Level 3.........................................              0%              0%              0%              0%
----------------------------------------------------------------------------------------------------------------
                                                  Transmission
----------------------------------------------------------------------------------------------------------------
AMT.............................................             40%             40%             40%             40%
Automatic with Neutral Idle.....................             10%             10%             10%             10%
DCT.............................................              5%              5%              5%              5%
----------------------------------------------------------------------------------------------------------------
                                               Other Technologies
----------------------------------------------------------------------------------------------------------------
Adjustable AESS w/Diesel APU....................             N/A             N/A             30%             30%
Adjustable AESS w/Battery APU...................             N/A             N/A             10%             10%
Adjustable AESS w/Automatic Stop-Start..........             N/A             N/A             10%             10%
Adjustable AESS w/FOH Cold, Main Engine Warm....             N/A             N/A             10%             10%
Adjustable AESS programmed to 5 minutes.........             N/A             N/A             40%             40%
Transmission Efficiency.........................             20%             20%             20%             20%
Axle Efficiency.................................             30%             30%             30%             30%
Predictive Cruise Control.......................             20%             20%             20%             20%
Accessory Improvements..........................             10%             10%             10%             10%
Air Conditioner Efficiency Improvements.........             10%             10%             10%             10%
Automatic Tire Inflation Systems................             20%             20%             20%             20%
Tire Pressure Monitoring System.................             20%             20%             20%             20%
----------------------------------------------------------------------------------------------------------------

(f) Derivation of the Final Phase 2 Tractor Standards
    The agencies used the technology effectiveness inputs and
technology adoption rates to develop GEM inputs to derive the HD Phase
2 fuel consumption and CO2 emissions standards for each
subcategory of Class 7 and 8 combination tractors. Note that we have
analyzed one technology pathway for each level of stringency, but
manufacturers will be free to use any combination of technology to meet
the standards, as well as the flexibility of averaging, banking and
trading, to meet the standard on average. The agencies derived a
scenario tractor for each subcategory by weighting the individual GEM
input parameters included in Table III-7 with the adoption rates in
Table III-8 through Table III-10. For example, the CdA value
for a 2021 MY Class 8 Sleeper Cab High Roof scenario case was derived
as 60 percent times 5.95 plus 30 percent times 5.40 plus 10 percent
times 4.90, which is equal to a CdA of 5.68 m\2\. Similar
calculations were made for tire rolling resistance, transmission types,
idle reduction, and other technologies. The agencies developed fuel
maps that achieved the CO2 emissions and fuel consumption
reductions described in Section III.D.1.b. The agencies then ran GEM
with a single set of vehicle inputs, as shown in Table III-18 through
Table III-21, to derive the final standards for each subcategory.
Additional detail is provided in the RIA Chapter 2.8.4.

                                     Table III-18--GEM Inputs for the 2021 MY Class 7 and 8 Tractor Standard Setting
--------------------------------------------------------------------------------------------------------------------------------------------------------
                      Class 7                                                                      Class 8
--------------------------------------------------------------------------------------------------------------------------------------------------------
                      Day cab                                            Day cab                                          Sleeper cab
--------------------------------------------------------------------------------------------------------------------------------------------------------
    Low roof          Mid roof        High roof         Low roof         Mid roof        High roof         Low roof         Mid roof        High roof
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                         Engine
--------------------------------------------------------------------------------------------------------------------------------------------------------
2021 MY 11L         2021 MY 11L      2021 MY 11L      2021 MY 15L      2021 MY 15L      2021 MY 15L      2021 MY 15L      2021 MY 15L      2021 MY 15L
 Engine 350 HP     Engine 350 HP    Engine 350 HP    Engine 455 HP    Engine 455 HP    Engine 455 HP    Engine 455 HP    Engine 455 HP    Engine 455 HP
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                               Aerodynamics (CdA in m\2\)
--------------------------------------------------------------------------------------------------------------------------------------------------------
         5.24             6.33             6.01             5.24             6.33             6.01             5.24             6.33             5.68
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                           Steer Tires (CRR in kg/metric ton)
--------------------------------------------------------------------------------------------------------------------------------------------------------
          6.0              6.0              6.0              6.0              6.0              6.0              6.0              6.0              6.0
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                           Drive Tires (CRR in kg/metric ton)
--------------------------------------------------------------------------------------------------------------------------------------------------------
          6.6              6.6              6.3              6.6              6.6              6.3              6.6              6.6              6.3
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                     Extended Idle Reduction Weighted Effectiveness
--------------------------------------------------------------------------------------------------------------------------------------------------------
          N/A              N/A              N/A              N/A              N/A              N/A             2.3%             2.3%             2.3%
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                       Transmission = 10 speed Manual Transmission
                                        Gear Ratios = 12.8, 9.25, 6.76, 4.90, 3.58, 2.61, 1.89, 1.38, 1.00, 0.73
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                               Drive Axle Ratio = 3.36 for day cabs, 3.31 for sleeper cabs
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                             6x2 Axle Weighted Effectiveness
--------------------------------------------------------------------------------------------------------------------------------------------------------
          N/A              N/A              N/A             0.3%             0.3%             0.3%             0.3%             0.3%             0.3%
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                     Transmission Type Weighted Effectiveness = 1.1%
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                           Neutral Idle Weighted Effectiveness
--------------------------------------------------------------------------------------------------------------------------------------------------------
         0.1%             0.1%             0.1%             0.1%             0.1%             0.1%            0.02%            0.02%            0.02%
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                       Direct Drive Weighted Effectiveness = 0.4%
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                  Transmission Efficiency Weighted Effectiveness = 0.2%
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                           Axle Efficiency Improvement = 0.6%
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                     Air Conditioner Efficiency Improvements = 0.1%
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                              Accessory Improvements = 0.1%
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                            Predictive Cruise Control = 0.4%
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                         Automatic Tire Inflation Systems = 0.3%
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                         Tire Pressure Monitoring System = 0.2%
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                             Phase 1 Credit Carry-over = 1%
--------------------------------------------------------------------------------------------------------------------------------------------------------

                                     Table III-19--GEM Inputs for the 2024 MY Class 7 and 8 Tractor Standard Setting
--------------------------------------------------------------------------------------------------------------------------------------------------------
                      Class 7                                                                      Class 8
--------------------------------------------------------------------------------------------------------------------------------------------------------
                      Day cab                                            Day cab                                          Sleeper cab
--------------------------------------------------------------------------------------------------------------------------------------------------------
    Low roof          Mid roof        High roof         Low roof         Mid roof        High roof         Low roof         Mid roof        High roof
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                         Engine
--------------------------------------------------------------------------------------------------------------------------------------------------------
2024 MY 11L        2024 MY 11L      2024 MY 11L      2024 MY 15L      2024 MY 15L      2024 MY 15L      2024 MY 15L      2024 MY 15L      2024 MY 15L
 Engine 350 HP    Engine 350 HP    Engine 350 HP    Engine 455 HP    Engine 455 HP    Engine 455 HP    Engine 455 HP    Engine 455 HP    Engine 455 HP
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                               Aerodynamics (CdA in m\2\)
--------------------------------------------------------------------------------------------------------------------------------------------------------
         5.16             6.25             5.82             5.16             6.25             5.82             5.16             6.25             5.52
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                           Steer Tires (CRR in kg/metric ton)
--------------------------------------------------------------------------------------------------------------------------------------------------------
          5.9              5.9              5.8              5.9              5.9              5.8              5.9              5.9              5.8
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                           Drive Tires (CRR in kg/metric ton)
--------------------------------------------------------------------------------------------------------------------------------------------------------
          6.4              6.4              6.0              6.4              6.4              6.0              6.4              6.4              6.0
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                     Extended Idle Reduction Weighted Effectiveness
--------------------------------------------------------------------------------------------------------------------------------------------------------
          N/A              N/A              N/A              N/A              N/A              N/A             2.5%             2.5%             2.5%
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                       Transmission = 10 speed Manual Transmission
                                        Gear Ratios = 12.8, 9.25, 6.76, 4.90, 3.58, 2.61, 1.89, 1.38, 1.00, 0.73
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                               Drive Axle Ratio = 3.31 for day cabs, 3.26 for sleeper cabs
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                             6x2 Axle Weighted Effectiveness
--------------------------------------------------------------------------------------------------------------------------------------------------------
          N/A              N/A              N/A             0.5%             0.5%             0.5%             0.5%             0.5%             0.5%
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                     Transmission Type Weighted Effectiveness = 1.6%
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                           Neutral Idle Weighted Effectiveness
--------------------------------------------------------------------------------------------------------------------------------------------------------
         0.2%             0.2%             0.2%             0.2%             0.2%             0.2%            0.03%            0.03%            0.03%
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                       Direct Drive Weighted Effectiveness = 1.0%
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                  Transmission Efficiency Weighted Effectiveness = 0.4%
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                           Axle Efficiency Improvement = 1.3%
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                     Air Conditioner Efficiency Improvements = 0.1%
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                              Accessory Improvements = 0.2%
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                            Predictive Cruise Control = 0.8%
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                Automatic Tire Inflation
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                         Tire Pressure Monitoring System = 0.5%
--------------------------------------------------------------------------------------------------------------------------------------------------------

                                     Table III-20--GEM Inputs for the 2027 MY Class 7 and 8 Tractor Standard Setting
--------------------------------------------------------------------------------------------------------------------------------------------------------
                      Class 7                                                                      Class 8
--------------------------------------------------------------------------------------------------------------------------------------------------------
                      Day cab                                            Day cab                                          Sleeper cab
--------------------------------------------------------------------------------------------------------------------------------------------------------
    Low roof          Mid roof        High roof         Low roof         Mid roof        High roof         Low roof         Mid roof        High roof
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                         Engine
--------------------------------------------------------------------------------------------------------------------------------------------------------
2027 MY 11L        2027 MY 11L      2027 MY 11L      2027 MY 15L      2027 MY 15L      2027 MY 15L      2027 MY 15L      2027 MY 15L      2027 MY 15L
 Engine 350 HP    Engine 350 HP    Engine 350 HP    Engine 455 HP    Engine 455 HP    Engine 455 HP    Engine 455 HP    Engine 455 HP    Engine 455 HP
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                               Aerodynamics (CdA in m\2\)
--------------------------------------------------------------------------------------------------------------------------------------------------------
         5.12             6.21             5.67             5.12             6.21             5.67             5.08             6.21             5.26
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                           Steer Tires (CRR in kg/metric ton)
--------------------------------------------------------------------------------------------------------------------------------------------------------
          5.8              5.8              5.6              5.8              5.8              5.6              5.8              5.8              5.6
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                           Drive Tires (CRR in kg/metric ton)
--------------------------------------------------------------------------------------------------------------------------------------------------------
          6.2              6.2              5.8              6.2              6.2              5.8              6.2              6.2              5.8
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                     Extended Idle Reduction Weighted Effectiveness
--------------------------------------------------------------------------------------------------------------------------------------------------------
          N/A              N/A              N/A              N/A              N/A              N/A               3%               3%               3%
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                       Transmission = 10 speed Manual Transmission
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                        Gear Ratios = 12.8, 9.25, 6.76, 4.90, 3.58, 2.61, 1.89, 1.38, 1.00, 0.73
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                               Drive Axle Ratio = 3.21 for day cabs, 3.16 for sleeper cabs
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                             6x2 Axle Weighted Effectiveness
--------------------------------------------------------------------------------------------------------------------------------------------------------
          N/A              N/A              N/A             0.6%             0.6%             0.6%             0.6%             0.6%             0.6%
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                     Transmission Type Weighted Effectiveness = 1.6%
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                           Neutral Idle Weighted Effectiveness
--------------------------------------------------------------------------------------------------------------------------------------------------------
         0.2%             0.2%             0.2%             0.2%             0.2%             0.2%            0.03%            0.03%            0.03%
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                       Direct Drive Weighted Effectiveness = 1.0%
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                  Transmission Efficiency Weighted Effectiveness = 0.7%
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                           Axle Efficiency Improvement = 1.6%
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                     Air Conditioner Efficiency Improvements = 0.3%
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                              Accessory Improvements = 0.2%
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                            Predictive Cruise Control = 0.8%
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                         Automatic Tire Inflation Systems = 0.4%
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                         Tire Pressure Monitoring System = 0.7%
--------------------------------------------------------------------------------------------------------------------------------------------------------

 Table III-21--GEM Inputs for 2021, 2024 and 2027 MY Heavy-Haul Tractor
                                Standards
------------------------------------------------------------------------
           2021 MY                   2024 MY               2027 MY
------------------------------------------------------------------------
Engine = 2021 MY 15L Engine   Engine = 2024 MY 15L  Engine = 2027 MY 15L
 with 600 HP.                  Engine with 600 HP.   Engine with 600 HP.
------------------------------------------------------------------------
                    Aerodynamics (CdA in m\2\) = 5.00
------------------------------------------------------------------------
Steer Tires (CRR in kg/       Steer Tires (CRR in   Steer Tires (CRR in
 metric ton) = 6.2.            kg/metric ton) =      kg/metric ton) =
                               6.0.                  5.8.
Drive Tires (CRR in kg/       Drive Tires (CRR in   Drive Tires (CRR in
 metric ton) = 6.6.            kg/metric ton) =      kg/metric ton) =
                               6.4.                  6.2.
Transmission = 18 speed       Transmission = 18     Transmission = 18
 Manual Transmission.          speed Manual          speed Manual
                               Transmission.         Transmission.
Drive axle Ratio = 3.70.....  Drive axle Ratio =    Drive axle Ratio =
                               3.70.                 3.70.
6x2 Axle Weighted             6x2 Axle Weighted     6x2 Axle Weighted
 Effectiveness = 0%.           Effectiveness = 0%.   Effectiveness = 0%.
Transmission benefit = 1.1%.  Transmission benefit  Transmission benefit
                               = 1.8%.               = 1.8%.

Transmission Efficiency =     Transmission          Transmission
 0.2%.                         Efficiency = 0.4%.    Efficiency = 0.7%.
Axle Efficiency = 0.3%......  Axle Efficiency =     Axle Efficiency =
                               0.7%.                 1.6%.
Predictive Cruise Control =   Predictive Cruise     Predictive Cruise
 0.4%.                         Control = 0.8%.       Control = 0.8%.
Accessory Improvements =      Accessory             Accessory
 0.1%.                         Improvements = 0.2%.  Improvements =
                                                     0.3%.
Air Conditioner Efficiency    Air Conditioner       Air Conditioner
 Improvements = 0.1%.          Efficiency            Efficiency
                               Improvements = 0.1%.  Improvements =
                                                     0.2%.
Automatic Tire Inflation      Automatic Tire        Automatic Tire
 Systems = 0.3%.               Inflation Systems =   Inflation Systems =
                               0.3%.                 0.4%.
Tire Pressure Monitoring      Tire Pressure         Tire Pressure
 System = 0.2%.                Monitoring System =   Monitoring System =
                               0.5%.                 0.7%.
------------------------------------------------------------------------

    The agencies ran GEM with a single set of vehicle inputs, as shown
in Table III-22, to derive the optional standards for each subcategory
of the Heavy Class 8 tractors (see Section III.C.(4)(a)).

                  Table III-22--GEM Inputs for 2021 MY Optional Heavy Class 8 Tractor Standards
                                     [Heavy Class 8 GEM inputs for 2021 MY]
----------------------------------------------------------------------------------------------------------------
                        Day cab                                                Sleeper cab
----------------------------------------------------------------------------------------------------------------
     Low roof           Mid roof          High roof           Low roof           Mid roof          High roof
----------------------------------------------------------------------------------------------------------------
                                            2021 MY 15L Engine 600 HP
----------------------------------------------------------------------------------------------------------------
                                           Aerodynamics (CdA in m \2\)
----------------------------------------------------------------------------------------------------------------
            5.2                6.3                6.0                5.2                6.3                5.7
----------------------------------------------------------------------------------------------------------------
                                       Steer Tires (CRR in kg/metric ton)
----------------------------------------------------------------------------------------------------------------
            6.1                6.1                6.1                6.1                6.1                6.1
----------------------------------------------------------------------------------------------------------------
                                       Drive Tires (CRR in kg/metric ton)
----------------------------------------------------------------------------------------------------------------
            6.8                6.8                6.5                6.8                6.8                6.5
----------------------------------------------------------------------------------------------------------------
                                 Extended Idle Reduction Weighted Effectiveness
----------------------------------------------------------------------------------------------------------------
            N/A                N/A                N/A               2.3%               2.3%               2.3%
----------------------------------------------------------------------------------------------------------------
                                   Transmission = 18 speed Manual Transmission
----------------------------------------------------------------------------------------------------------------
                                             Drive Axle Ratio = 3.73
----------------------------------------------------------------------------------------------------------------
                                 Transmission Type Weighted Effectiveness = 1.1%
----------------------------------------------------------------------------------------------------------------
                                       Neutral Idle Weighted Effectiveness
----------------------------------------------------------------------------------------------------------------
       0.1%                   0.1%               0.1%               0.1%               0.1%               0.1%
----------------------------------------------------------------------------------------------------------------
                                   Direct Drive Weighted Effectiveness = 0.4%
----------------------------------------------------------------------------------------------------------------
                              Transmission Efficiency Weighted Effectiveness = 0.2%
----------------------------------------------------------------------------------------------------------------
                                       Axle Efficiency Improvement = 0.6%
----------------------------------------------------------------------------------------------------------------
                                 Air Conditioner Efficiency Improvements = 0.1%
----------------------------------------------------------------------------------------------------------------
                                          Accessory Improvements = 0.1%
----------------------------------------------------------------------------------------------------------------
                                        Predictive Cruise Control = 0.4%
----------------------------------------------------------------------------------------------------------------
                                     Automatic Tire Inflation Systems = 0.3%
----------------------------------------------------------------------------------------------------------------
                                     Tire Pressure Monitoring System = 0.2%
----------------------------------------------------------------------------------------------------------------

    The level of the final Phase 2 2027 model year standards, and the
phase-in standards in model years 2021 and 2024 for each subcategory,
is shown in Table III-23.

                  Table III-23--Final Phase 2 2021, 2024, and 2027 Model Year Tractor Standards
----------------------------------------------------------------------------------------------------------------
                                                              Day cab               Sleeper cab     Heavy-haul
                                                 ---------------------------------------------------------------
                                                      Class 7         Class 8         Class 8         Class 8
----------------------------------------------------------------------------------------------------------------
                                  2021 Model Year CO[ihel2] Grams per Ton-Mile
----------------------------------------------------------------------------------------------------------------
Low Roof........................................           105.5            80.5            72.3            52.4
Mid Roof........................................           113.2            85.4            78.0
High Roof.......................................           113.5            85.6            75.7
----------------------------------------------------------------------------------------------------------------
                               2021 Model Year Gallons of Fuel per 1,000 Ton-Mile
----------------------------------------------------------------------------------------------------------------
Low Roof........................................        10.36346         7.90766         7.10216         5.14735
Mid Roof........................................        11.11984         8.38900         7.66208
High Roof.......................................        11.14931         8.40864         7.43615
----------------------------------------------------------------------------------------------------------------
                                  2024 Model Year CO[ihel2] Grams per Ton-Mile
----------------------------------------------------------------------------------------------------------------
Low Roof........................................            99.8            76.2            68.0            50.2
Mid Roof........................................           107.1            80.9            73.5
High Roof.......................................           106.6            80.4            70.7
----------------------------------------------------------------------------------------------------------------
                          2024 Model Year and Later Gallons of Fuel per 1,000 Ton-Mile
----------------------------------------------------------------------------------------------------------------
Low Roof........................................         9.80354         7.48527         6.67976         4.93124
Mid Roof........................................        10.52063         7.94695         7.22004
High Roof.......................................        10.47151         7.89784         6.94499
----------------------------------------------------------------------------------------------------------------
                                2027 Model Year CO[ihel2] Grams per Ton-Mile \a\
----------------------------------------------------------------------------------------------------------------
Low Roof........................................            96.2            73.4            64.1            48.3
Mid Roof........................................           103.4            78.0            69.6
High Roof.......................................           100.0            75.7            64.3
----------------------------------------------------------------------------------------------------------------
                          2027 Model Year and Later Gallons of Fuel per 1,000 Ton-Mile
----------------------------------------------------------------------------------------------------------------
Low Roof........................................         9.44990         7.21022         6.29666         4.74460
Mid Roof........................................        10.15717         7.66208         6.83694
High Roof.......................................         9.82318         7.43615         6.31631
----------------------------------------------------------------------------------------------------------------
Note:
\a\ The 2027 MY high roof tractor standards include a 0.3 m\2\ reduction in CdA as described in Section
  III.E.2.a.vii.

    The level of the Phase 2 2027 model year optional Heavy Class 8
standards is shown in Table III-24.

                             Table III-24--Phase 2 Optional Heavy Class 8 Standards
                                   [Optional heavy Class 8 tractor standards]
----------------------------------------------------------------------------------------------------------------
                                                          Low roof sleeper   Mid roof sleeper  High roof sleeper
 Low roof day cab   Mid roof day cab  High roof day cab         cab                cab                cab
----------------------------------------------------------------------------------------------------------------
                            2021 Model Year CO[ihel2] Standards (Grams per Ton-Mile)
----------------------------------------------------------------------------------------------------------------
           51.8               54.1               54.1               45.3               47.9               46.9
----------------------------------------------------------------------------------------------------------------
                     2021 MY and Later Fuel Consumption (Gallons of Fuel per 1,000 Ton-Mile)
----------------------------------------------------------------------------------------------------------------
        5.08841            5.31434            5.31434            4.44990            4.70530            4.60707
----------------------------------------------------------------------------------------------------------------

(g) Technology Costs of the Final Phase 2 Tractor Standards
    A summary of the technology package costs is included in Table III-
15 through Table III-17 for MYs 2021, 2024, and 2027, respectively,
with additional details available in the RIA Chapter 2.12.
    The agencies received several comments related to the APU, tire,
and aerodynamic technology costs used by the agencies at proposal. As
noted in Section III.C.3 above, ATA, First Industries, and Daimler
commented that APU costs are substantially higher than the figures in
the proposal. PACCAR commented that the cost of a diesel or battery-
based APU is $8,570 to $11,263. EMA commented that the direct per-
chassis cost of a diesel APU is approximately $8,500-$10,100 and
approximately $11,300 for battery/electric APUs. Volvo commented that
APU prices can vary between $9,500 and $11,000 depending on the type.
Schneider commented that an electronic APU will have an initial cost of
at least $5,000 and engine powered APUs are 2 to 3 times the electric
costs.

    EPA considered the comments and more closely evaluated NHTSA's
contracted TetraTech cost report found the retail price of a diesel-
powered APU with a DPF to be $10,000.\290\ The agencies used a retail
price of a diesel-powered APU to be $8,000 without a DPF and $10,000
with a DPF in the cost analysis for this final rulemaking.
---------------------------------------------------------------------------

    \290\ U.S. DOT/NHTSA. Commercial Medium- and Heavy-Duty Truck
Fuel Efficiency Technology Cost Study. May 2015. Page 71.
---------------------------------------------------------------------------

    ATA and First Industries commented that the LRR tire costs
calculations appear to be based on calculations on 1999 data indexed
for inflation. Michelin's comments stated that they estimate the cost
of low rolling resistance tires to be about $25 per tire. ATA commented
that the industry commonly sees a 40 percent reduction in useful life
and a 20 percent reduction in casing life resulting from low rolling
resistance tires. ATA and First Industries commented that the LRR tire
costs do not account for reduced tire life resulting in fewer retreads.
Schneider commented that WBS tire costs must include additional service
costs, cost of reduced tire life, and increased replacement tire costs
due to recaps not available, and reduced resale value. Volvo also
commented that heavy-duty fleets expect to retread tires as many as
five times and have concerns that tire casing durability may be
compromised with low rolling resistance tires. Volvo stressed that
retreading saves cost and about two thirds of the oil required to
produce a new tire.
    We have estimated the cost of lower rolling resistance tires based
on an estimate from TetraTech of $30 (retail, 2013$). We also have
applied a ``medium'' complexity markup value for the more advanced low
rolling resistance tires. We expect that, when replaced, the lower
rolling resistance tires would be replaced by equivalent performing
tires throughout the vehicle lifetime. As such, the incremental
increases in costs for lower rolling resistance tires would be incurred
throughout the vehicle lifetime at intervals consistent with current
tire replacement intervals. A recent study conducted by ATA's
Technology and Maintenance Council found through surveys of 51 fleets
that low rolling resistance tires and wide base single tires lasted
longer than standard tractor tires.\291\ Due to the uncertainty
regarding the life expectancy of the LRR tires, we maintained the
current tire replacement intervals in our cost analysis.
---------------------------------------------------------------------------

    \291\ Truckinginfo. TMC Survey Reveals Misinformed View of Fuel-
Efficient Tires. March 2015.
---------------------------------------------------------------------------

    ATA and First Industries commented that the estimated costs of
future aerodynamic devices appear low given the historical nature of
the proposed changes. ATA and First Industries also commented that the
agencies should describe in detail the component packages they expect
to satisfy each bin level, cost breakdowns of these individual
components, and how this technology will be modified over time to
maintain compliance with increasingly stringency levels. The agencies
included the technology cost of aerodynamic improvements, such as wheel
covers and active grill shutters, in RIA Chapter 2.11.
    The agencies also received comments associated with other costs
that should be considered related to the technologies, specifically 6x2
axle configurations, tire pressure monitoring and inflation system, and
APUs. ATA and First Industries commented that the agencies should
include additional tire wear and negative residual values associated
with 6x2 axles. Schneider commented that 6x2 axle configurations cost
should include loss on resale value, increased tire wear, and cost for
electronic technology to improve traction. ATA and First Industries
commented that the cost estimates for tire inflation systems and TPMS
must include warranty limitations, useful life, maintenance and
replacement costs, as well as costs of false warnings and increased
operation of the air compressor. Doran cited a FMCSA study that found
TPMS and ATIS reduce road calls for damaged tires and reduced number of
tire replacements and did not introduce unscheduled maintenance.
Schneider commented that an electronic APU will have maintenance of
$500 per year and engine powered APUs must also include maintenance
costs. Caterpillar requested that the agencies take a total cost of
ownership approach when considering the technology feasibility and
adoption rates.
    With respect to costs, all of the agencies' technology cost
analyses include both direct and indirect costs. Indirect costs include
items such as warranty. In terms of maintenance, the presence of tire
inflation management systems, should serve to improve tire maintenance
intervals and perhaps reduce vehicle downtime due to tire issues; they
may also carry with them some increased maintenance costs to ensure
that the tire inflation systems themselves remain in proper operation.
For the analysis, we have considered these two competing factors to
cancel each other out. The agencies also considered the maintenance
impact of 6x2 axles. As noted in the NACFE Confidence Report on 6x2
axles, the industry expects an overall reduction in maintenance costs
and labor for vehicles with a 6x2 configuration as compared to a 6x4
configuration.\292\ Among other savings, the reduction in number of
parts, such as the interaxle drive shaft, will reduce the number of
lubrication procedures needed and reduce the overall quantity of
differential fluid needed at change intervals. The agencies have taken
an approach to the maintenance costs for the 6x2 technology where we
believe that the overall impact will be zero. The agencies added
maintenance costs for diesel powered APUs, battery powered APUs, and
diesel fired heaters into the cost analysis for the final rulemaking,
as described in RIA Chapter 7.2.3. In response to Caterpillar's
comment, the agencies considered the total cost of ownership during the
payback calculations, included in RIA Chapter 7 of the final rule. The
payback calculations include the hardware costs of the new technologies
and their associated fixed costs, increased insurance, taxes, and
maintenance. The agencies found that for each category of vehicle--
tractor/trailers, vocational vehicles, and HD pickups and vans--
included in the Phase 2 rule that the fuel savings significantly exceed
the costs associated with the technologies over the lifetime of the
vehicles.
---------------------------------------------------------------------------

    \292\ North American Council for Freight Efficiency. Confidence
Findings on the Potential of 6x2 Axles. 2014.

          Table III-25--Class 7 and 8 Tractor Technology Incremental Costs in the 2021 Model Year \a\ \b\ Final Standard vs. the Flat Baseline
                                                                   [2013$ per vehicle]
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                      Class 7                                                 Class 8
                                         ---------------------------------------------------------------------------------------------------------------
                                                      Day cab                         Day cab                               Sleeper cab
                                         ---------------------------------------------------------------------------------------------------------------
                                           Low/mid roof      High roof     Low/mid roof      High roof       Low roof        Mid roof        High roof
--------------------------------------------------------------------------------------------------------------------------------------------------------
Engine \c\..............................            $284            $284            $284            $284            $284            $284            $284
Aerodynamics............................             164             299             164             299             119             119             349
Tires...................................              39               9              61              16              61              56              16
Tire inflation system...................             259             259             300             300             300             300             300
Transmission............................           4,096           4,096           4,096           4,096           4,096           4,096           4,096
Axle Efficiency.........................              71              71             101             101             101             101             101
Idle reduction..........................               0               0               0               0           1,998           1,998           1,909
Air conditioning........................              17              17              17              17              17              17              17
Other vehicle technologies..............             204             204             204             204             204             204             204
                                         ---------------------------------------------------------------------------------------------------------------
    Total...............................           5,134           5,240           5,228           5,317           7,181           7,175           7,276
--------------------------------------------------------------------------------------------------------------------------------------------------------
Notes:
\a\ Costs shown are for the 2021 model year and are incremental to the costs of a baseline 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 RIA (see 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 RIA (see 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.d.i).

       Table III-26--Class 7 and 8 Tractor Technology Incremental Costs in the 2024 Model Year \a\ \b\ Preferred Alternative vs. the Flat Baseline
                                                                   [2013$ per vehicle]
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                      Class 7                                                 Class 8
                                         ---------------------------------------------------------------------------------------------------------------
                                                      Day cab                         Day cab                               Sleeper cab
                                         ---------------------------------------------------------------------------------------------------------------
                                           Low/mid roof      High roof     Low/mid roof      High roof       Low roof        Mid roof        High roof
--------------------------------------------------------------------------------------------------------------------------------------------------------
Engine \c\..............................            $712            $712            $712            $712            $712            $712            $712
Aerodynamics............................             264             465             264             465             217             217             467
Tires...................................              40              12              65              20              65              65              20
Tire inflation system...................             383             383             477             477             477             477             477
Transmission............................           6,092           6,092           6,092           6,092           6,092           6,092           6,092
Axle Efficiency.........................             139             139             185             185             185             185             185
Idle reduction..........................               0               0               0               0           2,946           2,946           2,946
Air conditioning........................              32              32              32              32              32              32              32
Other vehicle technologies..............             374             374             374             374             374             374             374
                                         ---------------------------------------------------------------------------------------------------------------
    Total...............................           8,037           8,210           8,201           8,358          11,100          11,100          11,306
--------------------------------------------------------------------------------------------------------------------------------------------------------
Notes:
\a\ Costs shown are for the 2024 model year and are incremental to the costs of a baseline 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 RIA (see 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 RIA (see RIA 2.12).
\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.d.i).

       Table III-27--Class 7 and 8 Tractor Technology Incremental Costs in the 2027 Model Year \a\ \b\ Preferred Alternative vs. the Flat Baseline
                                                                   [2013$ per vehicle]
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                      Class 7                                                 Class 8
                                         ---------------------------------------------------------------------------------------------------------------
                                                      Day cab                         Day cab                               Sleeper cab
                                         ---------------------------------------------------------------------------------------------------------------
                                           Low/mid roof      High roof     Low/mid roof      High roof       Low roof        Mid roof        High roof
--------------------------------------------------------------------------------------------------------------------------------------------------------
Engine \c\..............................          $1,579          $1,579          $1,579          $1,579          $1,579          $1,579          $1,579
Aerodynamics............................             453             547             453             547             415             415             639

Tires...................................              43              12              70              20              70              70              20
Tire inflation system...................             469             469             594             594             594             594             594
Transmission............................           7,098           7,098           7,098           7,098           7,098           7,098           7,098
Axle Efficiency.........................             168             168             220             220             220             220             220
Idle reduction..........................               0               0               0               0           3,134           3,173           3,173
Air conditioning........................              45              45              45              45              45              45              45
Other vehicle technologies..............             380             380             380             380             380             380             380
                                         ---------------------------------------------------------------------------------------------------------------
    Total...............................          10,235          10,298          10,439          10,483          13,535          13,574          13,749
--------------------------------------------------------------------------------------------------------------------------------------------------------
Notes:
\a\ Costs shown are for the 2027 model year and are incremental to the costs of a baseline 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 RIA (see 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 RIA (see 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.d.i).

    The technology costs associated with the heavy-haul tractor
standards are shown below in Table III-28.

  Table III-28--Heavy-Haul Tractor Technology Incremental Costs in the 2021, 2024, and 2027 Model Year \a\ \b\
                                   Preferred Alternative vs. the Flat Baseline
                                               [2013$ per vehicle]
----------------------------------------------------------------------------------------------------------------
                                                                      2021 MY         2024 MY         2027 MY
----------------------------------------------------------------------------------------------------------------
Engine \c\......................................................            $284            $712          $1,579
Tires...........................................................              61              65              70
Tire inflation system...........................................             300             477             594
Transmission....................................................           4,096           6,092           7,098
Axle Efficiency.................................................             101             185             220
Air conditioning................................................              17              32              45
Other vehicle technologies......................................             204             374             380
                                                                 -----------------------------------------------
    Total.......................................................           5,063           7,937           9,986
----------------------------------------------------------------------------------------------------------------
Notes:
\a\ Costs shown are for the specified model year and are incremental to the costs of a baseline 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 RIA (see 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 RIA (see RIA 2.12 in particular).
\c\ Engine costs are for a heavy HD diesel engine meant for a combination tractor.

(2) Consistency of the Tractor Standards With the Agencies' Legal
Authority
    The HD Phase 2 standards are based on adoption rates for
technologies that the agencies regard as the maximum feasible for
purposes of EISA Section 32902(k) and appropriate under CAA section
202(a) for the reasons given in Section III.D.1(b) through (d) above;
see also RIA Chapter 2.8. The agencies believe these technologies can
be adopted at the estimated rates for these standards within the lead
time provided, as discussed above and in RIA Chapter 2.8. The 2021 and
2024 MY standards are phase-in standards on the path to the 2027 MY
standards and were developed using less aggressive application rates
and therefore have lower technology package costs than the 2027 MY
standards. Moreover, we project the cost of these technologies will be
rapidly recovered by operators due to the associated fuel savings, as
shown in the payback analysis included in Section IX below. The cost
per tractor to meet the 2027 MY standards is projected to range between
$10,200 and $13,700 (which includes the cost of the engine standards).
See Table III-25 above. Much or all of this will be recovered in the
form of fuel savings during the first two years of ownership. The
agencies note that while the projected costs per vehicle are
significantly greater than the costs projected for Phase 1, we still
consider that cost to be reasonable, especially given the relatively
short payback

period. In this regard the agencies note that the estimated payback
period for tractors of less than two years,\293\ is itself shorter than
the estimated payback period for light duty trucks in the 2017-2025
light duty greenhouse gas standards. That period was slightly over
three years, see 77 FR 62926-62927, which EPA found to be a highly
reasonable given the usual period of ownership of light trucks is
typically five years.\294\ The same is true here. Ownership of new
tractors is customarily four to six years, meaning that the greenhouse
gas and fuel consumption technologies pay for themselves early on and
the purchaser sees overall savings in succeeding years--while still
owning the vehicle.\295\ The agencies note further that the costs for
each subcategory are relatively proportionate; that is, costs of any
single tractor subcategory are not disproportionately higher (or lower)
than any other. Although the rule is technology-forcing (especially
with respect to aerodynamic and drivetrain efficiency improvements),
the agencies believe that manufacturers retain leeway to develop
alternative compliance paths, increasing the likelihood of the
standards' successful implementation. The agencies also regard these
reductions as cost-effective, even without considering payback period.
The agencies estimate the cost per metric ton of CO2eq
reduction without considering fuel savings to be $36 for tractor-
trailers in 2030 which compares favorably with the levels of cost
effectiveness the agencies found to be reasonable for light duty
trucks.296 297 See 77 FR 62922. The phase-in 2021 and 2024
MY standards are less stringent and less costly than the 2027 MY
standards and hence likewise reasonable. For these reasons, and because
the agencies have carefully considered lead time and shown that lead
time is adequate, EPA believes they are also reasonable under Section
202(a) of the CAA. Given that the agencies believe these standards are
technically feasible, are highly cost effective, and even more highly
cost effective when accounting for the fuel savings, and have no
apparent adverse potential impacts (e.g., there are no projected
negative impacts on safety or vehicle utility, and EPA has taken steps
to avoid adverse collateral consequences from use of APUs without
filter-based particulate controls), these standards represent a
reasonable choice under Section 202(a)(2) of the CAA and the maximum
feasible under NHTSA's EISA authority at 49 U.S.C. 32902(k)(2).
---------------------------------------------------------------------------

    \293\ See RIA Chapter 7.2.4.
    \294\ Auto Remarketing. Length of Ownership Returning to More
Normal Levels; New Registrations Continue Slow Climb. April 1, 2013.
Last accessed on February 26, 2015 at http://www.autoremarketing.com/trends/length-ownership-returning-more-normal-levels-new-registrations-continue-slow-climb.
    \295\ North American Council for Freight Efficiency. Barriers to
Increased Adoption of Fuel Efficiency Technologies in Freight
Trucking. July 2013. Page 24.
    \296\ See RIA Chapter 7.2.5 and Memo to Docket ``Tractor-Trailer
Cost per Ton Values.'' July 2016. EPA-HQ-OAR-2014-0827.
    \297\ If using a cost effectiveness metric that treats fuel
savings as a negative cost, net costs per ton of GHG emissions
reduced or per gallon of avoided fuel consumption will be negative
under these standards.
---------------------------------------------------------------------------

(3) Alternative Tractor Standards Considered
    The agencies developed and considered other alternative levels of
stringency for the Phase 2 program. The results of the analysis of
these alternatives are discussed below in Section X of the Preamble.
For tractors, the agencies developed the following alternatives as
shown in Table III-29. The agencies are not adopting standards
reflecting Alternative 2, because as already described, technically
feasible standards are available that provide for greater emission
reductions and reduced fuel consumption than provided under Alternative
2. The agencies are not adopting standards reflecting Alternative 4 or
Alternative 5 in their entirety because we do not believe to be
feasible considering lead time and other relevant factors. However, we
note that the tractor standards are predicated on the adoption of
engine technology beyond what was projected in Alternative 4 of the
NPRM. In addition, the final rule stringency includes additional
technologies for tractors that were not considered in any of the
alternatives analyzed in the NPRM--axle efficiency, transmission
efficiency, adjustable automatic engine shutdown systems, and tire
pressure monitoring systems.

     Table III-29--Summary of Alternatives Considered for the Final
                               Rulemaking
------------------------------------------------------------------------
      Alternatives 1a and 1b               No action alternatives
------------------------------------------------------------------------
Alternative 2.....................  Less Stringent than the Preferred
                                     Alternative applying off-the-shelf
                                     technologies.
Preferred Alternative.............  Final Phase 2 standards, fully
                                     phased-in by 2027 MY.
Alternative 4.....................  Alternative presented in the NPRM
                                     that pulls ahead the proposed 2027
                                     MY standards to 2024 MY.
Alternative 5.....................  Alternative based on very high
                                     market adoption of advanced
                                     technologies.
------------------------------------------------------------------------

E. Phase 2 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 are carrying over many aspects of the Phase 1 compliance
approach, but we are also adopting changes 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 overall Phase 2 regulatory structure is discussed in more
detail above in Section II. This section discusses tractor-specific
compliance provisions.
(a) Application and Certification Process
    For the Phase 2 final rule, the agencies are keeping many aspects
of the HD Phase 1 tractor compliance program. For example, the agencies
will 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 fuel efficiency and CO2
standards. Another aspect that we are carrying over is the overall
compliance approach. EMA's and the HD manufacturers' comments supported
the continued use of GEM and did not support chassis-based
certification.
    In Phase 1 and as finalized in Phase 2, the general compliance
process in terms of the pre-model year, during the model year, and post
model year activities remains unchanged. The manufacturers will 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 will 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 adopting a similar process for allowing credits for off-
cycle technologies that are not measured by the GEM simulation tool,
although the revised GEM now recognizes many more technologies than the
Phase 1 version of GEM, notably drivetrain and transmission
improvements, so fewer technologies would be candidates for off-cycle
credits (see Section I.B.v. for a more detailed discussion of off-cycle
requests). During the model year, the manufacturers will continue to
generate certification data and conduct GEM runs on each of the vehicle
configurations it builds. After the model year ends, the manufacturers
will 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 will
jointly coordinate on any enforcement action required.
(b) Compliance Requirements
    As proposed in Phase 2, the agencies did not adopt any provisions
in the final Phase 2 rules that significantly change the following
Phase 1 provisions:

 Useful life of tractors (40 CFR 1037.105(e) and 1037.106(e))
although added for NHTSA in Phase 2 (49 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), except for the addition of a heavy-haul family in Phase 2
(c) Drive Cycle Speed Targets 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 proposed to maintain the existing Phase 1 drive cycle
speed traces and weightings in Phase 2. In the Phase 2 proposal sleeper
cab 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 cabs
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
proposed 40 CFR 1037.510(c) and 80 FR 40242). In response to the Phase
2 NPRM, the American Trucking Associations (ATA) submitted comments
based on spot speed records throughout the month of May 2015. This
study found that Class 8 trucks operated at speeds of 55 mph or less 57
percent of the time. United Parcel Service (UPS) stated that their
Class 8 tractor-trailers average 54 miles per hour in part because they
use vehicle speed limiters in their fleet. UPS also shared ATA's
comments on the spot speed records. Daimler stated that they did not
see a benefit of increasing the amount of low speed operation for
tractors, unless the EPA-NREL work supported the need for a change.
    The agencies considered these comments along with the information
that was used to derive the drive cycle weightings in Phase 1. The
agencies did not receive any new drive cycle weighting data for
tractors from the EPA-NREL work. The agencies believe that the study
cited by ATA includes weightings of speed records, which represent the
fraction of time spent at a given speed. However, our drive cycle
weightings represent the fraction of vehicle miles traveled (VMT). The
agencies used the vehicle speed information provided in the ATA
comments and translated the weightings to VMT. Based on our assessment
shown in RIA Chapter 3.4.3, their findings produce weightings that are
approximately 74 percent of the vehicle miles traveled are at speeds
greater than 55 mph and 26 percent less than 55 mph. In addition, the
study cited by ATA represents ``Class 8 trucks'' which would include
day cab tractors, sleeper cab tractors, and heavy heavy-duty vocational
trucks. Based on this assessment, the agencies do not believe this new
information is significantly different than the drive cycle weightings
that were proposed. Therefore, we are adopting the drive cycle
weightings for tractors that we adopted for Phase 1 and proposed for
Phase 2.
    Both in the Phase 1 program and as proposed in the Phase 2 program,
the 55 mph and 65 mph drive cycles used in GEM assume a constant target
speed 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. In the Phase 2 NPRM, the
agencies requested 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. 80 FR 80242.
    In response, ACEEE commented that NREL found that constant speeds
on positive and negative grades misrepresent the real world operation
of HD trucks because there is a strong correlation between road grade
and average speed. Daimler commented that for regulatory purposes using
a constant speed cycle with representative road grade is appropriate,
noting as well that some manufacturers use a constant speed cycle in
their internal development processes and have found it correlates well
to real world operation. They also highlight the concern that it would
be extremely difficult to develop traffic patterns that represent a
national average. However, Daimler also stated in their comments that
they do see a benefit of allowing increased variability in the vehicle
speeds in the 55 and 65 mph cycles, for evaluating the effectiveness of
technologies such as predictive cruise control.
    After considering these comments and evaluating the final Phase 2
version of GEM, the agencies are adopting in the Phase 2 final rules
constant target speed for the 55 mph and 65 mph cycles, as adopted in
Phase 1. One key difference in Phase 2 is the addition of road grade in
these cruise cycles, as discussed below in Section III.E.2. The
addition of road grade to the cruise cycles brings the GEM simulation
of vehicles over the drive cycles closer to the real world operation
described by ACEEE and Daimler. Even though the cruise cycles will
continue to have constant target speeds (55 mph or 65 mph), the vehicle
may slow down from the target speed of the cycle on an uphill stretch
of road due to the addition of road grade in the Phase 2 cycles. If the
vehicle does slow down, the transmission shift logic built into GEM
will downshift the transmission to limit the amount of further vehicle
deceleration. Similarly, on the downhill portions of the cycles, the
driver control logic built into GEM will allow the vehicle to exceed
the

target speed by 3 mph prior to braking the vehicle.
(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 proposed to carry over
the total weight of the tractor-trailer combination used in GEM for
Phase 1. The agencies developed the tractor curb weight inputs for
Phase 2 from actual tractor weights measured in two of EPA's Phase 1
test programs. The 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.\298\ We
welcomed comment on the tractor weights we proposed.
---------------------------------------------------------------------------

    \298\ 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.
---------------------------------------------------------------------------

    Daimler commented that there is a large spread of weights within a
subcategory given the variety of different features that a vehicle
might incorporate in order to perform its task. The agencies' proposed
curb weights for tractors may be higher than Daimler's vehicles but in
Daimler's opinion align with some of their competitors' vehicles, and
therefore are reasonable. Based on no negative comment or newer data,
the agencies are adopting the Phase 1 tractor curb weights, as
proposed.
    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 volume is full before the weight limit is reached), and 30
percent are ``weighed out'' (operating weight equals 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).\299\
---------------------------------------------------------------------------

    \299\ 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.\300\ 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 proposed 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 for Phase 2. The agencies also proposed 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 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.''
---------------------------------------------------------------------------

    \300\ 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.
---------------------------------------------------------------------------

    The agencies requested comments and data to support changes to our
proposed payloads for Phase 2. 80 FR 40242. Daimler commented that the
payload weight is even more difficult to determine because weights
change based on economic conditions, such as when carriers continue to
try to reduce their dead volume and increase their weight per load.
Daimler suggested that the agencies might consider increasing the
proposed payloads, but did not provide data. In the absence of newer
data or other compelling comments, the agencies continue to believe
that it is appropriate to continue using the Phase 1 tractor payloads
for all of the Class 7 and 8 tractors, as proposed, except for heavy-
haul.
    Details of the predefined weights by regulatory subcategory, as
shown in Table III-30, are included in RIA Chapter 3.

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

(e) Tire Testing
    In Phase 1, 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 proposed to carry over
the Phase 1 testing provisions for tire rolling resistance into Phase
2. 80 FR 40243. We welcomed comments regarding the tire testing
provisions, but did not receive any. Therefore, based on the same
reasoning presented at proposal, we are adopting the Phase 1 tire
testing provisions in Phase 2.
    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 (80 FR 40243, citing to
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
will 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 proposed to allow the use of either Smithers or STL
laboratories for determining the tire rolling resistance value. The
agencies requested 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. The agencies
did not receive any comments on the issue. Therefore, again based on
the reasoning presented at proposal, we are adopting the Phase 1
testing approach for Phase 2.
(2) Key Differences in HD Phase 2 Compliance Provisions
    The agencies are adopting certain provisions in Phase 2 that are
significantly different from Phase 1. Details regarding some of these
key changes such as aerodynamic assessments, road grade in the drive
cycles, weight reduction, GEM inputs, emission control labels, and
chassis dynamometer testing are provided in this subsection.
(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
proposed to continue this general approach in HD Phase 2, but to make
several enhancements to the aerodynamic assessment of tractors. As
discussed below, we proposed some modifications to the aerodynamic test
procedures--the addition of wind averaged drag 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. As discussed in more detail in the following
subsections, we are adopting many of the proposed Phase 2 aerodynamic
test procedures, but with some additional revisions to the test
procedures. These procedures are then appropriately reflected in the
final Phase 2 aerodynamic bins.
(i) Phase 1 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 (coastdown) and a procedure to align results
from other aerodynamic test procedures with the reference method by
applying a correction factor (Falt-aero) to results from
alternative methods. The Phase 1 regulations require manufacturers to
use good engineering judgment in developing their corrections and
specify some minimum testing requirements.
(ii) Reference Aerodynamic Method in Phase 2
    Based on feedback received during the development of Phase 1, we
understood even before the Phase 2 NPRM was issued that there was
interest from some manufacturers to change the reference method in
Phase 2 from coastdown to constant speed testing. EPA 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 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 proposed to continue to use the enhanced coastdown procedure
for the reference method in Phase 2.\301\ 80 FR 40244. However, we
welcomed 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 welcomed comments on and suggested
revisions to the constant speed test procedure specifications set forth
in the proposal in Chapter <IP_ADDRESS> of the draft RIA and 40 CFR 1037.533
in the proposed regulations (40 CFR 1037.534 in the final regulations).
---------------------------------------------------------------------------

    \301\ Southwest Research Institute. ``Heavy Duty Class 8 Truck
Coastdown and Constant Speed Testing.'' April 2015.
---------------------------------------------------------------------------

    Several stakeholders provided comments both in favor and against
the use of coastdown as the reference aero method for Phase 2 for
tractors. CARB does not support the constant speed test as the
reference method until it can be demonstrated to be superior to the
coastdown methods. Their concerns included the cost associated with
vehicle modifications required in test preparation (such as the torque
meters

on the wheel hubs). Daimler did not support a change to constant speed
testing for the reference method and stated that more time is needed to
determine if constant speed testing would be a better alternative.
Navistar supports the coastdown as the reference method and does not
believe constant speed testing should be adopted even as an
alternative, unless significant further work is conducted. EMA stated
that they could not support the adoption of constant speed testing as
the reference method in Phase 2 because there is insufficient time in
the process to properly study whether constant speed is equivalent to
or better than coastdown testing. Further, EMA recommended that
constant speed testing be included only as a potential alternative to
be phased in at a future date if appropriate. Volvo opposed a change in
the aerodynamic reference test method to constant speed at this time
due to insufficient time to fully evaluate the new test method.
    Exa supported the use of constant speed testing as a reference
method because it is a real-world measurement with the ability to
evaluate wind-averaged drag. Exa also cited some concerns that
coastdown is limited to near zero wind yaw angle and does not
accurately represent the aerodynamics experienced on the road. MEMA
supported including the constant speed test based on research that has
demonstrated that it is reliable relative to coastdown tests and is
required in European aerodynamic test protocols. SABIC commented that
constant speed testing may help isolate the aerodynamic drag from
vibration, mechanical, and friction encountered at low speeds. SABIC
also cited research that suggested constant speed testing may provide
better repeatability than coastdown tests, and suggested that the U.S.
may be able to promote harmonization with the required European
constant speed testing.
    After consideration of the comments, the agencies are continuing to
use the Phase 1 approach of setting coastdown testing as the reference
method for tractor aerodynamic assessment in Phase 2. After developing
revised coastdown test procedures and data analysis methods for the
final rule, we have concluded that coastdown testing continues to
produce acceptable repeatability and can be conducted at a lower cost
than constant speed testing. However, we are finalizing some revisions
to the Phase 2 coastdown test procedures in response to comments and
discussed below. The agencies are also continuing to allow alternative
test methods to be used to determine the aerodynamic performance of
tractors in Phase 2, as long as the results are correlated back to the
reference method using a correlation factor (Falt-aero). Additional
details are included in the Falt-aero discussion below.
(iii) Coastdown Test Procedure Changes for Phase 2
    The agencies worked closely with the tractor manufacturers between
the Phase 2 NPRM and final rulemaking to develop robust coastdown test
procedures that are technically sound.\302\ EPA also continued to test
additional tractors after the proposal to better inform the test
procedure development. Based on this work, the agencies are adopting
aerodynamic test procedures that have been improved from those proposed
for Phase 2. The details of these procedures and their development are
included in RIA Chapter 3.2. Below is a summary of the changes to the
coastdown test procedures and data analysis method for the final rule.
---------------------------------------------------------------------------

    \302\ Memo to Docket. Aerodynamic Subteam Meetings with EMA.
July 2016. Docket EPA-HQ-OAR-2014-0827.
---------------------------------------------------------------------------

    The coastdown test procedure changes include the tested speed
range, the calibration of the equipment, and specification of yaw and
air speed measurements. The agencies proposed two test speed ranges for
coastdown testing--70 to 60 mph and 25 to 15 mph. EPA's evaluation of
the CdA values in relation to yaw angle showed that the 25
to 15 mph low-speed range specified in the NPRM test procedures
produced yaw curves that were flatter than expected and flatter than
demonstrated using other test methods, such as wind tunnels and CFD.
Upon further analysis, EPA found that by reducing the low-speed range
to even lower speeds, the yaw curve results were more representative.
The best speed range to alleviate this concern is a 15 to 5 mph low
speed range; however, requiring this would significantly reduce the
number of available days for testing in a given year because it would
lead to a wind speed limit of 3 mph. Therefore, the agencies are
adopting a low speed range of 20 to 10 mph to balance the yaw curve
representativeness with the real world testing implications. Along with
this test speed change, the component of the wind speed parallel to the
road or track will be limited to less than or equal to 6 mph. The
agencies are adopting Phase 2 coastdown test procedures that specify
the yaw measurement method resolution and accuracy requirements similar
to those proposed for constant speed testing. The calibration of the
yaw and air speed equipment will be conducted in a point-by-point
manner for each run.
    The coastdown data analysis changes include the analysis of low
speed pairs and filtering methods, adjustments for rear axle losses and
rolling resistance, and determination of the final CdA value
for coastdown. EPA found that the method proposed to analyze the
coastdown results of paired runs leads to an unexpected yaw curve
asymmetry. Upon further evaluation, EPA found that the yaw curve
asymmetry is mitigated by averaging the road load force and air speed
from every two opposite direction low-speed segments and using the
average with each of the high speed segments in the data analysis.
Therefore, the agencies are adopting this method for the Phase 2 final
rules. The filtering of the air speed, yaw, vehicle speed, and track
wind speed is necessary to remove outliers and replace the data with
the moving median value to reduce the variability of coastdown test
results. The agencies are specifying this filtering method in the final
rules. Coastdown testing measures all of the losses associated with the
vehicle, including aerodynamics, rolling resistance, and axle spin
losses. To isolate the aerodynamic CdA, it is important to
remove the losses associated with drive axle and tire rolling
resistance. For the final Phase 2 rules, the agencies are adopting the
SAE J2452 test procedures that require manufacturers to measure the
speed dependence of the tire rolling resistance for each of the steer,
drive, and trailer tire models used on the article undergoing a
coastdown test. The agencies are also requiring that manufacturers
measure the speed dependence of the drive axle spin losses for the
drive axle model used in the article undergoing a coastdown test using
a subset of the rear axle efficiency test procedure being adopted in
Phase 2.
    The agencies have also developed a process of identifying and
removing coastdown test result outliers for the final rules. First, the
median yaw angle of the data is determined. All results outside of a
range of plus or minus 1 yaw degree are removed. Then the mean
CdA value of the remaining data points is determined.
CdA values that lie outside of plus or minus two standard
deviations from the CdA mean are removed. At least 24 data
points are needed after removal of outliers for the results to be
valid. Finally, the mean CdA and mean effective yaw angle
are calculated from the remaining points. These values are then used to
adjust to reflect a 4.5 degree yaw angle result

based on an alternate method yaw curve results.
(iv) Improving Correlation of Coastdowns With Alternative Methods
(Falt-aero)
    As already noted, the agencies adopted in Phase 1 a 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
alternative test methods to the reference method results using
Falt-aero (see 40 CFR 1037.525).\303\ Manufacturers are able
to use any aerodynamic evaluation method in demonstrating a vehicle's
aerodynamic performance as long as they obtain our prior approval and
the method is aligned to the reference method. The agencies proposed to
continue to use this alignment method approach in Phase 2 to maintain
the testing flexibility that manufacturers have today. However, the
agencies proposed to increase the rigor in determining the
Falt-aero for Phase 2, including enhancing the minimum
testing requirements. Beginning in MY 2021, we proposed 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 proposed 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 proposed 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 requested comment on the amount of testing
required to accurately develop a Falt-aero value and the
burden associated with it. See 80 FR 40244.
---------------------------------------------------------------------------

    \303\ Falt-aero is an experimentally determined
factor that represents the ratio of coastdown results to results
from the alternative method. The agencies allow other functional
forms of the relationship consistent with good engineering judgment.
---------------------------------------------------------------------------

    The agencies received comments with regard to the need of
Falt-aero and the burden of determining it. Exa Corporation
(a supplier of CFD software) commented that it is not clear that the
Falt-aero factor would alleviate challenges associated with
their expectation that the absolute drag values will differ
substantially between different test methods and different facilities.
Exa suggested that the agencies require a certification procedure for
an alternate tool that includes a broad validation suite including
different types of vehicles from aerodynamic sleeper to less
aerodynamic day cabs. The HD vehicle manufacturers strongly recommended
that the agencies reduce the number of coastdown tests that must be
conducted each year. Navistar commented that only one
Falt-aero should be required for Phase 2. Navistar's testing
of their ProStar sleeper and day cabs found that the
Falt-aero only differed within less than one percent using
the same test facility. Navistar also commented that the data in the
Phase 2 NPRM draft RIA show that three different sleepers show
Falt-aero values within 0.4 percent. EMA commented that only
one Falt-aero value should be required, as supported by the
values shown in the Phase 2 Draft RIA where the Falt-aero
values were 1.09 +/-0.02 for three tested vehicles. EMA also commented
that the proposed requirements would be time-consuming, costly, and an
unreasonable burden. Daimler supported EMA's comments. The HD vehicle
manufacturers also submitted data to the agencies that show the
Falt-aero values were within a range of one percent. Volvo
shared data with the agencies that support that Falt-aero is
highly consistent for varying truck models when correcting the test
data under the conditions and methods that the industry has
recommended. Volvo therefore concluded that multiple
Falt-aero values are not necessary for Phase 2. PACCAR
provided results from three tractor models showing the spread of
Falt-aero is less than 0.3 percent.
    The agencies determined the Falt-aero values for all of
the tractors tested using different aerodynamic methods for Phase 2
using the aerodynamic test procedures and data analysis finalized for
Phase 2. As shown in further detail in RIA Chapter 3.2.1, the
Falt-aero values ranged between 1.13 and 1.20 for a single
CFD software. Therefore, the agencies concluded that a single
Falt-aero value is not sufficient for determining the
correlation of test methods for all tractors. Furthermore, based on the
comments and further refinement of our selective enforcement audit
(SEA) provisions in the Phase 2 final rule, we are adopting provisions
that require manufacturers to determine Falt-aero for a
minimum of one day cab and one sleeper cab in MYs 2021, 2024, and
2027.\304\ While this significantly reduces the test burden from the
levels proposed, it also only represents a minimum requirement. The
agencies believe that the improvements to the SEA requirements for
aerodynamics will further encourage the manufacturers to ensure that
they are accurately reflecting the Falt-aero for their entire tractor
fleet and that they may do additional Falt-aero
determinations beyond the minimum requirement in Phase 2. Without
confidence in their Falt-aero values, manufacturers would
risk SEA failures that could halt vehicle production. Even without
failing the SEA overall, failing individual vehicles would lead to
increased SEA testing. Thus, the SEA requirements will create a
stronger incentive for manufacturers to use good engineering judgment
for Falt-aero values.
---------------------------------------------------------------------------

    \304\ See Section III.E.(2)(a)(ix) for details on the SEA
requirements.
---------------------------------------------------------------------------

    The agencies also received comments from HD manufacturers stressing
that coastdown testing does not produce CdA values at zero
yaw as assumed. Even at calm test conditions, the resulting yaw angle
is something greater than zero degrees. The agencies evaluated our
aerodynamic test data and agree with the manufacturers. Therefore, we
are adopting Phase 2 provisions that use the effective yaw angle from
coastdown testing to determine the Falt-aero value (see 40
CFR 1037.525). See RIA Chapter 3.2.2 for additional detail.
(v) Computational Fluid Dynamics
    The agencies considered refinements to the computational fluid
dynamics (CFD) modeling method to determine the aerodynamic performance
of tractors in the NPRM. 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.\305\ The
agencies welcomed comment on the proposed revisions.
---------------------------------------------------------------------------

    \305\ 40 CFR 1037.532 ``Using computational fluid dynamics to
calculate drag area (CdA).''
---------------------------------------------------------------------------

    Daimler and EMA recommended that the agencies should raise the test
speed for CFD from the proposed 55 mph to 65 mph to be consistent with
GEM and the sleeper cab tractor weighting of 86 percent. Daimler
supported the agencies' other proposed revisions to CFD test
procedures.
    The agencies agree with the suggested comment to include
consistency between the test methods and are adopting CFD provisions
that include a test speed of 65 mph, along with the other proposed
revisions. The agencies finalized these changes through incorporation
of the SAE J2966 CFD guidelines with exceptions and clarifications to
keep other aspects of

the CFD simulations consistent with Phase 1.
(vi) Wind Averaged Drag Determination
    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.\306\ As noted in the NAS report, the wind
average drag coefficient is about 15 percent higher than the zero
degree coefficient of drag.\307\ 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.\308\ 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.
---------------------------------------------------------------------------

    \306\ See 2010 NAS Report, page 95.
    \307\ See 2010 NAS Report, Finding 2-4 on page 39. Also see 2014
NAS Report, Recommendation 3.5.
    \308\ 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
would potentially impact the overall technology effectiveness or change
the kinds of technology decisions made by the tractor manufacturers in
developing equipment to meet our HD Phase 2 standards. Therefore, we
proposed and are adopting aerodynamic test procedures that take into
account the wind averaged drag performance of tractors. The agencies
proposed 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 proposed and are adopting provisions that require
manufacturers 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. This
requirement commences in MY 2021.
    All stakeholders that commented on wind averaged drag supported its
use over zero yaw. ACEEE supports the shift to the use of wind averaged
drag in Phase 2. Exa supported the use of wind averaged drag because it
is a better predictor of real world fuel economy. Michelin supported
wind average drag assessments for a realistic and complete assessment
of aerodynamic performance and would prevent the unintended consequence
of incentivizing improvements that are better at zero wind conditions
but sacrifice cross-wind performance. SABIC Innovative Plastics
commented that it is imperative that wind effects be part of the
standard due to the real-world impact of wind. Plastics Industry Trade
Association supported wind average drag to better simulate real life
conditions.
    PACCAR and Daimler recommended the use of a surrogate angle of
4.5[deg] in lieu of the nine angles required for a full wind averaged
draft evaluation for CFD evaluated at 65 mph. PACCAR and Daimler
provided data to support the use of a single angle. PACCAR also stated
that there is significant CFD burden associated with the use of a nine
angle yaw sweep. According to PACCAR in a given year, this would add
approximately 4,000 additional simulations to their certification
burden. EMA and other tractor manufacturers supported the single
surrogate angle of 4.5[deg] as being equivalent to the full yaw sweep
result generated with SAE J1252.
    As discussed in further detail in RIA Chapter <IP_ADDRESS>.3, our data
support that 4.5[deg] results are a good surrogate for full wind
averaged drag results for wind tunnel and CFD assessments. Therefore,
we are adopting the 4.5[deg] surrogate angle in Phase 2.
    The agencies require that manufacturers use the following equation
to make the necessary adjustments to a coastdown result to obtain the
CdAwa value:

CdAwa =
CdAeffective yaw angle, coastdown *
(CdA4.5[deg]/
CdAeffective yaw angle)

    If the manufacturer has a CdA value from either a wind
tunnel or CFD, then they will use the following equation to obtain the
CdA wad value:

CdAwa = CdA4.5[deg] *
Falt-aero

    Because the agencies are adopting a 4.5[deg] surrogate angle, the
agencies are not adopting the proposed provisions 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.
(vii) Standard Trailer Definition
    Similar to the approach the agencies adopted in Phase 1, NHTSA and
EPA are adopting provisions such that the tractor performance in GEM is
judged assuming the tractor is pulling a standardized trailer.\309\ 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 intuits: Tractor-trailer pairings are almost
always optimized, but this does not indicate that a tractor always uses
the same trailer. EPA conducted an evaluation of over 4,000 tractor-
trailer combinations using live traffic cameras in 2010.\310\ The
results showed that approximately 95 percent of the tractors were
matched with the standard trailer specified (high roof tractor with dry
van trailer, mid roof tractor with tanker trailer, and low roof with
flatbed trailer). Therefore, the agencies are continuing the Phase 1
approach into Phase 2 GEM to use a predefined typical trailer in
assessing overall performance for test purposes. As such, the high roof
tractors will be paired with a standard dry van trailer; the mid roof
tractors will be paired with a tanker trailer; and the low roof
tractors will be paired with a flatbed trailer.
---------------------------------------------------------------------------

    \309\ See 40 CFR 1037.501(g).
    \310\ See Memo to Docket, Amy Kopin. ``Truck and Trailer Roof
Match Analysis.'' August 2010.
---------------------------------------------------------------------------

    However, the agencies proposed a change to the definition of the
standard dry van reference 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 \311\ and
EPA's

SmartWay Transport Partnership. The standard dry van 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.312 313 As the agencies look towards
these tractor 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. 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 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 eight percent
reduction in drag area.
---------------------------------------------------------------------------

    \311\ 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.
    \312\ 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.
    \313\ Frost & Sullivan, ``Strategic Analysis of North American
Semi-trailer Advanced Technology Market,'' Feb 2013.
---------------------------------------------------------------------------

    We proposed a definition of the standard dry van trailer in Phase
2--the trailer assumed during the certification process to be paired
with a high roof tractor--that includes a trailer skirt starting in
2021 model year. 80 FR 40245. Even though the agencies proposed that
new dry van trailer standards begin in 2018 MY, we did not propose 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 have
needed to revise the Phase 1 tractor standards. The details of the
trailer skirt definition are included in 40 CFR 1037.501(g)(1). We
requested comment on our HD Phase 2 standard trailer configuration. We
also welcomed comments on suggestions for alternative ways to define
the standard trailer, such as developing a certified computer aided
drawing (CAD) model.
    The agencies received support in comments for adopting a reference
trailer with skirts. Daimler supported the addition of side skirts to
the Phase 2 reference trailer and stated that it aligns with their
internal development process. Daimler also suggested that if the
agencies believe there will be significant adoption of trailers with
boat tails, then the agencies could update the CdA bin value
input to GEM and reduce it by 0.5 m\2\ to reflect the actual on-road
aerodynamics load without changing the standard trailer. The Plastics
Industry Trade Association stated that the proposed reference trailer
is representative of trailer aerodynamic improvements likely to emerge
during Phase 2. Navistar suggested that the standard trailer should be
more aerodynamic to reflect trailers that will be used during the life
of Phase 2 tractors. ACEEE supports the use of a more aerodynamic
reference trailer in Phase 2, however, they suggest an even more
aerodynamic reference trailer be required that is closer to the
aerodynamic packages projected to be installed on new trailers in 2027.
ACEEE and UCS suggested that Phase 2 should facilitate the transition
of promoting more tractor-trailer integration. ACEEE recommended
providing manufacturers the option to test tractors with advanced
trailers; correct the test result appropriately to account for the
benefit provided by the trailer alone to promote integration of
aerodynamically advanced tractors and trailers. UCS raised concerns
that because tractors and trailers are interchangeable and that there
is no guarantee that the Phase 2 tractors will pull the newest
trailers, therefore, the agencies should not revise the standard
trailer over the course of the rule.
    The agencies re-evaluated the proposal to include trailer skirts on
the Phase 2 reference trailer with consideration of the comments. Based
on testing conducted to support the trailer portion of Phase 2, we
found that on average a boat tail added to a dry van trailer with
skirts reduces wind averaged CdA by 0.6 m\2\.\314\ We still
project that the bulk of trailers that will be in operation during the
life of tractors produced early in Phase 2 will be represented by the
aerodynamic performance of a trailer with skirts. Therefore, we are
adopting the reference trailer as proposed. However, we also want to
recognize that the trailer fleet will continue to evolve over the
lifetime of tractors built and certified to Phase 2, especially from MY
2027 and later. We recognize that if we do not account for reduced
aerodynamic loads in the real world, then we may not be appropriately
evaluating the tractor powertrain. We considered changing the standard
trailer in MY 2027; however, this would lead to significant testing
burden for the manufacturers because they would have to determine new
CdA values for their entire fleet of tractors. Instead, we
are adopting Phase 2 GEM that beginning in MY 2027 will take the
CdA input for each vehicle and reduce it by 0.3 m\2\ to
reflect the lower aerodynamic loads that are a mix of trailers with
skirts and trailers with skirts and boat tails. This change has been
accounted for in both the baseline and standard setting of the
CO2 emissions and fuel consumption values.
---------------------------------------------------------------------------

    \314\ See RIA Chapter <IP_ADDRESS>.3.
---------------------------------------------------------------------------

    With respect to ACEEE's recommendation for the agencies to
facilitate the transition to more integrated tractor-trailers, such as
those demonstrated with SuperTruck, the agencies believe this would
require a significant change in tractor-trailer logistics to encourage
more matching of specific tractors to specific trailers in operation.