given the current
definition of trailer rear extremity in FMVSS 223.
---------------------------------------------------------------------------

    \208\ 49 CFR 571.223, 224.

 Table IV--1 Current NHTSA Statutes and Regulations Related to Trailers
------------------------------------------------------------------------
               Reference                              Title
------------------------------------------------------------------------
49 CFR 565.............................  Vehicle Identification Number
                                          (VIN) Requirements.
49 CFR 566.............................  Manufacturer Identification.
49 CFR 567.............................  Certification.
49 CFR 568.............................  Vehicles Manufactured in Two or
                                          More Stages.
49 CFR 569.............................  Regrooved Tires.
49 CFR 571.............................  Federal Motor Vehicle Safety
                                          Standards.
49 CFR 573.............................  Defect and Noncompliance
                                          Responsibility and Reports.
49 CFR 574.............................  Tire Identification and
                                          Recordkeeping.
49 CFR 575.............................  Consumer Information.
49 CFR 576.............................  Record Retention.
------------------------------------------------------------------------

(d) Additional DOT Regulations Related to Trailers
    In addition to NHTSA's regulations, DOT's Federal Highway
Administration (FHWA) regulates the weight and dimensions of motor
vehicles on the National Network.\209\ FHWA's regulations limit states
from setting truck size and weight limits beyond certain ranges for
vehicles used on the National Network. Specifically, vehicle weight and
truck tractor-semitrailer length and width are limited by FHWA.\210\
EPA and NHTSA do not anticipate any conflicts between FHWA's
regulations and those proposed in this rulemaking.
---------------------------------------------------------------------------

    \209\ 23 CFR 658.9.
    \210\ 23 CFR part 658.
---------------------------------------------------------------------------

(3) Agencies' Outreach in Developing This Proposal
    In developing this proposed rule, EPA and NHTSA staff met and
consulted with a wide range of organizations that have an interest in
trailer regulations. Staff from both agencies met representatives of
the Truck Trailer Manufacturers Association, the National Trailer
Dealers Association, and the American Trucking Association, including
their Fuel Efficiency Advisory Committee and their Technology and
Maintenance Council. We also met with and visited the facilities of
several individual trailer manufacturers, trailer aerodynamic device
manufacturing companies, and trailer tire manufacturers, as well as
visited an aerodynamic wind tunnel test facility and two independent
tire testing facilities. The agencies consulted with representatives
from California Air Resources Board, the International Council on Clean
Transportation, the North American Council for Freight Efficiency, and
several environmental NGOs.
    In addition to these informal meetings, and as noted above, EPA
also conducted several outreach meetings with representatives from
small business trailer manufacturers as required under section 609(b)
of the Regulatory Flexibility Act (RFA) and amended by the Small
Business Regulatory Enforcement Fairness Act of 1996 (SBREFA). EPA
convened a Small Business Advocacy Review (SBAR) Panel, and additional
information regarding the findings and recommendations of the Panel are
available in Section XIV below and in the Panel's final report.\211\
EPA worked with NHTSA to propose flexibilities in response to EPA's
SBAR Panel (as outlined in Section IV. F(6)(f) with more detail
provided in Chapter 12 of the draft RIA). We welcome comments from all
entities and the public to all aspects of this proposal.
---------------------------------------------------------------------------

    \211\ Final Report of the Small Business Advocacy Review Panel
on EPA's Planned Proposed Rule: Greenhouse Gas Emissions and Fuel
Efficiency Standards for Medium- and Heavy-Duty Engines and
Vehicles: Phase 2, January 15, 2015.
---------------------------------------------------------------------------

C. Proposed Phase 2 Trailer Standards

    This proposed rule proposes, for the first time, a set of
CO2 emission and fuel consumption standards for
manufacturers of new trailers that would phase in over a period of nine
years and continue to reduce CO2 emissions and fuel
consumption in the years to follow. The proposed standards are
expressed as overall CO2 emissions and fuel consumption
performance standards considering the trailer as an integral part of
the tractor-trailer vehicle.
    The agencies are proposing trailer standards that we believe well
implement our respective statutory obligations. The agencies believe
that a proposed set of standards with similar stringencies, but less
lead-time (referred to as ``Alternative 4'' and discussed in more
detail later) has the potential to be the maximum feasible alternative
within the meaning of section 32902 (k) of EISA, and appropriate under
EPA's CAA authority (sections 202 (a)(1) and (2)). However, based on
the evidence

currently before us, EPA and NHTSA have outstanding questions regarding
relative risks and benefits of Alternative 4 due to the timeframe
envisioned by that alternative. The proposed alternative (referred to
as ``Alternative 3'' and discussed in more detail later) is generally
designed to achieve the levels of fuel consumption and GHG reduction
that Alternative 4 would achieve, but with several years of additional
lead-time. Put another way, the Alternative 3 standards would result in
the same stringency as the Alternative 4 standards, but several years
later, meaning that manufacturers could, in theory apply new technology
at a more gradual pace and with greater flexibility. Additional lead-
time will also provide for a more gradual implementation of full
compliance program, which could be especially helpful for this newly-
regulated trailer industry. It is possible that the agencies could
adopt, in full or in part, stringencies from Alternative 4 in the final
rule. The agencies seek comment on the lead-time and market penetration
in these alternatives.
    The agencies are not proposing standards for CO2
emissions and fuel consumption from the transport refrigeration units
(TRUs) used on refrigerated box trailers. Additionally, EPA is not
proposing standards for hydrofluorocarbon (HFC) emissions from TRUs.
See Section IV.C.(4)
    It is worth noting that the proposed standards for box trailers are
based in part on the expectation that the proposed program would allow
emissions averaging. However, as discussed in Section IV.F. below,
given the specific structure and competitive nature of the trailer
industry, we request comment on the advantages and disadvantages of
implementing the proposed standards without an averaging program.
Commenters addressing the stringency of the proposed standards are
encouraged to address stringency in the context of compliance programs
with and without averaging.
(1) Trailer Designs Covered by This Proposed Rule
    As described previously, the trailer industry produces many
different trailer designs for many different applications. The agencies
are proposing standards for a majority of these trailers. Note that
these proposed regulations apply to trailers designed for being drawn
by a tractor when coupled to the tractor's fifth wheel. As described in
detail in Section IV.C below, the agencies are proposing standards that
would phase in between MY 2018 and 2027; the NHTSA standards would be
voluntary until MY 2021. The proposed standards would apply to most
types of trailers. For most box trailers, these standards would be
based on the use of various technologies to improve aerodynamic
performance, and on improved tire efficiency through low rolling
resistance tires and use of automatic tire inflation (ATI) systems. As
discussed below, the agencies have identified some trailers with
characteristics that limit the aerodynamics that can be applied, and
are proposing reduced the stringencies for those trailer types. As
described in Sections IV.D.(1)(d) and (2)(d) below, although
manufacturers can reduce trailer weight to reduce fuel costs by
reducing trailer weight, these standards are not predicated on weight
reduction for the industry.
    The most comprehensive set of proposed requirements would apply to
long box trailers, which include refrigerated and non-refrigerated
(dry) vans. Long box trailers are the largest trailer category and are
typically paired with high roof cab tractors that have high annual
vehicle miles traveled (VMT) and high average speeds, and therefore
offer the greatest potential for CO2 and fuel consumption
reductions. Many of the aerodynamic and tire technologies considered
for long box trailers in this proposal are similar to those used in
EPA's SmartWay program and required by California's Heavy-Duty
Greenhouse Gas Emission Reduction Regulation. Many manufacturers and
operators of box trailers have experience with these CO2-
and fuel consumption-reducing technologies. In addition to SmartWay
partners and those fleets affected by the California regulation, many
operators also seek such technologies in response to high fuel prices
and the prospect of improved fuel efficiency. As a result, more data
about the performance of these technologies exist for long box trailers
than for other trailer types. Short box vans do not have the benefit of
programs such as SmartWay to provide an incentive for development of
and a reliable evaluation and promotion of CO2- and fuel
consumption-reducing technologies for their trailers. In addition,
short box trailers are more frequently used in short-haul and urban
operations, which may limit the potential effectiveness of these
technologies. As such, EPA is proposing less stringent requirements for
manufacturers of short box trailers.
    Some trailer designs include features that can affect the
practicality or the effectiveness of devices that manufacturers may
consider to lower their CO2 emissions and fuel consumption.
We are proposing to recognize box trailers that are restricted from
using aerodynamic devices in one location on the trailer as ``partial-
aero'' box trailers.\212\ The proposed standards for these trailers are
based on the proposed standards for full-aero box-trailers, but would
be less stringent than when the program is fully phased in.
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    \212\ Examples of types of work-performing components,
equipment, or designs that the agencies might consider as warranting
recognition as partial-aero or non-aero trailers include side or end
lift gates, belly boxes, pull-out platforms or steps for side door
access, and drop-deck designs. See 40 CFR 1037.107 and 49 CFR
535.5(e).
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    We propose that box trailers that have work-performing devices in
two locations such that they inhibit the use of all practical
aerodynamic devices be considered ``non-aero'' box trailers in this
proposal. The proposed standards for non-aero box trailers are
predicated on the use of tire technologies--lower rolling resistance
tires and ATI. We are proposing similar standards for non-box trailers
(including applications such as dump trailers and agricultural trailers
that are designed to be used both on and off the highway).
    We are proposing to completely exclude several types of trailers
from this trailer program. These excluded trailers would include those
designed for dedicated in-field operations related to logging and
mining. In addition, we are proposing to exclude heavy-haul trailers
and trailers the primary function of which is performed while they are
stationary. For all of these excluded trailers, manufacturers would not
have any regulatory requirements under this program, and would not be
subject to the proposed trailer compliance requirements. We seek
comment on the appropriateness of excluding these types of trailers
from the proposed trailer program and whether other trailer designs
should be excluded. Section IV. C. (5) discusses these trailer types we
propose to exclude and the physical characteristics that would define
these trailers.
    In summary, the agencies are proposing separate standards for ten
trailer subcategories:

--Long box (longer than 50 feet \213\) dry vans
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    \213\ Most long trailers are 53 feet in length; we are proposing
a cut-point of 50 feet to avoid an unintended incentive for an OEM
to slightly shorten a trailer design in order to avoid the new
regulatory requirements.
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--Long box (longer than 50 feet) refrigerated vans
--Short box (50 feet and shorter) dry vans
--Short box (50 feet and shorter) refrigerated vans
--Partial-aero long box dry vans
--Partial-aero long box refrigerated vans
--Partial-aero short box dry vans

--Partial-aero short box refrigerated vans
--Non-aero box vans (all lengths of dry and refrigerated vans)
--Non-box trailers (tanker, platform, container chassis, and all other
types of highway trailers that are not box trailers)

    As discussed in the next section, partial-aero box trailers would
have the same standards as their corresponding full-aero trailers in
the early phase-in years, and would have separate, less stringent
standards as the program is fully implemented. Section IV. C. (5)
introduces these proposed partial-aero trailer standards and Section
IV. D. describes the technologies that could be applied to meet these
proposed standards.
(2) Proposed Fuel Consumption and CO2 Standards
    As described in previously, it is the combination of the tractor
and the trailer that form the useful vehicle, and trailer designs
substantially affect the CO2 emissions and diesel fuel
consumption of the tractors pulling them. Note that although the
agencies are proposing new CO2 and fuel consumption
standards for trailers separately from tractors, we set the numerical
level of the trailer standards (see Section IV.D below) in relation to
``standard'' reference tractors in recognition of their
interrelatedness. In other words, the regulatory standards refer to the
simulated emissions and fuel consumption of a standard tractor pulling
the trailer being certified.
    The agencies project that these proposed standards, when fully
implemented in MY (model year) 2027, would achieve fuel consumption and
CO2 emissions reductions of three to eight percent,
depending on trailer subcategory. These projected reductions assume a
degree of technology adoption into the future absent the proposed
program and are evaluated on a weighted drive cycle (see Section IV. D.
(3) . We expect that the MY 2027 standards would be met with high-
performing aerodynamic and tire technologies largely available in the
marketplace today. With a lead-time of more than 10 years, the agencies
believe that both trailer construction and bolt-on CO2- and
fuel consumption-reducing technologies will advance well beyond the
performance of their current counterparts that exist today. A
description of technologies that the agencies considered for this
proposal is provided in Section IV. D.
    The agencies designed this proposed trailer program to ensure a
gradual progression of both stringency and compliance requirements in
order to limit the impact on this newly-regulated industry. The
agencies are proposing progressively more stringent standards in three-
year stages leading up to the MY 2027.\214\ The agencies are proposing
several options to reduce compliance burden (see Section IV. F.) in the
early years as the industry gains experience with the program. EPA is
proposing to initiate its program in 2018 with modest standards for
long box dry and refrigerated vans that can be met with common
SmartWay-verified aerodynamic and tire technologies. In this early
stage, we expect that manufacturers of the other trailer subcategories
would meet those standards by using tire technologies only. Standards
that we propose for the next stages, which we propose to begin in MY
2021, MY 2024, and MY 2027, would gradually increase in stringency for
each subcategory, including the introduction of standards for shorter
box vans that we expect would be met by applying both aerodynamic and
tire technologies. NHTSA's regulations would be voluntary until MY 2021
as described in Section IV. C. (3).
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    \214\ These stages are consistent with NHTSA's stability
requirements under EISA.
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    Table IV-2 below presents the CO2 and fuel consumption
phase-in standards, beginning in MY 2018 that the agencies are
proposing for trailers. The standards are expressed in grams of
CO2 per ton-mile and gallons of fuel per 1,000 ton-miles to
reflect the load-carrying capacity of the trailers. Partial-aero
trailers would be subject to the same standards as their corresponding
``full aero'' trailers for MY 2018 through MY 2026. In MY 2027 and the
years to follow, partial-aero trailers would continue to meet the
standards for MY 2024.
    The agencies are not proposing CO2 or fuel consumption
standards predicated on aerodynamic improvements for non-box trailers
or non-aero box vans at any stage of this proposed program. Instead, we
are proposing design standards that would require manufacturers of
these trailers to adopt specific tire technologies and thus to comply
without aerodynamic devices. We believe that this approach would
significantly limit the compliance burden for these manufacturers and
request comment on this provision.\215\
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    \215\ The agencies are not proposing provisions to allow
averaging for non-box trailers, non-aero box trailers, or partial-
aero box trailers, and this reduced flexibility would likely have
the effect of requiring compliant tire technologies to be used.

                Table IV-2--Proposed Trailer CO2 and Fuel Consumption Standards for Box Trailers
----------------------------------------------------------------------------------------------------------------
                                   Subcategory                Dry van                    Refrigerated van
          Model year           ---------------------------------------------------------------------------------
                                     Length            Long            Short           Long            Short
----------------------------------------------------------------------------------------------------------------
2018-2020.....................  EPA Standard....              83             144              84             147
                                (CO2 Grams per
                                 Ton-Mile).
                                Voluntary NHTSA           8.1532         14.1454          8.2515         14.4401
                                 Standard.
                                (Gallons per
                                 1,000 Ton-Mile).
2021-2023.....................  EPA Standard....              81             142              82             146
                                (CO2 Grams per
                                 Ton-Mile).
                                NHTSA Standard..          7.9568         13.9489          8.0550         14.3418
                                (Gallons per
                                 1,000 Ton-Mile).
2024-2026.....................  EPA Standard....              79             141              81             144
                                (CO2 Grams per
                                 Ton-Mile).
                                NHTSA Standard..          7.7603         13.8507          7.9568         14.1454
                                (Gallons per
                                 1,000 Ton-Mile).
2027 +........................  EPA Standard....              77             140              80             144
                                (CO2 Grams per
                                 Ton-Mile).
                                NHTSA Standard..          7.5639         13.7525          7.8585         14.1454
                                (Gallons per
                                 1,000 Ton-Mile).
----------------------------------------------------------------------------------------------------------------

    Differences in the numerical values of these standards among
trailer subcategories are due to differences in the tractor-trailer
characteristics, as well as differences in the default payloads, in the