Overall, a total of 156 medium- and heavy-duty tires were included in this testing, which was comprised of 88 tires covering various commercial vocational vehicle types, such as bucket trucks, school buses, city delivery vehicles, city transit buses and refuse haulers among others; 47 tires intended for application to tractors; and 21 tires classified as light-truck (LT) tires intended for Class 4 vocational vehicles such as delivery vans.  In addition, approximately 20 of the tires tested were exchanged between the labs to assess inter-laboratory variability.  While all of the tires were tested using the ISO 28580 method, approximately 20 tires were also tested using SAE J1269 to compare the two test methods.
The test results for 88  commercial vocational vehicle tires (19.5" and 22.5" sizes)  showed a test average RRC of 7.4 kg/metric ton.  To comply with the proposed vocational vehicle fuel consumption and GHG emissions standards, a manufacturer would need to achieve an average tire RRC value of 8.1 kg/metric ton.  The measured average RRC of 7.4 kg/metric ton is better than the average value that would be needed to meet vocational vehicle standards.  Of those eighty-eight tires tested, twenty tires had RRC values worse than 8.1 kg/metric ton, two were at 8.1 kg/metric ton, and sixty-six tires were better than 8.1 kg/metric ton. Additional data analyses examining the tire data by tire size to determine the range and distribution of RRC values within each tire size showed each tire size generally had tires ranging from approximately 6.0 to 8.5 kg/metric ton, with a small number of tires in the 5.3  -  5.7 kg/metric ton range and a small number of tires in a range as high as 9.3  -  9.8 kg/ton. Review of the data showed that for each tire size and vehicle type, the majority of tires tested would enable compliance with vocational vehicle fuel consumption and GHG emission standards.
The test results for the 47 tires intended for tractor application showed an overall average of 6.9 kg/ton, the lowest overall average rolling resistance of the different tire applications tested. This is consistent with what the agencies heard through comments and meetings with tire suppliers whose efforts have focused on tractor applications, particularly for long-haul applications, which yield the highest fuel efficiency benefits from LRR tire technology.
Finally, the 21 LT tires intended for Class 4 vocational vehicles were comprised of two sizes; LT225/75R16 and LT245/75R16 with 11 and 10 samples tested, respectively. Some auto manufacturers have indicated that RRC values for tires fitted to these Class 4 vehicles typically have a higher RRC values than tires found on commercial vocational vehicles because of the smaller diameter wheel size and the ISO testing protocol. The test data showed the average RRC for LT225/75R16 tires was 9.1 kg/metric ton and the average for LT245/75R16 tires was 8.6 kg/metric ton. The range for the LT225/75R16 tires spanned 7.4 to 11.0 and the range for the LT245/75R16 tires ranged from 6.6 to 9.8 kg/metric ton. Overall, the average for the tested LT tires was 8.9 kg/metric ton.
Analysis of the EPA test data for all vocational vehicles, including LT tires, shows the test average RRC is 7.7 kg/metric ton and the standard deviation for is 1.2 kg/metric ton.  Review of the data shows that for each tire size and vehicle type, there are many tires available that would enable compliance with the proposed standards for vocational vehicles and tractors except for LT tires for Class 4 vocational vehicles where test results show the majority of these tires are worse than 8.1 kg/metric ton.
The agencies also reviewed the RRC data from the tires that were tested at both the STL and Smithers laboratories to assess inter-laboratory and test machine variability.  The agencies conducted statistical analysis of the data to gain better understanding of lab-to-lab correlation and developed an adjustment factor for data measured at each of the test labs .  When applied, this correction factor showed that for 77 of the 80 tires tested, the difference between the original RRC and a value corrected RRC was 0.01 kg/metric ton. The values for the remaining three tires were 0.03 kg/metric ton, 0.05 kg/metric ton and 0.07 kg/metric ton. 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 RRC values.  Further, in analyzing the data, the agencies considered both measurement variability and the value of the measurements relative to proposed standards.  The agencies concluded that although laboratory-to-laboratory and test machine-to-test machine measurement variability exists, the level observed is not excessive relative to the distribution of absolute measured RRC performance values and relative to the proposed standards.  Based on this, the agencies concluded that the test protocol and the proposed standards are reasonable for this program.
Summary of Final Rules
For vocational vehicles, the agencies intend to keep rolling resistance as an input to the GEM but with modifications to the proposed targets as a result of the testing completed by EPA since the NPRM and information from tire suppliers.
For vocational vehicles, the rolling resistance of each tire will be measured using the ISO 28850 test method for drive tires and steer tires planned for fitment to the vehicle being certified. Once the test RRC values are obtained, a manufacturer will input the RRC values for the drive and steer tires separately into the GEM model where, for vocational vehicles, the vehicle load is distributed equally over the steer and drive tires. Once entered, the amount of GHG reduction attributed to tire rolling resistance will be incorporated into the overall vehicle compliance value. The following table provides the revised target RRC values for vocational vehicles for 2014 and 2017 model years.
Table II-13: Vocational Vehicle  -  Target RRC Values for GEM Input

2014 MY
2017 MY
Tire Rolling Resistance (kg/metric ton)
7.7 kg/metric ton
7.7 kg/metric ton
These target standards are being revised based on the significant availability of tires for vocational vehicles applications which have performance better than the originally proposed 8.1 kg/metric ton target. As evidenced in the discussion of the EPA tire testing results, 63 of the 88 tires tested for vocational applications had RRC values better than the proposed target. The tires tested covered fitment to a wide range of vocational vehicle types and classes; thus agencies believe the original target value of 8.1 kg/metric ton was possibly too lenient after reviewing the testing data. Therefore, the agencies believe it is appropriate to reduce the proposed standard to an RRC value 7.7 kg/metric ton for non-LT tire type. As discussed previously, this value is the test average of all vocational tires tested (including LT) which takes a conservative approach over setting a target based on the average of only the non-LT Vocational tires tested. For LT tires, based on both the test data and in alignment with the comments from AAPC and Ford Motor Company, the agencies recognize the need to provide an alternative based on the test data and discussions with vehicles manufacturers. In lieu of having two sets of Light Heavy-Duty vocational vehicle standards, the agencies are finalizing an adjustment factor which applies to the RRC test results for LT tires. The agencies developed an adjustment factor dividing the overall vocational test average RRC of 7.7 by the LT Vocational Average of 8.9. This yields an adjustment factor of 0.87. For LT vocational vehicle tires, the measured RRC values will be multiplied by the 0.87 adjustment factor before entering the values in the GEM for compliance.
Based on the tire rolling resistance inputs noted above EPA is finalizing the following CO2 standards for the 2014 model year for the Class 2b through Class 8 vocational vehicle chassis, as shown in Table II-14.  Similarly, NHTSA is finalizing the following fuel consumption standards for the 2016 model year, with voluntary standards beginning in the 2014 model year.  For the EPA GHG program, the  standard applies throughout the useful life of the vehicle.
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 Section II.B.2.  As explained in Section II. D. (2) (c)(iv) below, engine performance is one of the inputs into the compliance model, and that input will change in 2017 MY to reflect the 2017 MY engine standards.  The 2017 MY vocational vehicle standards are not premised on manufacturers installing additional vehicle technologies. Thus, although chassis manufacturers will not be required to make further improvements in 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.  The agencies chose to set the vocational vehicle standard in 2017 to reflect the 2017 engine improvements even though chassis manufacturers are not affected by the change in stringency.
Table II-14: 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 2b-5
Medium Heavy-Duty  Class 6-7
Heavy Heavy-Duty Class 8
CO2 Emissions
387
234
226
NHTSA Fuel Consumption (gallon per 1,000 ton-mile) Standard Effective 2016 Model Year

Light Heavy-Duty
Class 2b-5
Medium Heavy-Duty  Class 6-7
Heavy Heavy-Duty    Class 8
Fuel Consumption
38.0
23.0
22.2
EPA CO2 (gram/ton-mile) Standard Effective 2017 Model Year

Light Heavy-Duty
Class 2b-5
Medium Heavy-Duty Class 6-7
Heavy Heavy-Duty   Class 8
CO2 Emissions
373
225
222
NHTSA Fuel Consumption (gallon per ton-mile) Standard Effective 2017 Model Year

Light Heavy-Duty
Class 2b-5
Medium Heavy-Duty Class 6-7
Heavy Heavy-Duty   Class 8
Fuel Consumption
36.6
22.1
21.8

  Off-Road and Low-Speed Vocational Vehicle Standards
There are several reasons that the agencies proposed to base the vocational vehicle standards on the use of low rolling resistance tires alone.  First, technologies that improve vehicle fuel efficiency and reduce CO2 emissions may not be equally effective on all vehicles depending on the kinds of work they do or if they travel at low speeds, as discussed above.  For example, some aerodynamic improvements could physically be applied to vocational vehicles, but because so many vocational vehicles rarely reach the sustained speeds that line-haul tractors do, applying aero features to vocational vehicles would result in very little benefit for those vehicles compared to the benefit expected for line-haul tractors.  The agencies believe it does not make sense to require technology without expected benefits, and commenters generally supported that approach in response to the NPRM.  Another important reason for basing the vocational vehicle standards on improvements to tires alone is the complexity associated with establishing a baseline emissions and fuel consumption rate for technology use in vocational vehicles, given the diversity of vehicles and duty cycles in this segment.  A baseline is needed since it is the benchmark against which standards are established.  Last and importantly, in order to be included in this regulation, technologies to reduce vocational vehicle emissions would need to be under the control of the chassis manufacturer.  The technologies available to chassis manufacturers are fairly limited.
	 Some vocational vehicles, because of 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 across an urban road, or if they are off-loaded from another vehicle onto a road and then 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.  The agencies are also targeting other vehicles that travel at low-speeds and meant to be used both on- and off-road, as the application of certain technologies to these vehicles not only may not provide the same level of benefits as it would for pure on-road vehicles, but it may also actually impair the vehicle's ability to do its off-road job.  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.
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, 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 trucks 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 are 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.  Therefore, these trucks were proposed to be exempted from vehicle standards but were still required to use certified engines, which would provide fuel consumption and CO2 emission reductions in all vocational applications.  To ensure that these trucks 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 limited.  As mentioned, the agencies were aware that the majority off road trucks primarily used off-road tires and are low speed vehicles as well.  Based upon this understanding, the agencies specifically proposed that a truck must meet the following requirements to qualify for an exemption from vocational vehicle standards:
         * 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 excluding 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 LRRTs.  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 responding 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 determined CRR values.
For the final rules, the agencies have considered the issues raised by commenters and have decided to adopt different criteria for exempting vocational vehicles and vocational tractors that primarily travel off-road than the agencies proposed in the NPRM.  The agencies believe that the intent underlying the exemption for vocational vehicles in the NPRM was correct but the proposals were either unsuitable for the industry or too restrictive to capture the 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 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 regulated by NHTSA.  These vocational vehicles will be exempted from complying with the vehicle standards of these rules but are still required to have certified engines.  As such, any vocational vehicle including vocational tractors primarily used off-road must meet the following criteria to be exempted from GHG and fuel consumption vehicle standards:
         * 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 characteristics making them unsuitable for operation on roads; 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 requirements to exempt any vocational vehicle that can operate in both on and off-road environments and having speed restricted tires rated at 55 mph or below.  The agencies' reasoning in adopting a speed restricted exemption for tires is that the majority of mixed service tires used for off-road use were identified as being restricted at 55 mph or less.  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 conventions tires.  Using a speed restriction as a criteria for exemption will also provide the possibility for certain low-speed vehicles to be inadvertently exempted as well (i.e., low speed city delivery tractors) but the risk of allowing the low volume of these vehicle to be exempted far outweighs the potential loss of creating a segment of vehicles that are precluded from performing their intended applications.  Therefore, the final rule includes an exemption for any mixed service off-road tire equipped on an applicable vocational vehicle that is speed restricted at 55 mph or less.
Manufacturers choosing to exempt vehicles based on the above criteria should 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).
Heavy-duty Engine Standards for Engines used in Vocational Vehicles
EPA is finalizing GHG standards 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.
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.  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 truck application, as shown in Table II-15 (40 CFR 1036.140).  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.  All heavy-duty engines are covered either under the heavy-duty pickup truck and van category or under the heavy-duty engine standards.
Table II-15: 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

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-16.
Table II-16: Vocational Diesel Engine Standards over the Heavy-Duty FTP Cycle
Model Year
Standard
Light Heavy-Duty Diesel
Medium Heavy-Duty Diesel
Heavy Heavy-Duty Diesel
2014-2016
CO2 Standard (g/bhp-hr)
600
600
567

Voluntary Fuel Consumption Standard (gallon/100 bhp-hr)
5.89
5.89
5.57
2017 and Later
CO2 Standard (g/bhp-hr)
576
576
555

Fuel Consumption (gallon/100 bhp-hr)
5.66
5.66
5.45

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 timeframe in a cost-effective manner.  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 truck manufacturer product plans to fall largely into three year cycles reflecting this regulatory environment.  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, with the caveat that opting in would cause the standards to become mandatory for the opt-in and subsequent model years.  NHTSA proposed that manufacturers could opt into the program by declaring their intent to opt in at the same time they submit the Pre-Certification Compliance Report, and that 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.
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 the 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).  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.
For vocational engines certified on the FTP cycle, the agencies proposed to require a 5 percent reduction for HHD engines and 9 percent for LHD and MHD engines.  For LHD and MHD engines in 2017 MY, the 9 percent reduction is based on the assumption that valvetrain friction reduction can be achieved in MHD engines in addition to turbo efficiency and accessory (water, oil, and ful pump) improvements, improved EGR cooler, and other approaches being used for HHD engines.
For LHD and MHD diesel engine standards, the agencies maintained the same emissions and fuel consumption standards for the two categories since 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.  Furthermore, as noted above, the technologies available to reduce fuel consumption and CO2 emissions from these two categories of engines are similar.
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 standards proposed in the NPRM, 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 this technology.  See Chapter 2 of the RIA for more details.  For MHD engines, the 9 percent reduction is based on the assumption that valvetrain friction reduction can be achieved in 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.
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.  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 LHD/MHD diesel engines but not for the HHD 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.
After consideration of the comments, EPA and NHTSA are adopting as proposed the HD diesel engine CO2 emission standards and fuel consumption standards for vocational vehicles are presented in Table II-16.  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 all standards 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 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.
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 trucks 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 trucks, 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 on the fact that engine manufacturers are expected to redesign and upgrade their products during MYs 2014-2017 in making our decisions about the cost-effectiveness of the standards and the availability of lead time.  The final two-step CO2 emission and fuel consumption standards recognize the opportunity for technology improvements over the rulemaking timeframe, while reflecting the typical diesel truck 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. 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.
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 specifically requested an "OBD phase-in" option in its comments to the NPRM.  They 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-17.
Table II-17 Comparison of CO2 reductions for the Engine Standards under the Alternative OBD Phase-in and Primary Phase-In

                                    HHD FTP
                                  LHD/MHD FTP

                     Primary Phase-in Standard (g/bhp-hr)
                     Optional Phase-in Standard (g/bhp-hr)
               Difference in Lifetime CO2 Engine Emissions (MMT)
                     Primary Phase-in Standard (g/bhp-hr)
                     Optional Phase-in Standard (g/bhp-hr)
               Difference in Lifetime CO2 Engine Emissions (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-18 presents the final HD diesel engine CO2 emission and fuel consumption standards under the optional "OBD phase-in" option.
Table II-18: Optional Heavy-Duty Engine Standard Phase-in
Model Year
Standard
Light Heavy-Duty Diesel
Medium Heavy-Duty Diesel
Heavy Heavy-Duty Diesel
2013
CO2 Standard (g/bhp-hr)
618
618
577

Voluntary Fuel Consumption Standard (gallon/100 bhp-hr)
6.07
6.07
5.67
2016 and Later
CO2 Standard (g/bhp-hr)
576
576
555

Fuel Consumption (gallon/100 bhp-hr)
5.66
5.66
5.45

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 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 timeframe, 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.  The discussion above 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 for use in vocational vehicles.  In the NPRM, the agencies proposed an optional engine standard for vocational vehicles based on a five percent reduction from the products own 2011 model year baseline level, but requested comment on whether a two percent reduction would be more appropriate.  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 and 3 percent is appropriate for HHD engines given technologies available for application to legacy products by model year 2014.  Unlike the majority of engine products in this segment, engine manufacturers have devoted few resources to developing technologies for these legacy products reasoning the investment would have little value if the engines are to be substantially redesigned or replaced in the next five years.  Hence while the technologies we have identified to achieve the proposed five percent reduction would theoretically work for these legacy products, there is inadequate leadtime for manufacturers to complete the pre application development needed to add the technology to these engines by 2014.  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.
As for HD diesel engines used in combination tractors, the agencies stress that this option for HD engines used in vocational vehicles is a temporary and limited option being implemented to address diverse manufacturer needs associated with complying with this first phase of the regulations.  As will be codified in 40 CFR 1036.620, this optional standard will be available only for the 2014 through 2016 model years, because we believe that manufacturers will have had ample opportunity to benchmark competitive products during redesign cycles and 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 final rules require that manufacturers making use of these provisions would need to exhaust all credits available to the averaging set prior to using this flexibility and would not be able to generate emissions credits from other engines in the same regulatory averaging set as the engines complying using this alternate approach.
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, 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 for all engines in the class.  Since the NHTSA standards are optional in 2014, manufacturers may choose not to adopt either the alternative engine standard or the regular voluntary standard by not participating in the NHTSA program in 2014, 2015, and 2016.
As discussed above in Section II.B.2.b, some commenters 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.  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.
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.  Unlike the purpose-built heavy-duty diesel engines typical of this segment, 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 anticipate that the manufacturers will have only one engine re-design within the 2014-18 model years under consideration within this proposal.  The agencies therefore proposed the following fuel consumption and CO2 emissions standards for gasoline engines for use in vocational vehicles, which represent a five percent reduction in CO2 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.

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.  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 subcategory to show compliance with both agencies' standards.

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 tractors be established by adding an adjustment factor to the full useful life emissions and fuel consumption results projected in the EPA certification process.  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 by the agencies 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 §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 be 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-19, 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-19:  Useful Life Periods

Years
Miles
Class 2b-5 Vocational Vehicles, Spark Ignited, and Light Heavy-Duty Diesel Engines
10
110,000
Class 6-7 Vocational Vehicles and Medium Heavy-Duty Diesel Engines
10
185,000
Class 8 Vocational Vehicles and Heavy Heavy-Duty Diesel Engines
10
435,000

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).
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 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 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 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 agencies developed the GEM for the specific purpose of this proposal to evaluate truck 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 agencies 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 are included in Chapter 4 of the RIA.
EPA and NHTSA have validated 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 agencies 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.  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/).
The agencies are finalizing 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.  Tires are the only technology on which the agencies' own feasibility analysis for these vehicles is predicated.  An example of the GEM input screen is included in Figure II-4.  The input values for the simulation model would be derived by the manufacturer from tire test procedure finalized by the agencies in this action.  The agencies are adopting as proposed that the remaining model inputs would be fixed values that are pre-defined by the agencies and are detailed in the RIA Chapter 4, including the engine fuel consumption map to be used in the simulation.

Figure II-4: Example GEM Input Screen
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.  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, by European regulations, and by the EPA SmartWay program.
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.  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 (RRC) 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.
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 RRC 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] RRC baseline values. RMA also argued that the SAE J1269 multi-point test can be used to accurately predict truck/bus tire RRC 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 §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 RRC 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 RRC 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.  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  and the California Air Resources Board (CARB) through a staff recommendation for a California regulation, 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.
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 latter part of 2011 with intentions for the lab to accommodate the light-duty tire fuel efficiency program and, potentially, reference testing for medium and heavy duty tires.
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 available, the agencies are postponing the use of these elements of ISO 28580 to a later date when they are available.
However, in the interim, the agencies note the lab-to-lab comparison results mentioned previously. This data showed there was very low variability between the two labs and the machines that were used for the tire testing. Based on the test data, the agencies judge the it is reasonable to implement the program with current levels of variability, and prior to finalizing a lab alignment procedure and before heavy-duty LATs are available.
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).
Finally, the agencies intends to include 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, that 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 RRC for this program.
The agencies also continue to believe the ISO test method is the most appropriate for this program because the method is the same one used by the NHTSA tire fuel efficiency consumer information program, by European regulations, and by the EPA SmartWay program.  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 explained 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 RRC values for GEM inputs.
As discussed above, the agencies are taking the approach of using RRC 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 and the California Air Resources Board (CARB) through a staff recommendation for a California regulation.  In the NPRM, the agencies proposed to use RRC, but for purposes of developing these final rules, the agencies also evaluated whether to use RRC 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, and thus how the information will be used, are much different for the two programs. 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.  RRC values generally follow an opposite trend, where tires that are larger and/or carry higher loads will generally have numerically lower RRC 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.
Additionally, the RRC metric for use in the MD/HD program is not susceptible to the skew associated with tire diameter.  Medium- and heavy-duty truck 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 RRC 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 RRC 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 truck 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 RRC (as opposed to the RRF) for refuse trucks were found to be among the best tested.  This finding can be explained by considering that RRC 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) RRC value than many other types of tires.  The amount of load tire can carry (test load) contributes to a very low reported RRC, thus confirming low rolling resistance tires below the proposed standards, as measured by RRC, are available to the industry regardless of segment or application.
Based on these considerations, the agencies have decided to use the RRC metric for the HD fuel efficiency and GHG emissions program.

Defined Vehicle Configurations in the GEM
As discussed above, the agencies are finalizing a methodology that chassis manufacturers would use to quantify the tire rolling resistance values to be input into the GEM.  Moreover, the agencies are  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 include the drive cycle, aerodynamics, truck curb weight, payload, engine characteristics, and drivetrain for each vehicle type, among others.
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 trucks 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 require 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.
Drive cycle
The drive cycles proposed for the vocational vehicles consist of the same three modes used for the Class 7 and8 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.  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.
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 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 US 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 truck fleet since they are not distinguished by different duty cycles.  They urged the agencies to sub-divide  vocational trucks 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 GEM, coupled with too much steady state operation with very little variation, is not representative of vocational vehicle operation.  In addition, Allison said that 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 which we are adopting treats all vocational applications equally and require the same technologies be applied to meet the standard.  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.  Similar to the issue of metrics discussed above, the agencies would revisit drive cycles and weightings in any future action which may develop standards which are specific to applications.
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 truck curb weight inputs based on industry information developed by ICF.  The final curb weights are 10,300 pounds for the LH trucks, 13,950 pounds for the MH trucks, and 29,000 pounds for the HH trucks.
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.  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.
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.  UMTRI suggested using 80,000 pounds total weight for tractors.  ATA said that typical 3 axle trucks (Class 2-8) have a total weight of 11,000 pounds.  ATA based their recommendations on FHWA Long-Term Pavement Data Base on truck weights over the last several years.
Upon further consideration, the agencies are reducing the weight of heavy heavy-duty vocational vehicle.  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.
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 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 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 2014 MY and 2017 MY so that there is stability in the vocational vehicle (not including engine) 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.
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.
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.  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.

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 off-cycle manufacturers further calibrate these designs 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.  With regard to GHG and fuel consumption control, the agencies believe it is more 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.
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 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 both 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 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 there already exists sufficient incentives 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 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 timeframe 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.
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.  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 technologies could be applied to any heavy-duty vehicle or engine, and not be limited to the vehicle category 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 truck standard.  In general, manufacturers can derive the fuel consumption and CO2 emissions reductions based on comparative test results using the final chassis testing procedures.
Summary of Final Flexibility and Credit Provisions
EPA and NHTSA are finalizing four flexibility provisions specifically for heavy-duty tractor 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 HD vocational vehicles can only be used by HD vehicles).  EPA is also adopting a N2O emission credit program, as described in Section IV below.
Deferral of Standards for Small Chassis Manufacturing and Small 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. 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, and therefore that the exemption will have a negligible impact on the GHG emissions and fuel consumption improvements from the final standards.
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.  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 proposal would have a negligible impact on the GHG emissions and fuel consumption reductions otherwise due to the standards.
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.
Other Standards Provisions
In addition to finalizing CO2 emission standards for heavy-duty vehicles and engines, EPA is also finalizing separate standards for N2O and CH4 emissions.  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).  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.
EPA requested comment in Section II.E.4 below on possible alternative CO2 equivalent approaches to provide near-term flexibility for 2012-14 MY light-duty vehicles. As described below, EPA is finalizing provisions allowing manufacturers to use CO2 credits, on a CO2-equivalent 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 nonmethane 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 act 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's proposal to extend certification requirements to all-electric HD vehicles and vehicles and engines designed to run on ethanol fuel.
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% of the current greenhouse gas emissions from heavy-duty trucks.
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 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.
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 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.
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. 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.
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 proposal.
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.
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. 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.
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 for exists 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.  The agencies reanalyzed a new data set, as shown in Table II-20, to derive the final N2O standard of 0.10 g/bhp-hr with a defined deterioration factor of 0.02 g/bhp-hr.
Table II-20: N2O Data Analysis
                                 Engine Family
                               Rated Power (HP)
                   Composite FTP Cycle N2O Result (g/bhp-hr)
                       EPA Data of 2007 Engine with SCR

                                     0.042
                   EPA Data of 2010 Production Intent Engine

                                     0.037
                                       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 reporting of N2O and requires that manufacturers either measure N2O or use a compliance statement based on good engineering judgment in lieu of direct N2O measurement (74 FR 56260, October 30, 2009).  The light-duty GHG final rule allows manufacturers to provide a compliance statement based on good engineering judgment through the 2014 model year, but requires measurement beginning in 2015 model year (75 FR 25324, May 7, 2010).  EPA is finalizing a consistent approach for heavy-duty engine manufacturers which allows them to delay direct measurement of N2O until the 2015 model year.
Manufacturers without the capability to measure N2O by the 2015 model year would need to acquire and install appropriate measurement equipment in response to this final program.  EPA has established four separate N2O measurement methods, all of which are commercially available today.  EPA expects that most manufacturers would use either photo-acoustic measurement equipment for stand-alone, existing FTIR instrumentation at a cost of $50,000 per unit or upgrade existing emission measurement systems with NDIR analyzers for $25,000 per test cell.
Overall, EPA believes that manufacturers of heavy-duty engines, both gasoline and diesel, would meet the final standard without implementing any new technologies, and beyond relatively small facilities costs for any company that still needs to acquire and install N2O measurement equipment, EPA does not project that manufacturers would incur significant costs associated with this final N2O standard.
 EPA is not adopting any vehicle-level N2O standards for heavy-duty vocational vehicles and combination tractors.  The N2O emissions would be controlled through the heavy-duty engine portion of the program. The only requirement of those truck manufacturers to comply with the N2O requirements is to install a certified engine.
What is EPA's  approach to controlling CH4?
CH4 is greenhouse gas with a GWP of 25.  It accounts for about 0.03 percent of the greenhouse gases from heavy-duty trucks.
EPA is finalizing a standard that would cap CH4 emission levels, with the expectation that current heavy-duty vehicles and engines meeting the heavy-duty emission standards would not increase their levels as explained earlier due to robust current controls and manufacturer compliance margin targets.  It would ensure that emissions would be addressed if in the future there are increases in the use of natural gas or any other alternative fuel. EPA believes that current heavy-duty emission standards, specifically the NMHC standards for both engine and chassis certified engines directly result in stringent CH4 control. It is believed that the current emission control technologies used to meet the stringent NMHC standards achieve the maximum feasible reductions and that no additional technologies are recognized that would result in additional CH4 reductions. The level of the standard would generally be achievable through normal emission control methods already required to meet heavy-duty emission standards for hydrocarbons and EPA is therefore not attributing any cost to this part of the final action. Since CH4 is produced in gasoline and diesel engines similar to other hydrocarbon components, controls targeted at reducing overall NMHC levels generally also work at reducing CH4 emissions.  Therefore, for gasoline and diesel vehicles, the heavy-duty hydrocarbon standards will generally prevent increases in CH4 emissions levels.  CH4 from heavy-duty vehicles is relatively low compared to other GHGs largely due to the high effectiveness of the current heavy-duty standards in controlling overall HC emissions.
EPA believes that this level for the standard would be met by current gasoline and diesel trucks and vans, and would prevent increases in future CH4 emissions in the event that alternative fueled vehicles with high methane emissions, like some past dedicated compressed natural gas vehicles, become a significant part of the vehicle fleet.   Currently EPA does not have separate CH4 standards because, unlike other hydrocarbons, CH4 does not contribute significantly to ozone formation.  However, CH4 emissions levels in the gasoline and diesel heavy-duty truck fleet have nevertheless generally been controlled by the heavy-duty HC emission standards.  Even so, without an emission standard for CH4, future emission levels of CH4 cannot be guaranteed to remain at current levels as vehicle technologies and fuels evolve.
In recent model years, a small number of heavy-duty trucks and engines were sold that were designed for dedicated use of natural gas.  While emission control designs on these recent dedicated natural gas-fueled vehicles demonstrate CH4 control can be as effective as gasoline or diesel equivalent vehicles, natural gas-fueled vehicles have historically produced significantly higher CH4 emissions than gasoline or diesel vehicles. This is because the fuel is predominantly methane, and most of the unburned fuel that escapes combustion without being oxidized by the catalyst is emitted as methane.  However, even if these vehicles meet the heavy-duty hydrocarbon standard and appear to have effective CH4 control by nature of the hydrocarbon controls, the heavy-duty standards do not require CH4 control and therefore some natural gas vehicle manufacturers have invested very little effort into methane control. While the final CH4 cap standard should not require any different emission control designs beyond what is already required to meet heavy-duty hydrocarbon standards on a dedicated natural gas vehicle (i.e., feedback controlled 3-way catalyst), the cap will ensure that systems provide robust control of methane much like a gasoline-fueled engine. We are not finalizing more stringent CH4 standards because we believe that the controls used to meet current heavy-duty hydrocarbon standards should result in effective CH4 control when properly implemented. Since CH4 is already measured under the current heavy-duty emissions regulations (so that it may be subtracted to calculate NMHC), the final standard would not result in additional testing costs.
Heavy-duty Pickup Truck and Van CH4 Standard
EPA is finalizing the proposed CH4 emission standard of 0.05 g/mi as measured on the Light-duty FTP and HFET drive cycles, to apply beginning with model year 2014 for HD pickups and vans subject to the  CO2 standards.  Similar to the CO2 standard approach, the CH4 emission level of a vehicle will be a composite of the Light-duty FTP and HFET cycles, with the same 55% city weighting and 45% highway weighting.
The level of the  standard is approximately two times the average heavy-duty gasoline and diesel truck and van levels.  As with N2O, this  standard level recognizes that manufacturers typically set emissions design targets with a compliance margin of approximately 50% of the standard.  Thus, we believe that the  standard should be met by current gasoline vehicles with no increase from today's CH4 levels.  Similarly, since current diesel vehicles generally have even lower CH4 emissions than gasoline vehicles, we believe that diesels will also meet the  standard with a larger compliance margin resulting in no change in today's CH4 levels.
Heavy-duty Engine CH4 Exhaust Emission Standard
EPA is adopting a heavy-duty engine CH4 emission standard of 0.10 g/hp-hr with a defined deterioration factor of 0.02 g/bhp-hr as measured on the composite Heavy-duty FTP, to apply beginning in model year 2014 for diesel engines and in 2016 model year for gasoline engines.  EPA is adopting a different CH4 standard than proposed based on additional data submitted to the agency which better represents the full range of current diesel and gasoline engine performance.  EPA is adopting CH4 standards for gasoline engines that become effective in 2016 model year to align with the first year of the gasoline engine CO2 standards.  Without this alignment, manufacturers would not have any flexibility, such as CO2eq credits, in meeting the CH4 cap and therefore would not be able to sell any engine with a CH4 level above the standard.  The final standard would cap CH4 emissions at a level currently achieved by diesel and gasoline heavy-duty engines.  The level of the standard would generally be achievable through normal emission control methods already required to meet 2007 emission standards for NMHC and EPA is therefore not attributing any cost to this part of this program (see 40 CFR 86.007-11).
The level of the final CH4 standard is twice the average CH4 emissions from gasoline engines from General Motors in addition to the four diesel engines in the ACES study.  As with N2O, this final level recognizes that manufacturers typically set emission design targets at about 50 percent of the standard.  Thus, EPA believes the final standard would be met by current diesel and gasoline engines with little if any technological improvements.  The agency believes a more stringent CH4 standard is not necessary due to effective CH4 controls in current heavy-duty technologies, since, as discussed above for N2O, EPA believes that the challenge of complying with the CO2 standards should be the primary focus of the manufacturers
CH4 is measured under the current 2007 regulations so that it may be subtracted to calculate NMHC.  Therefore EPA expects that the final standard would not result in additional testing costs.
EPA is not adopting any vehicle-level CH4 standards for heavy-duty combination tractors or vocational vehicles in this final action.  The CH4 emissions will be controlled through the heavy-duty engine portion of the program. The only requirement of these truck manufacturers to comply with the CH4 requirements is to install a certified engine.
Use of CO2 Credits
As proposed, if a manufacturer is unable to meet the N2O or CH4 cap standards, the EPA program will allow the manufacturer to comply using CO2 credits.  In other words, a manufacturer could offset any N2O or CH4 emissions above the standard by taking steps to further reduce CO2.  A manufacturer choosing this option would convert its measured N2O and CH4 test results that are in excess of the applicable standards into CO2eq to determine the amount of CO2 credits required.  For example, a manufacturer would use 25 Mg of positive CO2 credits to offset 1 Mg of negative CH4 credits or use 298 Mg of positive CO2 credits to offset 1 Mg of negative N2O credits.  By using the Global Warming Potential of N2O and CH4, the  approach recognizes the inter-correlation of these compounds in impacting global warming and is environmentally neutral for demonstrating compliance with the  individual emissions caps.
The final NHTSA fuel consumption program will not use CO2eq, as suggested above.  Measured performance to the NHTSA fuel consumption standards will be based on the measurement of CO2 with no adjustment for N2O and/or CH4.  For manufacturers that use the EPA alternative CO2eq credit, compliance to the EPA CO2 standard will not be directly equivalent to compliance to the NHTSA fuel consumption standard.
Amendment to Light-duty Vehicle N2O and CH4 Standards
EPA also requested comment on revising a portion of the light duty vehicle standards for N2O and CH4.  75 FR at 74211.  Specifically, EPA requested comments on two additional options for manufacturers to comply with N2O and CH4 standards to provide additional near-term flexibility.  EPA is finalizing one of those options, as discussed below.