difference is due to the change in the target rolling resistance from
8.1 to 7.7 kg/metric ton based on the agencies' test results. Second,
there are minor differences in the fuel consumption and CO2
emissions due to the small modifications made to the GEM, as noted in
RIA Chapter 4. Lastly, the final HHD vocational vehicle standard uses a
revised payload assumption of 15,000 pounds instead of the 38,000
pounds used in the NPRM, as described in Section II.D.3.c.iii. As a
result, the emission standards shown in Table II-15 for vocational
vehicles have changed from the standards published in the NPRM. The
changes for light heavy and medium heavy-duty vehicles are modest. The
change for heavy heavy-duty vocational vehicles is larger, due to the
difference in assumed payload.
    As with the 2017 MY standards for Class 7 and 8 tractors, EPA and
NHTSA are adopting more stringent vocational vehicle standards for the
2017 model year which reflect the CO2 emissions reductions
required through the 2017 model year engine standards. See also Section
II.B.2 explaining the same approach for the standards for combination
tractors. As explained in Section 0 below, engine performance is one of
the inputs into the GEM compliance model that has a pre-defined (i.e.
fixed) value established by the agencies, and that input will change in
the 2017 MY to reflect the 2017 MY engine standards. The 2017 MY
vocational vehicle standards are not premised on manufacturers
installing additional vehicle technologies, and a vocational vehicle
that complies with the standards in MY 2016 will also comply in MY 2017
with no vehicle (tire) changes. Thus, although chassis manufacturers
will not be required to make further improvements in the 2017 MY to
meet the standards, the standards will be more stringent to reflect the
engine improvements required in that year. This is because in 2017 MY
GEM vehicle modeling outputs (in grams per ton mile and gallons per
1,000 ton mile) will automatically decrease since engine efficiency
will improve in that year.

               Table II-15--Final Class 2b-8 Vocational Vehicle CO2 and Fuel Consumption Standards
----------------------------------------------------------------------------------------------------------------

----------------------------------------------------------------------------------------------------------------
                           EPA CO2 (gram/ton-mile) Standard Effective 2014 Model Year
----------------------------------------------------------------------------------------------------------------
                                       Light Heavy-Duty Class   Medium Heavy-Duty Class  Heavy Heavy-Duty Class
                                        2b-5.                    6-7.                     8
----------------------------------------------------------------------------------------------------------------
CO2 Emissions........................  388....................  234....................  226
----------------------------------------------------------------------------------------------------------------
           NHTSA Fuel Consumption (gallon per 1,000 ton-mile) Standard Effective 2016 Model Year \134\
----------------------------------------------------------------------------------------------------------------
                                       Light Heavy-DutyClass    Medium Heavy-Duty Class  Heavy Heavy-Duty Class
                                        2b-5.                    6-7.                     8
----------------------------------------------------------------------------------------------------------------
Fuel Consumption.....................  38.1...................  23.0...................  22.2
----------------------------------------------------------------------------------------------------------------
                           EPA CO2 (gram/ton-mile) Standard Effective 2017 Model Year
----------------------------------------------------------------------------------------------------------------
                                       Light Heavy-Duty Class   Medium Heavy-Duty Class  Heavy Heavy-Duty Class
                                        2b-5.                    6-7.                     8
----------------------------------------------------------------------------------------------------------------
CO2 Emissions........................  373....................  225....................  222
----------------------------------------------------------------------------------------------------------------

                 NHTSA Fuel Consumption (gallon per ton-mile) Standard Effective 2017 Model Year
----------------------------------------------------------------------------------------------------------------
                                       Light Heavy-Duty Class   Medium Heavy-Duty Class  Heavy Heavy-Duty Class
                                        2b-5.                    6-7.                     8
----------------------------------------------------------------------------------------------------------------
Fuel Consumption.....................  36.7...................  22.1...................  21.8
----------------------------------------------------------------------------------------------------------------

(iv) Off-Road and Low-Speed Vocational Vehicle Standards
    Some vocational vehicles, because they are primarily designed for
off-road use, may not be good candidates for low rolling resistance
tires. These vehicles may travel on-road for very limited periods of
time, such as in traveling on an urban road, or if they are off-loaded
from another vehicle onto a road and then are driven off-road. The
infrequent and limited exposure to on-road environments makes these
vehicles suitable candidates for providing an exemption from the
CO2 emissions and fuel consumption standards for vocational
vehicles (although the standards for HD engines used in vocational
vehicles would still apply).\135\ The agencies are also targeting other
vehicles that travel at low speeds and that are meant to be used both
on- and off-road. The application of certain technologies to these
vehicles may not provide the same level of benefits as it would for
pure on-road vehicles, and moreover, could even reduce the
functionality of the vehicle. In this case, the agencies want to ensure
that vehicle functionality is maintained to the maximum extent
possible, while avoiding the possibility that achievable benefits are
not realized because of the structure of the regulations. The sections
below explain this issue in more detail as it applies to tractors and
vocational vehicles.
---------------------------------------------------------------------------

    \134\ Manufacturers may voluntarily opt-in to the NHTSA fuel
consumption program in 2014 or 2015. Once a manufacturer opts into
the NHTSA program it must stay in the program for all the optional
MYs.
    \135\ See 75 FR at 74199.
---------------------------------------------------------------------------

    The agencies explained in the NPRM that certain vocational vehicles
have very limited on-road usage, and that although they would be
defined as ``motor vehicles'' per 40 CFR 85.1703, the fact that they
spend the most of their operations off-road might be reason for
excluding them from the vocational vehicle standards. Vocational
vehicles, such as those used on oil fields and construction sites,\136\
experience very little benefit from LRR tires or from any other
technologies to reduce GHG emissions and fuel consumption. The agencies
proposed to allow a narrow range of these de facto off-road vehicles to
be excluded from the proposed vocational vehicle standards if equipped
with special off-road tires having lug type treads. The agencies stated
in the NPRM that on/off road traction is the only tire performance
parameter which trades off with TRR so significantly that tire
manufacturers could be unable to develop tires meeting both a TRR
standard while maintaining or improving the characteristic allowing
them to perform off-road. See generally 75 FR at 74199-200. Therefore,
the agencies proposed to exempt these vehicles from the standards while
requiring them to use certified engines, which would provide fuel
consumption and CO2 emission reductions in all vocational
applications. To ensure that these vehicles were in fact used chiefly
off-road, the agencies proposed requirements that would allow exemption
of a vehicle provided the vehicle and the tires were speed restricted.
As mentioned, the agencies were aware that the majority of off road
trucks primarily use off-road tires and are low speed vehicles as well.
Based upon this understanding, the agencies specifically proposed that
a vehicle must meet the following requirements to qualify for an
exemption from vocational vehicle standards:
---------------------------------------------------------------------------

    \136\ Vehicles such as concrete mixers, off-road dump trucks,
backhoes and wheel loaders.
---------------------------------------------------------------------------

     Tires which are lug tires or contain a speed rating of
less than or equal to 60 mph; and
     A vehicle speed limiter governed to 55 mph.
    In response to the NPRM, EMA/TMA, Navistar and Volvo agreed with
the proposal to exclude off-road vocational vehicles from the standards
because these vehicles primarily operate off-road, but requested
broadening the exclusion to cover other types of vocational vehicles.
Several manufacturers (IAFC, FAMA, NTEA, NSWMA, AAPC, RMA, Navistar and
DTNA) requested the exemption of specific vehicle types, such as on/
off-road emergency vehicles, refuse vehicles, low speed transit buses
or school buses, because their usage was viewed as being incompatible
with LRR tires. Navistar opposed the application of the proposed
regulations to school buses, arguing that LRR tires may impact the ride
quality for children in school buses. However, Navistar also
acknowledged that a significant portion of the national fleet of school
buses already utilizes off-road tires designed with lug type tread
patterns (e.g., Kentucky). IAFC, FAMA and NTEA commented that fire
trucks and ambulances should also be exempted due to their part-time
off-road use such as in responding to a wildland fire or hazardous
materials incidents which would require operations on dirt and gravel
roads, fields or other off-road environments. Commenters also contended
that by requiring a 55-mph limitation, the proposed exemption would be
impractical for emergency vehicles due to the need to respond quickly
to life-threatening events. The refuse truck manufacturers and trade
associations, NSWMA and AAPC, commented that the solid waste industry
operates a variety of vocational vehicles that perform solely off-road
at landfills. These comments also requested an exemption for certain
refuse trucks (i.e., roll-off container trucks) that frequently go off-
road at construction sites. Other commenters (FAMA, IAFC and Oshkosh)
opposed compliance with the LRR standard for vocational vehicles for
on/off road mixed service tires with aggressive or lug treads, stating
that up to this point the industry has had very little interest in
improving the LRR aspects of these tires or even to conducting testing
to determine values for the coefficient of rolling resistance.
    For the final rules, the agencies have considered the issues raised
by commenters and have decided to adopt different criteria than
proposed for exempting vocational vehicles and vocational tractors that
primarily travel off-road. The agencies believe that the reasons for
proposing the exemption are equally applicable to a wider class of
vocational vehicles operating mostly off-road so that the proposals
were either unsuitable for the industry or too restrictive to capture
all the vehicles intended for the exemption. For example, the NPRM
proposal, by using tire tread patterns and VSLs as the basis for
qualifying vehicles for the exemption, was too restrictive because
other non-lug type tread patterns exist in the market as well as other
technologies which are equally capable of limiting the speed of the
vehicle, as mentioned by Volvo. Therefore, the

proposed exemption for off-road vocational vehicles will be replaced
with new criteria based on the vehicle application, whether it operates
at low speed and whether the vehicle has speed restricted tires. The
exemption is in part based on existing industry standards established
by NHTSA.\137\ As such, any vocational vehicle including vocational
tractors primarily used off-road or at low speeds must meet the
following criteria to be exempt from GHG and fuel consumption vehicle
standards:
---------------------------------------------------------------------------

    \137\ The heavy-duty off-road exemption is based in part on
requirements existing in NHTSA's Federal Motor Vehicle Safety
Standards (FMVSS) Nos. 119 and 121. In FMVSS No. 119, titled ``New
pneumatic tires for motor vehicles with a GVWR of more than 4,538
kilograms (10,000 pounds) and motorcycles,'' speed restricted tires
rated at a speed of 55 mph or less are subjected to lower test drum
speeds in the endurance test to account for their low design speeds
(e.g., off-road tires). The off-road vehicle exemptions adopted for
this heavy-duty program were based on the requirements used in FMVSS
No. 121, ``Air brake systems,'' to identify and exclude vocational
vehicles based upon their inability to meet on-highway stopping
distance requirements.
---------------------------------------------------------------------------

     Any vehicle primarily designed to perform work off-road
such as in oil fields, forests, or construction sites and having
permanently or temporarily affixed components designed to work in an
off-road environment (i.e., hazardous material equipment or off-road
drill equipment) or vehicles operating at low speeds making them
unsuitable for normal highway operation; and meeting one or more of the
following criteria:
     Any vehicle equipped with an axle that has a gross axle
weight rating (GAWR) of 29,000 pounds; or
     Any truck or bus that has a speed attainable in 2 miles of
not more than 33 mph; or
     Any truck that has a speed attainable in 2 miles of not
more than 45 mph, an unloaded vehicle weight that is not less than 95
percent of its gross vehicle weight rating (GVWR), and no capacity to
carry occupants other than the driver and operating crew.
    The agencies are also adopting in the final rules provisions to
exempt any vocational vehicle that can operate in both on and off-road
environments and has speed restricted tires rated at 55 mph or
below.\138\ The agencies' reasoning in adopting a speed restricted
exemption for tires is that the majority of mixed service tires used
for off-road use was identified as being restricted at 55 mph or
less.\139\ Also, as identified by FMVSS No. 119, speed restricted tires
at a rating of 55 mph or less are incapable of meeting the same on-road
performance standards as conventional tires. The agencies acknowledge
that using a speed restriction criteria could allow certain vehicles to
be exempted inappropriately (i.e., low speed city delivery tractors)
but the agencies believe this is preferable to creating a situation
where a segment of vehicles are precluded from performing their
intended applications. Therefore, the final rules include an exemption
for any mixed service (on and off-road) vocational vehicle equipped
with off-road tires that are speed restricted at 55 mph or less.
---------------------------------------------------------------------------

    \138\ See 40 CFR 1037.631.
    \139\ Particular tire use was identified during the FMVSS 119
rulemaking and confirmed through subsequent market research. See
``2010 Year Book the Tire and RIM Association Inc.''
---------------------------------------------------------------------------

    Manufacturers choosing to exempt vehicles based on the above
criteria will be required to provide a description of how they meet the
qualifications for each vehicle family group in their end-of-the year
and final year reports (see Section V).
    A manufacturer having an off-road vehicle failing to meet the
criteria under the agencies' off-road exemptions will be allowed to
submit a petition describing how and why their vehicles should qualify
for exclusion. The process of petitioning for an exemption is explained
in Sec.  1037.631 and Sec.  535.8. For each request, the manufacturer
will be required to describe why it believes an exemption is warranted
and address the following factors which the agencies will consider in
granting its petition:
     The agencies provide an exemption based on off-road
capability of the vehicle or if the vehicle is fitted with speed
restricted tires. Which exemption does your vehicle qualify under; and
     Are there any comparable tires that exist in the market to
carry out the desired application both on and off road for the subject
vehicle(s) of the petition which have LLR values that would enable
compliance with the standard?
(b) Heavy-Duty Engine Standards for Engines Installed in Vocational
Vehicles
    EPA is finalizing GHG standards \140\ and NHTSA is finalizing fuel
consumption standards for new heavy-duty engines installed in
vocational vehicles. The standards will vary depending on whether the
engines are diesel or gasoline powered since emissions and fuel
consumption profiles differ significantly depending on whether the
engine is gasoline or diesel powered. The agencies' analyses, as
discussed briefly below and in more detail later in this preamble and
in the RIA Chapter 2, show that these standards are appropriate and
feasible under each agency's respective statutory authorities.
---------------------------------------------------------------------------

    \140\ Specifically, EPA is finalizing CO2,
N2O, and CH4 emissions standards for new
heavy-duty engines over an EPA specified useful life period (See
Section 0 for the N2O and CH4 standards).
---------------------------------------------------------------------------

    The agencies have analyzed the feasibility of achieving the GHG and
fuel consumption standards, based on projections of what actions
manufacturers are expected to take to reduce emissions and fuel
consumption. EPA and NHTSA also present the estimated costs and
benefits of the heavy-duty engine standards in Section III below. In
developing the final rules, the agencies have evaluated the kinds of
technologies that could be utilized by engine manufacturers compared to
a baseline engine, as well as the associated costs for the industry and
fuel savings for the consumer and the magnitude of the GHG and fuel
consumption savings that may be achieved.
    EPA's existing criteria pollutant emissions regulations for heavy-
duty highway engines establish four service classes (three for
compression-ignition or diesel engines and one for spark ignition or
gasoline engines) that represent the engine's intended and primary
vehicle application, as shown in Table II-16 (40 CFR 1036.140 and
NHTSA's 49 CFR 535.4). The agencies proposed to use the existing
service classes to define the engine subcategories in this HD GHG
emissions and fuel consumption program. The agencies did not receive
any adverse comments to using this approach. Thus, the agencies are
adopting the four engine subcategories for this final action.

              Table II-16--Engine Regulatory Subcategories
------------------------------------------------------------------------
            Engine category                    Intended application
------------------------------------------------------------------------
Light Heavy-duty (LHD) Diesel..........  Class 2b through Class 5 trucks
                                          (8,501 through 19,500 pounds
                                          GVWR).
Medium Heavy-duty (MHD) Diesel.........  Class 6 and Class 7 trucks
                                          (19,501 through 33,000 pounds
                                          GVWR).
Heavy Heavy-duty (HHD) Diesel..........  Class 8 trucks (33,001 pounds
                                          and greater GVWR.
Gasoline...............................  Incomplete vehicles less than
                                          14,000 pounds GVWR and all
                                          vehicles (complete or
                                          incomplete) greater than
                                          14,000 pounds GVWR.
------------------------------------------------------------------------

(i) Diesel Engine Standards for Engines Installed in Vocational
Vehicles
    In the NPRM, the agencies proposed the following CO2 and
fuel consumption standards for HD diesel engines to be

installed in vocational vehicles, as shown in Table II-17.

                  Table II-17--Vocational Diesel Engine Standards Over the Heavy-Duty FTP Cycle
----------------------------------------------------------------------------------------------------------------
                                                                   Light heavy-    Medium heavy-   Heavy heavy-
              Model year                        Standard            duty diesel     duty diesel     duty diesel
----------------------------------------------------------------------------------------------------------------
2014-2016.............................  CO2 Standard (g/bhp-hr).             600             600             567
                                        Voluntary Fuel                      5.89            5.89            5.57
                                         Consumption Standard
                                         (gallon/100 bhp-hr).
2017 and Later........................  CO2 Standard (g/bhp-hr).             576             576             555
                                        Fuel Consumption (gallon/           5.66            5.66            5.45
                                         100 bhp-hr).
----------------------------------------------------------------------------------------------------------------

    The agencies explained in the NPRM that the standards were based on
our assessment of the findings of the 2010 NAS report and other
literature sources that there are technologies available to reduce fuel
consumption in all these engines by this level in the final time frame
in a cost-effective manner. Similar to the technology basis for HD
engines used in combination tractors, these technologies include
improved turbochargers, aftertreatment optimization, low temperature
exhaust gas recirculation, and engine friction reductions.
    The agencies proposed that the HD diesel engine CO2
standards for vocational vehicles would become effective in MY 2014 for
EPA, with more stringent CO2 standards becoming effective in
MY 2017, while NHTSA's fuel consumption standards would become
effective in MY 2017, which would be both consistent with the EISA
four-year minimum lead-time requirements and harmonized with EPA's
timing for stringency increases. The agencies explained that the three-
year timing, besides being required by EISA, made sense because EPA's
heavy-duty highway engine program for criteria pollutants had begun to
provide new emissions standards for the industry in three year
increments, which had caused the heavy-duty engine and vehicle
manufacturer product plans to fall largely into three year cycles
reflecting this regulatory environment.\141\ To further harmonize with
EPA, NHTSA proposed voluntary fuel consumption standards for HD diesel
engines for vocational vehicles in MYs 2014-2016, allowing
manufacturers to opt into the voluntary standards in any of those model
years.\142\ Manufacturers opting into the program must declare by
statement their intent to comply prior to or at the same time they
submit their first application for a certificate of conformity. A
manufacturer opting into the program would begin tracking credits and
debits beginning in the model year in which they opt in. Both agencies
proposed to allow manufacturers to generate and use credits to achieve
compliance with the HD diesel engine standards for vocational vehicles,
including averaging, banking, and trading (ABT), and deficit carry-
forward.
---------------------------------------------------------------------------

    \141\ See generally 75 FR at 74200-201.
    \142\ Once a manufacturer opts into the NHTSA program it must
stay in the program for all the optional MYs and remain standardized
with the implementation approach being used to meet the EPA emission
program.
---------------------------------------------------------------------------

    The agencies proposed to require HD diesel engine manufacturers to
achieve, on average, a three percent reduction in fuel consumption and
CO2 emissions for the 2014 standards over the baseline MY
2010 performance for the HHD diesel engines, and a five percent
reduction for the LHD and MHD diesel engines. The standards for the LHD
and MHD engine categories were proposed to be set at the same level
because the agencies found that there is an overlap in the displacement
of engines which are currently certified as LHDD or MHDD. The agencies
developed the baseline 2010 model year CO2 emissions from
data provided to EPA by manufacturers during the non-GHG certification
process. Analysis of CO2 emissions from 2010 model year LHD
and MHDD diesel engines showed little difference between LHD and MHD
diesel engine baseline CO2 performance in the 2010 model
year, which overall averaged 630 g CO2/bhp-hr (6.19 gal/100
bhp-hr).\143\ Furthermore, the technologies available to reduce fuel
consumption and CO2 emissions from these two categories of
engines are similar. The agencies considered combining these engine
categories into a single category, but decided to maintain these two
separate engine categories with the same standard level to respect the
different useful life periods associated with each category.
---------------------------------------------------------------------------

    \143\ Calculated using the conversion 10,180 g CO2/
gallon for diesel fuel.
---------------------------------------------------------------------------

    For vocational engines certified on the FTP cycle, the agencies
proposed to require a five percent reduction for HHD engines and nine
percent for LHD and MHD engines. For LHD and MHD engines in 2017 MY,
the nine percent reduction is based on the assumption that valvetrain
friction reduction can be achieved in LHD and MHD engines in addition
to turbo efficiency and accessory (water, oil, and fuel pump)
improvements, improved EGR cooler, and other approaches being used for
HHD engines.
    Commenters who discussed the HD diesel engine standards generally
did not differentiate between the standards for engines used in
combination tractors and the engines used in vocational vehicles. As
explained above in Section II.B.2.b, some commenters, such as EMA/TMA,
Cummins, DTNA, and other manufacturers, supported the proposed
standards, as long as the flexibilities proposed in the NPRM were
finalized as proposed. Volvo argued that the standards are being phased
in too quickly. Environmental groups and NGOs commented that the
standards should be more stringent and reflect the potential for
greater fuel consumption and CO2 emissions reductions
through the use of additional technologies outlined in the 2010 NAS
study.
    In response to those comments, the agencies refer back to our
discussion in Section II.B.2.b. The agencies believe that the
additional reductions may be achieved through the increased development
of the technologies evaluated for the 2014 model year standard, but the
agencies' analysis indicates that this type of advanced engine
development will require a longer development time than MY 2014. The
agencies are therefore providing additional lead time to allow for the
introduction of this additional technology, and waiting until 2017 to
increase stringency to levels reflecting application of
turbocompounding. See Chapter 2 of the RIA for more details.
    While it made sense to set standards at the same level for LHD and
MHD diesel engines for vocational vehicles, the agencies found that it
did not make sense to set HHD standards at the same level. Based on
manufacturer-submitted

CO2 data for the non-GHG emissions certification process,
the agencies found that the baseline for HHD diesel engines was much
lower than for LHD/MHD diesel engines--584 g CO2/bhp-hr
(5.74 gal/100 bhp-hr) on average for HHD, compared to 630 g
CO2/bhp-hr (6.19 gal/100 bhp-hr) on average for LHD/
MHD.\144\ In addition to the differences in the baseline performance,
the agencies believe that there may be some technologies available to
reduce fuel consumption and CO2 emissions that may be
appropriate for the HHD diesel engines but not for the LHD/MHD diesel
engines, such as turbocompounding. Therefore, the agencies are setting
a different standard level for HHD diesel engines to be used in
vocational vehicles. Additional discussion on technical feasibility is
included in Section III below and in Chapter 2 of the RIA.
---------------------------------------------------------------------------

    \144\ Calculated using the conversion 10,180 g CO2/
gallon for diesel fuel.
---------------------------------------------------------------------------

    After consideration of the comments, EPA and NHTSA are adopting as
proposed the CO2 emission standards and fuel consumption
standards for heavy-duty diesel engines installed in vocational
vehicles are presented in Table II-17. Consistent with proposal, the
first set of standards take effect with MY 2014 (mandatory standards
for EPA, voluntary standards for NHTSA), and the second set take effect
with MY 2017 (mandatory for both agencies).
    Compliance with the standards for engines installed in vocational
vehicles will be evaluated based on the composite HD FTP cycle. In the
NPRM, the agencies proposed standards based on the Heavy-duty FTP cycle
for engines used in vocational vehicles reflecting their primary use in
transient operating conditions (typified by both frequent accelerations
and decelerations), as well as in some steady cruise conditions as
represented on the Heavy-duty FTP. The primary reason the agencies
proposed two separate certification cycles for HD diesel engines--one
for HD diesel engines used in combination tractors and the other for HD
diesel engines used in vocational vehicles--is to encourage engine
manufacturers to install technologies appropriate to the intended use
of the engine with the vehicle.\145\
---------------------------------------------------------------------------

    \145\ See generally 75 FR at 74201.
---------------------------------------------------------------------------

    DTNA, Cummins, EMA/TMA, and Honeywell commented that certain
vocational vehicle applications would achieve greater fuel consumption
and CO2 emissions reductions in-use by using an engine
designed to meet the SET-based standard. They stated that some
vocational vehicles operate at steady-state more frequently than in
transient operation, such as motor coaches, and thus should be able to
have an engine certified on a steady-state cycle to better reflect the
vehicle's real use.
    In response, while the agencies recognize the value to
manufacturers of having additional flexibility that allows them to meet
the standards in a way most consistent with how their vehicles and
engines will ultimately be used, we remain concerned about increasing
flexibility in ways that might impair fuel consumption and
CO2 emissions reductions. The agencies are therefore
providing the option in these final rules for some vocational vehicles,
but not others, to have SET certified engines. Heavy heavy-duty
vocational engines will be allowed to be SET certified for vocational
vehicles, since SET certified HHD engines must meet more stringent GHG
and fuel consumption standards than FTP certified engines. We believe
this will provide manufacturers additional flexibility while still
achieving the expected fuel consumption and CO2 emissions
reductions. However, medium heavy-duty vocational engines will not be
allowed to be SET-certified, because medium heavy-duty engines
certified on the FTP must meet a more stringent standard than engines
certified on the SET, and the agencies are not confident that fuel
consumption and CO2 emissions reduction levels would
necessarily be maintained.
    As discussed above in Section II.B.2.b, the agencies place
important weight in making our decisions about the cost-effectiveness
of the standards and the availability of lead time on the fact that
engine manufacturers are expected to redesign and upgrade their
products during MYs 2014-2017. The final two-step CO2
emission and fuel consumption standards recognize the opportunity for
technology improvements over the rulemaking time frame, while
reflecting the typical diesel truck manufacturers' and diesel engine
manufacturers' product plan cycles. Over these four model years there
will be an opportunity for manufacturers to evaluate almost every one
of their engine models and add technology in a cost-effective way,
consistent with existing redesign schedules, to control GHG emissions
and reduce fuel consumption. The time-frame and levels for the
standards, as well as the ability to average, bank and trade credits
and carry a deficit forward for a limited time, are expected to provide
manufacturers the time needed to incorporate technology that will
achieve the final GHG and fuel consumption reductions, and to do this
as part of the normal engine redesign process. This is an important
aspect of the final rules, as it will avoid the much higher costs that
would occur if manufacturers needed to add or change technology at
times other than these scheduled redesigns.\146\ This time period will
also provide manufacturers the opportunity to plan for compliance using
a multi-year time frame, again in accord with their normal business
practice. Further details on lead time, redesigns and technical
feasibility can be found in Section III.
---------------------------------------------------------------------------

    \146\ See 75 FR at 25467-68.
---------------------------------------------------------------------------

    The agencies recognize, however, that the schedule of changes for
the final standards may not be the most cost-effective one for all
manufacturers. For HD diesel engines for use in tractors, the agencies
discussed above in Section II.B.2.b our decision in this final program
to allow an ``OBD phase-in'' option for meeting the standards, based on
comments received from several industry organizations indicating that
aligning technology changes for multiple regulatory requirements would
provide them with greater flexibility. In the context of HD diesel
engines for use in vocational vehicles, Volvo, EMA/TMA, and DDC
specifically requested an ``OBD phase-in'' option in its comments to
the NPRM. DDC argued that bundling design changes where possible can
reduce the burden on industry for complying with regulations, so
aligning the introduction of the OBD, GHG, and fuel consumption
standards could help reduce the resources devoted to validation of new
product designs and certification.
    The agencies have the same interest in providing this flexibility
for manufacturers of HD diesel engines for use in vocational vehicles
as in providing it for manufacturers of HD diesel engines for use in
combination tractors, as long as equivalent emissions and fuel savings
are maintained. Thus, in order to provide additional flexibility for
manufacturers looking to align their technology changes with multiple
regulatory requirements, the agencies are finalizing an alternate ``OBD
phase-in'' option for meeting the HD diesel engine standards which
delivers equivalent CO2 emissions and fuel consumption
reductions as the primary standards for the engines built in the 2013
through 2017 model years, as shown in Table II-18.

    Table II-18--Comparison of CO2 reductions for the Engine Standards Under the Alternative OBD Phase-in and
                                                Primary Phase-In
----------------------------------------------------------------------------------------------------------------
                                 HHD FTP                                                LHD/MHD FTP
----------------------------------------------------------------------------------------------------------------
                                                               Difference                             Difference
                                      Primary      Optional   in lifetime    Primary      Optional   in lifetime
                                      phase-in     phase-in    CO2 engine    phase-in     phase-in    CO2 engine
                                    standard (g/ standard (g/  emissions   standard (g/ standard (g/  emissions
                                      bhp-hr)      bhp-hr)       (MMT)       bhp-hr)      bhp-hr)       (MMT)
----------------------------------------------------------------------------------------------------------------
Baseline..........................          584          584  ...........          630          630
2013 MY Engine....................          584          577           20          630          618           14
2014 MY Engine....................          567          577          -28          600          618          -22
2015 MY Engine....................          567          577          -28          600          618          -22
2016 MY Engine....................          567          555           34          600          576           29
2017 MY Engine....................          555          555            0          576          576            0
Net Reductions (MMT)..............  ...........  ...........           -3  ...........  ...........            0
----------------------------------------------------------------------------------------------------------------

     Table II-19 presents the final HD diesel engine CO2
emission and fuel consumption standards under the optional ``OBD phase-
in'' option.

                            Table II-19--Optional Heavy-Duty Engine Standard Phase-in
----------------------------------------------------------------------------------------------------------------
                                                                   Light heavy-    Medium heavy-   Heavy heavy-
              Model year                        Standard            duty diesel     duty diesel     duty diesel
----------------------------------------------------------------------------------------------------------------
2013..................................  CO2 Standard (g/bhp-hr).             618             618             577
                                        Voluntary Fuel                      6.07            6.07            5.67
                                         Consumption Standard
                                         (gallon/100 bhp-hr).
2016 and Later........................  CO2 Standard (g/bhp-hr).             576             576             555
                                        Fuel Consumption (gallon/           5.66            5.66            5.45
                                         100 bhp-hr).
----------------------------------------------------------------------------------------------------------------

    In order to ensure equivalent CO2 and fuel consumption
reductions and orderly compliance, and to avoid gaming, the agencies
are requiring that if a manufacturer selects the OBD phase-in option,
it must certify its engines starting in the 2013 model year and
continue using this phase-in through the 2016 model year. Manufacturers
may opt into the OBD phase-in option through the voluntary NHTSA
program, but must opt in in the 2013 model year and continue using this
phase-in through the 2016 model year. Manufacturers that opt in to the
voluntary NHTSA program in 2014 and 2015 will be required to meet the
primary phase-in schedule and may not adopt the OBD phase-in option.
    As discussed above in Section II.B.2.b, while the agencies believe
that the HD diesel engine standards are appropriate, cost-effective,
and technologically feasible in the rulemaking time frame, we also
recognize that when regulating a category of engines for the first
time, there will be individual products that may deviate significantly
from the baseline level of performance, whether because of a specific
approach to criteria pollution control, or due to engine calibration
for specific applications or duty cycles. That earlier discussion
described HD diesel engines for use in combination tractors, but the
same supporting information is relevant to the agencies' consideration
of an alternate standard for HD diesel engines installed in vocational
vehicles. In the NPRM, the agencies proposed an optional engine
standard for HD diesel engines installed in vocational vehicles based
on a five percent reduction from the engine's own 2011 model year
baseline level, but requested comment on whether a two percent
reduction would be more appropriate.\147\ The comments received in
response did not directly address engines for vocational vehicles, but
the agencies believe that the information provided by Navistar and
others is equally applicable to HD diesel engines for combination
tractors and for vocational vehicles. Our assessment for the final
standards is that a 2.5 percent reduction is appropriate for LHD and
MHD engines installed in vocational vehicles and 3 percent is
appropriate for HHD engines installed in vocational vehicles given the
technologies available for application to legacy products by model year
2014.\148\ Unlike the majority of engine products in this segment,
engine manufacturers have devoted few resources to developing
technologies for these legacy products reasoning that the investment
would have little value if the engines are to be substantially
redesigned or replaced in the next five years. Hence, although the
technologies we have identified to achieve the proposed five percent
reduction would theoretically work for these legacy products, there is
inadequate lead time for manufacturers to complete the pre-application
development needed to add the technology to these engines by 2014. The
mix of technologies available off the shelf for legacy engines varies
between engine lines within OEMs and varies among OEMs as well. On
average, based on our review of manufacturer development history and
current plans, we project that for the legacy products approximately
half of the defined technologies appropriate for the 2014 standard will
be available and ready for application by 2014 for older legacy engine
designs. Hence, we have concluded that if we limit the reductions to
those improvements which reflect further enhancements of already
installed systems rather than the addition or replacement of
technologies with fully developed new on the shelf components, the
potential improvement for the 2014 model year will be 2.5 percent for
LHD and MHD engines and 3 percent HHD engines.
---------------------------------------------------------------------------

    \147\ See 75 FR at 74202.
    \148\ To be codified at 40 CFR 1036.620.
---------------------------------------------------------------------------

    Just as for HD diesel engines used in combination tractors, the
agencies stress that this option for HD engines used in vocational
vehicles is temporary and

limited and is being adopted to address diverse manufacturer needs
associated with complying with this first phase of the regulations.
This optional, alternative standard will be available only for the 2014
through 2016 model years, because we believe that manufacturers will
have had ample opportunity to make appropriate changes to bring their
product performance into line with the rest of the industry after that
time. This optional standard will not be available unless and until a
manufacturer has exhausted all available credits and credit
opportunities, and engines under the alternative standard could not
generate credits.
    The agencies note that manufacturers choosing to utilize this
option in MYs 2014-2016 will have to make a greater relative
improvement in MY 2017 than the rest of the industry, since they will
be starting from a worse level. For compliance purposes, in MYs 2014-
2016 emissions from engines certified and sold at the alternate level
will be averaged with emissions from engines certified and sold at more
stringent levels to arrive at a weighted average emissions level for
all engines in the subcategory. Again, this option can only be taken if
all other credit opportunities have been exhausted and the manufacturer
still cannot meet the primary standards. If a manufacturer chooses this
option to meet the EPA emission standards in MY 2014-2016, and wants to
opt into the NHTSA fuel consumption program in these same MYs it must
follow the exact path followed under the EPA program utilizing
equivalent fuel consumption standards.
    As discussed above in Section II.B.2.b, Volvo argued that
manufacturers could game the standard by establishing an artificially
high 2011 baseline emission level. This could be done, for example, by
certifying an engine with high fuel consumption and GHG emissions that
is either: (1) Not sold in significant quantities; or (2) later altered
to emit fewer GHGs and consume less fuel through service changes. In
order to mitigate this possibility, the agencies are requiring either
that the 2011 model year baseline must be developed by averaging
emissions over all engines in an engine averaging set certified and
sold for that model year so as to prevent a manufacturer from
developing a single high GHG output engine solely for the purpose of
establishing a high baseline or meet additional criteria. The agencies
are allowing manufacturers to combine light heavy-duty and medium
heavy-duty diesel engines into a single averaging set for this
provision because the engines have the same GHG emissions and fuel
consumption standards. If a manufacturer does not certify all engine
families in an averaging set to the alternate standards, then the
tested configuration of the engine certified to the alternate standard
must have the same engine displacement and its rated power within 5
percent of the highest rated power as the baseline engine. In addition,
the tested configurations must have a BSFC equivalent to or better than
all other configurations within the engine family and represent a
configuration that is sold to customers.
(ii) Gasoline Engine Standard
    Heavy-duty gasoline engines are also used in vocational vehicle
applications. The number of engines certified in the past for this
segment of vehicles is very limited and has ranged between three and
five engine models.\149\ Unlike the heavy-duty diesel engines typical
of this segment which are built for vocational vehicles, these gasoline
engines are developed for heavy-duty pickup trucks and vans primarily,
but are also sold as loose engines to vocational vehicle manufacturers,
for use in vocational vehicles such as some delivery trucks. Some
fleets still prefer gasoline engines over diesel engines. In the past,
this was the case since gasoline stations were more prevalent than
stations that sold diesel fuel. Because they are developed for HD
pickups and vans, the agencies evaluated these engines in parallel with
the heavy-duty pickup truck and van standard development. As in the
pickup truck and van segment, the agencies anticipated that the
manufacturers will have only one engine re-design within the 2014-2018
model years under consideration within the proposal. The agencies
therefore proposed fuel consumption and CO2 emissions
standards for gasoline engines for use in vocational vehicles, which
represent a five percent reduction in CO2 emissions and fuel
consumption in the 2016 model year over the 2010 MY baseline through
use of technologies such as coupled cam phasing, engine friction
reduction, and stoichiometric gasoline direct injection.
---------------------------------------------------------------------------

    \149\ EPA's heavy-duty engine certification database at http://www.epa.gov/otaq/certdata.htm#largeng.
---------------------------------------------------------------------------

    In our meetings with all three of the major manufacturers in the HD
pickup and van segment, confidential future product plans were shared
with the agencies. Reflecting those plans and our estimates for when
engine changes will be made in alignment with those product plans, we
had concluded for proposal that the 2016 model year reflects the most
logical model year start date for the heavy-duty gasoline engine
standards. In order to meet the standards we are finalizing for heavy-
duty pickups and vans, we project that all manufacturers will have
redesigned their gasoline engine offerings by the start of the 2016
model year. Given the small volume of loose gasoline engine sales
relative to complete heavy-duty pickup sales, we think it is
appropriate to set the timing for the heavy-duty gasoline engine
standard in line with our projections for engine redesigns to meet the
heavy-duty pickup truck standards. Therefore, NHTSA's final fuel
consumption standard and EPA's final CO2 standard for heavy-
duty gasoline engines are first effective in the 2016 model year.
    The baseline 2010 model year CO2 performance of these
heavy-duty gasoline engines over the Heavy-duty FTP cycle is 660 g
CO2/bhp-hr (7.43 gal/100 bhp-hr) in 2010 based on non-GHG
certification data provided to EPA by the manufacturers. The agencies
are finalizing 2016 model year standards that require manufacturers to
achieve a five percent reduction in CO2 compared to the 2010
MY baseline through use of technologies such as coupled cam phasing,
engine friction reduction, and stoichiometric gasoline direct
injection. Additional detail on technology feasibility is included in
Section III and in the RIA Chapter 2. As shown in Table II-20, NHTSA is
finalizing as proposed a 7.06 gallon/100 bhp-hr standard for fuel
consumption while EPA is adopting as proposed a 627 g CO2/
bhp-hr standard tested over the Heavy-duty FTP, effective in the 2016
model year. Similar to EPA's non-GHG standards approach, manufacturers
may generate and use credits by the same engine averaging set to show
compliance with both agencies' standards.

            Table II-20--Heavy-Duty Gasoline Engine Standards
------------------------------------------------------------------------
                                                             Gasoline
            Model year                                        engine
                                                             standard
------------------------------------------------------------------------
2016 and Later....................  CO2 Standard (g/bhp-             627
                                     hr).
                                    Fuel Consumption                7.06
                                     (gallon/100 bhp-hr).
------------------------------------------------------------------------

(c) In-Use Standards
    Section 202(a)(1) of the CAA specifies that emissions standards are
to be applicable for the useful life of the vehicle. The in-use
standards that EPA

is finalizing apply to individual vehicles and engines. NHTSA is not
finalizing in-use standards that would apply to the vehicles and
engines in a similar fashion.
    EPA proposed that the in-use standards for heavy-duty engines
installed in vocational vehicles be established by adding an adjustment
factor to the full useful life emissions results projected in the EPA
certification process to account for measurement variability inherent
in testing done at different laboratories with different engines. The
agency proposed a two percent adjustment factor and requested comments
and additional data during the proposal to assist in developing an
appropriate factor level. The agency received additional data during
the comment period which identified production variability which was
not accounted for at proposal. Details on the development of the final
adjustment factor are included in RIA Chapter 3. Based on the data
received, EPA determined that the adjustment factor in the final rules
should be higher than the proposed level of two percent. EPA is
finalizing a three percent adjustment factor for the in-use standard to
provide a reasonable margin for production and test-to-test variability
that could result in differences between the initial emission test
results and emission results obtained during subsequent in-use testing.
    We are finalizing regulatory text (in Sec.  1036.150) to allow
engine manufacturers to used assigned deterioration factors (DFs)
without performing their own durability emission tests or engineering
analysis. However, the engines would still be required to meet the
standards in actual use without regard to whether the manufacturer used
the assigned DFs. This allowance is being adopted as an interim
provision applicable only for this initial phase of standards.
    Manufacturers will be allowed to use an assigned additive DF of 0.0
g/bhp-hr for CO2 emissions from any conventional engine
(i.e., an engine not including advance or innovative technologies).
Upon request, we could allow the assigned DF for CO2
emissions from engines including advance or innovative technologies,
but only if we determine that it would be consistent with good
engineering judgment. We believe that we have enough information about
in-use CO2 emissions from conventional engines to conclude
that they will not increase as the engines age. However, we lack such
information about the more advanced technologies.
    EPA proposed that the useful life for these engines and vehicles
with respect to GHG emissions be set equal to the respective useful
life periods for criteria pollutants. EPA proposed that the existing
engine useful life periods, as included in Table II-21, be broadened to
include CO2 emissions and fuel consumption for both engines
and vocational vehicles. The agency did not receive any adverse
comments with this approach and is finalizing the useful life periods
as proposed (see 40 CFR 1036.108(d) and 1037.105). While NHTSA will use
useful life considerations for establishing fuel consumption
performance for initial compliance and for ABT, NHTSA does not intend
to implement an in-use compliance program for fuel consumption, because
it is not required under EISA and because it is not currently
anticipated there will be notable deterioration of fuel consumption
over the engines' useful life.

                    Table II-21--Useful Life Periods
------------------------------------------------------------------------
                                               Years           Miles
------------------------------------------------------------------------
Class 2b-5 Vocational Vehicles, Spark                 10         110,000
 Ignited, and Light Heavy-Duty Diesel
 Engines................................
Class 6-7 Vocational Vehicles and Medium              10         185,000
 Heavy-Duty Diesel Engines..............
Class 8 Vocational Vehicles and Heavy                 10         435,000
 Heavy-Duty Diesel Engines..............
------------------------------------------------------------------------

(2) Test Procedures and Related Issues
    The agencies are finalizing test procedures to evaluate fuel
consumption and CO2 emissions of vocational vehicles in a
manner very similar to Class 7 and Class 8 combination tractors. This
section describes the simulation model for demonstrating compliance,
engine test procedures, and a test procedure for evaluating hybrid
powertrains (a potential means of generating credits, although not part
of the technology package on which the final standard for vocational
vehicles is premised).
(a) Computer Simulation Model
    As previously mentioned, to achieve the goal of reducing emissions
and fuel consumption for both trucks and engines, we are finalizing
separate engine and vehicle-based emission and fuel consumption
standards for vocational vehicles and engines used in those vehicles.
For the vocational vehicles, engine manufacturers are subject to the
engine standards, and chassis manufacturers are required to install
certified engines in their chassis. The chassis manufacturer is subject
to a separate vehicle-based standard that uses the final vehicle
simulation model, the GEM, to evaluate the impact of the tire design to
determine compliance with the vehicle standard.
    A simulation model, in general, uses various inputs to characterize
a vehicle's properties (such as weight, aerodynamics, and rolling
resistance) and predicts how the vehicle would behave on the road when
it follows a driving cycle (vehicle speed versus time). On a second-by-
second basis, the model determines how much engine power needs to be
generated for the vehicle to follow the driving cycle as closely as
possible. The engine power is then transmitted to the wheels through
transmission, driveline, and axles to move the vehicle according to the
driving cycle. The second-by-second fuel consumption of the vehicle,
which corresponds to the engine power demand to move the vehicle, is
then calculated according to the fuel consumption map embedded in the
compliance model. Similar to a chassis dynamometer test, the second-by-
second fuel consumption is aggregated over the complete drive cycle to
determine the fuel consumption of the vehicle.
    NHTSA and EPA are finalizing an approach consistent with the
proposal to evaluate fuel consumption and CO2 emissions
respectively through a simulation of whole-vehicle operation,
consistent with the NAS recommendation to use a truck model to evaluate
truck performance. The EPA developed the GEM for the specific purpose
of this rulemaking to evaluate vehicle performance. The GEM is similar
in concept to a number of vehicle simulation tools developed by
commercial and government entities. The model developed by the EPA and
finalized here was designed for the express purpose of vehicle
compliance demonstration and is therefore simpler and less configurable
than similar

commercial products. This approach gives a compact and quicker tool for
evaluating vehicle compliance without the overhead and costs of a more
complicated model. Details of the model, including changes made to the
model to address concerns of the peer reviewers and commenters are
included in Chapter 4 of the RIA. An example of the GEM input screen is
shown in Figure II-4.
[GRAPHIC] [TIFF OMITTED] TR15SE11.004

    EPA and NHTSA have validated the GEM simulation of vocational
vehicles against a commonly used simulation tool used in industry, GT-
Drive, for each vocational vehicle subcategory. Prior to using GT-Drive
as a comparison tool, the agencies first benchmarked a GT-Drive
simulation of the combination tractor tested at Southwest Research
against the experimental test results from the chassis dynamometer in
the same manner as done for GEM. Then the EPA developed three
vocational vehicle models (LHD, MHD, and HHD) and simulated them using
both GEM and GT-Drive. Overall, the GEM and GT-Drive predicted the fuel
consumption and CO2 emissions for all three vocational
vehicle subcategories with differences of less than 2 percent for the
three test cycles--the California ARB Transient cycle, 55 mph cruise,
and 65 mph cruise cycle.\150\ The final simulation model is described
in greater detail in RIA Chapter 4 and is available for download by
interested parties at (http://www.epa.gov/otaq/).
---------------------------------------------------------------------------

    \150\ See RIA Chapter 4, Table 4-8.
---------------------------------------------------------------------------

    The agencies are requiring that for demonstrating compliance, a
chassis manufacturer would measure the performance of tires, input the
values into GEM, and compare the model's output to the standard. As
explained earlier, low rolling resistance tires are the only technology
on which the agencies' own feasibility analysis for these vehicles is
predicated. The input values for the simulation model will be derived
by the manufacturer from the final tire test procedure described in
this action. The remaining model inputs will be fixed values pre-
defined by the agencies. These are detailed in the RIA Chapter 4,
including the engine fuel consumption map to be used in the simulation.
(b) Tire Rolling Resistance Assessment
    In terms of how tire rolling resistance would be measured, the
agencies proposed to require that the tire rolling resistance input to
the GEM be determined using ISO 28580:2009(E), Passenger car, truck and
bus tyres--Methods of measuring rolling resistance--Single point test
and correlation of measurement results.\151\ The agencies stated that
they believed the ISO test method was the most appropriate for this
program because the method is the same one used by the NHTSA tire fuel
efficiency consumer information program,\152\ by European
regulations,\153\ and by the EPA SmartWay program.
---------------------------------------------------------------------------

    \151\ See http://www.iso.org/iso/iso_catalogue/catalogue_tc/catalogue_detail.htm?csnumber=44770.
    \152\ 75 FR 15893, March 30,2010.
    \153\ See http://www.energy.ca.gov/2009publications/CEC-600-2009-010/CEC-600-2009-010-SD-REV.PDF (last accessed May 9, 2011).
---------------------------------------------------------------------------

    The NPRM also discussed the potential for tire-to-tire variability
to confound rolling resistance measurement results for LRR tires--that
is, different tires of the same tire model could turn out to have
different rolling resistance measurements when run on

the same test. NHTSA's research during the development of the light-
duty vehicle tire fuel efficiency consumer information program
identified several sources of variability including test procedures,
test equipment and the tires themselves, but found that all of the
existing test methods had similar levels of and sources of
variability.\154\ The agencies proposed to address production tire-to-
tire variability by specifying that three tire samples within each tire
model be tested three times each, and that the average of the nine
tests would be used as the Rolling Resistance Coefficient (CRR) for the
tire, which would be the basis for the rolling resistance value for
that tire that the manufacturer would enter into the GEM. The agencies
requested comment on this proposed method.\155\
---------------------------------------------------------------------------

    \154\ 75 FR 15893, March 30, 2010.
    \155\ See generally 75 FR at 74204.
---------------------------------------------------------------------------

    The agencies received many comments on the subject of tire rolling
resistance, including suggestions for alternative test procedures and
compliance issues. Regarding whether the agencies should base tire CRR
inputs for the GEM on the use of the ISO 28580 test procedure, the
American Automotive Policy Council (AAPC) argued that the agencies
should instead require the SAE J2452 Coastdown test method for
calculating tire rolling resistance, which the commenter stated was
preferred by OEMs because it simulates the use of tires on actual
vehicles rather than the ISO procedure which tests the tire by itself.
The Rubber Manufacturers Association (RMA) argued, in contrast, that
the agencies should use the SAE J1269 multi-point test, which is
currently the basis for the EPA SmartWay\TM\ CRR baseline values. RMA
also argued that the SAE J1269 multi-point test can be used to
accurately predict truck/bus tire CRR at various loads and inflations,
including at the ISO 28580 load and inflation conditions, and that
therefore the agencies should use the SAE test, or if the agencies want
to use ISO, they should accept results from the SAE test and just
correlate them. Regarding compliance obligations, RMA further argued
that it was not clear how or in what format testing information would
need to be provided in order to be in compliance with the proposed
requirement at Sec.  1037.125(i).
    The agencies analyzed many comments on the subject of tire rolling
resistance. One of the primary concerns raised in comments was that the
proposed test protocol and measurement methodology would not adequately
address production tire variability and measurement variability.
Commenters stated that machine-to-machine differences are a significant
source of variation, and this variation would make it difficult for
manufacturers to be confident that the agency would assign the same CRR
to a tire was tested for compliance purposes. Commenters argued that
the ISO 28580 test method is unique in that it specifies a procedure to
correlate results between different test equipment (i.e., different
rolling resistance test machines), but not all aspects of the ISO
procedure have been completely defined. Commenters stated that under
ISO 28580, the lab alignment procedure depends on the specification of
a reference test machine to which all other labs will align their
measurement results. RMA particularly emphasized the need for
establishing a tire testing reference lab for use with ISO 28580,
referencing the European Tyre and Rim Technical Organization (ETRTO)
estimate that CRR values could vary as much as 20 percent absent an
inter-laboratory alignment procedure. RMA stated the agencies should
specify a reference laboratory with the designation proposed in a
supplemental notice that provides public comment. In addition, RMA
commented that the extra burden proposed by the agencies for testing
three tires, three times each is nine times more burdensome than what
is required through the ISO procedure.
    Based on the additional tire rolling resistance research conducted
by the agencies, we have decided to use the ISO 28580 test procedure,
as proposed, to measure tire performance for these final rules.
    The agencies believe this test procedure provides two advantages
over other test methods. First, the ISO 28580 test method is unique in
that it specifies a procedure to correlate results between different
test equipment (i.e., different tire rolling resistance test machines).
This is important because NHTSA's research conducted for the light-duty
tire fuel efficiency program indicated that machine-to-machine
differences are a source of variation.\156\ In addition, the ISO 28580
test procedure is either used, or proposed to be used, by several
groups including the European Union through Regulation (EC) No 661/2009
\157\and the California Air Resources Board (CARB) through a staff
recommendation for a California regulation,\158\ and the EPA SmartWay
program. Using the ISO 28580 may help reduce burden on manufacturers by
allowing a single test protocol to be used for multiple regulations and
programs. While we recognize that commenters recommended the use of
other test procedures, like SAE J1269, the agencies have determined
there is no established data conversion method from the SAE J1269
vehicle condition for vocational vehicle tires to the ISO 28580 single
point condition at this time, and that given our reasonable preference
for the ISO procedure, it would not be practical to attempt to include
the use of the SAE J1269 procedure as an optional way of determining
CRR values for the GEM inputs.
---------------------------------------------------------------------------

    \156\ 75 FR 15893, March 30, 2010.
    \157\ See http://eur-lex.europa.eu/LexUriServ/LexUriServ.do?uri=OJ:L:2009:200:0001:0024:EN:PDF (last accessed May
8, 2011).
    \158\ See http://www.energy.ca.gov/2009publications/CEC-600-2009-010/CEC-600-2009-010-SD-REV.PDF (last accessed May 9, 2011).
---------------------------------------------------------------------------

    The agencies received comments from the Rubber Manufacturers
Association, Michelin, and Bridgestone which identified the need to
develop a reference lab and alignment tires. Because the ISO has not
yet specified a reference lab and machine for the ISO 28580 test
procedure, NHTSA announced in its March 2010 final rule concerning the
light-duty tire fuel efficiency consumer information program that NHTSA
would specify this laboratory for the purposes of implementing that
rule so that tire manufacturers would know the identity of the machine
against which they may correlate their test results. NHTSA has not yet
announced the reference test machine(s) for the tire fuel efficiency
consumer information program. Therefore, for the light-duty tire fuel
efficiency rule, the agencies are postponing the specification of a
procedure for machine-to-machine alignment until a tire reference lab
is established. The agencies anticipate establishing this lab in the
future with intentions for the lab to accommodate the light-duty tire
fuel efficiency program.
    Under the ISO 28580 lab alignment procedure, machine alignment is
conducted using batches of alignment tires of two models with defined
differences in rolling resistance that are certified on a reference
test machine. ISO 28580 specifies requirements for these alignment
tires (``Lab Alignment Tires'' or LATs), but exact tire sizes or models
of LATs are not specifically identified in ISO 28580. Because the test
procedure has not been finalized and heavy-duty LATs are not currently
defined, the agencies are postponing the use of these elements of ISO
28580 to

a future rulemaking. The agencies also note the lab-to-lab comparison
conducted in the most recent EPA tire test program mentioned
previously. The agencies reviewed the CRR data from the tires that were
tested at both the STL and Smithers laboratories to assess inter-
laboratory and machine variability. The agencies conducted statistical
analysis of the data to gain better understanding of lab-to-lab
correlation and developed an adjustment factor for data measured at
each of the test labs. Based on these results, the agencies believe the
lab-to-lab variation for the STL and Smithers laboratories would have
very small effect on measured CRR values. Based on the test data, the
agencies judge that it is reasonable to implement the HD program with
current levels of variability, and to allow the use of either Smithers
or STL laboratories for determining the CRR value in the HD program, or
demonstrate that the test facilities will not bias results low relative
to Smithers or STL laboratories.
    RMA also commented that the extra burden proposed by the agencies
for testing three tires, three times each is nine times more burdensome
than what is required through the ISO procedure. Since the proposal,
EPA obtained replicate test data for a number of Class 8 combination
tractor tires from various manufacturers. Some of these were tires
submitted to SmartWay for verification, while some were tires tested by
manufacturers for other purposes. Three tire model samples for 11 tire
models were tested using the ISO 28580 test.\159\ A mean and a standard
deviation were calculated for each set of three replicate measurements
performed on each tire of the 3-tire sample. The coefficient of
variability (COV) of the CRR was calculated by dividing the standard
deviation by the mean. The values of COV ranged from 0 percent (no
measurable variability) to six percent. In addition, during the period
September 2010 and June 2011, EPA contracted with Smithers-Rapra to
select and test for rolling resistance using ISO 28580 for a
representative sample of Class 4-8 vocational vehicle tires. As part of
the test, 10 tires were selected for replicate testing.\160\ Three
replicate tests were conducted for each of the tires, to evaluate test
variability only. The COV of the RRC results ranged from
nearly 0 to 2 percent, with a mean of less than 1 percent. Based on the
results of these two testing programs, the agencies determined that the
impact of production variability is greater than the impact of
measurement variability. Thus, the agencies concluded that the extra
burden of testing a single tire three times was not necessary to obtain
accurate results, but the variability of RRC results due to
manufacturing of the tires is significant to continue to require
testing of three tire samples for each tire model. In summary, we are
allowing manufacturers to determine the rolling resistance coefficient
of the heavy-duty tires by testing three tire samples one time each.
---------------------------------------------------------------------------

    \159\ Bachman, Joseph. EPA Memorandum to the Docket. Heavy-Duty
Tire Evaluation. Docket EPA-HQ-OAR-2010-0162. July 2011.
    \160\ Bachman, Joseph. EPA Memorandum to the Docket. Heavy-Duty
Tire Evaluation. Docket EPA-HQ-OAR-2010-0162. July 2011.
---------------------------------------------------------------------------

    For the final rules, the agencies are also including a warm up
cycle as part of the procedure for bias ply tires to allow these tires
to reach a steady temperature and volume state before ISO 28580
testing. This procedure is similar to a procedure that was developed
for the light-duty tire fuel efficiency consumer information program,
and was adopted from a procedure defined in Federal motor vehicle
safety standard No. 109 (FMVSS No. 109).\161\
---------------------------------------------------------------------------

    \161\ See 49 CFR 571.109.
---------------------------------------------------------------------------

    Finally, the agencies are including testing and reporting for
`single-wide' or `super-single' type tires. These tires replace the
traditional `dual' wheel tire combination with a single wheel and tire
that is nearly as wide as the dual combination with similar load
capabilities. These tire types were developed as a fuel saving
technology. The tires provide lower rolling resistance along with a
reduction in weight when compared to a typical set of dual wheel tire
combinations; and are one of the technologies included in the EPA
SmartWay\TM\ program. The agencies have learned that there is limited
testing equipment available that is capable of testing single wide
tires; single wide tires require a wider test machine drum than
required for conventional tires. Although the number of machines
available is limited, the agencies believe the equipment is adequate
for the testing and reporting of CRR for this program.
    As discussed above, the agencies are taking the approach of using
CRR for the HD fuel efficiency and greenhouse gas program to align with
the measurement methodology already employed or proposed by the EPA
SmartWay program, the European Union Regulation (EC) No 661/2009 \162\
and the California Air Resources Board (CARB) through a staff
recommendation for a California regulation.\163\ In the NPRM, the
agencies proposed to use CRR, but for purposes of developing these
final rules, the agencies also evaluated whether to use CRR or Rolling
Resistance Force (RRF) as the measurement for tire rolling
resistance for the GEM input. The agencies considered RRF
largely because in the NPRM for Passenger Car Tire Fuel Efficiency
(TFE) program, NHTSA had proposed to use RRF. A key
distinction between these two programs, and their associated metrics,
are the differences in how the measurement data are used and who uses
the data. In particular, the HD fuel efficiency and GHG emissions
program is a compliance program using information developed by and for
technical personnel at manufacturers and agencies to determine a
vehicle's compliance with regulations. The TFE program, in contrast, is
a consumer education program intended to inform consumers making
purchase decisions regarding the fuel saving benefits of replacement
passenger car tires. The target audiences are much different for the
two programs which in turn affect how the information will be used. The
agencies believe that RRF may be more intuitive for non-
technical people because tires that are larger and/or that carry higher
loads will generally have numerically higher RRF values than
smaller tires and/or tires that carry lower loads. CRR values generally
follow an opposite trend, where tires that are larger and/or carry
higher loads will generally have numerically lower CRR values than
smaller tires and/or tires that carry lower loads. The agencies believe
this key distinction helps define the type of metrics to be used and
communicated in accordance with their respective purposes.
---------------------------------------------------------------------------

    \162\ See Note 157, above.
    \163\ See Note 158, above.
---------------------------------------------------------------------------

    Additionally, the CRR metric for use in the MD/HD program is not
susceptible to the skew associated with tire diameter. Medium- and
heavy-duty vehicle tires are available in a small fraction of the tire
sizes of the passenger market and, for the most part, are larger tires
than those found on passenger cars. When viewing CRR over a larger
range of sizes, small diameter tires tend to appear as having a lower
performance, which is not necessarily accurate, with the converse
occurring as the diameter increases.
    Using the CRR value for determining the rolling resistance also
takes into account the load carrying capability for the tire being
tested, which, intuitively, can lead to some potentially confusing
results. Several vocational vehicle manufacturers argued in their
comments that LRR tires were not available for, e.g., vehicles like
refuse trucks, which tend to use large diameter tires to carry very
heavy loads. Based on the agencies'

testing, in fact, the measured CRR (as opposed to the RRF)
for refuse trucks were found to be among the best tested. This finding
can be explained by considering that CRR is calculated by dividing the
measured rolling resistance force by the tire's load capacity rating.
Although the tire may have a relatively high rolling resistance force,
the tire load capacity rating is also very high, resulting in an
overall lower (better) CRR value than many other types of tires. The
amount of load tire can carry (test load) contributes to a very low
reported CRR, thus confirming low rolling resistance tires meeting the
standards, as measured by CRR, are available to the industry regardless
of segment or application.
    Based on these considerations, the agencies have decided to use the
CRR metric for the HD fuel efficiency and GHG emissions program.
(c) Defined Vehicle Configurations in the GEM
    As discussed above, the agencies are finalizing a methodology that
chassis manufacturers will use to quantify the tire rolling resistance
values to be input into the GEM. Moreover, the agencies are defining
the remaining GEM inputs (i.e., specifying them by rule), which differ
by the regulatory subcategory (for reasons described in the RIA Chapter
4). The defined inputs, among others, include the drive cycle,
aerodynamics, vehicle curb weight, payload, engine characteristics, and
drivetrain for each vehicle type.
(i) Metric
    Based on NAS's recommendation and feedback from the heavy-duty
truck industry, NHTSA and EPA proposed standards for vocational
vehicles that would be expressed in terms of moving a ton of payload
over one mile. Thus, NHTSA's proposed fuel consumption standards for
these vehicles would be represented as gallons of fuel used to move one
ton of payload one thousand miles, or gal/1,000 ton-mile. EPA's
proposed CO2 vehicle standards would be represented as grams
of CO2 per ton-mile. The agencies received comments that a
payload-based metric is not appropriate for all types of vocational
vehicles, specifically buses. The agencies recognize that a payload-
based approach may not be the most representative of an individual
vocational application; however, it best represents the broad
vocational category. The metric which we proposed treats all vocational
applications equally and requires the same technologies be applied to
meet the standard. Thus, the agencies are adopting the proposed metric,
but will revisit the issue of metrics in any future action, if
required, depending on the breadth of each standard.
(ii) Drive cycle
    The drive cycles proposed for the vocational vehicles consisted of
the same three modes used for the Class 7 and 8 combination tractors.
The proposed cycle included the Transient mode, as defined by
California ARB in the HHDDT cycle, a constant speed cycle at 65 mph and
a 55 mph constant speed mode. The agencies proposed different
weightings for each mode for vocational vehicles than those proposed
for Class 7 and 8 combination tractors, given the known difference in
driving patterns between these two categories of vehicles. The same
reasoning underlies the agencies' use of the Heavy-duty FTP cycle to
evaluate compliance with the standards for diesel engines used in
vocational vehicles.
    The variety of vocational vehicle applications makes it challenging
to establish a single cycle which is representative of all such trucks.
However, in aggregate, the vocational vehicles typically operate over
shorter distances and spend less time cruising at highway speeds than
combination tractors. The agencies evaluated for proposal two sources
for mode weightings, as detailed in RIA Chapter 3. The agencies
proposed the mode weightings based on the vehicle speed characteristics
of single unit trucks used in EPA's MOVES model which were developed
using Federal Highway Administration data to distribute vehicle miles
traveled by road type.\164\ The proposed weighted CO2 and
fuel consumption value consisted of 37 percent of 65 mph Cruise, 21
percent of 55 mph Cruise, and 42 percent of Transient performance.
---------------------------------------------------------------------------

    \164\ The Environmental Protection Agency. Draft MOVES2009
Highway Vehicle Population and Activity Data. EPA-420-P-09-001,
August 2009 http://www.epa.gov/otaq/models/moves/techdocs/420p09001.pdf.
---------------------------------------------------------------------------

    The agencies received comments stating that the proposed drive
cycles and weightings are not representative of individual vocational
applications, such as buses and refuse haulers. A number of groups
commented that the vocational vehicle cycle is not representative of
real world driving and recommended changes to address that concern.
Several organizations proposed the addition of new drive cycles to make
the test more representative.
    Bendix suggested using the Composite International Truck Local and
Commuter Cycle (CILCC) as the general purpose mixed urban/freeway
cycles and to use four representative cycles: mixed urban, freeway,
city bus, refuse, and utility. Bendix suggested using the Standardized
On-Road Test (SORT) cycles for vocational vehicles operating in the
urban environment in addition to SORT cycles for 3 different
vocations--with separate weightings. They stated that SORT with an
average speed of 11.2 mph, lines up most closely with the average of
transit bus duty cycles at 9.9 mph as well as the overall U.S. National
average of 12.6 mph. As alternative approaches they suggested adopting
the Orange County duty cycle for the urban transit bus vocation, or
creating an Urban Transit Bus cycle with several possible weighting
factors--all with very high percentage transient (90% to 100%), very
low 55 mph (0% to 7%), very low 65 mph (0% to 3%), and an average speed
of 15 to 17 mph. Bendix supported their assertions about urban bus
vehicle speed with data from the 2010 American Public Transportation
Association (APTA) `Fact Book' and other sources. In contrast, Bendix
stated, the GEM cycle average speed is currently 32.6 mph. Such high
speeds at steady state will penalize technologies such as
hybridization.
    Clean Air Task Force said the agencies have not adequately
addressed the diversity of the vocational vehicle fleet since they are
not distinguished by different duty cycles. They urged the agencies to
sub-divide vocational vehicles by expected use, with separate test
cycles for each sub-group in order to capture the full potential
benefits of hybridization and other advanced technologies in a
meaningful and accurate way in future rulemakings for MY2019 and later
trucks.
    Two groups cautioned that unintended consequences could result from
the lack of diversity in duty cycles. DTNA said that the single drive
cycle proposed for all vehicles by the agencies would likely lead to
unintended consequences--such as customers being driven for regulatory
reasons to purchase a transmission that does not suit their actual
operation. Similarly, Volvo said medium- and heavy-duty vehicles are
uniquely built for specific applications but it will not be feasible to
develop regulatory protocols that can accurately predict efficiency in
each application duty cycle. This trade-off could result in unintended
or negative consequences in parts of the market.
    Several commenters suggested changing the weightings of the cycle
to more accurately reflect real world driving. Allison stated that the
vocational vehicle cycle includes too much steady state driving time.
They suggested (with supporting data from

the Oakridge National Laboratory analysis) reducing steady state
driving at 60 mph to minimal or no time on the cycle to address this
problem. Allison commented that GEM contains lengthy accelerations to
reach 55 and 65 miles per hour--much longer than is required in real
world driving. They supported this statement with data from a testing
program conducted at Oakridge National Laboratory showing medium- and
heavy-duty vehicles accelerate more rapidly than in the GEM drive
cycle. According to Allison, this long acceleration time in the GEM,
coupled with too much steady state operation with very little
variation, is not representative of vocational vehicle operation. In
addition, Allison said that the GEM does not adequately account for
shift time, clutch profile, turbo lag, and other impacts on both steady
state and transient operation. The impact, they state, is that the
cycle will hinder proper deployment of technologies to reduce fuel
consumption and GHG emissions.
    BAE focused their comments on urban transit bus operation. They
stated the weighting factors for steady state operation are
inconsistent with urban transit bus cycles.
    Other commenters suggested the agencies develop chassis dynamometer
tests based on the engine (FTP) test. Cummins said that chassis
dynamometer testing should allow the use of average vehicle
characteristics to determine road load and make use of the vehicle FTP
and SET cycles. Others commented that the correlation between the FTP
and the UDDS is poor.
    After careful consideration of the comments, the agencies are
adopting the proposed drive cycles. The final drive cycles and
weightings represent the straight truck operations which dominate the
vehicle miles travelled by vocational vehicles. The agencies do not
believe that application-specific drive cycles are required for this
final action because the program is based on the generally-applicable
use of low rolling resistance tires. The drive cycles that we are
adopting treat all vocational applications equally predicate standard
stringency on use of the same technology (LRR tires) to meet the
standard. The drive cycles in the final rule accurately reflect the
performance of this technology. The agencies are also finalizing, as
proposed, the mode weightings based on the vehicle speed
characteristics of single unit trucks used in EPA's MOVES model which
were developed using Federal Highway Administration data to distribute
vehicle miles traveled by road type.\165\ Similar to the issue of
metrics discussed above, the agencies may revisit drive cycles and
weightings in any future regulatory action to develop standards
specific to applications.
---------------------------------------------------------------------------

    \165\ The Environmental Protection Agency. Draft MOVES2009
Highway Vehicle Population and Activity Data. EPA-420-P-09-001,
August 2009 http://www.epa.gov/otaq/models/moves/techdocs/420p09001.pdf.
---------------------------------------------------------------------------

(iii) Empty Weight and Payload
    The total weight of the vehicle is the sum of the tractor curb
weight and the payload. The agencies are proposed to specify each of
these aspects of the vehicle. The agencies developed the proposed
vehicle curb weight inputs based on industry information developed by
ICF.\166\ The proposed curb weights were 10,300 pounds for the LHD
trucks, 13,950 pounds for the MHD trucks, and 29,000 pounds for the HHD
trucks.
---------------------------------------------------------------------------

    \166\ ICF International. ``Investigation of Costs for Strategies
to Reduce Greenhouse Gas Emissions for Heavy-Duty On-Road
Vehicles.'' July 2010. Pages 16-20. Docket ID EPA-HQ-OAR-
2010-0162-0044.
---------------------------------------------------------------------------

    NHTSA and EPA proposed payload requirements for each regulatory
category developed from Federal Highway statistics based on averaging
the payloads for the weight categories represented within each vehicle
subcategory.\167\ The proposed payloads were 5,700 pounds for the Light
Heavy-Duty trucks, 11,200 pounds for Medium Heavy-Duty trucks, and
38,000 pounds for Heavy Heavy-Duty trucks.
---------------------------------------------------------------------------

    \167\ 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 received comments from several stakeholders regarding
the proposed curb weights and payloads for vocational vehicles. BAE
said a Class 8 transit bus has a typical curb weight of 27,000 pounds
and maximum payload of 15,000 pounds. Daimler commented that Class 8
buses have a GVWR of 42,000 pounds. Autocar said that Class 8 refuse
trucks typically have a curb weight of 31,000 to 33,000 pounds, typical
average payload of 10,000 pounds, and typical maximum payload of 20,000
pounds.
    Upon further consideration, the agencies are reducing the assigned
weight of heavy heavy-duty vocational vehicles. While we still believe
the proposed values are appropriate for some vocational vehicles, we
reduced the total weight to bring it closer to some of the lighter
vocational vehicles. The agencies are adopting final curb weights of
10,300 pounds for the LHD trucks, 13,950 pounds for the MHD trucks, and
27,000 pounds for the HHD trucks. The agencies are also adopting
payloads of 5,700 pounds for the Light Heavy-Duty trucks, 11,200 pounds
for Medium Heavy-Duty trucks, and 15,000 pounds for Heavy Heavy-Duty
trucks. Additional information is available in RIA Chapter 3.
(iv) Engine
    As the agencies are finalizing separate engine and vehicle
standards, the GEM will be used to assess the compliance of the chassis
with the vehicle standard. To maintain the separate assessments, the
agencies are adopting the proposed approach of using fixed values that
are predefined by the agencies for the engine characteristics used in
GEM, including the fuel consumption map which provides the fuel
consumption at hundreds of engine speed and torque points. If the
agencies did not standardize the fuel map, then a vehicle that uses an
engine with emissions and fuel consumption better than the standards
would require fewer vehicle reductions than those being finalized. As
proposed, the agencies are using diesel engine characteristics in the
GEM, as most representative of the largest fraction of engines in this
market. The agencies did not receive any adverse comments to using this
approach.
    The agencies are finalizing two distinct sets of fuel consumption
maps for use in GEM. The first fuel consumption map would be used in
GEM for the 2014 through 2016 model years and represent a diesel engine
which meets the 2014 model year engine CO2 emissions
standards. A second fuel consumption map would be used beginning in the
2017 model year and represents a diesel engine which meets the 2017
model year CO2 emissions and fuel consumption standards and
accounts for the increased stringency in the final MY 2017 standard).
The agencies have modified the 2017 MY heavy heavy-duty diesel fuel map
used in the GEM for the final rulemaking to address comments received.
Details regarding this change can be found in RIA Chapter 4.4.4.
Effectively there is no change in stringency of the vocational vehicle
standard (not including the engine) between the 2014 MY and 2017 MY
standards for the full rulemaking period. These inputs are reasonable
(indeed, seemingly necessitated) given the separate final regulatory
requirement that vocational vehicle chassis manufacturers use only
certified engines.

(v) Drivetrain
    The agencies' assessment of the current vehicle configuration
process at the truck dealer's level is that the truck companies provide
software tools to specify the proper drivetrain matched to the buyer's
specific circumstances. These dealer tools allow a significant amount
of customization for drive cycle and payload to provide the best
specification for the customer. The agencies are not seeking to disrupt
this process. Optimal drivetrain selection is dependent on the engine,
drive cycle (including vehicle speed and road grade), and payload. Each
combination of engine, drive cycle, and payload has a single optimal
transmission and final drive ratio. The agencies are specifying the
engine's fuel consumption map, drive cycle, and payload; therefore, it
makes sense to specify the drivetrain that matches.
(d) Engine Metrics and Test Procedures
    EPA proposed that the GHG emission standards for heavy-duty engines
under the CAA would be expressed as g/bhp-hr while NHTSA's proposed
fuel consumption standards under EISA, in turn, be represented as gal/
100 bhp-hr. The NAS panel did not specifically discuss or recommend a
metric to evaluate the fuel consumption of heavy-duty engines. However,
as noted above they did recommend the use of a load-specific fuel
consumption metric for the evaluation of vehicles.\168\ An analogous
metric for engines is the amount of fuel consumed per unit of work. The
g/bhp-hr metric is also consistent with EPA's current standards for
non-GHG emissions for these engines. The agencies did not receive any
adverse comments related to the metrics for HD engines; therefore, we
are adopting the metrics as proposed.
---------------------------------------------------------------------------

    \168\ See NAS Report, Note 21, at page 39.
---------------------------------------------------------------------------

    With regard to GHG and fuel consumption control, the agencies
believe it is appropriate to set standards based on a single test
procedure, either the Heavy-duty FTP or SET, depending on the primary
expected use of the engine. EPA's criteria pollutant standards for
engines currently require that manufacturers demonstrate compliance
over the transient Heavy-duty FTP cycle; over the steady-state SET
procedure; and during not-to-exceed testing. EPA created this multi-
layered approach to criteria emissions control in response to engine
designs that optimized operation for lowest fuel consumption at the
expense of very high criteria emissions when operated off the
regulatory cycle. EPA's use of multiple test procedures for criteria
pollutants helps to ensure that manufacturers calibrate engine systems
for compliance under all operating conditions. We are not concerned if
manufacturers further calibrate these engines off cycle to give better
in-use fuel consumption while maintaining compliance with the criteria
emissions standards as such calibration is entirely consistent with the
goals of our joint program. Further, we believe that setting standards
based on both transient and steady-state operating conditions for all
engines could lead to undesirable outcomes.
    It is critical to set standards based on the most representative
test cycles in order for performance in-use to obtain the intended (and
feasible) air quality and fuel consumption benefits. We are finalizing
standards based on the composite Heavy-duty FTP cycle for engines used
in vocational vehicles reflecting these vehicles' primary use in
transient operating conditions typified by frequent accelerations and
decelerations as well as some steady cruise conditions as represented
on the Heavy-duty FTP. The primary reason the agencies are finalizing
two separate diesel engine standards--one for diesel engines used in
tractors and the other for diesel engines used in vocational vehicles--
is to encourage engine manufacturers to install engine technologies
appropriate to the intended use of the engine with the vehicle. The
current non-GHG emissions engine test procedures also require the
development of regeneration emission rates and frequency factors to
account for the emission changes during a regeneration event (40 CFR
86.004-28). EPA and NHTSA proposed not to include these emissions from
the calculation of the compliance levels over the defined test
procedures. Cummins and Daimler supported and stated sufficient
incentives already exist for manufacturers to limit regeneration
frequency. Conversely, Volvo opposed the omission of IRAF requirements
for CO2 emissions because emissions from regeneration can be
a significant portion of the expected improvement and a significant
variable between manufacturers
    For the proposal, we considered including regeneration in the
estimate of fuel consumption and GHG emissions and decided not to do so
for two reasons. First, EPA's existing criteria emission regulations
already provide a strong motivation to engine manufacturers to reduce
the frequency and duration of infrequent regeneration events. The very
stringent 2010 NOX emission standards cannot be met by
engine designs that lead to frequent and extend regeneration events.
Hence, we believe engine manufacturers are already reducing
regeneration emissions to the greatest degree possible. In addition to
believing that regenerations are already controlled to the extent
technologically possible, we believe that attempting to include
regeneration emissions in the standard setting could lead to an
inadvertently lax emissions standard. In order to include regeneration
and set appropriate standards, EPA and NHTSA would have needed to
project the regeneration frequency and duration of future engine
designs in the time frame of this program. Such a projection would be
inherently difficult to make and quite likely would underestimate the
progress engine manufacturers will make in reducing infrequent
regenerations. If we underestimated that progress, we would effectively
be setting a more lax set of standards than otherwise would be
expected. Hence in setting a standard including regeneration emissions
we faced the real possibility that we would achieve less effective
CO2 emissions control and fuel consumption reductions than
we will achieve by not including regeneration emissions. Therefore, the
agencies are finalizing an approach as proposed which does not include
the regenerative emissions.
(e) Hybrid Powertrain Technology
    Although the final vocational vehicle standards are not premised on
use of hybrid powertrains, certain vocational vehicle applications may
be suitable candidates for use of hybrids due to the greater frequency
of stop-and-go urban operation and their use of power take-off (PTO)
systems. Examples are vocational vehicles used predominantly in stop-
start urban driving (e.g., delivery trucks). As an incentive, the
agencies are finalizing to provide credits for the use of hybrid
powertrain technology as described in Section IV. Under the advanced
technology credit provisions, credits generated by use of hybrid
powertrains could be used to meet any of the heavy-duty standards, and
are not restricted to the averaging set generating the credit, unlike
the other credit provisions in the final rules. The agencies are
finalizing that any credits generated using such advanced technologies
could be applied to any heavy-duty vehicle or engine, and not be
limited to the averaging set generating the credit. Section IV below
also details the final approach to account for the use of a hybrid
powertrain when evaluating compliance with the vehicle standard. In
general, manufacturers can derive the fuel consumption and
CO2 emissions

reductions based on comparative test results using the final chassis
testing procedures.
(3) Summary of Final Flexibility and Credit Provisions
    EPA and NHTSA are finalizing four flexibility provisions
specifically for heavy-duty vocational vehicle and engine
manufacturers, as discussed in Section IV below. These are an
averaging, banking and trading program for emissions and fuel
consumption credits, as well as provisions for early credits, advanced
technology credits, and credits for innovative vehicle or engine
technologies which are not included as inputs to the GEM or are not
demonstrated on the engine FTP test cycle. With the exception of the
advanced technology credits, credits generated under these provisions
can only be used within the same averaging set which generated the
credit (for example, credits generated by HHD vocational vehicles can
only be used by HHD vehicles). EPA is also adopting a temporary
provision whereby N2O emission credits can be used to comply
with the CO2 emissions standard, as described in Section IV
below.
(3) Deferral of Standards for Small Chassis Manufacturing Business and
Small Business Engine Companies
    EPA and NHTSA are finalizing an approach to defer greenhouse gas
emissions and fuel consumption standards from small vocational vehicle
chassis manufacturers meeting the SBA size criteria of a small business
as described in 13 CFR 121.201 (see 40 CFR 1036.150 and 1037.150). The
agencies will instead consider appropriate GHG and fuel consumption
standards for these entities as part of a future regulatory action.
This includes both U.S.-based and foreign small volume heavy-duty truck
and engine manufacturers.
    The agencies have identified ten chassis entities that appear to
fit the SBA size criterion of a small business.\169\ The agencies
estimate that these small entities comprise less than 0.5 percent of
the total heavy-duty vocational vehicle market in the United States
based on Polk Registration Data from 2003 through 2007,\170\ and
therefore that the exemption will have a negligible impact on the GHG
emissions and fuel consumption improvements from the final standards.
---------------------------------------------------------------------------

    \169\ The agencies have identified Lodal, Indiana Phoenix,
Autocar LLC, HME, Giradin, Azure Dynamics, DesignLine International,
Ebus, Krystal Koach, and Millenium Transit Services LLC as potential
small business chassis manufacturers.
    \170\ M.J. Bradley. Heavy-duty Vehicle Market Analysis. May
2009.
---------------------------------------------------------------------------

    EPA and NHTSA have also identified three engine manufacturing
entities that appear to fit the SBA size criteria of a small business
based on company information included in Hoover's.\171\ Based on 2008
and 2009 model year engine certification data submitted to EPA for non-
GHG emissions standards, the agencies estimate that these small
entities comprise less than 0.1 percent of the total heavy-duty engine
sales in the United States. The final exemption from the standards
established under this rulemaking would have a negligible impact on the
GHG emissions and fuel consumption reductions otherwise due to the
standards.
---------------------------------------------------------------------------

    \171\ The agencies have identified Baytech Corporation, Clean
Fuels USA, and BAF Technologies, Inc. as three potential small
businesses.
---------------------------------------------------------------------------

    To ensure that the agencies are aware of which companies would be
exempt, we are finalizing as proposed to require that such entities
submit a declaration to EPA and NHTSA containing a detailed written
description of how that manufacturer qualifies as a small entity under
the provisions of 13 CFR 121.201, as described in Section V below.

E. Other Standards

    In addition to finalizing CO2 emission standards for
heavy-duty vehicles and engines, EPA is also finalizing separate
standards for N2O and CH4 emissions.\172\ NHTSA
is not finalizing comparable separate standards for these GHGs because
they are not directly related to fuel consumption in the same way that
CO2 is, and NHTSA's authority under EISA exclusively relates
to fuel efficiency. N2O and CH4 are important
GHGs that contribute to global warming, more so than CO2 for
the same amount of emissions due to their high Global Warming Potential
(GWP).\173\ EPA is finalizing N2O and CH4
standards which apply to HD pickup trucks and vans as well as to all
heavy-duty engines. EPA is not finalizing N2O and
CH4 standards for the Class 7 and 8 tractor or Class 2b-8
chassis manufacturers because these emissions would be controlled
through the engine program.
---------------------------------------------------------------------------

    \172\ NHTSA's statutory responsibilities relating to reducing
fuel consumption are directly related to reducing CO2
emissions, but not to the control of other GHGs.
    \173\ The global warming potentials (GWP) used in this rule are
consistent with the 2007 Intergovernmental Panel on Climate Change
(IPCC) Fourth Assessment Report (AR4). At this time, the 1996 IPCC
Second Assessment Report (SAR) GWP values are used in the official
U.S. greenhouse gas inventory submission to the United Nations
Framework Convention on Climate Change (per the reporting
requirements under that international convention). N2O
has a GWP of 298 and CH4 has a GWP of 25 according to the
2007 IPCC AR4.
---------------------------------------------------------------------------

    EPA requested comment on possible alternative CO2
equivalent approaches to provide near-term flexibility for 2012-14 MY
light-duty vehicles. As described below, EPA is finalizing alternative
provisions allowing manufacturers to use CO2 credits, on a
CO2-equivalent (CO2eq) basis, to meet the
N2O and CH4 standards, which is consistent with
many commenters' preferred approach.
    Almost universally across current engine designs, both gasoline-
and diesel-fueled, N2O and CH4 emissions are
relatively low today and EPA does not believe it would be appropriate
or feasible to require reductions from the levels of current gasoline
and diesel engines. This is because for the most part, the same
hardware and controls used by heavy-duty engines and vehicles that have
been optimized for non-methane hydrocarbon (NMHC) and NOX
control indirectly result in highly effective control of N2O
and CH4. Additionally, unlike criteria pollutants, specific
technologies beyond those presently implemented in heavy-duty vehicles
to meet existing emission requirements have not surfaced that
specifically target reductions in N2O or CH4.
Because of this, reductions in N2O or CH4 beyond
current levels in most heavy-duty applications would occur through the
same mechanisms that result in NMHC and NOX reductions and
would likely result in an increase in the overall stringency of the
criteria pollutant emission standards. Nevertheless, it is important
that future engine technologies or fuels not currently researched do
not result in increases in these emissions, and this is the intent of
the final ``cap'' standards. The final standards would primarily
function to cap emissions at today's levels to ensure that
manufacturers maintain effective N2O and CH4
emissions controls currently used should they choose a different
technology path from what is currently used to control NMHC and
NOX but also largely successful methods for controlling
N2O and CH4. As discussed below, some
technologies that manufacturers may adopt for reasons other than
reducing fuel consumption or GHG emissions could increase
N2O and CH4 emissions if manufacturers do not
address these emissions in their overall engine and aftertreatment
design and development plans. Manufacturers will be able to design and
develop the engines and aftertreatment to avoid such emissions
increases through appropriate emission control technology selections
like those already used and available

today. Because EPA believes that these standards can be capped at the
same level, regardless of type of HD engine involved, the following
discussion relates to all types of HD engines regardless of the
vehicles in which such engines are ultimately used. In addition, since
these standards are designed to cap current emissions, EPA is
finalizing the same standards for all of the model years to which the
rules apply.
    EPA believes that the final N2O and CH4 cap
standards will accomplish the primary goal of deterring increases in
these emissions as engine and aftertreatment technologies evolve
because manufacturers will continue to target current or lower
N2O and CH4 levels in order to maintain typical
compliance margins. While the cap standards are set at levels that are
higher than current average emission levels, the control technologies
used today are highly effective and there is no reason to believe that
emissions will slip to levels close to the cap, particularly
considering compliance margin targets. The caps will protect against
significant increases in emissions due to new or poorly implemented
technologies. However, we also believe that an alternative compliance
approach that allows manufacturers to convert these emissions to
CO2eq emission values and combine them with CO2
into a single compliance value would also be appropriate, so long as it
did not undermine the stringency of the CO2 standard. As
described below, EPA is finalizing that such an alternative compliance
approach be available to manufacturers to provide certain flexibilities
for different technologies.
    EPA requested comments in the NPRM on the approach to regulating
N2O and CH4 emissions including the
appropriateness of ``cap'' standards, the technical bases for the
levels of the final N2O and CH4 standards, the
final test procedures, and the final timing for the standards. In
addition, EPA requested any additional emissions data on N2O
and CH4 from current technology engines. We solicited
additional data, and especially data for in-use vehicles and engines
that would help to better characterize changes in emissions of these
pollutants throughout their useful lives, for both gasoline and diesel
applications. As is typical for EPA emissions standards, we are
finalizing that manufacturers should establish deterioration factors to
ensure compliance throughout the useful life. We are not at this time
aware of deterioration mechanisms for N2O and CH4
that would result in large deterioration factors, but neither do we
believe enough is known about these mechanisms to justify finalizing
assigned factors corresponding to no deterioration, as we are
finalizing for CO2, or for that matter to any predetermined
level. In addition to N2O and CH4 standards, this
section also discusses air conditioning-related provisions and EPA
provisions to extend certification requirements to all-electric HD
vehicles and vehicles and engines designed to run on ethanol fuel.
(1) What is EPA's Approach to Controlling N2O?
    N2O is a global warming gas with a GWP of 298. It
accounts for about 0.3 percent of the current greenhouse gas emissions
from heavy-duty trucks.\174\
---------------------------------------------------------------------------

    \174\ Value adapted from ``Inventory of U.S. Greenhouse Gas
Emissions and Sinks: 1990-2007''. April 2009.
---------------------------------------------------------------------------

    N2O is emitted from gasoline and diesel vehicles mainly
during specific catalyst temperature conditions conducive to
N2O formation. Specifically, N2O can be generated
during periods of emission hardware warm-up when rising catalyst
temperatures pass through the temperature window when N2O
formation potential is possible. For current heavy-duty gasoline
engines with conventional three-way catalyst technology, N2O
is not generally produced in significant amounts because the time the
catalyst spends at the critical temperatures during warm-up is short.
This is largely due to the need to quickly reach the higher
temperatures necessary for high catalyst efficiency to achieve emission
compliance of criteria pollutants. N2O formation is
generally only a concern with diesel and potentially with future
gasoline lean-burn engines with compromised NOX emissions
control systems. If the risk for N2O formation is not
factored into the design of the controls, these systems can but need
not be designed in a way that emphasizes efficient NOX
control while allowing the formation of significant quantities of
N2O. However, these future advanced gasoline and diesel
technologies do not inherently require N2O formation to
properly control NOX. Pathways exist today that meet
criteria emission standards that would not compromise N2O
emissions in future systems as observed in current production engine
and vehicle testing \175\ which would also work for future diesel and
gasoline technologies. Manufacturers would need to use appropriate
technologies and temperature controls during future development
programs with the objective to optimize for both NOX and
N2O control. Therefore, future designs and controls at
reducing criteria emissions would need to take into account the balance
of reducing these emissions with the different control approaches while
also preventing inadvertent N2O formation, much like the
path taken in current heavy-duty compliant engines and vehicles.
Alternatively, manufacturers who find technologies that reduce criteria
or CO2 emissions but see increases N2O emissions
beyond the cap could choose to offset N2O emissions with
reduction in CO2 as allowed in the CO2eq option
discussed in Section II.E.3.
---------------------------------------------------------------------------

    \175\ Memorandum ``N2O Data from EPA Heavy-Duty
Testing''.
---------------------------------------------------------------------------

    EPA is finalizing an N2O emission standard that we
believe would be met by most current-technology gasoline and diesel
vehicles at essentially no cost to the vehicle, though the agency is
accounting for additional N2O measurement equipment costs.
EPA believes that heavy-duty emission standards since 2008 model year,
specifically the very stringent NOX standards for both
engine and chassis certified engines, directly result in stringent
N2O control. It is believed that the current emission
control technologies used to meet the stringent NOX
standards achieve the maximum feasible reductions and that no
additional technologies are recognized that would result in additional
N2O reductions. As noted, N2O formation in
current catalyst systems occurs, but their emission levels are
inherently low, because the time the catalyst spends at the critical
temperatures during warm-up when N2O can form is short. At
the same time, we believe that the standard would ensure that the
design of advanced NOX control systems for future diesel and
lean-burn gasoline vehicles would control N2O emission
levels. While current NOX control approaches used on current
heavy-duty diesel vehicles do not compromise N2O emissions
and actually result in N2O control, we believe that the
standards would discourage any new emission control designs for diesels
or lean-burn gasoline vehicles that achieve criteria emissions
compliance at the cost of increased N2O emissions. Thus, the
standard would cap N2O emission levels, with the expectation
that current gasoline and diesel vehicle control approaches that comply
with heavy-duty vehicle emission standards for NOX would not
increase their emission levels, and that the cap would ensure that
future diesel and lean-burn gasoline vehicles with advanced
NOX controls would appropriately control their emissions of
N2O.

(a) Heavy-Duty Pickup Truck and Van N2O Exhaust Emission
Standard
    EPA is finalizing the proposed per-vehicle N2O emission
standard of 0.05 g/mi, measured over the Light-duty FTP and HFET drive
cycles. Similar to the CO2 standard approach, the
N2O emission level of a vehicle would be a composite of the
Light-duty FTP and HFET cycles with the same 55 percent city weighting
and 45 percent highway weighting. The standard would become effective
in model year 2014 for all HD pickups and vans that are subject to the
CO2 emission requirements. Averaging between vehicles would
not be allowed. The standard is designed to prevent increases in
N2O emissions from current levels, i.e., a no-backsliding
standard.
    The N2O standard level is approximately two times the
average N2O level of current gasoline and diesel heavy-duty
trucks that meet the NOX standards effective since 2008
model year.\176\ Manufacturers typically use design targets for
NOX emission levels at approximately 50 percent of the
standard, to account for in-use emissions deterioration and normal
testing and production variability, and we expect manufacturers to
utilize a similar approach for N2O emission compliance. We
are not adopting a more stringent standard for current gasoline and
diesel vehicles because the stringent heavy-duty NOX
standards already result in significant N2O control, and we
do not expect current N2O levels to rise for these vehicles
particularly with expected manufacturer compliance margins.
---------------------------------------------------------------------------

    \176\ Memorandum ``N2O Data from EPA Heavy-Duty
Testing.''
---------------------------------------------------------------------------

    Diesel heavy-duty pickup trucks and vans with advanced emission
control technology are in the early stages of development and
commercialization. As this segment of the vehicle market develops, the
final N2O standard would require manufacturers to
incorporate control strategies that minimize N2O formation.
Available approaches include using electronic controls to limit
catalyst conditions that might favor N2O formation and
considering different catalyst formulations. While some of these
approaches may have associated costs, EPA believes that they will be
small compared to the overall costs of the advanced NOX
control technologies already required to meet heavy-duty standards.
    The light-duty GHG rule requires that manufacturers begin testing
for N2O by 2015 model year. The manufacturers of complete
pickup trucks and vans (Ford, General Motors, and Chrysler) are already
impacted by the light-duty GHG rule and will therefore have this
equipment and capability in place for the timing of this rulemaking.
    Overall, we believe that manufacturers of HD pickups and vans (both
gasoline and diesel) would meet the standard without implementing any
significantly new technologies, only further refinement of their
existing controls, and we do not expect there to be any significant
costs associated with this standard.
(b) Heavy-Duty Engine N2O Exhaust Emission Standard
    EPA proposed a per engine N2O emissions standard of 0.05
g/bhp-hr for heavy-duty engines, but is finalizing a standard of 0.10
g/bhp-hr based on additional data submitted to the agency which better
represents the full range of current diesel and gasoline engine
performance. The final N2O standard becomes effective in
2014 model year for diesel engines, as proposed. However, EPA is
finalizing N2O standards for gasoline engines that become
effective in 2016 model year to align with the first year of the
CO2 gasoline engine standards. Without this alignment,
manufacturers would not have any flexibility, such as CO2eq
credits, in meeting the N20 cap and therefore would not have
any recourse to comply if an engine's N2O emissions were
above the standard. The standard remains the same over the useful life
of the engine. The N2O emissions would be measured over the
composite Heavy-duty FTP cycle because it is believed that this cycle
poses the highest risk for N2O formation versus the
additional heavy-duty compliance cycles. The agencies received comments
from industry suggesting that the N2O and CH4
emissions be evaluated over the same test cycle required for
CO2 emissions compliance. In other words, the commenters
wanted to have the N2O emissions measured over the SET for
engines installed in tractors. The agencies are not adopting this
approach for the final action because we do not have sufficient data to
set the appropriate N2O level using the SET. The agencies
are not requiring any additional burden by requiring the measurement to
be conducted over the Heavy-Duty FTP cycle because it is already
required for criteria emissions. Averaging of N2O emissions
between HD engines will not be allowed. The standard is designed to
prevent increases in N2O emissions from current levels,
i.e., a no-backsliding standard.
    The proposed N2O level was twice the average
N2O level of primarily pre-2010 model year diesel engines as
demonstrated in the ACES Study and in EPA's testing of two additional
engines with selective catalytic reduction aftertreatement
systems.\177\ Manufacturers typically use design targets for
NOX emission levels of about 50 percent of the standard, to
account for in-use emissions deterioration and normal testing and
production variability, and manufacturers are expected to utilize a
similar approach for N2O emission compliance.
---------------------------------------------------------------------------

    \177\ Coordinating Research Council Report: ACES Phase 1 of the
Advanced Collaborative Emissions Study, 2009. (This study included
detailed chemical characterization of exhaust species emitted from
four 2007 model year heavy heavy diesel engines).
---------------------------------------------------------------------------

    EPA sought comment about deterioration factors for N2O
emissions. See 75 FR 74208. Industry stakeholders recommended that the
agency define a DF of zero. While we believe it is also possible that
N2O emissions will not deteriorate in use, very little data
exist for aged engines and vehicles. Therefore, the value we are
assigning is conservative, specifically additive DF of 0.02 g/bhp-hr.
While the value is conservative, it is small enough to allow compliance
for all engines except those very close to the standards. For engines
too close to the standard to use the assigned DFs, the manufacturers
would need to demonstrate via engineering analysis that deterioration
is less than assigned DF.
    EPA sought additional data on the level of the proposed
N2O level of 0.05 g/bhp-hr. See 75 FR 74208. The agency
received additional data of 2010 model year engines from the Engine
Manufacturers Association.\178\ The agencies reanalyzed a new data set,
as shown in Table II-22, to derive the final N2O standard of
0.10 g/bhp-hr with a defined deterioration factor of 0.02 g/bhp-hr.
---------------------------------------------------------------------------

    \178\ Engine Manufacturers Association. EMA N2O Email
03--22--2011. See Docket EPA-HQ-OAR-2010-0162.

                     Table II-22--N2O Data Analysis
------------------------------------------------------------------------
                                                           Composite FTP
                                            Rated power      cycle N2O
              Engine family                    (HP)       result  (g/bhp-
                                                                hr)
------------------------------------------------------------------------
EPA Data of 2007 Engine with SCR........  ..............           0.042
EPA Data of 2010 Production Intent        ..............           0.037
 Engine.................................
A.......................................             450          0.0181
A.......................................             600          0.0151
B.......................................             360          0.0326
C.......................................             380          0.0353
D.......................................             560          0.0433
D.......................................             455          0.0524
E.......................................             600          0.0437
F.......................................             500          0.0782
G.......................................             483          0.1127
H.......................................             385          0.0444
H.......................................             385          0.0301
H.......................................             385          0.0283
J.......................................             380          0.0317
========================================================================
                                                    Mean           0.043
                                                2 * Mean            0.09
------------------------------------------------------------------------

    Engine emissions regulations do not currently require testing for
N2O. The Mandatory GHG Reporting final rule requires