Naphthalene.....................................              99               3             269              15
Ethanol.........................................           2,704               2          19,950              16
----------------------------------------------------------------------------------------------------------------

    The totals shown in Table III-6 represent the sum of 71 species
including the toxics in Table III-5, 15 polycyclic aromatic hydrocarbon
(PAH) compounds in gas and particle phase, and additional gaseous
compounds such as toluene, xylenes, styrene, hexane, 2,2,4-
trimethylpentane, n-hexane, and propionaldehyde (see Appendix 7A of the
RIA). As shown, in 2030, the overall onroad inventory of total toxics
will be reduced by 15 percent, with nearly one

half of the vehicle program reductions coming from the evaporative
standards.

        Table III-6--Reductions in Total Mobile Source Air Toxics
                           [Annual U.S. tons]
------------------------------------------------------------------------
                                           2018               2030
------------------------------------------------------------------------
Total reduction...................             15,583             64,558
Reduction from pre-Tier 3 fleet                11,981              3,517
 due to sulfur standard...........
Reduction from Tier 3 fleet due to              3,602             61,041
 vehicle and sulfur standards.....
Exhaust...........................             13,340             34,595
Evaporative.......................              2,243             29,963
Percent reduction in onroad toxics                 3%                15%
 emissions........................
------------------------------------------------------------------------

6. SO2
    SO2 emissions from mobile sources are a direct function
of sulfur in the fuel, and reducing sulfur in gasoline will result in
immediate reductions in SO2 from the on and off-road fleet.
The reductions, shown in Table III-7, are a function of the sulfur
level and fuel consumption. This is reflected in the relative
contribution of on-road vehicles and off-road equipment, where off-road
gasoline consumption accounts for approximately 5 percent of overall
gasoline use.\216\
---------------------------------------------------------------------------

    \216\ U.S. Energy Information Administration, Annual Energy
Outlook 2013 (April 15, 2013).

        Table III-7--Projected SO2 Reductions From Tier 3 Program
                           [Annual U.S. tons]
------------------------------------------------------------------------
                                           2018               2030
------------------------------------------------------------------------
Total reduction...................             15,565             13,261
Reduction from onroad vehicles due             14,813             12,399
 to sulfur standard...............
Reduction from off-road equipment                 752                862
 due to sulfur standard...........
Percent reduction in onroad SO2                   56%                56%
 emissions........................
------------------------------------------------------------------------

7. Greenhouse Gases
    Reductions in nitrous oxide (N2O) emissions and methane
(CH4) emissions, both potent greenhouse gas emissions, are
projected for gasoline cars and trucks as a result of the sulfur and
tailpipe standards. A study conducted by the University of California-
Riverside found a 29 percent reduction in N2O emissions over
the FTP when sulfur was reduced from 30 to 5 ppm,\217\ while EPA
research described in Section IV.A.6 on sulfur effects found a 26
percent reduction in CH4 emissions when sulfur was reduced
from 28 to 5 ppm.\218\
---------------------------------------------------------------------------

    \217\ Huai, et al. (2004), Estimates of the emission rates of
nitrous oxide from light-duty vehicles using different chassis
dynamometer test cycles, Atmospheric Environment 6621-6629
    \218\ The Effects of Ultra-Low Sulfur Gasoline on Emissions from
Tier 2 Vehicles in the In-Use Fleet, EPA-420-R-14-002,
---------------------------------------------------------------------------

    Several studies have established correlations between reductions in
tailpipe NOX emissions and reductions in N2O from
gasoline cars and trucks,219 220 221 222 as well as
correlations between reductions in tailpipe HC emissions and reductions
in CH4.223 224 Studies by Winer, et al (2005) and
Behrentz et al (2004) reported N2O: NOX ratios of
0.06 and 0.095, respectively, and supported the application of
N2O: NOX ratios to NOX emissions as a
reasonable method for estimating N2O emission inventories.
CARB has also used N2O: NOX ratio to develop the
N2O emissions inventories for the LEV III program, based on
a regression analysis suggesting N2O: NOX ratio
of 0.04, on average.\225\
---------------------------------------------------------------------------

    \219\ Michaels, H. (1998) Emissions of Nitrous Oxide from
Highway Mobile Sources, U.S. EPA EPA420-R-98-009.
    \220\ Behrentz, et al. (2004), Measurements of nitrous oxide
emissions from light-duty motor vehicles: A pilot study, Atmospheric
Environment 4291-4303.
    \221\ Meffert, et. al (2000) Analysis of Nitrous Oxide Emissions
from Light Duty Passenger Cars, SAE 2000-01-1952.
    \222\ Winer, et al. (2005) Estimates of Nitrous Oxide Emissions
and the Effects of Catalyst Composition and Aging, State of
California Air Resources Board 02-313.
    \223\ Meszler, D. (2004), Light Duty Vehicle Methane and Nitrous
Oxide Emissions: Greenhouse Gas Impacts, Study for Northeast States
Center for a Clean Air Future.
    \224\ Graham, L., Greenhouse Gas Emissions from 1997-2005 Model
Year Light Duty Vehicles, Environment Canada ERMD Report
04-44.
    \225\ LEV III Moblie Source Emissions Inventory Technical
Support Document--Appendix T, January 2012, last accessed on 01/15/
14 at the following URL: http://www.arb.ca.gov/regact/2012/leviiighg2012/levappt.pdf.
---------------------------------------------------------------------------

    As detailed in Chapter 7.3 of the RIA, the N2O
reductions are estimated by employing two different methodologies,
resulting in a range of reductions. The first method applies the
relationship between N2O and NOX from a
regression model \226\ to NOX inventories from both Tier 3
and pre-Tier 3 vehicles. The second method applies the regression of
N2O and NOX only to Tier 3 vehicles and uses the
UC Riverside sulfur results to estimate the N2O reductions
from pre-Tier 3 vehicles. Using a 100-year global warming potential of
298 for N2O according to the 2007 IPCC AR4,\227\ the
estimated N2O reduction is 2.2 million metric tons of carbon
dioxide equivalent (MMTCO2e) in 2018, growing to the range
between 3.8 to 4.0 MMTCO 2e in 2030. For 2018, there was an
agreement between the two methodologies described above, resulting in a
single estimate. MOVES can be used to directly estimate CH4
reductions from the sulfur and vehicle standards, estimating an
additional 0.1 MMTCO2e

reduction in 2018, growing to 0.3 MMTCO2e in 2030. The total
GHG reduction from the Tier 3 rule is 2.3 MMTCO2e in 2018,
and between 4.1 and 4.3 MMTCO2e in 2030.
---------------------------------------------------------------------------

    \226\ U.S. EPA, 2014, Memorandum to Docket: Regression Analysis
of Nitrous Oxide and Oxides of Nitrogen from Motor Vehicles.
    \227\ The global warming potentials (GWP) used in this rule are
consistent with the 100-year time frame values in the 2007
Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment
Report (AR4). At this time, the 1996 IPCC Second Assessment Report
(SAR) 100-year GWP values are used in the official U.S. greenhouse
gas inventory submission to the United Nations Framework Convention
on Climate Change (per the reporting requirements under that
international convention, which were last updated in 2006).
N2O has a 100-year GWP of 298 and CH4 has a
100-year GWP of 25 according to the 2007 IPCC AR4.
---------------------------------------------------------------------------

    These reductions will be partially offset by CO2
emissions associated with higher energy use required in the process of
removing sulfur within the refinery. As an extension of our refinery-
by-refinery cost modeling described in Section VII.B., we calculated
the CO2 emission impacts of Tier 3 gasoline sulfur control.
We estimated refinery-specific changes in process energy and then
applied emission factors that correspond to those changes, on a
refinery-by-refinery basis. As described in Chapter 4.5 of the RIA, the
results showed an increase of up to 1.9 MMTCO2e in 2018 and
1.6 MMTCO2e in 2030 for all U.S. refineries complying with
the lower sulfur standards assuming that the sulfur standards are fully
phased-in. In 2018, the combined impact of CH4 and
N2O emission reductions from the vehicles and CO2
emission increases from the refineries shows a slight net decrease on a
CO2 equivalent basis. While still small, this net decrease
grows to a range between 2.5 to 2.7 MMTCO2e by 2030.
    We do not expect the Tier 3 vehicle standards to result in any
discernible changes in vehicle CO2 emissions or fuel
economy. Emissions of the pollutants that are controlled by the Tier 3
program--NMOG, NOX, and PM--are not a function of the amount
of fuel consumed, since manufacturers need to design their catalytic
emission control systems to reduce these emissions regardless of their
engine-out levels.

C. How will air pollution be reduced?

    Reductions in emissions of NOX, VOC, PM2.5
and air toxics expected as a result of the Tier 3 standards are
projected to lead to significant improvements in air quality. The air
quality modeling predicts significant improvements in ozone
concentrations due to the Tier 3 standards. Ambient PM2.5
and NO2 concentrations are also expected to improve as a
result of the Tier 3 program. Decreases in ambient concentrations of
air toxics are projected with the Tier 3 standards, including notable
nationwide reductions in benzene concentrations. Our air quality
modeling also predicts improvements in visibility and sulfur
deposition, as well as substantial decreases in nitrogen deposition as
a result of the Tier 3 standards. The results of our air quality
modeling of the impacts of the Tier 3 rule are summarized in the
following section.
1. Ozone
    The air quality modeling done for this action projects that in
2018, with all current and required controls in effect but excluding
the emissions changes expected to occur as a result of the Tier 3
standards or any other additional controls, at least 19 counties, with
a projected population of over 37 million people, would have projected
design values above the level of the 2008 8-hour ozone standard of 75
ppb. In 2030 the modeling projects that in the absence of Tier 3
standards or any other additional controls there will be 6 counties
with a population of over 19 million people with projected design
values above the level of the 2008 8-hour ozone standard of 75 ppb. An
additional 37 million people will be living in the 43 counties that
will be close to (within 10 percent of) the level of the ozone
standard.
    Air quality modeling indicates that this action will meaningfully
decrease ozone design value concentrations in many areas of the
country, including those that are projected to be exceeding, or close
to exceeding, the ozone standard. In 2018, the majority of the design
value decreases are between 0.5 and 1.0 ppb. In 2030, the Tier 3 rule
will result in larger decreases in ozone design values, with the
majority of counties projecting decreases of between 0.5 and 1.0 ppb,
and over 250 more counties with decreases greater than 1.0 ppb. Since
the Tier 3 standards go into effect during the period when some areas
are still working to attain the ozone NAAQS, the projected air quality
changes will help state and local agencies in their effort to attain
and maintain the ozone standard.
2. Particulate Matter
    The air quality modeling conducted for this action projects that in
2018, with all current controls in effect but excluding the emissions
changes expected to occur as a result of Tier 3 standards or any other
additional controls, at least 14 counties, with a projected population
of over 20 million people, would have projected design values above the
level of the annual standard of 12 [mu]g/m\3\ and at least 24 counties,
with a projected population of over 18 million people, would have
projected design values above the level of the 24-hour standard of 35
[mu]g/m\3\. In 2030, the modeling projects that in the absence of Tier
3 standards or any other additional controls there will be 13 counties,
with a projected population of over 21 million people, with projected
design values above the level of the annual standard of 12 [mu]g/m\3\
and 18 counties, with a projected population of over 12 million people,
with projected design values above the level of the 24-hour standard of
35 [mu]g/m\3\. Since the Tier 3 standards go into effect during the
period when some areas are still working to attain the 2006 and 2012
PM2.5 NAAQS, the projected air quality changes will be
useful to state and local agencies in their effort to attain and
maintain the PM2.5 standards.
    The Tier 3 standards will reduce 24-hour and annual
PM2.5 design values due to projected tailpipe reductions in
primary PM2.5, SO2, NOX and VOCs from
reductions in fuel sulfur and engine controls. In 2018 the standards
will have a small impact on annual PM2.5 design values in
the majority of modeled counties. However, in over 200 counties annual
PM2.5 design values are projected to decrease by greater
than 0.01 [mu]g/m\3\. In 2030 annual PM2.5 design values in
the majority of modeled counties will decrease by between 0.01 and 0.05
[mu]g/m\3\ and in over 140 additional counties design values are
projected to decrease by greater than 0.05 [mu]g/m\3\. In addition, in
2018 24-hour PM2.5 design values in over 200 counties are
projected to decrease by between 0.05 and 0.15 [mu]g/m\3\ and in 2030
24-hour PM2.5 design values in over 180 counties decrease by
at least 0.15 [mu]g/m\3\.
3. Nitrogen Dioxide
    Although our modeling indicates that by 2030 the majority of the
country will experience decreases of less than 0.1 ppb in their annual
NO2 concentrations due to this rule, annual NO2
concentrations are projected to decrease by more than 0.3 ppb in most
urban areas. These emissions reductions would also likely decrease 1-
hour NO2 concentrations and help any potential nonattainment
areas to attain and maintain the standard. Additional information on
the emissions reductions that are projected with this rule is available
in Section 7.2.1 of the RIA.
4. Air Toxics
    Our modeling indicates that the impacts of final Tier 3 standards
include notable nationwide reductions in benzene and generally small
decreases in ambient concentrations of other air toxics, mainly in
urban areas. Although reductions are greater in 2030 (when 70 percent
of the miles travelled are from vehicles that meet the fully phased-in
Tier 3 standards) than in 2017 (the first year of the final program),
our modeling projects there will be small immediate reductions in
ambient concentrations of air toxics due to the Tier 3 sulfur controls.
Furthermore, the full reduction of the vehicle program will be realized

after 2030, when the fleet has fully turned over to vehicles meeting
the fully phased-in Tier 3 standards. Air toxics pollutants dominated
by primary emissions (or a decay product of a directly emitted
pollutant), such as benzene, are impacted more than air toxics that
primarily result from photochemical transformation.
    Specifically, in 2030, our modeling projects that the Tier 3 rule
will decrease ambient benzene concentrations across much of the country
on the order of 1 to 5 percent, with reductions ranging from 10 to 25
percent in some urban areas. Our modeling also shows reductions of 1,3-
butadiene and acrolein concentrations in 2030 ranging between 1 and 25
percent and 1 and 10 percent respectively, with 1,3-butadiene decreases
of at least 0.005 [mu]g/m\3\ in urban areas. These toxics are national
risk drivers and the reductions in ambient concentrations from this
rule will result in reductions in risks from cancer and noncancer
health effects. In some parts of the country (mainly urban areas),
ethanol and formaldehyde concentrations are projected to decrease on
the order of 1 to 10 percent and 1 to 2.5 percent respectively in 2030
as a result of the Tier 3 rule. Decreases in ethanol concentrations are
expected due to reductions in VOC as a result of the Tier 3 standards.
Changes in ambient acetaldehyde concentrations are generally less than
1 percent across the U.S., although the Tier 3 rule may decrease
acetaldehyde concentrations in some urban areas by 1 to 2.5 percent in
2030. Changes in ambient naphthalene concentrations are generally
between 1 and 10 percent in 2030 with absolute decreases of up to 0.005
[mu]g/m\3\.
    Although the reductions in ambient air toxics concentrations
expected from the Tier 3 standards are generally small, they are
projected to benefit the majority of the U.S. population. As shown in
Table III-8, over 75 percent of the total U.S. population is projected
to experience a decrease in ambient benzene and 1,3-butadiene
concentrations of at least 1 percent. Over 60 percent of the U.S
population is projected to experience at least a 1 percent decrease in
ambient ethanol and acrolein concentrations, and over 35 percent would
experience a similar decrease in ambient formaldehyde concentrations
with the Tier 3 standards.

  Table III-8--Percent of Total Population Experiencing Changes in Annual Ambient Concentrations of Toxic Pollutants in 2030 as a Result of the Tier 3
                                                                        Standards
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                              Benzene        Acrolein      1,3-Butadiene   Formaldehyde       Ethanol      Acetaldehyde     Naphthalene
        Percent change (percent)             (percent)       (percent)       (percent)       (percent)       (percent)       (percent)       (percent)
--------------------------------------------------------------------------------------------------------------------------------------------------------
<=-50...................................  ..............  ..............  ..............  ..............  ..............  ..............  ..............
>-50 to <=-25...........................  ..............  ..............  ..............  ..............  ..............  ..............  ..............
>-25 to <=-10...........................            2.29            0.75           19.07  ..............  ..............  ..............           10.74
>-10 to <=-5............................           20.63           12.72           27.29  ..............            5.39  ..............           31.56
>-5 to <=-2.5...........................           27.50           25.17           15.37            0.60           24.08  ..............           20.58
>-2.5 to <=-1...........................           28.60           24.62           18.33           35.34           34.10           11.77           14.98
>-1 to <1...............................           20.97           36.74           19.93           64.06           36.43           88.23           22.14
>=1 to <2.5.............................  ..............  ..............  ..............  ..............  ..............  ..............  ..............
>=2.5 to <5.............................  ..............  ..............  ..............  ..............  ..............  ..............  ..............
>=5 to <10..............................  ..............  ..............  ..............  ..............  ..............  ..............  ..............
>=10 to <25.............................  ..............  ..............  ..............  ..............  ..............  ..............  ..............
>=25 to <50.............................  ..............  ..............  ..............  ..............  ..............  ..............  ..............
>=50....................................  ..............  ..............  ..............  ..............  ..............  ..............  ..............
--------------------------------------------------------------------------------------------------------------------------------------------------------

    In addition, as described in Section <IP_ADDRESS>.2 of the RIA, our
modeling projects that acrolein concentrations would decrease to levels
below the inhalation reference concentration for acrolein (0.02 [mu]g/
m\3\) for over 5 million people in 2030, meaning that as a result of
the Tier 3 standards, 5 million fewer Americans will be exposed to
ambient levels of acrolein high enough to present a potential for
adverse health effects.
5. Visibility
    Air quality modeling conducted for this final action was used to
project visibility conditions in 137 mandatory class I federal areas
across the U.S. The results show that in 2030 all the modeled areas
will continue to have annual average deciview levels above background
and the Tier 3 rule will improve visibility in all these areas.\228\
The average visibility at all modeled mandatory class I federal areas
on the 20 percent worst days is projected to improve by 0.02 deciviews,
or 0.16 percent, in 2030. Section <IP_ADDRESS> of the RIA contains more
detail on the visibility portion of the air quality modeling.
---------------------------------------------------------------------------

    \228\ The level of visibility impairment in an area is based on
the light-extinction coefficient and a unitless visibility index,
called a ``deciview,'' which is used in the valuation of visibility.
The deciview metric provides a scale for perceived visual changes
over the entire range of conditions, from clear to hazy. Under many
scenic conditions, the average person can generally perceive a
change of one deciview. The higher the deciview value, the worse the
visibility. Thus, an improvement in visibility is a decrease in
deciview value.
---------------------------------------------------------------------------

6. Nitrogen and Sulfur Deposition
    Our air quality modeling projects substantial decreases in nitrogen
deposition as a result of the Tier 3 standards. The standards will
result in annual percent decreases of greater than 2.5 percent in most
major urban areas and greater than 5 percent in a few areas. In
addition, smaller decreases, in the 1 to 2.5 percent range, will occur
over much of the rest of the country. The impacts of the Tier 3
standards on sulfur deposition are smaller, ranging from no change to
decreases of over 2.5 percent in some areas. For maps of 2030
deposition impacts and additional information on these impacts see
Section <IP_ADDRESS> of the RIA.
7. Environmental Justice
    Environmental justice (EJ) is a principle asserting that all people
deserve fair treatment and meaningful involvement with respect to
environmental laws, regulations, and policies. EPA seeks to provide the
same degree of protection from environmental health hazards for all
people. As referenced below, numerous studies have found that some
environmental hazards are more prevalent in areas with high population
fractions of racial/ethnic minorities and people with low socioeconomic
status (SES), as would be expected on the basis of those areas' share
of the general population.
    As discussed in Section II of this document, concentrations of many
air pollutants are elevated near high-traffic

roadways. If minority populations and low-income populations
disproportionately live near such roads, then an issue of EJ may be
present. Such disparities may be due to multiple factors.\229\
---------------------------------------------------------------------------

    \229\ Depro, B.; Timmins, C. (2008) Mobility and environmental
equity: Do housing choices determine exposure to air pollution?
North Caroline State University Center for Environmental and
Resource Economic Policy.
---------------------------------------------------------------------------

    People with low SES often live in neighborhoods with multiple
stressors and health risk factors, including reduced health insurance
coverage rates, higher smoking and drug use rates, limited access to
fresh food, visible neighborhood violence, and elevated rates of
obesity and some diseases such as asthma, diabetes, and ischemic heart
disease. Although questions remain, several studies find stronger
associations between air pollution and health in locations with such
chronic neighborhood stress, suggesting that populations in these areas
may be more susceptible to the effects of air
pollution.230 231 232 233 Household-level stressors such as
parental smoking and relationship stress also may increase
susceptibility to the adverse effects of air
pollution.234 235
---------------------------------------------------------------------------

    \230\ Clougherty, J.E.; Kubzansky, L.D. (2009) A framework for
examining social stress and susceptibility to air pollution in
respiratory health. Environ Health Perspect 117: 1351-1358.
Doi:10.1289/ehp.0900612 [Online at http://dx.doi.org].
    \231\ Clougherty, J.E.; Levy, J.I.; Kubzansky, L.D.; Ryan, P.B.;
Franco Suglia, S.; Jacobson Canner, M.; Wright, R.J. (2007)
Synergistic effects of traffic-related air pollution and exposure to
violence on urban asthma etiology. Environ Health Perspect 115:
1140-1146. doi:10.1289/ehp.9863 [Online at http://dx.doi.org].
    \232\ Finkelstein, M.M.; Jerrett, M.; DeLuca, P.; Finkelstein,
N.; Verma, D.K.; Chapman, K.; Sears, M.R. (2003) Relation between
income, air pollution and mortality: a cohort study. Canadian Med
Assn J 169: 397-402.
    \233\ Shankardass, K.; McConnell, R.; Jerrett, M.; Milam, J.;
Richardson, J.; Berhane, K. (2009) Parental stress increases the
effect of traffic-related air pollution on childhood asthma
incidence. Proc Natl Acad Sci 106: 12406-12411. doi:10.1073/
pnas.0812910106 [Online at http://dx.doi.org].
    \234\ Lewis, A.S.; Sax, S.N.; Wason, S.C.; Campleman, S.L (2011)
Non-chemical stressors and cumulative risk assessment: An overview
of current initiatives and potential air pollutant interactions. Int
J Environ Res Public Health 8: 2020-2073. Doi:10.3390/ijerph8062020
[Online at http://dx.doi.org].
    \235\ Rosa, M.J.; Jung, K.H.; Perzanowski, M.S.; Kelvin, E.A.;
Darling, K.W.; Camann, D.E.; Chillrud, S.N.; Whyatt, R.M.; Kinney,
P.L.; Perera, F.P.; Miller, R.L (2010) Prenatal exposure to
polycyclic aromatic hydrocarbons, environmental tobacco smoke and
asthma. Respir Med (In press). doi:10.1016/j.rmed.2010.11.022
[Online at http://dx.doi.org].
---------------------------------------------------------------------------

    To address the existing conditions in areas near major roadways, in
comparison with other locations, we reviewed existing scholarly
literature examining the topic, and conducted our own evaluation of two
national datasets: The U.S. Census Bureau's American Housing Survey for
calendar year 2009 and the U.S. Department of Education's database of
school locations.
    Existing publications that address EJ issues generally report that
populations living near major roadways (and other types of
transportation infrastructure) tend to be composed of larger fractions
of nonwhite residents. People living in neighborhoods near such sources
of air pollution also tend to be lower in income than people living
elsewhere. Numerous studies evaluating the demographics and
socioeconomic status of populations or schools near roadways have found
that they include a greater percentage of minority residents, as well
as lower SES (indicated by variables such as median household income).
Locations in these studies include Los Angeles, CA; Seattle, WA; Wayne
County, MI; Orange County, FL; and the State of California
236 237 238 239 240 241
---------------------------------------------------------------------------

    \236\ Marshall, J.D. (2008) Environmental inequality: Air
pollution exposures in California's South Coast Air Basin.
    \237\ Su, J.G.; Larson, T.; Gould, T.; Cohen, M.; Buzzelli, M.
(2010) Transboundary air pollution and environmental justice:
Vancouver and Seattle compared. GeoJournal 57: 595-608. doi:10.1007/
s10708-009-9269-6 [Online at http://dx.doi.org].
    \238\ Chakraborty, J.; Zandbergen, P.A. (2007) Children at risk:
Measuring racial/ethnic disparities in potential exposure to air
pollution at school and home. J Epidemiol Community Health 61: 1074-
1079. doi: 10.1136/jech.2006.054130 [Online at http://dx.doi.org].
    \239\ Green, R.S.; Smorodinsky, S.; Kim, J.J.; McLaughlin, R.;
Ostro, B. (2003) Proximity of California public schools to busy
roads. Environ Health Perspect 112: 61-66. doi:10.1289/ehp.6566
[http://dx.doi.org].
    \240\ Wu, Y; Batterman, S.A. (2006) Proximity of schools in
Detroit, Michigan to automobile and truck traffic. J Exposure Sci &
Environ Epidemiol. doi:10.1038/sj.jes.7500484 [Online at http://dx.doi.org].
    \241\ Su, J.G.; Jerrett, M.; de Nazelle, A.; Wolch, J. (2011)
Does exposure to air pollution in urban parks have socioeconomic,
racial, or ethnic gradients? Environ Res 111: 319-328.
---------------------------------------------------------------------------

    More recently, three publications report nationwide analyses that
compare the demographic patterns of people who do or do not live near
major roadways.242 243 244 All three of these studies found
that people living near major roadways are more likely to be minorities
or low in SES. They also found that the outcomes of their analyses
varied between regions within the U.S. However, only one such study
looked at whether such conclusions were confounded by living in a
location with higher population density and how demographics differ
between locations nationwide. In general, it found that higher density
areas have higher proportions of low income and minority residents.
---------------------------------------------------------------------------

    \242\ Rowangould, G.M. (2013) A census of the US near-roadway
population: Public health and environmental justice considerations.
Transportation Research Part D; 59-67.
    \243\ Tian, N.; Xue, J.; Barzyk. T.M. (2013) Evaluating
socioeconomic and racial differences in traffic-related metrics in
the United States using a GIS approach. J Exposure Sci Environ
Epidemiol 23: 215-222.
    \244\ Boehmer, T.K.; Foster, S.L.; Henry, J.R.; Woghiren-
Akinnifesi, E.L.; Yip, F.Y. (2013) Residential proximity to major
highways--United States, 2010. Morbidity and Mortality Weekly Report
62(3): 46-50.
---------------------------------------------------------------------------

    We analyzed two national databases that allowed us to evaluate
whether homes and schools were located near a major road. One database,
the American Housing Survey (AHS), includes descriptive statistics of
over 70,000 housing units across the nation. The study is conducted
every two years by the U.S. Census Bureau. We analyzed data from the
2009 AHS. The second database we analyzed was the U.S. Department of
Education's Common Core of Data, which includes enrollment and location
information for schools across the U.S.
    In analyzing the 2009 AHS, we focused on whether or not a housing
unit was located within 300 feet of ``4-or-more lane highway, railroad,
or airport.'' \245\ We analyzed whether there were differences between
houses and householders in such locations and those not in them.\246\
We included other variables, such as land use category, region of
country, and housing type. We found that homes with a nonwhite
householder were 22-34 percent more likely to be located within 300
feet of these large transportation facilities, while homes with a
Hispanic householder were 17-33 percent more likely. Households near
large transportation facilities were, on average, lower in income and
educational attainment, more likely to be a rental property and located
in an urban area.
---------------------------------------------------------------------------

    \245\ This variable primarily represents roadway proximity.
According to the Central Intelligence Agency's World Factbook, in
2010, the United States had 6,506,204 km or roadways, 224,792 km of
railways, and 15,079 airports. Highways thus represent the
overwhelming majority of transportation facilities described by this
factor in the AHS.
    \246\ Bailey, C. (2011) Demographic and Social Patterns in
Housing Units Near Large Highways and other Transportation Sources.
Memorandum to docket.
---------------------------------------------------------------------------

    In examining schools near major roadways, we examined the Common
Core of Data (CCD) from the U.S. Department of Education, which
includes information on all public elementary and secondary schools and
school districts nationwide.\247\ To determine school proximities to
major roadways, we used a geographic

information system (GIS) to map each school and roadways based on the
U.S. Census's TIGER roadway file.\248\ We found that minority students
were overrepresented at schools within 200 meters of the largest
roadways, and that schools within 200 meters of the largest roadways
also had higher than expected numbers of students eligible for free or
reduced-price lunches. For example, Black students represent 21.57
percent of students at schools located within 200 meters of a primary
road, whereas Black students represent 16.62 percent of students in all
U.S. schools. Hispanic students represent 30.13 percent of students at
schools located within 200 meters of a primary road, whereas Hispanic
students represent 21.93 percent of students in all U.S. schools.
---------------------------------------------------------------------------

    \247\ http://nces.ed.gov/ccd/.
    \248\ Pedde, M.; Bailey, C. (2011) Identification of Schools
within 200 Meters of U.S. Primary and Secondary Roads. Memorandum to
the docket.
---------------------------------------------------------------------------

    Overall, there is substantial evidence that people who live or
attend school near major roadways are more likely to be of a minority
race, Hispanic ethnicity, and/or low SES. The emission reductions from
this rule are projected to result in widespread air quality
improvements, but the impact on pollution levels in close proximity to
roadways is expected to be most direct. Thus, this rule is likely to
help in mitigating the disparity in racial, ethnic, and economically-
based exposures.

IV. Vehicle Emissions Program

    In the 14 years since EPA finalized the Tier 2 Vehicle Program,
manufacturers of light-duty vehicles have continued to develop a wide
range of improved technologies capable of reducing emissions,
especially exhaust hydrocarbons, nitrogen oxides (NOX), and
particulate matter (PM), and evaporative hydrocarbons. The California
LEV II program has been instrumental in the auto industry's continuous
technology improvements by requiring year after year reductions in
fleet average exhaust hydrocarbon levels. In addition, California set
performance standards that have resulted in the introduction of
advanced exhaust and evaporative emission controls in partial zero
emission vehicles (PZEVs). Overall, this progress in vehicle technology
has made it possible for manufacturers to achieve emission reductions
with a number of today's vehicles that go well beyond the requirements
of the Tier 2 program.
    Extensive data from existing Tier 2 (and California LEV II)
vehicles presented in the NPRM and received since the proposal have
demonstrated the potential for further significant reductions. For
exhaust emissions, these opportunities include addressing: Emissions
produced at start-up; emissions under high-speed, high-load conditions;
the effects of sulfur in gasoline; the effects of increased oil
consumption; and the effects of age on vehicles and control systems. In
addition, technologies now exist that have inherently low evaporative
emission characteristics and demonstrate improved in-use durability.
Based on this body of data, we are adopting more stringent standards
designed to reduce emissions, primarily exhaust non-methane organic
gases (NMOG), NOX, and PM and evaporative hydrocarbon
emissions from new vehicles. As discussed in detail below and in the
final RIA, we have concluded that, in conjunction with the reductions
in fuel sulfur also required in this action, the new vehicle emissions
standards are feasible, accounting for costs, across the fleet in the
timeframe of the program. We believe that simultaneous reductions in
fuel sulfur will be a key factor in enabling the entire fleet of
vehicles subject to Tier 3 to meet the new emission standards in-use,
throughout the life of the vehicles (see Section IV.A.6 below).
    We received a large number and wide range of comments on the
proposed vehicle emission program, and we have carefully considered all
of them. (The Summary and Analysis of Comments document addresses the
comments received; it is located in the docket for this rulemaking and
also on EPA's Web site at www.epa.gov/otaq/tier3.htm.) With very few
exceptions, we are finalizing the Tier 3 vehicle emission program as
proposed, including the levels of the new emission standards and the
phase-in schedules. In several cases, as discussed in detail below, the
comments and/or newer technical information have resulted in
adjustments to the proposed program, including when the requirements
begin, what fuel is used for vehicle compliance testing, and what the
PM standard level is for testing under aggressive driving conditions.
The final Tier 3 vehicle provisions, like the proposal, also harmonize
closely with California's LEV III program.
    This section describes in detail the program for reducing tailpipe
and evaporative emissions from light-duty vehicles (LDVs, or passenger
cars), light-duty trucks (LDT1s, 2s, 3s, and 4s), Medium-Duty Passenger
Vehicles (MDPVs), and certain heavy-duty vehicles (HDVs). Sections IV.A
and IV.B discuss the tailpipe emission standards and time lines, and
other provisions for new LDVs, LDTs, and MDPVs and for new heavy-duty
vehicles up to 14,000 lbs Gross Vehicle Weight Rating (GVWR). Section
IV.C presents the new Tier 3 evaporative emissions standards and
program and Section IV.D describes the new evaporative emissions leak
test. Section IV.E presents improvements to the existing Onboard
Diagnostics (OBD) provisions. In Section IV.F, we describe new
provisions to update our federal certification fuel to better match
today's in-use fuel. We also discuss in this section the compliance
flexibilities for small auto manufacturing companies and small-volume
manufacturers (IV.G) as well as new testing and test procedure
provisions and other compliance provisions (IV.H).

A. Tier 3 Tailpipe Emission Standards for Light-Duty Vehicles, Light-
Duty Trucks, and Medium-Duty Passenger Vehicles

1. How the Tier 3 Program Is Harmonized With the California LEV III
Program
    In describing the Tier 3 program for light- and heavy-duty vehicles
in this preamble, we discuss how the provisions are consistent with the
California Air Resources Board (CARB) LEV III program.\249\ During the
development of the proposed rule and in their comments, auto
manufacturers stressed to us the importance of their being able to
design and produce a single fleet of vehicles for all 50 states that
simultaneously complies with requirements under the Tier 3 program and
the LEV III program, as well as greenhouse gas/CAFE requirements they
are facing in the same timeframe. To the extent that the federal and
California programs are consistent, special versions of vehicles with
different emission control hardware and calibrations for different
geographic areas will be unnecessary. This will allow manufacturers to
avoid the additional costs of parallel design, development,
calibration, and manufacturing. Consistency among programs also
eliminates the need to supply aftermarket parts for repair of multiple
versions of a vehicle. We believe that the most effective and efficient
national program will result from close coordination between CARB LEV
III and federal Tier 3 program elements and their implementation.
---------------------------------------------------------------------------

    \249\ See California Low-Emission Vehicles (LEV) & GHG 2012
regulations adopted by the State of California Air Resources Board,
March 22, 2012, Resolution 12-21 incorporating by reference
Resolution 12-11, which was adopted January 26, 2012. Available at
http://www.arb.ca.gov/regact/2012/leviiighg2012/leviiighg2012.htm
(last accessed December 2, 2013).

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    To that end, we worked closely with CARB and the vehicle
manufacturers, the latter both individually and through their trade
associations, to align the two programs. The Tier 3 program is
identical to LEV III in most major respects for light-duty vehicles
(and heavy-duty vehicles, as described in sections below). The levels
and the timing of the declining fleet-average NMOG+NOX
standards are identical to those in LEV III. The Tier 3 emissions bins
to which manufacturers will certify individual vehicle models in order
to comply with the fleet-average standards, are also identical to those
in LEV III. Similarly, the light-duty Tier 3 FTP PM standards and
percent phase-in match those for LEV III through MY 2024.
    We note there are a few light-duty Tier 3 and LEV III provisions
that are different, for reasons discussed below. For example, the LEV
III program and the Tier 3 program have different light-duty PM
requirements late in the program (i.e., after MY 2024 (IV.A.3.b.)), and
the two programs have different final NMOG+NOX standards for
small volume manufacturers (IV.G.1). As also discussed below, we are
finalizing a revised SFTP (US06) PM standard, and CARB has commented
that it plans to take similar action in near future. CARB also
indicated in their comments that they intend to consider several
additional actions to further align several minor aspects of LEV III
with the Tier 3 program once Tier 3 is finalized.
    Beyond the provisions mentioned above, the differences between the
programs are not major and most will exist only in the transitional
years of the Tier 3 program. These additional differences result from
the fact that the LEV III requirements begin slightly earlier and that
a limited phase-in of some provisions is necessary for a smooth
transition to overall aligned programs. These temporary differences
include the process for how early compliance credits are generated and
used (e.g., Section IV.A.7.a); how quickly manufacturers will need to
move toward certifying all of their vehicle models to longer useful-
life values (e.g., Section IV.A.7.c) and on the new test fuel (e.g.,
Section IV.A.7.d); and transitional emissions bins to facilitate the
transition from Tier 2 to Tier 3 (Section IV.A.7.n).
2. Summary of the Tier 3 FTP and SFTP Tailpipe Standards
a. Major Comments on and Significant Changes to the Proposal
    As mentioned above, we are finalizing most aspects of the
comprehensive Tier 3 vehicle program as we proposed them. The levels of
the FTP and SFTP standards for the key tailpipe pollutants of concern--
the sum of NMOG and NOX emissions, expressed as
NMOG+NOX, and PM--are the same as proposed (except for the
numerically lower final PM SFTP (US06) standard, as discussed below).
In addition, the timing of the requirements remains the same as in the
NPRM, starting with MY2017 and MY2018 and phasing in according to the
same declining fleet-average schedule for the NMOG+NOX
standards and the same percent-of-sales phase-in schedule for the PM
standards. We continue to believe that these elements form a robust
framework for the Tier 3 vehicle program and closely harmonize with the
respective elements of California's LEV III program.
    There are several important provisions of the light-duty Tier 3
program that we have revised from the proposal, based on further
consideration and information that we received from commenters. We
discuss each of these in detail later in this section and summarize
them here.
     As described below in Section IV.A.2.c, each of the four
primary Tier 3 emission standards has an associated alternative phase-
in option for heavier light-duty vehicles that a manufacturer can
choose if it prefers a later start date (to provide 4 years of lead
time) and a stable standard.\250\ We proposed that a manufacturer
choosing these options be required to apply the alternative phase-in
schedule to its entire light-duty fleet. In response to comments from
automakers that this restriction would be unnecessarily burdensome, we
reconsidered this provision. For the reasons discussed below, we are
allowing a manufacturer to apply the alternative phase-in schedules to
only their heavier light-duty vehicles, instead of their entire light-
duty fleet. However, manufacturers have largely indicated that they
plan on adopting the primary program which is harmonized with LEV III.
---------------------------------------------------------------------------

    \250\ In this preamble, ``heavier light-duty vehicles'' refers
to LDVs and LDTs greater than 6,000 lbs GVWR and MDPVs, and
``lighter light-duty vehicles'' refers to LDVs and LDTs up to 6,000
lbs GVWR.
---------------------------------------------------------------------------

     This Tier 3 rule provides an opportunity for EPA to
reassess the degree to which the gasoline used for vehicle emissions
testing and certification reflects in-use gasoline around the country.
In the case of ethanol content, we proposed that the emissions test
fuel contain 15 percent ethanol (E15), anticipating a significant shift
to higher ethanol content in use in the near future. For several
reasons described below (Section IV.F.1), this shift in in-use fuel is
not materializing as quickly as expected, and E10 continues to be
almost universal today. We received a near consensus among comments
from stakeholders that E10 test fuel is more appropriate. We agree that
E10 most appropriately reflects in-use gasoline around the country
today and into the foreseeable future, and thus we are finalizing E10
for the test fuel. In addition, as discussed in Section IV.F.1, we are
finalizing a fuel volatility specification for test fuel of 9 psi RVP,
as proposed.
     We are finalizing a set of standards for PM as measured on
the aggressive-driving segment of the SFTP test cycle (the US06 cycle)
based on US06 PM test data that we published as part of the NPRM, along
with more recent test data developed by California. Our review of these
data has led us to finalize numerically lower levels for the US06 PM
standards than we proposed. The data presented in the NPRM as well as
the data provided by California clearly show that the proposed US06 PM
standards were inappropriately high, that US06 PM emissions are not
closely related to vehicle weight, and that lower values for the
standards would achieve the goal of the program to bring all vehicles
in the light-duty fleet to the US06 PM levels that are being met by
many vehicles today. Based on the body of available data, we are
establishing 6 mg/mi as the long-term US06 PM standard. (This compares
to the proposed standards of 10 and 20 mg/mi for lighter and heavier
light-duty vehicles, respectively.) However, because there remains some
uncertainty about how manufacturers will achieve this level in the
early years of the program, we are setting the standard at 10 mg/mi for
the early years of the program, for MYs 2017 and 2018. Similarly, we
are providing a less-stringent standard of 10 mg/mi for testing of in-
use vehicles in recognition of the challenges of the requirements as
vehicles age.
     In the Tier 3 program, as for vehicle emission control
programs in the past, manufacturers are responsible for the emissions
performance of the vehicle for a specified ``useful life'' of the
vehicle. EPA proposed that vehicles meet the Tier 3 standards for
150,000 miles or 15 years, identical to the LEV III program's approach.
We proposed an option for lighter light-duty vehicles to certify to a
shorter useful life of 120,000 miles or 10 (or 11, as applicable)
years, as set in the Tier 2 program. We proposed that manufacturers
certifying to the shorter useful life would need to meet numerically
lower NMOG+NOX standards (85 percent of the respective

150,000-mile NMOG+NOX standards). We also proposed that a
manufacturer choosing the shorter useful life for one vehicle model
would need to use that useful life and associated standards for all of
its lighter vehicles. Auto industry commenters stated that applying the
provision across a manufacturer's fleet would create an onerous
compliance burden. We have reconsidered our proposed approach, and as
discussed in Section IV.A.7.c below, we will allow a manufacturer to
split its lighter light-duty fleet among models certified for either
the 150,000 mile or 120,000 mile useful life and associated standards.
     Another area of substantial comment, primarily from the
petroleum refining industry, questioned the technological need of auto
manufacturers for lower in-use sulfur levels in order to meet the Tier
3 vehicle emission standards. In contrast, auto manufacturers and
emissions control system manufacturers commented that lower sulfur
gasoline is critical to meet the Tier 3 standards. After careful
consideration of the comments, we continue to believe that the large
body of data presented in the NPRM, supplemented by newer data that
consistently reinforces the earlier conclusions, strongly supports our
determination of the need for average in-use gasoline sulfur levels to
be at 10 ppm sulfur or lower for manufacturers to meet the Tier 3
vehicle standards across their fleets for the useful life of the
vehicles. See Section IV.A.6 below for a detailed discussion of the
need for gasoline sulfur control.
b. Structure of the Primary Tier 3 Tailpipe Standards
    As proposed, compliance with the standards is based on vehicle
testing using test procedures that represent a range of vehicle
operation, including the Federal Test Procedure (FTP) and the
Supplemental Federal Test Procedure (SFTP). The Tier 3 FTP and SFTP
NMOG+NOX standards are fleet-average standards, meaning that
the manufacturer calculates the sales-weighted average emissions of the
vehicles it sells in each model year, accounting for any Tier 3
emissions credits or deficits, and compares that average to the
applicable standard for that model year. The fleet average standards
for NMOG+NOX evaluated over the FTP are the same values as
proposed and are summarized in Table IV-2 and discussed in detail
below. For lighter light-duty vehicles, the standards begin in MY 2017
at a level representing a 46 percent reduction from the current Tier 2
requirements for lighter vehicles and then become increasingly
stringent, culminating in an 81 percent reduction in MY 2025. The FTP
NMOG+NOX program includes separate fleet average standards
for heavier vehicles that begin in MY 2018 and then converge with the
standards for lighter vehicles at 30 milligrams per mile (mg/mi) in MY
2025 and later, as proposed.251 252
---------------------------------------------------------------------------

    \251\ The declining NMOG+NOX fleet-average standards
consist of one set of declining standards that applies to light-duty
vehicles (LDVs) and small light trucks (LDT1s) and a second set of
declining standards that applies to heavier light trucks (LDT2s,
LDT3s. LDT4s), and MDPVs.
    \252\ This preamble presents the new Tier 3 standards in terms
of milligrams per mile (mg/mi) for convenience. Throughout the
associated Tier 3 regulatory language we continue to present the
standards in terms of grams per mile (g/mi) for consistency with
earlier programs.
---------------------------------------------------------------------------

    Manufacturers will determine their fleet average FTP
NMOG+NOX emission values as we proposed, based on the per-
vehicle ``bin standards'' to which they certify each vehicle model.
Manufacturers will be free to certify vehicles to any of the bins, so
long as the sales-weighted average of the NMOG+NOX values
from the selected bins meets the fleet average standard for that model
year. Table IV-1 presents the per-vehicle bin standards. Similarly, the
fleet average NMOG+NOX standards measured over the SFTP are
summarized in Table IV-4 and discussed in detail below. The SFTP
NMOG+NOX fleet average standards decline from MY 2017 until
MY 2025. In this case, the same standards apply to both lighter and
heavier vehicles. In MY 2025, the SFTP NMOG+NOX standard
reaches its fully phased-in fleet average level of 50 mg/mi.
    Also as proposed, the new Tier 3 PM standards apply to each vehicle
separately. The PM standards are per-vehicle cap standards and not
fleet-average standards. Also, in contrast to the declining
NMOG+NOX standards, the PM standard on the FTP is a constant
3 mg/mi for all vehicles and for all model years, phasing in to an
increasing percentage of vehicle sales beginning in MY 2017 for
vehicles at or below 6,000 lbs Gross Vehicle Weight Rating (GVWR) and
in MY 2018 for vehicles above 6,000 lbs GVWR. As discussed in Section
IV.A.3.b above, based on data generated by EPA and CARB test programs,
most current light-duty vehicles are already performing at or below the
3 mg/mi level. However, some vehicles are emitting above this level,
due to such factors as excessive fueling during cold start and
combustion chamber and fuel system designs that are not optimized for
low PM emissions. The intent of the 3 mg/mi standard is to bring all
light-duty vehicles to the PM level typical of that being demonstrated
by most light-duty vehicles today. To address the uncertainties that
will accompany the introduction of new technologies, the program
includes a separate in-use FTP PM standard of 6 mg/mi for the testing
of in-use vehicles during the phase-in period, as proposed, as
described in more detail below.
    As presented in Table IV-3, for vehicles at or below 6000 lbs GVWR,
these FTP PM certification and in-use standards phase in over several
years, beginning with a requirement that at least 20 percent of a
company's U.S. sales of these vehicles comply with the Tier 3 standards
in MY 2017. We are also finalizing an option for a manufacturer to
choose to certify 10 percent of its total light-duty fleet sales--
including LDVs and LDT over 6,000 lbs GVWR and MDPVs--to the Tier 3 FTP
PM standards in MY 2017. Manufacturers would reach a 100 percent
compliance requirement in MY 2021.
    Finally, the Tier 3 program includes PM standards evaluated over
the US06 cycle (a component of the SFTP test that captures higher
speeds and accelerations). Based on emissions test data presented in
the NPRM and additional data submitted in public comments, and as
presented in Table IV-5 and further discussed in Section IV.A.4.b
below, we are establishing a single long-term US06 PM standard of 6 mg/
mi for both lighter and heavier vehicles, a level that is numerically
lower than what we proposed. However, because there remains some
uncertainty about how manufacturers will decide to achieve this level
in the early years of the program, we are setting the standard through
MY 2018 at 10 mg/mi. The US06 PM standards phase in using the same 20-
20-40-70-100 percent schedule, and on the same vehicles, as the new FTP
PM standards. The 10 mg/mi standard applies in MYs 2017 and 2018 (at a
percent-of-sales requirement of 20 percent, and the long-term 6 mg/mi
standard applies in MYs 2019 and later, increasing from 40 to 100
percent of sales. This US06 standard will apply to the same vehicle
models that a manufacturer chooses to certify to the FTP PM standard
during the percent phase-in period. As in the case of the FTP PM
standards, the intent of the standard is to bring the emission
performance of all vehicles to that already being demonstrated by many
vehicles in the current light-duty fleet. As proposed, we include a
separate in-use US06 PM standard during in the middle years of the
program, but at a different numerical level and during

different years than proposed (as discussed in Section IV.A.4.b below).
    We did not propose new emission requirements for any vehicle or
fuel over the cold temperature test cycles (i.e., the 20 [deg]F cold
carbon monoxide (CO) and non-methane hydrocarbon (NMHC) tests), but
requested comment on that decision. Only the automakers commented on
this topic, agreeing with EPA's approach of not changing its cold
temperature requirements. As indicated in the proposal, we are not
establishing any new cold temperature requirements in this rule.
c. Alternate Phase-In Schedules
    For heavier light-duty vehicles (i.e., LDVs and LDTs greater than
6,000 lbs GVWR, plus MDPVs), EPA is also finalizing alternative phase-
in schedules for each of the four primary vehicle emission standards:
FTP NMOG+NOX, FTP PM, SFTP NMOG+NOX, and US06
PM.\253\ These alternative phase-ins are available if a manufacturer
prefers stable standards and four full years of lead time, as specified
in the Clean Air Act for heavier vehicles. We describe each of the
alternative phase-ins in more detail below, including several ways in
which we have revised the proposed provisions.
---------------------------------------------------------------------------

    \253\ Tier 3 standards for CO and HCHO phase in with the
NMOG+NOX standards, as applicable.
---------------------------------------------------------------------------

    EPA received comment on the proposed alternative phase-in
provisions, primarily from automakers and their trade associations.
These comments questioned whether the proposed structure of and
restrictions on the use of the alternative phase-ins were so onerous as
to unduly restrict a manufacturer from choosing the alternative phase-
ins and their lead time and stability provisions as set forth in the
Clean Air Act. The commenters criticized the proposed requirement that
a manufacturer using the alternative phase-ins apply the alternative
schedules to its entire light-duty fleet, both below and above 6,000
lbs GVWR. EPA had proposed this provision to minimize the complexity of
complying with the alternative phase-in if a manufacturer's heavier and
lighter light-duty vehicles had different compliance structures.
    In consideration of these concerns, we have removed from the
alternative phase-in provisions the requirement that a manufacturer
apply the alternative schedules to its entire light-duty fleet
including vehicles below 6,000 lbs GVWR. For the practical functioning
of the program, the final rule requires that any manufacturer choosing
to use the alternative phase-in apply all four alternative phase-in
schedules to its entire light-duty fleet above 6,000 lbs GVWR. We
believe that the alternative phase-ins allow manufacturers to comply
with emission standards in a time frame that is clearly feasible and
fully compliant with the CAA requirements for lead time and regulatory
stability. To the extent that manufacturers choose to use them, the
alternative would result in overall emission reductions essentially
identical to those of the primary program.
    The alternative phase-in schedules would begin to apply to each
vehicle for either MY 2019 or MY 2020, depending on exactly when the
manufacturer begins production of the vehicle. (See Section 86.1811-
17(b)(8)(i) for how we implement this provision.) For models that begin
MY 2019 production after the fourth anniversary of the signing of this
final rule, the alternative phase-in would provide four full years of
lead time and would first apply for MY 2019. The phase-in obligation
would be calculated based only on those vehicles beginning production
after the fourth anniversary date. For models beginning production
before that date, the alternative phase-in would first apply for MY
2020, and the phase-in percentage for MY 2020 would be based on the
manufacturer's entire fleet of heavier light-duty vehicles. Based on
historical certification patterns, few models begin production before
mid-calendar-year, so we expect that the vast majority of MY 2019
vehicles will begin production after the 4-year anniversary and thus
the alternative phase-ins, if chosen, will typically apply beginning in
MY 2019.
    At the time of certification for MY 2018, a manufacturer must
declare whether it intends to apply the alternative phase-in schedules
to its heavier light-duty vehicles. A manufacturer choosing the
alternative phase-ins would be committed to this phase-in approach for
the duration of the phase-ins, and could not later choose the fleet-
average approach for NMOG+NOX standards. For all vehicles
below 6,000 lbs GVWR, the primary program will apply, beginning in MY
2017. For a manufacture's vehicles subject to the alternative phase-
ins, there would be no new tailpipe emissions requirements beyond the
Tier 2 program until the beginning of the alternative phase-in
schedules; that is, MY 2019 or 2020, as explained above.
    As discussed above, a manufacturer choosing the alternative phase-
in approach for its heavier light-duty vehicles would be required to
use all four phase-ins together. The next paragraphs explain how each
of the alternative phase-ins requires an increasing percent of the
manufacturer's sales to comply with the alternative standards. Thus,
until the end of the phase-ins, some percent of a manufacturer's
affected vehicles will meet the new standard and the remainder of that
year's sales will not yet comply with Tier 3. For the practical
functioning of the program, a manufacturer choosing the alternative
phase-ins would be required to comply with exactly the same segment of
their fleet in each model year for all four alternative phase-ins. For
example, a manufacturer that complies with the 70 percent MY 2020
requirement for the FTP NMOG+NOX standard with a segment of
its vehicle fleet must meet the 70 percent MY 2020 requirement for the
FTP PM standard with the same set of vehicles. Vehicles covered by the
alternative phase-in programs would be considered ``Final Tier 3''
vehicles and thus would also need to comply with the Tier 3
certification fuel and full useful life provisions.
    For the FTP and SFTP NMOG+NOX alternative phase-in
schedules, once the phase-in is complete for a segment of a
manufacturer's fleet, the standards continue for that set of vehicles
through MY 2024, after which the full Tier 3 program applies regardless
of the phase-in strategy. Thus, the fleet-average standards that
decline through MY 2024 do not apply for these vehicles.
    Although manufacturers would implement all four alternative phase-
in schedules together, as discussed above, each alternative phase-in
has unique characteristics. The following paragraphs explain the unique
provisions of each.
(1) Alternative Phase-In Schedule for the FTP NMOG+NOX
Standard
    Instead of the primary FTP NMOG+NOX declining fleet
average standards, a manufacturer choosing the alternative phase-ins
would comply with a stable fleet average FTP NMOG+NOX
standard of 30 mg/mi that would apply to an increasing percentage of a
manufacturer's combined sales of LDVs and LDTs above 6,000 lbs GVWR and
MDPVs. This percent phase-in would match the percentages in the primary
PM percent phase-in schedule, as discussed above--specifically, 40
percent of MY 2019 heavier light-duty vehicles (excluding those
vehicles with production beginning before the 4-year anniversary), 70
percent of all of its heavier light-duty vehicles in MY 2020, and 100
percent compliance in MY 2021 and later model years.

(2) Alternative Phase-In Schedule for the FTP PM Standard
    Instead of the primary FTP PM percent phase-in schedule, a
manufacturer choosing the alternative phase-ins would postpone the
beginning of its FTP PM phase-in for its LDVs and LDTs above 6,000 lbs
GVWR and MDPVs until MY 2019 or 2020 (depending on the dates production
begins for its vehicle models, as discussed above). The manufacturer
would then comply with the 3 mg/mi per-vehicle FTP PM standard (and the
6 mg/mi in-use standard) on an increasing percentage of these vehicles,
following the 40-70-100 percentage phase-in of the primary PM program--
specifically, 40 percent of MY 2019 heavier light-duty vehicles
(excluding those vehicles with production beginning before the 4-year
anniversary), 70 percent of all of its heavier light-duty vehicles in
MY 2020, and 100 percent compliance in MY 2021 and later model years.
(3) Alternative Phase-In Schedule for the SFTP NMOG+NOX
Standard
    As with the other alternative phase-ins, instead of the primary
SFTP NMOG+NOX declining fleet average standards, a
manufacturer choosing the alternative phase-ins would comply with a
stable fleet average SFTP NMOG+NOX standard of 50 mg/mi that
would apply to an increasing percentage of a manufacturer's combined
sales of LDVs and LDTs above 6000 lbs GVWR and MDPVs. This percent
phase-in again would match the percentages in the primary PM percent
phase-in schedule, as discussed above--specifically, 40 percent of MY
2019 heavier light-duty vehicles (excluding those vehicles with
production beginning before the 4-year anniversary), 70 percent of all
of its heavier light-duty vehicles in MY 2020, and 100 percent
compliance in MY 2021 and later model years.
(4) Alternative Phase-In Schedule for the US06 PM Standard
    Finally, instead of the primary US06 PM percent phase-in schedule,
a manufacturer choosing the alternative phase-ins would postpone the
beginning of the US06 phase-in for its LDVs and LDTs above 6,000 lbs
GVWR and MDPVs until MY 2019 or 2020 (depending on the dates production
begins for its vehicle models, as discussed above). The manufacturer
would then comply with the 10 mg/mi US06 PM standard for 40 percent of
MY 2019 heavier light-duty vehicles (excluding those vehicles with
production beginning before the 4-year anniversary), 70 percent of all
of its heavier light-duty vehicles in MY 2020, with 100 percent
compliance in MY 2021, and then 100 percent compliance with the 6 mg/mi
standard in MY 2022 and later model years.
    The next sections describe in more detail the new Tier 3 standards,
how they will be implemented over time, and the technological
approaches that we believe are or will be available to manufacturers in
order to comply.
3. FTP Standards
    As summarized above, we are finalizing, largely as proposed, new
standards for the primary pollutants of concern for this rule (NMOG,
NOX, and PM) as measured on the FTP. The following
paragraphs describe in more detail these FTP standards for
NMOG+NOX and PM, as well as for carbon monoxide (CO) and
formaldehyde (HCHO).
a. FTP NMOG+NOX Standards
    The Tier 3 NMOG and NOX standards are expressed in terms
of the sum of the two pollutants--NMOG+NOX in mg/mi.\254\ We
received no comments recommending a different approach. The California
LEV III standards are also expressed as NMOG+NOX; aligning
Tier 3 with LEV III is an important element of facilitating a national
program.
---------------------------------------------------------------------------

    \254\ See California Low-Emission Vehicles (LEV) & GHG 2012
regulations adopted by the State of California Air Resources Board,
March 22, 2012, Resolution 12-21 incorporating by reference
Resolution 12-11, which was adopted January 26, 2012. Available at
http://www.arb.ca.gov/regact/2012/leviiighg2012/leviiighg2012.htm
(last accessed December 2, 2013).
---------------------------------------------------------------------------

    EPA received a number of comments about how the proposed
NMOG+NOX standards transition from the existing Tier 2
standards, but there was little comment recommending different levels
of the standards themselves, especially later in the program. Based on
our extensive evaluation of existing and emerging vehicle technologies
(see Section IV.A.5) and the level of sulfur in gasoline that will be
available during the implementation timeframe of this rule, and
considering the comments we received, we continue to believe that the
fully phased-in level for the fleet-average FTP NMOG+NOX
standard of 30 mg/mi is the most stringent level that we can reasonably
establish. As discussed in Sections IV.A.5 and IV.A.6 below, when
necessary margins of compliance and the demonstrated effects of fuel
sulfur on emissions performance are considered, the 30 mg/mi standard
is effectively very close to zero. The 30 mg/mi Tier 3
NMOG+NOX standard is also consistent with the final LEV III
standard.
    A key compliance mechanism adapted from the Tier 2 program is a
``bin'' structure for the FTP emission standards. For these purposes, a
bin is a set of several standards that must be complied with as a
group. Thus, as proposed, each FTP Tier 3 bin has an
NMOG+NOX standard and a PM standard, as well as CO and HCHO
standards.
    We intend for the Tier 3 CO and HCHO standards to prevent new
engine and emission control designs that result in increases in CO and
HCHO emissions, compared to levels being achieved today. The standards
are based on the comparable current LEV II and Tier 2 bin standards for
these pollutants, which we believe are sufficiently protective at this
time. There were no comments on the proposed CO and HCHO standards. The
current standards are not technology-forcing, and we believe that this
will continue to be the case as Tier 3 technologies are developed.
    Table IV-1 presents the bin structure for light-duty vehicle,
light-duty truck, and MDPV FTP standards.

                            Table IV-1--Tier 3 FTP Standards for LDVs, LDTs and MDPVs
                                                     [mg/mi]
----------------------------------------------------------------------------------------------------------------
                                                                      NMOG+NOX   PM\a\ (mg/            HCHO (mg/
                                Bin                                   (mg/mi)       mi)     CO (g/mi)     mi)
----------------------------------------------------------------------------------------------------------------
Bin 160...........................................................          160          3        4.2          4
Bin 125...........................................................          125          3        2.1          4
Bin 70............................................................           70          3        1.7          4
Bin 50............................................................           50          3        1.7          4

Bin 30............................................................           30          3        1.0          4
Bin 20............................................................           20          3        1.0          4
Bin 0.............................................................            0          0          0          0
----------------------------------------------------------------------------------------------------------------
\a\ In MYs 2017-20, the PM standard applies only to that segment of a manufacturer's vehicles covered by the
  percent of sales phase-in for that model year.

    Consistent with the Tier 2 principle of vehicle and fuel
neutrality, the same Tier 3 standards apply to all LDVs, LDTs, or
MDPVs, regardless of the fuel they use, as proposed. That is, vehicles
certified to operate on any fuel (e.g., gasoline, diesel fuel, E85,
CNG, LNG, hydrogen, and methanol) are all subject to the same
standards.
    The Tier 3 NMOG+NOX standards as measured on the FTP
will reduce the combined fleet-average emissions gradually from MY 2017
through 2025, as shown in Table IV-2 below. Beginning in MY 2017, there
are two separate sets of fleet-average standards for, first, LDVs and
LDT1s and, second, all other LDTs (LDT2s, LDT3s, and LDT4s) and MDPVs.
Both fleet-average standards decline annually, converging in MY 2025.
These declining average standards are identical to CARB's LEV III
standards.\255\
---------------------------------------------------------------------------

    \255\ See California Low-Emission Vehicles (LEV) & GHG 2012
regulations adopted by the State of California Air Resources Board,
March 22, 2012, Resolution 12-21 incorporating by reference
Resolution 12-11, which was adopted January 26, 2012. Available at
http://www.arb.ca.gov/regact/2012/leviiighg2012/leviiighg2012.htm
(last accessed January 14, 2014).
---------------------------------------------------------------------------

    As proposed and as discussed above (Section IV.A.2.a), the
declining fleet-average NMOG+NOX FTP standards begin in MY
2017 for light-duty vehicles and light-duty trucks with a GVWR up to
and including 6,000 lbs and in MY 2018 for light-duty vehicles and
light-duty trucks with a GVWR greater than 6,000 lbs and MDPVs. The
standards apply to the heavier vehicles a year later to facilitate the
transition to a 50-state program for all manufacturers. During this
transition period, as described above, there will be two fleet-average
NMOG+NOX standards for each model year, one for LDVs and
LDT1s and one for all other LDTs (LDT2s, LDT3s, and LDT4s) and for
MDPVs that decline essentially linearly from MY 2017 through MY 2025.
At that point, the two fleet-average standards converge and stabilize
for all later model years at the same level, 30 mg/mi, as shown in
Table IV-2.

                   Table IV-2--Tier 3 LDV, LDT, and MDPV Fleet Average FTP NMOG+NOX Standards
                                                     [mg/mi]
----------------------------------------------------------------------------------------------------------------
                                                                        Model year
                                         -----------------------------------------------------------------------
                                                                                2025
                                           2017    2018    2019    2020    2021    2022    2023    2024     and
                                            \a\                                                            later
----------------------------------------------------------------------------------------------------------------
LDV/LDT1 \b\............................      86      79      72      65      58      51      44      37      30
LDT2,3,4 and MDPV.......................     101      92      83      74      65      56      47      38  ......
----------------------------------------------------------------------------------------------------------------
\a\ For LDVs and LDTs over 6,000 lbs GVWR and MDPVs, the fleet average standards apply beginning in MY 2018.
\b\ These standards apply for a 150,000 mile useful life. Manufacturers can choose to certify their LDVs and
  LDV1s to a useful life of 120,000 miles. If a vehicle model is certified to the shorter useful life, a
  proportionally lower numerical fleet average standard applies, calculated by multiplying the respective
  150,000 mile standard by 0.85 and rounding to the nearest mg/mi. See Section IV.A.7.c.

    As discussed above (Section IV.A.2.c), for LDVs and LDTs above
6,000 lbs GVWR and MDPVs, EPA is also providing an alternative phase-in
of the fleet-average 30 mg/mi FTP NMOG+NOX standard.
b. FTP PM Standards
    We are establishing new FTP standards for PM emissions at the
proposed levels--3 mg/mi, with a temporary standard of 6 mg/mi for in-
use vehicle testing--as summarized in Table IV-3 below. These levels
are intended to ensure that all new vehicles will perform at a level
representing what is already being achieved by well-designed emission
control technologies today.
    Many commenters were either silent on or supportive of the proposed
FTP PM standard levels. However, some commenters--including CARB and
several NGOs and auto industry suppliers--supported a more stringent
standard of 1 mg/mi, which the California LEV III program phases in
beginning in MY 2025. After detailed consideration of these comments
and information available at this time, we continue to believe that the
PM standards that we are finalizing for the federal Tier 3 program are
the most stringent technically feasible standards within the
implementation timeframe of this rule. (See Section 1.5.1 of the RIA.)
We will continue to work closely with CARB in this area. Specifically,
our agencies will continue our parallel evaluations of how improved
gravimetric PM measurement methods can reduce PM mass measurement
variability at very low PM levels and how this relates to the evolving
technological capabilities of automakers to reach very low PM levels
with sufficient compliance margins.
    PM emissions over the FTP are generally attributed to the cold
start, when PM formation from combustion of the fuel is facilitated by
the operating conditions, including a cold combustion chamber and fuel
enrichment. During cold-start operation, PM control is less effective,
especially the oxidation by the catalytic converter of semi-volatile
organic compounds from the lubricating oil. We believe that for
vehicles that are not already at the Tier 3 levels, the new

standards can be achieved with improvements to the fuel controls during
the cold start, without the need for any new technology or hardware. We
also expect that manufacturers will pay close attention to maintaining
low PM emissions during the implementation of newer technologies like
gasoline direct injection (GDI) and turbocharged engines. Improvements
in cold-start exhaust catalyst performance for NMOG+NOX
control will also reduce emissions of semi-volatile organic PM. For
these reasons, cold start PM levels are relatively independent of
vehicle application and therefore we are finalizing a single FTP PM
standard for all light-duty vehicles, as proposed.
    Unlike the NMOG+NOX FTP standard, it is not necessary
for the FTP PM standard to phase in on a declining curve over time,
since most manufacturers are already producing vehicles that meet the
new standards. We are finalizing the proposed PM FTP percent-of-sales
phase-in during the first 5 years of the Tier 3 program in response to
concerns expressed by automakers about logistical, facilities, and
compliance challenges with a standard in the range of 3 mg/mi in the
early years of the program. Beginning in MY 2017 (and in MY 2018 for
LDVs and LDTs over 6,000 lbs GVWR and MDPVs), manufacturers will need
to comply with the PM standard with a minimum of 20 percent of their
U.S. sales. As shown in Table IV-3, the percentage of the
manufacturer's sales that need to comply increases each year, reaching
100 percent in MY 2021. In addition to this percent phase-in, we are
also establishing, as proposed, a separate PM standard of 6 mg/mi that
will apply only for in-use testing of vehicles certified to the new
standards, and only during the percent phase-in period.
    Due to the MY 2018 start date for vehicles over 6,000 lbs GVWR,
manufacturers that have few or no vehicle models over 6,000 lbs GVWR
will be required to certify a larger percentage of their total light-
duty sales in MY 2017 than full line manufacturers. While we believe
that most manufacturers will likely choose a single large-volume
durability group to meet the 2017 requirements, we are also including
an option that a manufacturer could use to comply with the MY 2017 PM
requirements. Under this option, a manufacturer may choose to certify
10 percent of its total light-duty vehicle sales in MY 2017 to the new
PM standards, including light-duty vehicles over 6,000 lbs. This
approach is consistent with the CARB LEV III program, which requires
that 10 percent of all light-duty vehicle sales meet the new PM
standards in MY 2017.
    Because of the expected time and expense of performing emission
tests on the improved PM test procedures, we are limiting the number of
tests using the new procedures that a manufacturer needs to perform at
certification and during in-use testing, as proposed. Specifically,
manufacturers will only be required to test vehicles representing a
minimum of 25 percent of a model's durability test groups during
certification each model year (and a minimum of 2 durability
groups).\256\ Manufacturers may select which durability groups to test,
but will need to rotate the groups tested each year to eventually cover
their whole fleet. Similarly, manufacturers performing in-use testing
under the In-Use Verification Program can limit their testing to 50
percent of their low- and high-mileage test vehicles. Again,
manufacturers will need to rotate their vehicle models so that each
model will be tested every other year. Overall, we believe that the
flexibility that these provisions provide will facilitate the
expeditious implementation of the Tier 3 program, with no significant
impact on the benefits of the program.
---------------------------------------------------------------------------

    \256\ Durability groups are a subset of engine families. Several
engine families may have the same durability group.

                         Table IV-3--Summary of Tier 3 LDV, LDT, and MDPV FTP Standards
----------------------------------------------------------------------------------------------------------------
                                                                   Model year
                                            --------------------------------------------------------
        Program element            Units      2017                                                      Notes
                                               \a\    2018    2019    2020    2021    2022    2023+
----------------------------------------------------------------------------------------------------------------
NMOG+NOX Standard (fleet        mg/mi......           Per declining fleet averages (see Table IV-2) \b\
 average).
----------------------------------------------------------------------------------------------------------------
PM Standards
----------------------------------------------------------------------------------------------------------------
Phase-in......................  %..........   20\c\      20      40      70     100     100     100  ...........
----------------------------------------------------------------------------------------------------------------
FTP:
    Certification.............  mg/mi......       3       3       3       3       3       3       3  Note d.
    In-use....................  mg/mi......       6       6       6       6       6       3       3  Note e.
----------------------------------------------------------------------------------------------------------------
\a\ For LDVs and LDTs above 6,000 lbs GVWR and MDPVs, the FTP PM standards apply beginning in MY 2018.
\b\ The percent phase-in does not apply to the declining fleet average standards.
\c\ Manufacturers comply in MY 2017 with 20 percent of their LDV and LDT fleet under 6,000 lbs GVWR, or
  alternatively with 10 percent of their total LDV, LDT, and MDPV fleet.
\d\ Manufacturers must test 25 percent of each model year's durability groups, and a minimum of 2.
\e\ Manufacturers must test 50 percent of their combined low- and high- mileage in-use vehicles.

    As discussed in Section IV.A.2.c above, for LDVs and LDTs above
6,000 lbs GVWR and MDPVs, EPA is providing an alternative phase-in of
the 3 mg/mi FTP PM standard.
4. SFTP Standards
    In addition to addressing vehicle emissions during typical driving,
as addressed by the FTP standards presented above, the Tier 3 program
also addresses emissions during more severe driving conditions. Thus,
we are finalizing NMOG+NOX and PM standards as measured on
the SFTP. The SFTP (and specifically the US06 component of the test) is
designed to simulate, among other conditions, higher speeds and higher
acceleration rates, and thus higher loads. As described below, most
commenters were supportive of or silent on the proposed SFTP
NMOG+NOX standards and the associated declining fleet-
average phase-in schedule, but several commenters stated that the level
of the standards should be more stringent than proposed. Based on our
analysis of the stringency

of the program, discussed in Section IV.A.5 below and in Chapter 1 of
the RIA, we disagree that more stringent SFTP NMOG+NOX
standards are necessary or appropriate at this time, and we are
finalizing the standards and phase-in schedule as proposed. However, we
are finalizing more stringent SFTP standards for PM, which focus on the
US06 test component, based on newer data and public comments. These are
also described below.
    The Tier 3 SFTP standards are necessary to address emissions during
high-load conditions, when engines can go into a fuel ``enrichment''
mode and the engine's controls may temporarily create a rich air/fuel
mixture to protect exhaust components from thermal damage. Enrichment
can increase emissions of NMOG+NOX and PM, primarily due to
the incomplete combustion that occurs under rich conditions and the
diminished effectiveness of the catalyst in these circumstances.
However, enrichment can be minimized or eliminated in current and
future engines, where components can be thermally protected even under
high-load conditions by careful electronic management of the air/fuel
mixture and the combustion process. We are finalizing these SFTP
standards, as well as limitations on the amount of enrichment that
drivers can command (see Section IV.A.4.c below) to address this
important source of vehicle emission.
    We are also finalizing an SFTP composite CO standard of 4.2 g/mi
for all model years 2017 (or 2018 for LDVs and LDTs over 6000 lbs GVWR
and MDPVs) and later. This standard represents no effective change from
the current Tier 2 SFTP CO standard, which we believe is already at a
level that is sufficiently stringent.
a. SFTP NMOG+NOX Standards
    We are finalizing the Tier 3 SFTP NMOG+NOX standards and
declining fleet-average phase-in schedule as proposed and as presented
in Table IV-5 below. Most commenters were generally supportive of these
standards or silent about them. However, several commenters stated that
the proposed standards are too lenient, based on their evaluation of
vehicle emission test data we presented in the NPRM. We have considered
these comments and have reviewed the data from the NPRM. Our conclusion
from that data continues to be that the SFTP NMOG+NOX
emission levels that we are finalizing ensure that manufacturers
essentially eliminate fuel enrichment events and their emissions
consequences, thereby resulting in important emissions reductions. See
Chapter 1 of the RIA for an analysis of this data. We do not believe
that significant additional reductions would result from SFTP weighted
NMOG+NOX standards more stringent than the 50 mg/mi fully
phased-in level. In addition, we believe that the 50 mg/mi standard
will ensure that the SFTP performance of future vehicles with future
technologies continues to be comparable to that of the current fleet.
The SFTP emissions value for certification of gaseous pollutants will
continue to be calculated as a weighted composite value of emissions on
three cycles (0.35 x FTP + 0.28 x US06 + 0.37 x SC03), as is done for
the Tier 2 SFTP standards.
    To provide flexibility in meeting the fleet-average standards,
manufacturers will, as proposed, determine the specific SFTP composite
standard for each individual vehicle family and report that self-
selected standard and the measured emission performance. (These self-
selected standards are analogous to ``family emission limits,'' or
``FELs,'' used in other programs (e.g., heavy-duty highway engine
standards).) For each family, a manufacturer will choose any composite
NMOG+NOX standard, up to 180 mg/mi, in even 10 mg/mi
increments. The manufacturer will then calculate the sales-weighted
average of all the selected standards of the families across its fleet
and compare that emissions value to the applicable fleet-average
standards for that model year. Table IV-4 presents the declining fleet-
average SFTP NMOG+NOX standards.
    As discussed in Section IV.A.2.c above, for LDVs and LDTs above
6,000 lbs GVWR and MDPVs, EPA is providing an alternative phase-in of
the 50 mg/mi SFTP NMOG+NOX standard.
b. US06 PM Standards
    We are finalizing a single short-term US06 PM standard of 10 mg/mi
for MYs 2017 and 2018 (or only for MY 2018 for LDVs and LDTs over 6,000
lbs GVWR and MDPVs) and a single long-term standard of 6 mg/mi for MY
2019 and later. These standards are numerically lower than those we
proposed, and less complex in their structure. As discussed below and
in Chapter 1 of the RIA, a substantial body of more recent PM data from
a variety of vehicles tested on the US06 cycle has given us greater
understanding of the feasible level of control of these emissions, both
currently and in the timeframe of the Tier 3 standards, including what
level of control we may reasonably require for the light-duty fleet.
The standards we are finalizing reflect this review. Much of the more
recent data was developed late in the development of the NPRM and,
although we made it available in the rulemaking docket to inform
potential commenters, the proposed standards did not reflect
consideration of the newer data. Since the NPRM, additional data from
CARB have become available, and we have considered all of this
information in finalizing the US06 PM standards.
    We believe that the fully phased-in US06 PM standard of 6 mg/mi
will achieve the goal that we presented in the NPRM--to maintain the
performance being achieved by current well-performing vehicles taking
into account reasonable compliance margins. Comments from stakeholders
representing states, including CARB, and several NGOs urged EPA to
finalize more stringent standards than those proposed, in some cases
advocating for standards below 6 mg/mi. Conversely, auto industry
commenters generally supported the proposed standards. We have
concluded that the body of recent data clearly shows that the long-term
6 mg/mi standard, is the appropriate level to prevent any significant
``backsliding'' in US06 PM emissions as new vehicles and technologies
enter the fleet. At the same time, the 6 mg/mi standard provides a
reasonable compliance margin--about 50% above the average levels of
current vehicles, which are averaging about 4 mg/mi. A long-term
standard numerically lower than 6 mg/mi would run counter to our intent
to bring the emissions performance of all vehicles to that already
being demonstrated by many vehicles in the current light-duty fleet. We
believe the long-term US06 PM standard we are finalizing is appropriate
based on all of the information available at this time and will not
hinder introduction of new technologies manufacturers may choose for
compliance with the other Tier 3 standards or other rules.

    The short-term, less-stringent US06 standard of 10 mg/mi
(applicable in MYs 2017 and 2018) responds to automaker concerns about
uncertainties stemming from simultaneous regulatory requirements and
rapidly evolving exhaust and engine technologies in the coming years.
We recognize that vehicle control technologies for both criteria and
GHG emissions are evolving and will continue to do so, including an
expected expansion of gasoline direct injection (GDI) technologies (see
IV.A.5.c and the RIA). Also, the transition to lower sulfur in-use
gasoline required by this rule may create temporary additional
challenges in consistently achieving lower US06 PM emissions (see
IV.A.6 and the RIA). We believe that most manufacturers will implement
similar if not identical emission control strategies to comply (or,
more often, to continue to comply with) with both the 10 mg/mi and the
6 mg/mi standards. In so doing, we expect them to use the temporary
additional compliance margin provided by the 10 mg/mi standard to
reduce uncertainties about potential variability in performance (in use
and, in particular, later in vehicle life) during the early years of
developing and commercializing their control technologies.\257\
---------------------------------------------------------------------------

    \257\ We note that the purpose of the percent phase-in schedule
for the FTP and US06 PM standards is to facilitate the expansion of
manufacturers' PM testing facilities, which have been relatively
limited in their availability prior to these new emission standards.
While effectively providing more time for technology development as
well as for expansion of facilities, we believe that the PM
standards are designed to be fully feasible in the early years of
the program and do not themselves require the phase-in relief,
especially given the short-term 10 mg/mi standard and the temporary
relaxed in-use testing standards.
---------------------------------------------------------------------------

    The 10 mg/mi standard will expire after MY 2018, and the long-term
standard of 6 mg/mi will take effect. As the implementation of the
program continues, we believe a limited degree of relief for testing of
in-use vehicles is appropriate. Manufacturers commented that because of
the industry's general lack of experience with stringent PM standards,
especially as the newly-designed vehicles age, less stringent standards
for in-use testing would reduce near-term concerns about performance
variability early in the program. We agree, and we are finalizing a
separate standard of 10 mg/mi for in-use vehicle testing for the
intermediate years of the program, MYs 2019 through MY 2023. This
standard is numerically lower than the proposed in-use standards--again
because of the availability of improved US06 test data as described
above--but the purpose of providing an in-use standard remains the
same. The in-use standard, in conjunction with the short-term 10 mg/mi
standard represents a longer duration for the in-use standard than we
had proposed, again based on comments from the industry about their
compliance concerns with new US06 standards. For MY 2024 and later,
there will be no separate in-use standard and all vehicles will need to
meet the long-term standard at certification and in use.
    EPA proposed that different US06 PM standards apply to lighter and
heavier vehicles. The newer US06 PM test data discussed above also make
clear that the US06 PM performance of current vehicles is not closely
related to vehicle weight, although the earlier data had indicated that
this might be the case. Several commenters urged EPA to finalize a
single standard for vehicles above and below 6,000 lbs GVWR based on
the newer data. At the same time, auto manufacturers generally
supported the proposed vehicle weight distinction, asserting a higher
degree of uncertainty about the emission performance of their larger
vehicles, especially in the early years of the program and in light of
simultaneous technology challenges. The newer data clearly show that
larger vehicles today are generally achieving US06 PM levels very
similar to smaller vehicles, and well below the proposed standards. We
are not finalizing separate US06 standards for heavier and lighter
vehicles because separate standards are unwarranted based on a review
of the newer data. However, we believe that the short-term 10 mg/mi
standard, as well as the temporary in-use vehicle testing standard,
will significantly reduce manufacturer compliance uncertainties in the
early years of the program for all vehicles, as discussed above.
    As with the FTP PM standards, manufacturers will comply with the
US06 PM standards with the same increasing minimum percentage of their
vehicles, as shown in Table IV.5. Also as with the FTP PM phase-in, we
are providing the option for a manufacturer to choose to certify 10
percent of its total light-duty vehicle sales in MY 2017 to the new
US06 PM standards, including light-duty vehicles over 6,000 lbs GVWR.
    As discussed in Section IV.A.2.c above, for LDVs and LDTs more than
6,000 lbs GVWR and MDPVs, EPA is also providing an alternative phase-in
of the US06 PM standards.
    All of the SFTP/US06 standards are shown in Table IV-4 and Table
IV-5.

                                      Table IV-4--Tier 3 LDV, LDT, and MDPV SFTP Composite Fleet Average Standards
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                Model year
                                         ---------------------------------------------------------------------------------------------------------------
                                           2017 \a\     2018       2019       2020       2021       2022       2023       2024        2025 and later
--------------------------------------------------------------------------------------------------------------------------------------------------------
NMOG+NOX (mg/mi)........................        103         97         90         83         77         70         63         57  50
--------------------------------------------------------------------------------------------------------------------------------------------------------
CO (g/mi)...............................                                                      4.2 \a\
--------------------------------------------------------------------------------------------------------------------------------------------------------
\a\ For LDVs and LDTs above 6,000 lbs GVWR and MDPVs, the NMOG+NOX and CO standards apply beginning in MY 2018.

                                             Table IV-5--Summary of LDV, LDT, and MDPV Tier 3 SFTP Standards
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                Model year
                                                            ------------------------------------------------------------------------
            Program element                    Units           2017                                                                         Notes
                                                               \a\      2018     2019     2020     2021     2022     2023    2024+
--------------------------------------------------------------------------------------------------------------------------------------------------------
NMOG+NOX Standard (fleet average).....  mg/mi..............                  Per declining fleet average for cars and trucks (see Table IV-4) \b\
--------------------------------------------------------------------------------------------------------------------------------------------------------
PM Standards:
    Phase-in..........................  %..................   20 \c\       20       40       70      100      100      100      100  ...................

US06:
    LDV, LDT, MDPV: Certification.....  mg/mi..............       10       10        6        6        6        6        6        6  Note d.
    LDV, LDT, MDPV: In-Use............                                              10       10       10       10       10
--------------------------------------------------------------------------------------------------------------------------------------------------------
\a\ For LDVs and LDTs above 6,000 lbs GVWR and MDPVs, the standards apply beginning in MY 2018.
\b\ The percent phase-in does not apply to the declining fleet average standards.
\c\ Manufacturers comply in MY 2017 with 20 percent of their LDV and LDT fleet under 6,000 lbs GVWR, or alternatively with 10 percent of their total
  LDV, LDT, and MDPV fleet.
\d\ Manufacturers must test 25 percent of each model year's durability groups, minimum of 2.

c. Enrichment Limitation for Spark-Ignition Engines
    To prevent emissions that result from excessive enrichment from
auxiliary emission control devices (AECD) that are substantially
present during the SFTP cycles, we are finalizing limitations on the
magnitude of enrichment that can be commanded, including enrichment
episodes encountered during in-use operation. During conditions where
enrichment is demonstrated to be present on the SFTP, the nominal air-
to-fuel ratio cannot be richer at any time than the leanest air-to-fuel
ratio required to obtain maximum torque (lean best torque or LBT). An
air-to-fuel ratio of LBT plus a tolerance of 4 percent additional
enrichment will be allowed in actual vehicle testing to protect for any
in-use variance in the air-to-fuel ratio from the nominal LBT air-to-
fuel determination, for such reasons as air or fuel distribution
differences from production variances or aging.
    LBT is defined as the leanest air-to-fuel ratio required at a speed
and load point with a fixed spark advance to make peak torque.
Specifically, an increase in fuel will not result in an increase in
torque while maintaining a fixed spark advance. LBT is determined by
setting the spark advance to a setting that is less than or equal to
the spark advance required for best torque (MBT) and maintaining that
spark advance when sweeping the air-to-fuel ratio. This fixed spark
advance requirement is intended to prevent torque changes related to
spark changes masking true LBT. One manufacturer commented that there
is no universally accepted definition or procedure to determine LBT so
we should retain the Tier 2 LBT requirements. We believe that the
proposed definition provides sufficient clarity and will generally
agree with most manufacturers' internal definition of LBT.
Additionally, we are finalizing the flexibility that manufacturers may
request approval of an alternative LBT definition for a unique
technology or control strategy. The Agency may determine that an
enrichment amount is excessive or not necessary and therefore deem that
the approach does not meet the air-to-fuel ratio requirements.
    Enrichment required for thermal protection will continue to be
allowed upon demonstration of necessity to the Agency, based upon
temperature limitations of the engine or exhaust components.
Manufacturers will be required to provide descriptions of all
components requiring thermal protection, temperature limitations of the
components, how the enrichment strategy will detect over-temperature
conditions and correct them, and a justification regarding why the
enrichment is the minimum necessary to protect the specific components.
The Agency may determine that the enrichment is not justified or is not
the minimum necessary based on the use of engineering judgment using
industry-reported thermal protection requirements.
    A manufacturer commented that this requirement to report enrichment
requirements for component protection for every application is
burdensome and unnecessary. EPA believes that closer review of off-
cycle enrichment by the agency, including enrichment for component
protection, is necessary to ensure emissions are well controlled under
all operating conditions. While this requirement may in some cases
require additional resources at certification, this information has
generally been required to be maintained by manufactures to support use
of enrichment as an auxiliary emission control device (AECD) and
therefore should be an exercise of reporting existing records for most
manufacturers.
    The requirements described in this section apply for vehicles
certified to any of the Tier 3 standards.
5. Feasibility of the NMOG+NOX and PM Standards
    In the proposal, we concluded that all of the Tier 3 emissions
standards are technologically feasible in the time frame of the
program. The technical conclusions we reached at that time have been
further reinforced by information we received in the public comments or
has otherwise become available and placed in the docket for this
rulemaking. After considering the comments received and with additional
supporting information in Chapter 1 of the RIA, we conclude that the
Tier 3 standards are feasible and reasonable, considering lead-time
provided and expected compliance costs.
    For each of the emission standards, the lead time provided by the
program is more than sufficient for all manufacturers to comply. First,
manufacturers in many cases are already adopting complying technologies
for reasons other than this rulemaking. For example, many of the
technologies that manufacturers have begun to develop for model years
as early as MY 2014 in response to the CARB LEV III FTP and SFTP
NMOG+NOX standards for the California market will likely
represent steps toward compliance with this national program.
Similarly, manufacturers have been producing some limited vehicle
offerings since as early as MY 2000 that comply with our final MY 2025
standards in response to the CARB PZEV requirements. In addition, as
described above, our program incorporates a number of phase-in
provisions that will ease the transition to compliance, including time
some manufacturers may need to install PM testing capability and to
ramp up production on a national scale. This feasibility assessment is
based on a variety of complementary technical data, studies, and
analyses. As described below, these include our analysis of the
stringency of the standards as compared to current Tier 2 emission
levels. We also discuss below our observation that manufacturers are
currently certifying several vehicle models under the California LEV II
program that could likely achieve the Tier 3 NMOG+NOX and PM
standards or similar levels. EPA has assessed the

emissions control challenges manufacturers will generally face (e.g.,
cold start NMOG reductions and running (warmed-up) NOX
emissions under typical and more aggressive driving conditions) and the
corresponding technologies that we expect to be available to
manufacturers to meet these challenges. Our feasibility assessment
accounts for the fact that the Tier 3 program will apply to all types
of new vehicles, ranging from small cars to large pick-up trucks and
MDPVs and representing a wide diversity in applications and in specific
engine designs.
    It is important to note that our primary assessment of the
feasibility of engine and emission control technologies is based on the
assumption that vehicles will be certified on gasoline with a fuel
sulfur content of 10 ppm and operated on in-use gasoline with an
average of 10 ppm sulfur.\258\ Therefore, our primary assessment does
not incorporate the degradation of emission control system caused by
higher levels of sulfur content, as is discussed in Section IV.A.6
below and further discussed in the RIA. This assessment reinforces the
critical role of gasoline sulfur control in making it possible for EPA
to establish emission standards at these very stringent levels. See
Section IV.6 below for a full discussion of our current knowledge of
the effects of gasoline sulfur on current Tier 2 vehicle emissions as
well as our projections of how we expect that sulfur will affect
compliance on vehicles with standards in the range of the Tier 3
standards. The projections are based on extensive EPA testing of Tier 2
vehicles as well as targeted evaluation of passenger cars and heavier
trucks performing at or near the Tier 3 Bin 30 (30 mg/mi
NMOG+NOX) including manufacturer supplied data of a
prototype Tier 3 light-duty truck as discussed in Section IV.6.
---------------------------------------------------------------------------

    \258\ Our technology, feasibility, and cost assessments are also
consistent with an assumption that certification fuel will contain
10 percent ethanol and will have other properties as specified in
Section IV.F below.
---------------------------------------------------------------------------

    Since there are multiple aspects to the Tier 3 program, it is
necessary to consider technical feasibility in light of the different
program requirements and their interactions with each other. In many
cases, manufacturers will be able to address more than one requirement
with the same general technological approach (e.g., faster catalyst
light-off can improve both FTP NMOG+NOX and PM emissions).
At the same time, the feasibility assessment must consider that
different technologies may be needed on different types of vehicle
applications (e.g., cars versus trucks) and must consider the relative
effectiveness of these technologies in reducing emissions for the full
useful life of the vehicle while operating on expected in-use fuel. For
example, certain smaller vehicles with correspondingly small engines
may be less challenged to meet FTP standards than larger vehicles with
larger engines. Conversely, these smaller vehicles may have more
difficulty meeting the more aggressive SFTP requirements than vehicles
with larger and more powerful engines. Additionally, the ability to
meet the SFTP emission requirements can also be impacted by the path
taken to meet the FTP requirements (e.g., larger volume catalysts for
US06 emissions control vs. smaller catalysts for improved FTP cold-
start emissions control). Throughout the following discussion, we
address how these factors, individually and in interaction with each
other, affect the feasibility of the final program.
a. FTP NMOG+NOX Standards
    The Tier 3 emission requirements include stringent
NMOG+NOX standards on the FTP that will require new vehicle
hardware in order to achieve the 30 mg/mi fleet average level in MY
2025. The type of new hardware that will be required will vary
depending on the specific application and emission challenges. Smaller
vehicles with corresponding smaller engines will generally need less
new hardware while larger vehicles may need additional hardware and
improvements beyond what will be needed for the smaller vehicles. While
some vehicles, especially larger light trucks, may face higher costs in
meeting the standards, it is important to remember that not every
vehicle needs to meet the standard. The program has been structured to
provide higher emission standard ``bins'' (see Table IV-1 above) to
which manufacturers may certify more challenged vehicles, so long as
these vehicles are offset with vehicles certified in lower emission
bins such that the fleet-wide average meets the standards. We believe
that the availability of the less-stringent bins will allow for the
balancing of feasibility and cost considerations of compliance
strategies for all vehicles. In the Tier 2 program, manufacturers took
advantage of this flexibility, especially in the early years of the
program. Then, as technologies improved and/or became less expensive
and the need for averaging diminished, manufacturers began certifying
all or most of their fleets to the average bin (Tier 2 Bin 5). We
anticipate that manufacturers will follow a similar trend with the Tier
3 standards, relying on fleet averaging more significantly in the
transitional years but certifying increasing numbers of their vehicles
to the final fleet average standard of 30 mg/mi in the later years of
the program.
    In order to assess the technical feasibility of a 30 mg/mi
NMOG+NOX national fleet average FTP standard, EPA conducted
two supporting analyses. The initial analyses performed were of the
current Tier 2 and LEV II fleets. This provided a baseline for the
current federal fleet emissions performance, as well as the emissions
performance of the California LEV II fleet. The second consideration
was a modal analysis of typical vehicle emissions under certain
operating conditions. In this way EPA determined the specific emissions
performance challenges that vehicle manufacturers will face in meeting
the lower fleet average emission standards. Each of these
considerations is described in greater detail below.
    The current Tier 2 federal fleet is certified to an average of Tier
2 Bin 5, equivalent to 160 mg/mi NMOG+NOX.\259\ As an
example, for MY 2009 when the Tier 2 program was fully implemented
across all vehicle types, 92 percent of LDVs and LDT1s were certified
to Tier 2 Bin 5 and 91 percent of LDT2s through LDT4s were certified to
Tier 2 Bin 5. This trend has generally continued through MY 2013 as the
most recent certification results indicate that manufacturers are
continuing to certify primarily to Tier 2 Bin 5 standards for the
federal fleet however there has been a shift to more certifications
using the cleaner bins as discussed in the RIA. This is not an
unexpected result as there is no motivation prior to implementation of
the Tier 3 rulemaking for vehicle manufacturers to produce a federal
fleet that over-complies with respect to the existing Tier 2 standards.
By comparison, in the California fleet where compliance with the
declining fleet average NMOG requirement and the ``PZEV'' program
requires manufacturers to certify vehicles to cleaner levels, only 30
percent of the LDVs and LDT1s are certified to Tier 2 Bin 5 and 60
percent are certified to cleaner bins such as Tier 2 Bin 3 and 4. The
situation regarding the truck fleet in California is similarly
stratified, with 37 percent of the LDT2s through LDT4s being certified
to Tier 2

Bin 5 and 55 percent being certified to the cleaner Tier 2 Bin 3 and 4.
In many cases identical vehicles are being certified to a lower
standard in California and a higher standard federally simply because
there is no incentive to over perform to the federal standards. We note
that vehicles certified to a lower standard in California are operated
on gasoline with an average sulfur content of 10 ppm and thereby are
able to maintain their emissions performance in-use. Based on these
patterns of federal and California certification, EPA believes that
much of the existing Tier 2 fleet could currently be certified to a
lower federal fleet average immediately, with no significant
feasibility concerns, if lower sulfur gasoline were made available
nationwide.
---------------------------------------------------------------------------

    \259\ The Tier 2 program does not combine NMOG and
NOX emissions into one fleet-average standard. The fleet-
average standard in that program is for NOX emissions
alone. The NOX fleet-average requirement of .07 gm/mi is
the same level as the Bin 5 NOX standard.
---------------------------------------------------------------------------

    Regardless of the Tier 2 bin standards at which manufacturers
choose to certify their vehicles, actual measured emissions performance
of these vehicles is typically well below the numerical standards. This
difference is referred to as ``compliance margin'' and is a result of
manufacturers' efforts to address all the sources of variability,
including:

 Test-to-test variability (within one test site and lab-to-lab)
 Build variation expectations
 Manufacturing tolerances and stack-up
 Vehicle operation (for example: driving habits, ambient
temperature, etc.)
 Fuel composition
 The effects of fuel sulfur on exhaust catalysts and oxygen
sensors
 The effects of other fuel components, including ethanol and
gasoline additives
 Oil consumption
 The impact of oil additives and oil ash on exhaust catalysts
and oxygen sensors

    For MY 2009 thru MY 2013, the compliance margin for a Tier 2 Bin 5
vehicle averaged approximately 60 percent. In other words, actual
vehicle emissions performance was on average about 40 percent of a 160
mg/mi NMOG+NOX standard, or about 64 mg/mi. By comparison,
for California-certified vehicles, the average Super Ultra Low Emission
Vehicle (SULEV) compliance margin was somewhat less for the more
stringent standards, approximately 50 percent. We believe that the
recent California experience is a likely indicator of compliance
margins that manufacturers will design for in order to comply with the
Tier 3 FTP standards. Thus, a typical Tier 2 Bin 5 vehicle, performing
at 40 percent of the current standard (i.e., at about 64 mg/mi) will
need improvements sufficient to reach about 15 mg/mi (50 percent of a
30 mg/mi standard).
    To understand how the several currently-used technologies described
below could be used by manufacturers to reach the stringent Tier 3-
NMOG+NOX standards, it is helpful to consider emissions
formation in common modes of operation for gasoline engines, or modal
analysis.\260\ The primary challenge faced by manufacturers for
producing Tier 3 compliant light-duty gasoline vehicle powertrains will
be keeping warmed-up running emissions at effectively zero emissions
levels while reducing the emissions during cold-start operation which,
based on modal analysis of a gasoline-powered vehicle being operated on
the FTP cycle, occurs during about the first 50 seconds after engine
start. Thus, we believe that to comply with the Tier 3 FTP standards,
manufacturers will focus on effective control of these cold-start
emissions while maintaining zero running emissions; this is only
possible when sulfur levels in the fuel do not degrade catalyst
performance. As discussed below, light-duty manufacturers are already
applying several technologies capable of significant reductions in
these cold start emissions to vehicles currently on the road.
---------------------------------------------------------------------------

    \260\ A modal analysis provides a second-by-second view of the
total amount of emissions over the entire cycle being considered.
---------------------------------------------------------------------------

    During the analysis of current vehicles certified to the cleanest
emission levels (Tier 2 Bin 2 and LEV II SULEV) it was noted that no
large pick-ups equipped with their application specific engines were
performing at the 30 mg/mi NMOG+NOX level. We believe that
these applications may be the most challenging due to the fact that the
design criteria required to provide the utility aspect may have direct
impact on their ability to implement some of the technologies described
in section IV.A.5.d below. Since these vehicles represent a substantial
and important part of the light- duty fleet, EPA performed a technical
feasibility study directly targeting this class of vehicles.
    In order to assess the technical feasibility of a 30 mg/mi FTP
NMOG+NOX standard, EPA purchased a 2011 Chevrolet Silverado
heavy-light-duty (LDT4) pickup truck with a developmental goal of
modifying the truck to achieve exhaust emission levels in compliance
with the Tier 3 Bin 30 emissions standards including a reasonable
compliance margin. The truck was equipped with a 5.3L V8 with General
Motors' ``Active Fuel Management'' cylinder deactivation system. This
particular truck was chosen as an example of a Tier 3 prototype in part
because cylinder deactivation is a key technology for light-truck
compliance with future GHG standards and in part because it achieved
very low emissions in the OEM, Tier 2-compliant configuration
(certified to Tier 2 Bin 4). A prototype exhaust system was obtained
from MECA consisting of high-cell-density (900 cpsi) thin-wall (2.5
mil), high-PGM, close-coupled Pd-Rh catalysts with an additional under-
body Pd-Rh catalyst. The total catalyst volume was approximately 116
in\3\ with a specific PGM loading of 125 g/ft\3\ and approximate
loading ratio of 0:80:5 (Pt:Pd:Rh). Third-party (non-OEM) EMS
calibration tools were used to modify the powertrain calibration in an
effort to improve catalyst light-off performance. The final test
configuration used approximately 4 degrees of timing retard and
approximately 200 rpm higher idle speed relative to the OEM
configuration during and immediately following cold-start. The exhaust
catalyst system and HEGO sensors were bench aged to an equivalent
150,000 miles using standard EPA accelerated catalyst bench-aging
procedures. The truck was tested on California LEV III E10
certification fuel at 9 ppm gasoline sulfur levels.
    The EPA Tier 3 prototype Silverado achieved NMOG+NOX
emissions of 18 mg/mi on the 9 ppm S fuel. The NMOG+NOX
emissions were approximately 60% of the Bin 30 standard and thus are
consistent with meeting the Tier 3 Bin 30 exhaust emissions standard
with a moderate compliance margin. The technologies used on the
prototype Silverado to achieve these emission levels are common
approaches used today on smaller vehicles. They do not compromise any
of the design utility of this vehicle class and are some of the same
approaches we expect manufacturers to use to meet the Tier 3 Bin 30
exhaust emissions standards.
b. SFTP NMOG+NOX Standards
    The increase in the stringency of the SFTP NMOG+NOX
standards, specifically across the US06 cycle, will generally only
require additional focus on fuel control of the engines and diligent
implementation of new technologies that manufacturers are already
introducing or are likely to introduce in response to the current and
2017 LD GHG emission standards. These include downsized gasoline direct
injection (GDI) and turbocharged engines, which may also include

improvements to the engine and emission control hardware to tolerate
higher combustion and exhaust temperatures expected in these future
GHG-oriented engine designs when under higher loads. The upgraded
materials or components will enable manufacturers to rely less on fuel
enrichment during high-speed/high-load operation to protect components
from overheating. This fuel enrichment is currently the source of
elevated VOC, NOX, and PM emissions seen in a subset of the
current Tier 2 fleet.
    With respect to enrichment, the primary method available to
manufacturers to protect the catalyst and other exhaust components from
over-temperature conditions has been changes to the fuel/air mixture by
increasing the fuel fraction, but this is no longer the only tool
available to manufacturers for this purpose. With the application of
electronic throttle controls, variable valve timing, exhaust gas
recirculation and other exhaust temperature influencing technologies on
nearly every light-duty vehicle, the manufacturer has the ability to
systematically control the operation and combustion processes of the
engine to minimize or altogether avoid areas and modes of operation
where thermal issues can occur. While some of these solutions could in
some cases result in a small and temporary reduction in vehicle
performance (absolute power levels), we believe that it could be an
effective way to reduce NMOG+NOX emissions over the SFTP
test.
    Additionally, some components, especially catalysts, can experience
accelerated thermal deterioration that occurs when operating at higher
temperatures for more time than expected under normal operation (e.g.,
trailer towing, mountain grades). Some upgrades of existing vehicle
emission control technology, like catalyst substrates and washcoats may
be required to limit thermal deterioration and ensure vehicle emissions
compliance throughout the useful life of the vehicle.
    In order to assess the technical feasibility of a 50 mg/mi
NMOG+NOX national fleet average SFTP standard, EPA conducted
an analysis of SFTP levels of Tier 2 and LEV II vehicles. The analysis
was performed on the US06 results from current Tier 2 and LEV II
vehicles tested in the in-use verification program (IUVP) by
manufacturers and submitted to EPA. This analysis provided a baseline
for the current Tier 2 and LEV II fleet emissions performance, as well
as the SFTP emissions performance capability of the cleanest vehicles
meeting the Tier 3 FTP standards. The analysis concluded that most
vehicles in the IUVP testing program are already capable of meeting the
composite SFTP standard of 50 mg/mi when the Tier 3 FTP standard levels
are factored into the composite calculation. With the technological
improvements already underway as discussed above, we believe all MY
2017 and later vehicles will be able to comply with the SFTP standards,
either directly or through the flexibility of the averaging, banking
and trading program. For further information on the analysis see
Chapter 1 of the RIA.
c. FTP and SFTP PM Standards
    As described above for NMOG+NOX over the SFTP, the
increase in the stringency of the FTP and SFTP PM standards will
generally also only require additional focus on fuel control of the
engines and attention to PM emissions during the implementation of new
technologies like gasoline direct injection (GDI) and turbocharged
engines. Some upgrades of existing vehicle emission control technology
may be required to ensure vehicle emissions performance is maintained
throughout the useful life of the vehicle. These upgrades may include
improvements to the engine to control wear that could result in
increased PM from oil consumption and selection of GDI systems that
will be capable of continuing to perform optimally even as the systems
age.
    We based our conclusions about the ability of manufacturers to meet
the PM standards largely on the PM performance of the existing fleet,
both on the FTP and SFTP. In the case of FTP testing of current
vehicles, data on both low and high mileage light-duty vehicles
demonstrate that the majority of vehicles are currently achieving
levels at or below the Tier 3 FTP PM standards.
    The testing results can be found in Chapter 1 of the RIA. A small
number of vehicles are at or just over the Tier 3 FTP PM standard at
low mileage and could require calibration changes and/or catalyst
changes to meet the new standards. It is our expectation that the same