The majority of Americans continue to be exposed to ambient concentrations of air toxics at levels which have the potential to cause adverse health effects.  The levels of air toxics to which people are exposed vary depending on where people live and work and the kinds of activities in which they engage, as discussed in detail in U.S. EPA's most recent Mobile Source Air Toxics Rule.  According to the National Air Toxic Assessment (NATA) for 2005, mobile sources were responsible for 43 percent of outdoor toxic emissions and over 50 percent of the cancer risk and noncancer hazard associated with primary emissions.  Mobile sources are also large contributors to precursor emissions which react to form secondary concentrations of air toxics.  Formaldehyde is the largest contributor to cancer risk of all 80 pollutants quantitatively assessed in the 2005 NATA.   Mobile sources were responsible for over 40 percent of primary emissions of this pollutant in 2005, and are major contributors to formaldehyde precursor emissions. Benzene is also a large contributor to cancer risk, and mobile sources account for over 70 percent of ambient exposure.   Over the years, EPA has implemented a number of mobile source and fuel controls which have resulted in VOC reductions, which also reduced formaldehyde, benzene and other air toxic emissions.
Near-Roadway Pollution
Locations in close proximity to major roadways generally have elevated concentrations of many air pollutants emitted from motor vehicles.  Hundreds of such studies have been published in peer-reviewed journals, concluding that concentrations of CO, NO, NO2, benzene, aldehydes, particulate matter, black carbon, and many other compounds are elevated in ambient air within approximately 300-600 meters (about 1,000-2,000 feet) of major roadways.  Highest concentrations of most pollutants emitted directly by motor vehicles are found at locations within 50 meters (about 165 feet) of the edge of a roadway's traffic lanes.
A recent large-scale review of air quality measurements in vicinity of major roadways between 1978 and 2008 concluded that the pollutants with the steepest concentration gradients in vicinities of roadways were CO, ultrafine particles, metals, elemental carbon (EC), NO, NOX, and several VOCs.  These pollutants showed a large reduction in concentrations within 100 meters downwind of the roadway.  Pollutants that showed more gradual reductions with distance from roadways included benzene, NO2, PM2.5, and PM10.  In the review article, results varied based on the method of statistical analysis used to determine the trend.
For pollutants with relatively high background concentrations relative to near-road concentrations, detecting concentration gradients can be difficult.  For example, many aldehydes have high background concentrations as a result of photochemical breakdown of precursors from many different organic compounds.  This can make detection of gradients around roadways and other primary emission sources difficult.  However, several studies have measured aldehydes in multiple weather conditions, and found higher concentrations of many carbonyls downwind of roadways.[,]  These findings suggest a substantial roadway source of these carbonyls.
In the past 15 years, many studies have been published with results showing that populations who live, work, or go to school near high-traffic roadways experience higher rates of numerous adverse health effects, compared to populations far away from major roads.  In addition, numerous studies have found adverse health effects associated with spending time in traffic, such as commuting or walking along high-traffic roadways.  The health outcomes with the strongest evidence linking them with traffic-associated air pollutants are respiratory effects, particularly in asthmatic children, and cardiovascular effects.
Numerous reviews of this body of health literature have been published as well.  In 2010, an expert panel of the Health Effects Institute (HEI) published a review of hundreds of exposure, epidemiology, and toxicology studies.  The panel rated how the evidence for each type of health outcome supported a conclusion of a causal association with traffic-associated air pollution as either "sufficient," "suggestive but not sufficient," or "inadequate and insufficient."  The panel categorized evidence of a causal association for exacerbation of childhood asthma as "sufficient."  The panel categorized evidence of a causal association for new onset asthma as between "sufficient" and as "suggestive but not sufficient."  "Suggestive of a causal association" was how the panel categorized evidence linking traffic-associated air pollutants with exacerbation of adult respiratory symptoms and lung function decrement.  It categorized as "inadequate and insufficient" evidence of a causal relationship between traffic-related air pollution and health care utilization for respiratory problems, new onset adult asthma, chronic obstructive pulmonary disease (COPD), nonasthmatic respiratory allergy, and cancer in adults and children.  Other literature reviews have been published with conclusions similar to the HEI panel's.[,][,]  Health outcomes with few publications suggest the possibility of other effects still lacking sufficient evidence to draw definitive conclusions.  Among these outcomes with a small number of positive studies are neurological impacts (e.g., autism and reduced cognitive function) and reproductive outcomes (e.g., preterm birth, low birth weight).[,][,][,]
In addition to health outcomes, particularly cardiopulmonary effects, conclusions of numerous studies suggest mechanisms by which traffic-related air pollution affects health.  Numerous studies indicate that near-roadway exposures increase systemic inflammation, affecting organ systems, including blood vessels and lungs.[,][,][,]  Long-term exposures in near-road environments have been associated with inflammation-associated conditions, such as atherosclerosis and asthma.[,][,]
Several studies suggest that some factors may increase susceptibility to the effects of traffic-associated air pollution.  Several studies have found stronger respiratory associations in children experiencing chronic social stress, such as in violent neighborhoods or in homes with high family stress.[,][,]
The risks associated with residence, workplace, or schools near major roads are of potentially high public health significance due to the large population in such locations.  According to the 2009 American Housing Survey, over 22 million homes (17.0 percent of all U.S. housing units) were located within 300 feet of an airport, railroad, or highway with four or more lanes.  This corresponds to a population of more than 50 million U.S. residents in close proximity to high-traffic roadways or other transportation sources. As discussed in Section III, populations near major roads have higher fractions of minority residents and lower socioeconomic status.  Furthermore, on average, Americans spend more than an hour traveling each day, bringing nearly all residents into a high-exposure microenvironment for part of the day.
EPA continues to research near-road air quality, including the types of pollutants found in high concentrations near major roads and health problems associated with the mixture of pollutants near roads.
Environmental Impacts of Motor Vehicles and Fuels
Plant and Ecosystem Effects of Ozone
Elevated ozone levels contribute to environmental effects, with impacts to plants and ecosystems being of most concern.  Ozone can produce both acute and chronic injury in sensitive species depending on the concentration level and the duration of the exposure.  Ozone effects also tend to accumulate over the growing season of the plant, so that even low concentrations experienced for a longer duration have the potential to create chronic stress on vegetation.  Ozone damage to plants includes visible injury to leaves and impaired photosynthesis, both of which can lead to reduced plant growth and reproduction, resulting in reduced crop yields, forestry production, and use of sensitive ornamentals in landscaping.  In addition, the impairment of photosynthesis, the process by which the plant makes carbohydrates (its source of energy and food), can lead to a subsequent reduction in root growth and carbohydrate storage below ground, resulting in other, more subtle plant and ecosystems impacts.
These latter impacts include increased susceptibility of plants to insect attack, disease, harsh weather, interspecies competition and overall decreased plant vigor.  The adverse effects of ozone on forest and other natural vegetation can potentially lead to species shifts and loss from the affected ecosystems, resulting in a loss or reduction in associated ecosystem goods and services.  Lastly, visible ozone injury to leaves can result in a loss of aesthetic value in areas of special scenic significance like national parks and wilderness areas.  The final 2006 Ozone Air Quality Criteria Document presents more detailed information on ozone effects on vegetation and ecosystems.
Visibility
Visibility can be defined as the degree to which the atmosphere is transparent to visible light.  Visibility impairment is caused by light scattering and absorption by suspended particles and gases.  Visibility is important because it has direct significance to people's enjoyment of daily activities in all parts of the country.  Individuals value good visibility for the well-being it provides them directly, where they live and work, and in places where they enjoy recreational opportunities.  Visibility is also highly valued in significant natural areas, such as national parks and wilderness areas, and special emphasis is given to protecting visibility in these areas.  For more information on visibility see the final 2009 PM ISA.
EPA is pursuing a two-part strategy to address visibility impairment.  First, EPA developed the regional haze program which was put in place in July 1999 to protect the visibility in Mandatory Class I Federal areas.  There are 156 national parks, forests and wilderness areas categorized as Mandatory Class I Federal areas.  These areas are defined in CAA section 162 as those national parks exceeding 6,000 acres, wilderness areas and memorial parks exceeding 5,000 acres, and all international parks which were in existence on August 7, 1977.  Second, EPA has concluded that PM2.5 causes adverse effects on visibility in other areas that are not protected by the Regional Haze Rule, depending on PM2.5 concentrations and other factors that control their visibility impact effectiveness such as dry chemical composition and relative humidity (i.e., an indicator of the water composition of the particles). EPA revised the PM2.5 standards in December 2012 and established a target level of protection that is expected to be met through attainment of the existing secondary standards for PM2.5.
Current Visibility Levels
As mentioned in Section II.B.2.c, millions of people live in nonattainment areas for the PM2.5 NAAQS.  These populations, as well as large numbers of individuals who travel to these areas, are likely to experience visibility impairment.  In addition, while visibility trends have improved in mandatory class I federal areas, the most recent data show that these areas continue to suffer from visibility impairment.  In summary, visibility impairment is experienced throughout the U.S., in multi-state regions, urban areas, and remote mandatory class I federal areas.
Atmospheric Deposition
Wet and dry deposition of ambient particulate matter delivers a complex mixture of metals (e.g., mercury, zinc, lead, nickel, aluminum, cadmium), organic compounds (e.g., polycyclic organic matter, dioxins, furans) and inorganic compounds (e.g., nitrate, sulfate) to terrestrial and aquatic ecosystems.  The chemical form of the compounds deposited depends on a variety of factors including ambient conditions (e.g., temperature, humidity, oxidant levels) and the sources of the material.  Chemical and physical transformations of the compounds occur in the atmosphere as well as the media onto which they deposit.  These transformations in turn influence the fate, bioavailability and potential toxicity of these compounds.  Atmospheric deposition has been identified as a key component of the environmental and human health hazard posed by several pollutants including mercury, dioxin and PCBs.
Adverse impacts on water quality can occur when atmospheric contaminants deposit to the water surface or when material deposited on the land enters a waterbody through runoff.  Potential impacts of atmospheric deposition to waterbodies include those related to both nutrient and toxic inputs.  Adverse effects to human health and welfare can occur from the addition of excess nitrogen via atmospheric deposition.  The nitrogen-nutrient enrichment contributes to toxic algae blooms and zones of depleted oxygen, which can lead to fish kills, frequently in coastal waters.  Deposition of heavy metals or other toxics may lead to the human ingestion of contaminated fish, impairment of drinking water, damage to freshwater and marine ecosystem components, and limits to recreational uses.  Several studies have been conducted in U.S. coastal waters and in the Great Lakes Region in which the role of ambient PM deposition and runoff is investigated.[,][,][,][,]
Atmospheric deposition of nitrogen and sulfur contributes to acidification, altering biogeochemistry and affecting animal and plant life in terrestrial and aquatic ecosystems across the United States.  The sensitivity of terrestrial and aquatic ecosystems to acidification from nitrogen and sulfur deposition is predominantly governed by geology.  Prolonged exposure to excess nitrogen and sulfur deposition in sensitive areas acidifies lakes, rivers and soils.  Increased acidity in surface waters creates inhospitable conditions for biota and affects the abundance and nutritional value of preferred prey species, threatening biodiversity and ecosystem function.  Over time, acidifying deposition also removes essential nutrients from forest soils, depleting the capacity of soils to neutralize future acid loadings and negatively affecting forest sustainability.  Major effects include a decline in sensitive forest tree species, such as red spruce (Picea rubens) and sugar maple (Acer saccharum), and a loss of biodiversity of fishes, zooplankton, and macro invertebrates.
In addition to the role nitrogen deposition plays in acidification, nitrogen deposition also leads to nutrient enrichment and altered biogeochemical cycling.  In aquatic systems increased nitrogen can alter species assemblages and cause eutrophication.  In terrestrial systems nitrogen loading can lead to loss of nitrogen sensitive lichen species, decreased biodiversity of grasslands, meadows and other sensitive habitats, and increased potential for invasive species.  For a broader explanation of the topics treated here, refer to the description in Section 6.3.2 of the RIA.
Adverse impacts on soil chemistry and plant life have been observed for areas heavily influenced by atmospheric deposition of nutrients, metals and acid species, resulting in species shifts, loss of biodiversity, forest decline, damage to forest productivity and reductions in ecosystem services.  Potential impacts also include adverse effects to human health through ingestion of contaminated vegetation or livestock (as in the case for dioxin deposition), reduction in crop yield, and limited use of land due to contamination.
Atmospheric deposition of pollutants can reduce the aesthetic appeal of buildings and culturally important articles through soiling, and can contribute directly (or in conjunction with other pollutants) to structural damage by means of corrosion or erosion.  Atmospheric deposition may affect materials principally by promoting and accelerating the corrosion of metals, by degrading paints, and by deteriorating building materials such as concrete and limestone.  Particles contribute to these effects because of their electrolytic, hygroscopic, and acidic properties, and their ability to adsorb corrosive gases (principally sulfur dioxide).
Current Nitrogen and Sulfur Deposition
Over the past two decades, the EPA has undertaken numerous efforts to reduce nitrogen and sulfur deposition across the U.S.  Analyses of long-term monitoring data for the U.S. show that deposition of both nitrogen and sulfur compounds has decreased over the last 17 years.  The data show that reductions were more substantial for sulfur compounds than for nitrogen compounds.  In the eastern U.S., where data are most abundant, total sulfur deposition decreased by about 44 percent between 1990 and 2007, while total nitrogen deposition decreased by 25 percent over the same time frame.  These numbers are generated by the U.S. national monitoring network and they likely underestimate nitrogen deposition because neither ammonia nor organic nitrogen is measured.  Although total nitrogen and sulfur deposition has decreased over time, many areas continue to be negatively impacted by deposition.  Deposition of inorganic nitrogen and sulfur species routinely measured in the U.S. between 2005 and 2007 were as high as 9.6 kilograms of nitrogen per hectare (kg N/ha) averaged over three years and 20.8 kilograms of sulfur per hectare (kg S/ha) averaged over three years.
Environmental Effects of Air Toxics
Emissions from producing, transporting and combusting fuel contribute to ambient levels of pollutants that contribute to adverse effects on vegetation.  Volatile organic compounds, some of which are considered air toxics, have long been suspected to play a role in vegetation damage.  In laboratory experiments, a wide range of tolerance to VOCs has been observed.  Decreases in harvested seed pod weight have been reported for the more sensitive plants, and some studies have reported effects on seed germination, flowering and fruit ripening.  Effects of individual VOCs or their role in conjunction with other stressors (e.g., acidification, drought, temperature extremes) have not been well studied.  In a recent study of a mixture of VOCs including ethanol and toluene on herbaceous plants, significant effects on seed production, leaf water content and photosynthetic efficiency were reported for some plant species.
Research suggests an adverse impact of vehicle exhaust on plants, which has in some cases been attributed to aromatic compounds and in other cases to nitrogen oxides.[,],
How Would This Proposal Reduce Emissions and Air Pollution?
Effects of the Proposed Vehicle and Fuel Changes on Mobile Source Emissions
The vehicle and fuel standards that EPA is proposing would significantly reduce the tailpipe and evaporative emissions of light- and heavy-duty vehicles in several ways, as described in this section.  In addition, the proposed gasoline sulfur standard would reduce emissions of SO2 from existing gasoline-powered vehicles and equipment.  As described in Section II, all of these emission reductions would in turn improve air quality nationwide and reduce the health effects associated with air pollution from mobile sources.
As with the Tier 2 program, EPA is proposing to implement closely-coordinated requirements for both automakers and refiners in the same rulemaking action. The proposed vehicle emission standards and gasoline sulfur standards represent a "systems approach" to reducing vehicle-related exhaust and evaporative emissions.  By recognizing the relationships among the various sources of emissions addressed by this proposed rule, we have been able to integrate the provisions into a single, coordinated program.
How Do Vehicles Produce the Emissions Addressed in this Proposal?
The degree to which vehicles produce exhaust and evaporative emissions depends on the design and functionality of the engine and the associated exhaust and evaporative emission controls, in concert with the properties of the fuel on which the vehicle is operating.  In the following paragraphs, we discuss how light- and heavy-duty vehicles produce each of these types of emissions, both from the tailpipe and from the fuel system.
Tailpipe (Exhaust) Emissions
 Which pollutants are emitted at the vehicle's tailpipe and their quantities depend on how the fuel is combusted in the engine and how the resulting gases are treated in the exhaust system.  Historically, much of tailpipe emission control has focused on hydrocarbon compounds (HC) and NOX.  The portion of hydrocarbons that is methane is minimally reactive in forming ozone.  Thus, for emission control purposes, the focus is generally on non-methane hydrocarbons (NMHC), which are also expressed as non-methane organic gases (NMOG) in order to account for oxygenates (usually ethanol) now usually present in the fuel.
Tailpipe hydrocarbon emissions also include several toxic pollutants, including benzene, acetaldehyde, and formaldehyde.  To varying degrees, the mass emissions of these pollutants are reduced along with other hydrocarbons by the catalytic converter and improved engine controls.
Light- and heavy-duty gasoline vehicles also emit PM and CO.  PM forms directly as a combustion product (primarily as elemental carbon, usually called soot) and also indirectly as semi-volatile hydrocarbon compounds that form particles in the exhaust system or soon after exiting the tailpipe.  CO is a product of incomplete fuel combustion.
When operating properly, modern exhaust emission controls (centering on the catalytic convertor) can reduce much of the HC (including toxics), NOX and CO exiting the engine.  However, tailpipe emissions are increased during periods of vehicle startup, as catalytic convertors must warm up to be effective; during subsequent operation due to the interference of sulfur in the gasoline; during high load operating events, as the catalyst is overwhelmed or its operation is modified to protect against permanent damage; and as a vehicle ages, as the catalyst degrades in performance due to the effects of high temperature operation and contaminants in the fuel and lubricating oil.
Evaporative Emissions
Gasoline vehicles also produce vapors in the fuel tank and fuel system that can be released as evaporative emissions.  These vapors are primarily the lighter, more volatile hydrocarbon compounds in the gasoline, which, like exhaust hydrocarbons, contribute to concentrations of VOCs in the atmosphere.
As discussed in Section IV below, vehicle evaporative ("evap") control systems are designed to block or capture vapors as they are generated.  Vapors are generated in the vehicle fuel tank and fuel system (and released to the atmosphere if not adequately controlled) as fuel heats up due to ambient temperature increase and/or vehicle operation.  Fuel vapors are also released when they permeate through hose material, when they leak at connections or due to damaged components, and during refueling events.
In general, the evap emission controls on current vehicles (and that would be improved under this proposed rule) consist of a canister filled with activated charcoal and connected by hoses to the fuel system.  The hoses direct generated vapors to the canister, which collects the vapors on the carbon and stores them until the system experiences a "purge" event.  During purge, the engine draws fresh air through the canister, carrying vapors released by the carbon to the engine to be combusted and restoring the capacity of the canister.  Evaporative emissions occur when vapors are emitted to the atmosphere because the evap system is compromised, the carbon canister is overwhelmed, or vapors permeate or leak.  As such, evaporative emission controls also involve proper material selection for fuel system components, careful design of these components, and onboard diagnostics to check the system for failure.
How Would the Proposed Changes to Gasoline Sulfur Content Affect Vehicle Emissions?
Gasoline vehicles depend to a great degree on catalytic converters to reduce levels of pollutants in their exhaust, including NMOG and NOX, as well as PM (specifically, the volatile hydrocarbon fraction), CO, and most air toxics.  The presence of sulfur in gasoline has a strong impact on these emissions, particularly NOX, due to its impact on proper catalyst operation.
Sulfur naturally occurs in crude oil and thus in gasoline.  In vehicle catalytic converters, the precious metals that catalyze the reactions that convert the pollutants become significantly less efficient when sulfur is deposited (adsorbed) onto them.  The Tier 2 rulemaking required refiners to take steps to reduce sulfur levels in gasoline by approximately 90 percent, to an average of 30 ppm.  At the time there were indications that sulfur reductions below 30 ppm may continue to provide additional emission benefits.  However, the data was insufficient to quantify the benefits to the existing fleet, and the Tier 2 vehicle standards could be achieved without lowering sulfur further.  As a result, to minimize the cost of the Tier 2 program, the sulfur standard was not further reduced below 30 ppm.
As discussed in Section IV.A.6, subsequent research provides a compelling case that even this level of sulfur degrades the emission performance of vehicles on the road today, and inhibits necessary further reductions in vehicle emissions performance, which depend on optimum catalyst performance to reach emission targets.  A study conducted by EPA and the auto industry in support of the Mobile Source Air Toxics (MSAT) rule found significant reductions in NOX, CO and total HC when nine Tier 2 vehicles were tested on low sulfur fuel, relative to 32-ppm fuel.    In particular, the study found a nearly 50 percent increase in NOX when sulfur was increased from 6 ppm to 32 ppm.  Another recent study by Umicore showed reductions of 41 percent for NOX and 17 percent for HC on a PZEV operating on fuel with 33-ppm and 3-ppm fuel.
A larger study recently completed by EPA confirmed these results, showing significant reductions in FTP-composite NOX (23 percent), CO (12 percent) and total HC (13 percent) on the 5-ppm fuel, relative to 28-ppm fuel.  For NOX, the majority of overall reductions were driven by large reductions on warmed-up periods of the test cycle (Bag 2), which showed a 59 percent reduction between 28 and 5-ppm fuel, consistent with the role of sulfur in catalyst degradation discussed above.  Applying individual bag reductions to in-use activity patterns from EPA emission models suggests an overall NOX reduction of nearly 40 percent on the road.
Based on these studies, the benefits of the proposed Tier 3 sulfur standard are significant in two ways:  they enable vehicles designed to the proposed Tier 3 tailpipe exhaust standards to meet these standards for the duration of their useful life, and they facilitate immediate emission reductions from all the vehicles on the road at the time the sulfur controls are implemented.
How Would Emissions Be Reduced?
The proposed standards would reduce emissions of VOC, NOX (including NO2), direct PM2.5, CO, SO2, and air toxics.  The proposed sulfur standards would reduce emissions from the on-road fleet immediately upon implementation, so to reflect these early reductions, we present emission reductions in calendar year 2017. The proposed vehicle standards would begin to reduce emissions as the cleaner cars and trucks begin to enter the fleet in model year 2017.  The magnitude of reduction would grow as more Tier 3 vehicles enter the fleet.  Therefore, we also present emission reductions in calendar year 2030, when model year 2017 and later cars and trucks contribute nearly 90 percent of fleet-wide vehicle miles travelled.  Although 2030 is the farthest year that is feasible for air quality modeling, the full reduction of the vehicle program would be realized after 2030, when the fleet has fully turned over to Tier 3 vehicles.  In Chapter 7 of the RIA, we present emission reductions projected in 2050, as well as additional calendar years between 2017 and 2030.
Emission reductions are estimated on an annual basis, for all 50 U.S. states plus the District of Columbia, Puerto Rico and the U.S. Virgin Islands.   The reductions were estimated using a version of EPA's MOVES model updated for this analysis, as described in detail in Chapter 7 of the RIA.  This version of MOVES includes our most recent data on how vehicle emissions are affected by changes in sulfur, ethanol, and other fuel properties. We estimated emission reductions compared to a reference case that assumed partial RFS2 implementation by 2017, with full implementation in 2022 and beyond.  The ethanol scenarios used for the reference and control cases were the "post-EPAct/EISA" scenario defined in Chapter 7 of the RIA, reflecting a mix of E10 and E15 in 2017, and E15 only in 2030.  The reference case also assumed continuation of the Tier 2 vehicle program indefinitely, and an average sulfur level of 30 ppm (10 ppm in California).
As discussed throughout this preamble, implementation of the proposed Tier 3 standards is aligned with the 2017 LD GHG standards to achieve significant criteria pollutant and GHG emissions reductions while providing regulatory certainty and compliance efficiency to the auto and oil industries.  The 2017 LD GHG standards were still in a preliminary state of development (pre-proposal) at the time we finalized our assumptions for the Tier 3 emissions, air quality, and cost analyses, so we were not able to reflect them in these analyses.  However, we continue to expect vehicle criteria pollutant performance to be neutral under the GHG program, because exhaust and evaporative emissions are not proportional to the amount of fuel burned; rather, our standards are expressed on a per-mile basis, not on a per-gallon basis.  Vehicle criteria emissions are almost exclusively controlled by a vehicle's emissions aftertreatment system and not by the efficiency of the engine.
The majority of the NMOG that is emitted from a gasoline engine is generated during cold start, before the catalyst is lit off, and NOX is often created during higher load operation.  Optimizing catalyst efficiency, minimizing thermal parasitics, minimizing fuel system leaks, and lower gasoline sulfur will be key enablers for all vehicles to meet the Tier 3 standards, regardless of the vehicle's fuel efficiency.  Because we do not expect the increase in fuel efficiency to result in lower criteria pollutant emissions, we did not claim in the 2017 LD GHG rule any reductions attributable to the ability of vehicles to meet lower criteria emission levels (see 77 FR 62899-62901, October 15, 2012).  In other words, in the 2017 LD GHG rule, we assumed that, absent the proposed Tier 3 standards, the light-duty fleet would continue to meet the Tier 2 standards.  Thus, we believe that the inclusion of the light-duty GHG standards in our cost and benefit analyses for the proposed Tier 3 standards would have had little or no impact on the results or our conclusions, as discussed in Sections 7.1.2 and <IP_ADDRESS>.1 of the draft RIA.  Nevertheless, for the final rulemaking we will include the LD GHG requirements in the analysis.
The analysis described here does account for the following national onroad rules:
         * Tier 2 Motor Vehicle Emissions Standards and Gasoline Sulfur Control Requirements (65 FR 6698, February 10, 2000)
         * Heavy-Duty Engine and Vehicle Standards and Highway Diesel Fuel Sulfur Control Requirements (66 FR 5002, January 18, 2001)
         * Mobile Source Air Toxics Rule (72 FR 8428, February 26, 2007)
         * Regulation of Fuels and Fuel Additives: Changes to Renewable Fuel Standard Program (75 FR 14670, March 26, 2010)
         * Light-Duty Vehicle Greenhouse Gas Emission Standards and Corporate Average Fuel Economy Standards for 2012-2016 (75 FR 25324, May 7, 2010)
The analysis also accounts for many other national rules and standards.  In addition, the modeling accounts for state and local rules including local fuel standards, Inspection/Maintenance programs, Stage II refueling controls, the National Low Emission Vehicle Program (NLEV), and the section 177 states LEV and LEVII programs.  See the Tier 3 emissions modeling TSD for more detail.
A summary of emission reductions projected to result from Tier 3, relative to the reference case, is shown in calendar years 2017 and 2030 for NOX, VOC, direct PM2.5, CO, SO2, and total air toxics in Table III-1.   For many pollutants, the immediate reductions in 2017 are significant; for example, combined NOX and VOC emissions would be reduced by over 300,000 tons.   By 2030, combined NOX and VOC emissions would be reduced by roughly 750,000 tons, one quarter of the onroad inventory.  Many of the modeled air toxics would be significantly reduced as well, including benzene, 1,3-butadiene, acetaldehyde, acrolein and ethanol (ranging from 20 to nearly 40 percent of the national onroad inventory by 2030).  The relative reduction in overall emissions would continue to increase beyond 2030 as more of the fleet continues to turn over to Tier 3 vehicles; for example, by 2050, when nearly all of the fleet would have turned over to Tier 3 standards, we estimate the Tier 3 program would reduce onroad emissions of NOX and VOC nearly 40 percent from the level of emissions projected without Tier 3 controls.
Table III-1 Estimated Emission Reductions from the Proposed Tier 3 Standards
(Annual U.S. short tons) a

2017
2030

Tons
% of Onroad Inventory
Tons
% of Onroad Inventory
NOX
284,381
8%
524,790
28%
VOC
44,782
3%
226,028
23%
CO
746,683
4%
5,765,362
30%
Direct PM2.5
121
0.1%
7,458
10%
Benzene
1,625
4%
8,582
36%
SO2
16,261
51%
17,267
51%
1,3-Butadiene
322
5%
1,087
37%
Formaldehyde
727
3%
2,707
12%
Acetaldehyde
762
3%
4,414
26%
Acrolein
23
1%
184
15%
Ethanol
2,684
2%
27,821
24%
        [a] This analysis assumed emissions reductions from the Tier 3 vehicle standards would occur in all states.  For the final rule we will account for LEV III vehicle standards in states that have subsequently adopted it.
Reductions for each pollutant are discussed in the following sections, focusing on the contribution of program elements to the total reductions summarized above.
NOX
The proposed sulfur standards would significantly reduce NOX emissions immediately upon implementation of the program.   As discussed above, recent research on the impact of sulfur on Tier 2 technology vehicles shows the potential for significant reductions in NOX emissions from the existing fleet of Tier 2 vehicles by lowering sulfur levels to 10 ppm.   Prior research shows that NOX emissions would also be expected to decrease from the fleet of older (pre-Tier 2) light-duty vehicles as well as heavy-duty gasoline vehicles, although at to a lesser extent than for Tier 2 vehicles.
Table III-2 shows the reduction in NOX emissions, in annual short tons, projected in calendar years 2017 and 2030.  The reductions are split into those attributable to the introduction of low sulfur fuel in the pre-Tier 3 fleet (defined for this analysis as model years prior to 2017); and reductions attributable to vehicle standards enabled by low sulfur fuel (model year 2017 and later).  As shown, upon implementation of the proposed sulfur standards, total onroad NOX emissions are projected to drop 8 percent. This is primarily due to large reductions from Tier 2 gasoline vehicles, which contribute about one-quarter of the NOX emissions from the on-road fleet in 2017.  The relative reduction grows as cleaner vehicles turn over into the fleet.   By 2030, we project that the reduction in overall onroad NOX inventory would be close to 30 percent.
Table III-2 Projected NOX Reductions from Tier 3 Program (Annual U.S. Tons)a

2017
2030
Total reduction
284,381
524,790
Reduction from pre-Tier 3 fleet due to sulfur standard
264,653
66,286
Reduction from Tier 3 fleet due to vehicle and sulfur standards
19,728
458,504
Percent reduction in onroad NOX emissions
8%
28%
 [a] This analysis assumed emissions reductions from the Tier 3 vehicle standards would occur in all states.  For the final rule we will account for LEV III vehicle standards in states that have subsequently adopted it.
VOC
Table III-3 shows the reduction in VOC emissions, in annual short tons, projected in calendar years 2017 and 2030 resulting from the proposed standards.  In 2017, as with NOX, we project reductions from the pre-Tier 3 fleet with the proposed fuel standards.    By 2030 the reduction in overall onroad VOC emissions would be over 20 percent, the majority of this from the Tier 3 fleet. The proposed evaporative standards are projected to account for roughly one quarter of the overall vehicle program reduction in 2030.
Table III-3 Projected VOC Reductions from Tier 3 Program (Annual U.S. Tons)a

2017
2030
Total reduction
44,782
226,028
Reduction from pre-Tier 3 fleet due to sulfur standard
39,561
13,739
Reduction from Tier 3 fleet due to vehicle and sulfur standards
5,222
212,289

                                                                        Exhaust
                                                                         41,433
                                                                        168,264
                                                                   Evaporative
                                                                          3,349
                                                                         57,764
Percent reduction in onroad VOC emissions
3%
23%
[a] This analysis assumed emissions reductions from the Tier 3 vehicle standards would occur in all states.  For the final rule we will account for LEV III vehicle standards in states that have subsequently adopted it.
CO
Table III-4 shows the reductions for CO, broken down by pre- and post-Tier 3 in the manner described for NOX and VOC above.  Based on research showing sizeable CO reductions from lower sulfur fuel, the immediate reductions in the onroad fleet from sulfur control are also significant.  The CO exhaust standards are projected to reduce onroad CO emissions 30 percent by 2030.
Table III-4 Projected CO Reductions from Tier 3 Program (Annual U.S. Tons)

2017
2030
Total reduction
746,683
5,765,362
Reduction from pre-Tier 3 fleet due to sulfur standard
608,502
139,074
Reduction from Tier 3 fleet due to vehicle and sulfur standards
138,181
5,626,288
Percent reduction in onroad CO emissions
4%
30%
[a] This analysis assumed emissions reductions from the Tier 3 vehicle standards would occur in all states.  For the final rule we will account for LEV III vehicle standards in states that have subsequently adopted it.

Direct PM2.5
Reductions in direct emissions of PM2.5 are projected to result solely from the proposed vehicle tailpipe standards, so meaningful reductions are realized mainly as the fleet turns over.  By 2030, we project a reduction of about 7,500 tons annually, which represents approximately 10 percent of the onroad direct PM2.5 inventory.  However, since the PM standards are mainly focused on improving engine durability through the end of a vehicle's useful life, the relative reduction in onroad emissions is projected to grow to 17 percent with full fleet turnover in 2050.  Reductions in NOX and VOC emissions would also reduce secondary PM formation, which is quantified as part of the air quality analysis described in Section III.C.
Air Toxics
Emissions of air toxics also would be reduced by the proposed sulfur, exhaust and evaporative standards.   Air toxics are generally a subset of compounds making up VOC, so the reduction trends tend to track the VOC reductions presented above.  Table III-5 presents reductions for certain key air toxics, and Table III-6 presents reductions for the sum of 71 different toxic compounds.
Table III-5 Reductions for Certain Individual Compounds (Annual U.S. Tons)

                             Tons Reduced in 2017
                        % Reduction in Onroad Emissions
                             Tons Reduced in 2030
                        % Reduction in Onroad Emissions
Acetaldehyde
                                     762
                                      3%
                                    4,414
                                      26%
Formaldehyde
                                      727
                                      3%
                                    2,707
                                      12%
Acrolein
                                      23
                                      1%
                                     184
                                      15%
1,3-Butadiene
                                     322
                                      5%
                                    1,087
                                      37%
Benzene
                                    1,625
                                      4%
                                    8,581
                                      36%
Naphthalene
                                      96
                                      2%
                                     420
                                      17%
Ethanol
                                     2,684
                                      2%
                                    27,821
                                      24%
a This analysis assumed emissions reductions from the Tier 3 vehicle standards would occur in all states.  For the final rule we will account for LEV III vehicle standards in states that have subsequently adopted it.
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 (Appendix 7A in the draft RIA).  As shown, in 2030 the overall onroad inventory of total toxics would be reduced by over 20 percent, with nearly one third of the vehicle program reductions coming from the proposed evaporative standards.
Table III-6 Reductions in Total Mobile Source Air Toxics (Annual U.S. Tons)

2017
2030
Total reduction
15,156
89,685
Reduction from pre-Tier 3 fleet due to sulfur standard
12,452
5,022
Reduction from Tier 3 fleet due to vehicle and sulfur standards
2,683
84,663
                                                                        Exhaust
                                                                         13,748
                                                                         64,144
                                                                   Evaporative
                                                                          1,408
                                                                         25,541
Percent reduction in onroad toxics emissions
3%
23%
[a] This analysis assumed emissions reductions from the Tier 3 vehicle standards would occur in all states.  For the final rule we will account for LEV III vehicle standards in states that have subsequently adopted it.
SO2
SO2 emissions from mobile sources are a direct function of sulfur in the fuel, and reducing sulfur in gasoline would 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.
Table III-7 Projected SO2 Reductions from Tier 3 Program (Annual U.S. Tons)

2017
2030
Total reduction
16,261
17,267
Reduction from onroad vehicles due to sulfur standard
15,494
16,370
Reduction from off-road equipment due to sulfur standard
767
897
Percent reduction in onroad SO2 emissions
51%
51%
Greenhouse Gases
Reductions in nitrous oxide (N2O) emissions and methane (CH4) emissions, both potent greenhouse gas emissions, are projected for gasoline cars and trucks due to the proposed sulfur and tailpipe standards.   A study conducted by the University of California at Riverside found a 29 percent reduction in N2O emissions over the FTP when sulfur was reduced from 30 to 5 ppm, while EPA research described in Section IV.A on sulfur effects found a 25 percent reduction in CH4 emissions when sulfur was reduced from 28 to 5 ppm.  Several studies have established correlations between reductions in tailpipe NOX emissions and reductions in N2O from gasoline cars and trucks, [,][,] as well as correlations between reductions in tailpipe HC emissions and reductions in CH4.[,] One such study (Behrentz et al.) reported an N2O: NOX ratio of 0.095+-0.035, and supported the application of N2O: NOX ratios to NOX emissions as a reasonable method for estimating N2O emission inventories.  As detailed in RIA Chapter 7.3, a range of N2O reductions  is bounded by applying this ratio to NOX reductions projected for this proposal (from Table III-1), and applying the UC Riverside sulfur results to MOVES N2O inventories for pre-Tier 3 vehicles.  Using a 100-year global warming potential of 298 for N2O according to the 2007 IPCC AR4,  the range of reductions calculated for N2O is from 2.9 to 7.3 million metric tons of carbon dioxide equivalent (MMTCO2e) in 2017, growing to 12.3 to 13.5 MMTCO2e in 2030.  MOVES can be used to directly estimate CH4 reductions from the sulfur and vehicle standards, estimating an additional 0.1 MMTCO2e reduction in 2017, growing to 0.5 MMTCO2e in 2030.   The range of total GHG reductions from the Tier 3 rule is 3.0 to 7.4 MMTCO2e in 2017, growing to 12.8 to 14.0 MMTCO2e in 2030.
These reductions would be offset to some degree by CO2 emissions associated with higher energy use required in the process of removing sulfur within the refinery.  To assess the potential refinery permitting implications of the Tier 3 proposal, we calculated the CO2 emission impacts on a refinery-by-refinery basis.  We used the projected refinery-specific changes from our refinery-by-refinery modeling (see Chapter 5 of the draft RIA) to estimate changes in process energy and then applied emission factors that correspond to those changes.  The results showed an increase of up to 4.6 MMTCO2e in 2017 for all U.S. refineries complying with the lower sulfur standards assuming that the proposed sulfur standards are fully phased-in.  The actual increase is expected to be considerably lower, since this is a permitting analysis and refineries will not be operating at their permit capacity.  The actual increase will also be a function of several factors, including technology options selected by the refineries and the projected use of averaging, banking and trading in avoiding the need for investments at some refineries. As a result, 4.6 MMTCO2e represents an upper-bound estimate of the possible increase in refinery CO2 emissions due to the need for additional process heat and hydrogen production to enable the additional hydrotreating required.
In 2017, the range of potential decrease in CH4 and N2O emissions overlaps with the range of projected increase in CO2 from refinery processes, suggesting that a net increase or decrease in GHG emissions cannot be quantified with certainty.  However, we estimate the program would result in net GHG reductions as the program continues into the future, as shown by our 2030 estimates.
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 we have designed the program to address  -  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.  However, there may be some slight reduction of vehicle mass if manufacturers explore lighter exhaust manifold materials in order to reduce thermal mass and promote earlier catalyst light-off.  EPA invites comments on any potential impacts of the proposed Tier 3 program on vehicle CO2 emissions and fuel economy.
How Would Air Pollution Be Reduced?
Reductions in emissions of NOX, VOC, PM2.5 and air toxics expected as a result of the proposed Tier 3 standards are projected to lead to significant decreases in ambient concentrations of ozone, PM2.5, and air toxics. The results of our air quality modeling of the impacts of the Tier 3 proposal are summarized in the following section.   The air quality modeling predicts significant improvements in ozone concentrations due to the proposed Tier 3 standards.  Ambient PM2.5 and NO2 concentrations are also expected to improve as a result of the proposed Tier 3 program.  Decreases in ambient concentrations of air toxics are projected with the proposed 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 proposed standards.
Ozone
The air quality modeling done for this proposal projects that in 2017, with all current controls in effect but excluding the emissions changes expected to occur as a result of this proposed action or any other additional controls, at least 40 counties, with a projected population of almost 50 million people, would have projected design values above the level of the 2008 8-hour ozone standard of 75 ppb.  Even in 2030 the modeling projects that in the absence of additional controls there would be 12 counties with a population of almost 32 million people with projected design values above the level of the 2008 8-hour ozone standard of 75 ppb.  Since the emission changes from this proposal go into effect during the period when some areas are still working to attain the ozone NAAQS, the projected emission changes would help state and local agencies in their effort to attain and maintain the ozone standard.
Air quality modeling indicates ozone design value concentrations would decrease dramatically in many areas of the country as a result of this action and in some places those decreases would be enough to change the projected design values from being above the NAAQS to being below the NAAQS.  The decreases in ozone design values are likely due to projected tailpipe reductions in NOX and VOCs from reductions in fuel sulfur and engine controls.
In 2017, the majority of the design value decreases are between 0.5 and 1.0 ppb.  The projected population-weighted average design value concentration without the proposed rule is 71.3 ppb in 2017.  The proposed rule would also reduce the projected ozone design values in three counties from above the level of the standard to below.  These three counties are Bucks County in Pennsylvania, Arlington County in Virginia and St Louis County in Missouri.  The projected population in these three counties in 2017 is almost 2 million people.  In 2030, the proposed rule would result in larger decreases in ozone design values, with the majority of counties projecting decreases of between 1.0 and 1.5 ppb, and over 200 more counties with decreases greater than 1.5 ppb.  The projected population-weighted average design value concentration without the proposed rule is 66.7 ppb in 2030.  There are also two more counties whose projected design values would be reduced from above the level of the ozone standard to below by the proposed rule in 2030.  These counties are Hudson County in New Jersey and Brazoria County in Texas.  The projected population in these two counties in 2030 is over 1 million people.
Table III-8 and Table III-9 show the average change in 2017 and 2030 8-hour ozone design values for: (1) all counties with 2005 baseline design values, (2) counties with 2005 baseline design values that exceeded the 2008 ozone standard, (3) counties with 2005 baseline design values that did not exceed the 2008 standard, but were within 10 percent of it, (4) counties with 2017/2030 design values that exceeded the 2008 ozone standard, and (5) counties with 2017/2030 design values that did not exceed the standard, but were within 10 percent of it.  Counties within 10 percent of the standard are intended to reflect counties that although not violating the standards, will also be impacted by changes in ozone as they work to ensure long-term maintenance of the ozone NAAQS.  All of these metrics show a decrease in 2017 and 2030, indicating in five different ways the overall improvement in air quality.
On a population-weighted basis, the average modeled future-year 8-hour ozone design values are projected to decrease by 0.47 ppb in 2017 and 1.55 ppb in 2030.  On a population-weighted basis design values in those counties that are projected to be above the 2008 ozone standard in 2017 and 2030 are projected to decrease by 0.30 and 1.62 ppb respectively due to the proposed standards.

Table III-8 Average Change in Projected 8-hour Ozone Design Value in 2017c
Average[a]
Number of U.S. Counties
2020 Population[b]
Change in 2017 design value (ppb)
All
676

238,026,106

-0.50
All, population-weighted

-0.47
Counties whose 2005 base year is violating the 2008 8-hour ozone standard
393

176,910,535

-0.56
Counties whose 2005 base year is violating the 2008 8-hour ozone standard, population-weighted

-0.51
Counties whose 2005 base year is within 10 percent of the 2008 8-hour ozone standard
201

40,516,171

-0.47
Counties whose 2005 base year is within 10 percent of the 2008 8-hour ozone standard, population-weighted

-0.42
Counties whose 2017 control case is violating the 2008 8-hour ozone standard
37

47,659,433

-0.35
Counties whose 2017 control case is violating the 2008 8-hour ozone standard, population-weighted

-0.30
Counties whose 2017 control case is within 10 percent of the 2008 8-hour ozone standard
124

68,625,934

-0.51
Counties whose 2017 control case is within 10 percent of the 2008 8-hour ozone standard, population-weighted

-0.49
  [a] Averages are over counties with 2005 modeled design values
  [b] Population numbers based on Woods & Poole data.  Woods & Poole Economics, Inc. 2001.  Population by Single Year of Age CD.
  c This analysis assumed emissions reductions from Tier 3 vehicle standards would occur in all states and did not account for emission reductions associated with LEV III vehicle standards in California and other states that have subsequently adopted it.  The analysis for the final rule will account for LEV III vehicle standards.

Table III-9 Average Change in Projected 8-hour Ozone Design Value in 2030c
Average[a]
Number of U.S. Counties
2030 Population[b]
Change in 2030 design value (ppb)
All
676

261,497,900

-1.35
All, population-weighted

-1.55
Counties whose 2005 base year is violating the 2008 8-hour ozone standard
393

194,118,748

-1.54
Counties whose 2005 base year is violating the 2008 8-hour ozone standard, population-weighted

-1.69
Counties whose 2005 base year is within 10 percent of the 2008 8-hour ozone standard
201

44,436,103

-1.18
Counties whose 2005 base year is within 10 percent of the 2008 8-hour ozone standard, population-weighted

-1.25
Counties whose 2030 control case is violating the 2008 8-hour ozone standard
10

30,619,714

-1.49
Counties whose 2030 control case is violating the 2008 8-hour ozone standard, population-weighted

-1.62
Counties whose 2030 control case is within 10 percent of the 2008 8-hour ozone standard
40

21,541,863

-1.37
Counties whose 2030 control case is within 10 percent of the 2008 8-hour ozone standard, population-weighted

-1.50
  [a] Averages are over counties with 2005 modeled design values
  [b] Population numbers based on Woods & Poole data.  Woods & Poole Economics, Inc. 2001.  Population by Single Year of Age CD.
  c This analysis assumed emissions reductions from Tier 3 vehicle standards would occur in all states and did not account for emission reductions associated with LEV III vehicle standards in California and other states that have subsequently adopted it.  The analysis for the final rule will account for LEV III vehicle standards.

Particulate Matter
The air quality modeling conducted for this proposal projects that in 2030, with all current controls in effect but excluding the emissions changes expected to occur as a result of this proposal or any other additional controls, at least 14 counties, with a projected population of over 28 million people, would have projected design values above the level of the annual standard of 12 ug/m3 and at least 21 counties, with a projected population of over 31 million people, would have projected design values above the level of the 24-hour standard of 35 ug/m3.  Since the emission changes from this proposed action would go into effect during the period when some areas are still working to attain the PM2.5 NAAQS, the projected emission changes would be useful to state and local agencies in their effort to attain and maintain the PM2.5 standard.
 The proposed rule would reduce 24-hour and annual PM2.5 design values in 2030.  Annual PM2.5 design values in the majority of modeled counties would decrease by between 0.01 and 0.05 ug/m3 and in over 100 additional counties design values are projected to decrease by greater than 0.05 ug/m3.   The projected population-weighted average design value concentration without the proposed rule is 9.5 ug/m3 in 2030.  The average modeled future-year annual PM2.5 design values in 2030 decrease by 0.06 ug/m3 on a population-weighted basis.  Design values in those counties that are projected to be above the annual PM2.5 standard in 2030 decrease even more, by 0.11 ug/m3 on a population-weighted basis, due to the proposed standards.  In addition, the average modeled future-year 24-hour PM2.5 design values in 2030 decrease by 0.20 ug/m3 on a population-weighted basis.  The projected population-weighted average design value concentration without the proposed rule is 24.3 ug/m3 in 2030.  The decreases in PM2.5 design values are likely due to the projected tailpipe reductions in primary PM2.5, NOX and VOCs.  The proposed rule has little impact on PM2.5 design values for the majority of counties in 2017, although our air quality modeling underestimated the PM decreases that would result from this proposal (see Section <IP_ADDRESS> of the draft RIA for more detail).
Table III-10 and Table III-11 present the average change in 2030 annual and 24-hour PM2.5 design values for: (1) all counties with 2005 baseline design values, (2) counties with 2005 baseline design values that exceeded the PM2.5 standard, (3) counties with 2005 baseline design values that did not exceed the standard, but were within 10 percent of it, (4) counties with 2030 design values that exceeded the PM2.5 standard, and (5) counties with 2030 design values that did not exceed the standard, but were within 10 percent of it.  Counties within 10 percent of the standard are intended to reflect counties that although not violating the standards, will also be impacted by changes in PM2.5 as they work to ensure long-term maintenance of the annual and/or 24-hour PM2.5 NAAQS.  All of these metrics show a decrease in 2030.  On a population-weighted basis, there is a 0.06 ug/m3 decrease in the average modeled future-year annual PM2.5 design values in 2030 and a decrease of 0.11 ug/m3 in those counties that are projected to be above the annual PM2.5 standard in 2030.  In addition, the average population-weighted modeled future-year 24-hour PM2.5 design values are projected to decrease by 0.20 ug/m3 due to the proposed standards and design values in those counties that are projected to be above the 24-hour PM2.5 standard in 2030 would decrease by 0.32 ug/m3.

Table III-10 Average Change in Projected Annual PM2.5 Design Values in 2030c
Average[a]
Number of U.S. Counties
2030 Population
Change in 2030 design value (g/m3)
All
                                      576
                                     247,415,381
                                     -0.05
All, population-weighted

                                     -0.06
Counties whose 2005 base year is violating the annual PM2.5 standard
                                      314
                                    152,109,569
                                     -0.05
Counties whose 2005 base year is violating the annual PM2.5  standard, population-weighted

                                     -0.07
Counties whose 2005 base year is within 10 percent of the annual PM2.5  standard
                                      83
                                     31,863,376
                                     -0.05
Counties whose 2005 base year is within 10 percent of the annual PM2.5  standard, population-weighted

                                     -0.05
Counties whose 2030 control case is violating the annual PM2.5  standardd
                                      14
                                     28,624,758
                                     -0.11
Counties whose 2030 control case is violating the annual PM2.5  standard, population-weightedd

                                     -0.10
Counties whose 2030 control case is within 10 percent of the annual PM2.5  standard
                                      28
                                     23,840,272
                                     -0.07
Counties whose 2030 control case is within 10 percent of the annual PM2.5  standard, population-weighted

                                     -0.09
  [a] Averages are over counties with 2005 modeled design values
  [b] Population numbers based on Woods & Poole data.  Woods & Poole Economics, Inc. 2001.  Population by Single Year of Age CD.
  c This analysis assumed emissions reductions from Tier 3 vehicle standards would occur in all states and did not account for emission reductions associated with LEV III vehicle standards in California and other states that have subsequently adopted it.  The analysis for the final rule will account for LEV III vehicle standards.
  d Eight of these counties are in California, see Table 7-35 in the DRIA.

Table III-11 Average Change in Projected 24-hour PM2.5 Design Values in 2030c
Average[a]
Number of U.S. Counties
2030 Population[b]
Change in 2030 design value (ug/m3)
All
569
245,111,480
-0.16
All, population-weighted

-0.20
Counties whose 2005 base year is violating the 2006 24-hour PM2.5 standard
108
91,474,036
-0.29
Counties whose 2005 base year is violating the 2006 24-hour PM2.5 standard, population-weighted

-0.27
Counties whose 2005 base year is within 10 percent of the 2006 24-hour PM2.5 standard
140
53,990,060
-0.18
Counties whose 2005 base year is within 10 percent of the 2006 24-hour PM2.5 standard, population-weighted

-0.21
Counties whose 2030 control case is violating the 2006 24-hour PM2.5 standard[d]
21
31,002,272
-0.50
Counties whose 2030 control case is violating the 2006 24-hour PM2.5 standard, population-weighted[d]

-0.32
Counties whose 2030 control case is within 10 percent of the 2006 24-hour PM2.5 standard
7
4,212,913
-0.37
Counties whose 2030 control case is within 10 percent of the 2006 24-hour PM2.5 standard, population-weighted

-0.50
  [a] Averages are over counties with 2005 modeled design values
  [b] Population numbers based on Woods & Poole data.  Woods & Poole Economics, Inc. 2001.  Population by Single Year of Age CD.
  c This analysis assumed emissions reductions from Tier 3 vehicle standards would occur in all states and did not account for emission reductions associated with LEV III vehicle standards in California and other states that have subsequently adopted it.  The analysis for the final rule will account for LEV III vehicle standards.
  d Eleven of these counties are in California, see Table 7-37 in the DRIA.

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 proposal, 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 proposal is available in Section 7.2.1 of the draft RIA.
Air Toxics
Our modeling indicates that the impacts of proposed Tier 3 standards include generally small decreases in ambient concentrations of air toxics, especially in urban areas, with notable nationwide reductions in benzene.  Although reductions are greater in 2030 (when Tier 3 cars and trucks would contribute nearly 90 percent of fleet-wide vehicle miles travelled) than in 2017(the first year of the proposed program), our modeling projects there would be small immediate reductions in ambient concentrations of air toxics due to the proposed sulfur controls in 2017.  Furthermore, the full reduction of the vehicle program would be realized after 2030, when the fleet has fully turned over to Tier 3 vehicles.  Air toxics pollutants dominated by primary emissions (or a decay product of a directly emitted pollutant) have the largest impacts, rather than air toxics that primarily result from photochemical transformation.  Specifically, in 2030, our modeling projects that the proposal would 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, with 1,3-butadiene decreases of at least 0.005 μg/m³ in urban areas.  These toxics are national risk drivers and the reductions in ambient concentrations from this proposed rule would 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 5 percent in 2030 as a result of the proposal.  Decreases in ethanol concentrations are expected due to reductions in VOC as a result of the proposed standards. Changes in ambient acetaldehyde concentrations are generally less than 1 percent across the U.S., although the proposal may decrease acetaldehyde concentrations in some urban areas by 1 to 2.5 percent in 2030.
Although the reductions in ambient air toxics concentrations expected from the proposed Tier 3 standards are generally small, they are projected to benefit the majority of the U.S. population.  As shown in Table III-12, over 80 percent of the total U.S. population is projected to experience a decrease in ambient benzene and acrolein concentrations of at least 2.5 percent, with more than 90 percent of the populations projected to experience 1,3-butadiene concentrations of similar magnitude.  Over 80 percent of the U.S population is projected to experience at least a 1 percent decrease in ambient ethanol concentrations, and over 60 percent would experience a similar decrease in ambient formaldehyde concentrations with the proposed standards.
Table III-12 Percent of Total Population Experiencing Changes in Annual Ambient Concentrations of Toxic Pollutants in 2030 as a Result of the Proposed Standardsa
                                PERCENT CHANGE
                                    BENZENE
                                   ACROLEIN
                                 1,3-Butadiene
                                 Formaldehyde
                                    Ethanol
                                 ACETALDEHYDE
                                    <= -50

                              > -50 to <= -25

                                     0.1%

                              > -25 to <= -10
                                     2.8%
                                     0.7%
                                     56.8%

                              > -10 to <= -5
                                     23.7%
                                     36.8%
                                     30.8%

                              > -5 to <= -2.5
                                     54.5%
                                     43.7%
                                     7.1%
                                     1.2%
                                     33.0%
                                     0.3%
                              > -2.5 to <= -1
                                     17.7%
                                     15.3%
                                     3.4%
                                     63.2%
                                     55.3%
                                     25.1%
                               > -1 to < 1
                                     1.4%
                                     3.5%
                                     1.7%
                                     35.6%
                                     11.6%
                                     74.6%
                               >= 1 to < 2.5

                                     0.0%

                               >= 2.5  to < 5

                               >= 5 to < 10

                               >= 10 to < 25

                               >= 25 to < 50

                                    >= 50

[a] This analysis assumed emissions reductions from Tier 3 vehicle standards would occur in all states and did not account for emission reductions associated with LEV III vehicle standards in California and other states that have subsequently adopted it.  The analysis for the final rule will account for LEV III vehicle standards.

Visibility
Air quality modeling conducted for this proposed action was used to project visibility conditions in 139 mandatory class I federal areas across the U.S.  The results show that in 2030 all the modeled areas would continue to have annual average deciview levels above background and the proposed rule would improve visibility in all these areas.  The average visibility at all modeled mandatory class I federal areas on the 20 percent worst days is projected to improve by 0.04 deciviews, or 0.28 percent, in 2030.  Section <IP_ADDRESS> of the draft RIA contains more detail on the visibility portion of the air quality modeling.
Nitrogen and Sulfur Deposition
Our air quality modeling projects substantial decreases in nitrogen deposition as a result of the proposed standards.  The standards would result in annual percent decreases of greater than 5 percent in most major urban areas and greater than 7 percent in a few areas.  In addition, smaller decreases, in the 1 to 1.5 percent range, would occur over most of the rest of the country.  The impacts of the proposed standards on sulfur deposition are smaller, ranging from no change to decreases of over 2 percent in some areas.  For maps of 2030 deposition impacts and additional information on these impacts see Section <IP_ADDRESS> of the draft RIA.
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.
 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.[,][,][,]  Household-level stressors such as parental smoking and relationship stress also may increase susceptibility to the adverse effects of air pollution.[,]
 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 [,][,][,][,][,]
  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."  We analyzed whether there were differences between houses and householders in such locations and those not in them.  We found that houses with a nonwhite householder were 22-34 percent more likely to be located within 300 feet of these large transportation facilities, while houses 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.
 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.  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.  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.
 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 reduction of near-roadway concentrations of many pollutants, discussed above, is likely to help in mitigating this disparity in racial, ethnic, and economically-based exposures.
Proposed Vehicle Emissions Program
In the more than 10 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 key exhaust emissions, especially hydrocarbons, nitrogen oxides (NOX), and particulate matter (PM).  The California LEV II program has been instrumental in the continuous technology improvements by requiring year after year reductions in fleet average hydrocarbon levels in addition to requiring the introduction of advanced exhaust and evaporative emission controls in partial zero emission vehicles (PZEVs).  This progress in vehicle technology has made it possible for manufacturers to achieve emission reductions well beyond the requirements of the Tier 2 program if gasoline sulfur levels are lowered further.
Extensive data from existing Tier 2 (and California LEV II) vehicles show the opportunity for further reductions, especially in 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 vehicle and control systems age.  For these reasons, we are proposing more stringent standards designed to reduce emissions, primarily non-methane organic gases (NMOG), NOX, and PM from new vehicles.  As discussed in detail below and in the draft RIA, we have concluded that, in conjunction with the reductions in fuel sulfur proposed in this action, the proposed vehicle emissions standards are feasible and cost-effective across the fleet in the proposed timeframe.  We believe that simultaneous reductions in fuel sulfur would be a key factor in enabling the entire fleet of light-duty vehicles to meet the proposed emission standards in-use, throughout the life of the vehicle.
This section describes in detail the proposed 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 heavy-duty vehicles (HDVs).  Sections IV.A and B discuss the proposed tailpipe emission standards and time lines, and other provisions for new light-duty vehicles and MDPVs and for new heavy-duty vehicles up to 14,000 lbs Gross Vehicle Weight Rating (GVWR).  Section IV.C presents the proposed evaporative emissions standards and program as well as proposed improvements to the existing Onboard Diagnostics (OBD) provisions.  In Section IV.D, we describe our proposal to update our federal certification fuel to better match today's in-use fuel and to be forward-looking with respect to potential future gasoline ethanol and sulfur content.  We also discuss in this section proposed compliance flexibilities for small companies and small-volume manufacturers (IV.E) and test procedure and other compliance provisions (IV.F).
Tailpipe Emission Standards for Light-Duty Vehicles, Light-Duty Trucks, and Medium-Duty Passenger Vehicles
Overview
The proposed Tier 3 standards are very similar in structure to those in the Tier 2 program.  As with the Tier 2 program, the proposed standards would apply to all LDVs and LDTs below 8,500 lbs GVWR, and MDPVs (8,500 to 10,000 lbs GVWR).  (We discuss the proposed standards for heavy-duty vehicles up to 14,000 lbs GVWR other than MDPVs, in Section IV.B below.)  Also as with Tier 2, manufacturers would select from several "bins" of emission standards such that the average of their vehicles' emissions complies with the proposed fleet-average standards.
In the discussions of the various elements of our proposed program for light- and heavy-duty vehicles throughout this preamble, we describe how the provisions would be consistent with the California Air Resources Board (CARB) LEV III program.   Auto manufacturers have stressed to us the importance of their being able to design and produce a single fleet of vehicles in all 50 states that would comply with requirements under the Tier 3 program and the LEV III program, as well as greenhouse gas/CAFE requirements in the same timeframe.  Consistency among the federal and California programs means that special versions of vehicles with different emission control hardware and calibrations would not be necessary for different geographic areas.  This would allow manufacturers to avoid the additional costs of parallel design, development, calibration, and manufacturing.  Consistency among programs would also eliminate the need to supply aftermarket parts for repair of multiple versions of a vehicle.  We believe that the most cost-effective national program will result from close coordination of CARB LEV III and federal Tier 3 program elements and their implementation.  To that end, we worked closely with CARB and the vehicle manufacturers, both individually and through their trade associations, to align the two programs.
The Tier 3 program we are proposing is identical to LEV III in most major respects for both light-duty and heavy-duty vehicle exhaust and evaporative emissions requirements, as discussed in detail below in this section.  The levels and the timing of the light-duty and heavy-duty declining fleet-average NMOG+NOx standards that we are proposing would be identical to those in LEV III.  Also, the Tier 3 emissions bins to which manufacturers would certify individual vehicle models in order to comply with the average standards, for both light- and heavy-duty vehicles, would also be identical to those in LEV III.  Similarly, the proposed Tier 3 per-vehicle PM standards match LEV III standards through MY 2024.  In addition, our proposed primary evaporative emissions standards and onboard diagnostics requirements are also identical to the LEV III requirements.
We note there are a few proposed Tier 3 provisions that CARB and EPA understand would be different, for reasons discussed below.  Specifically, these include the LEV III program and our proposed Tier 3 program would have different light-duty PM requirements late in the program (i.e., after MY 2024 (IV.A.3.b.)), would require different test fuels (E10 and E15, respectively (IV.A.3.c)), and only EPA would have an evaporative leak test (IV.C.5.b).  EPA and CARB will continue to work toward additional consistency between our programs whenever practicable as both programs are implemented.  Beyond these three provisions, the differences between the programs would not be major and would exist only in the early transitional years of the Tier 3 program.  These differences would result from the fact that the LEV III requirements begin slightly earlier and that a limited phase-in of some provisions would be necessary for a smooth transition to overall aligned programs.  These temporary differences would include the process for how early compliance credits would be generated and used (e.g., Section IV.A.7.a); how quickly manufacturers would need move toward certifying all of their vehicle models to longer useful-life values (e.g., Section IV.A.7.b) and on the new test fuel (e.g., Section IV.A.7.c); and transitional emissions bins to facilitate the transition from Tier 2 to Tier 3 (IV.A.7.m).  Similarly, the primary Tier 3 evaporative standards would have a brief phase in period, temporarily resulting in requirements that would be slightly different from those in LEV III.
The proposed Tier 3 program is designed primarily to reduce exhaust and evaporative emissions during summer ambient temperature conditions when NMOG, NOX and PM emissions contribute to air quality concerns.  We are not proposing new emission requirements for any vehicle or fuel over the cold temperatures test cycles (i.e., the 20 °F cold CO and NMHC tests).  However, we seek comment on the need for doing so, including vehicles operating on E85 fuel, and on the appropriate form and level for any such cold-temperature requirements.
Summary of Proposed FTP and SFTP Tailpipe Standards
We are proposing a comprehensive program that would address the key pollutants of concern.  We are proposing new standards for the sum of NMOG and NOX emissions, presented as NMOG+NOX, and PM.  As discussed in Section III above, these proposed standards would result in very significant improvements in vehicle emissions from the levels of the Tier 2 program.  For these pollutants, we are proposing standards as measured on test procedures that represent a range of vehicle operation, including the Federal Test Procedure (FTP) and the Supplemental Federal Test Procedure (SFTP).  Unless otherwise specified, the proposed FTP and SFTP standards would apply to vehicles operating on gasoline, diesel, and alternative fuels, including both flexible fuel and dedicated alternative fuel vehicles.
The proposed FTP and SFTP NMOG+NOX standards would be fleet-average standards, meaning that the manufacturer would calculate the average emissions of the vehicles it sells in each model year and compare that average to the applicable standard for that model year.  The proposed fleet average standards for NMOG+NOX evaluated over the FTP are summarized in Table I-1. (For comparison, the average NMOG and NOX standard for the Tier 2 program, when added together, equal 160 mg/mi).  The standards would begin in MY 2017 at a level representing a 46 percent reduction from the current Tier 2 requirements for lighter vehicles and would become increasingly stringent, culminating in an 81 percent reduction in MY 2025.  The proposed FTP NMOG+NOX program includes separate fleet average standards for lighter and heavier vehicles that would converge at 30 milligrams per mile (mg/mi) in MY 2025 and later.[,]
Manufacturers would determine their fleet average FTP NMOG+NOX emission values based on the per-vehicle "bin standards" to which they certified each vehicle model.  As with the Tier 2 program, manufacturers would be free to choose to certify vehicles to any of the bins, so long as the sales-weighted average of the NMOG+NOX values from the selected bins met the fleet average standard for that model year.  Table IV-1 presents the per-vehicle bin standards. Similarly, the proposed fleet average NMOG+NOX standards measured over the SFTP are summarized in Table I-2.  The proposed SFTP NMOG+NOX fleet average standards decline from MY 2017 until MY 2025.  In this case, the same standards would apply to both lighter and heavier vehicles.  In MY 2025, the SFTP NMOG+NOX standard would reach its fully phased-in fleet average level of 50 mg/mi. We are also proposing PM standards as part of this Tier 3 program.  The proposed PM standards would apply to each vehicle separately (i.e., not as a fleet average).  Also, in contrast to the declining NMOG+NOX standards, the proposed certification PM standard on the FTP is 3 mg/mi for all vehicles and for all model years, but phasing in beginning in MY 2017 for vehicles at or below 6,000 lbs GVWR and in MY 2018 for vehicles above 6,000 lbs GVWR.  Based on EPA and CARB test programs, most current light duty vehicles are already performing at or below this level.  However, some vehicles are emitting above this level, due to such factors as combustion chamber designs, and fuel and oil consumption controls that are not optimized for low PM emissions.  The intent of the proposed 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 proposed program also 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 described in more detail below.  As presented in Table I-3, for vehicles at or below 6000 lbs GVWR, these FTP certification and in-use standards would be phased in beginning with a requirement that at least 20 percent of a company's U.S. sales meet the standards in MY 2017 and reaching a 100 percent compliance requirement in MY 2021.  The proposed standards represent a significant numerical reduction from the Tier 2 PM emission standards of 10 mg/mi for light-duty vehicles. Finally, the proposed Tier 3 program includes PM standards evaluated over the US06 cycle (a component of the SFTP test, discussed further below) at a level of 10 mg/mi for vehicles at or below 6,000 lbs GVWR and 20 mg/mi for heavier vehicles.  We are proposing separate standards for different sizes of vehicles because PM generation typically increases when vehicles are carrying heavier loads and/or when they are pulling trailers.  The US06 PM standards would phase in on the same schedule as the FTP PM standards, reaching 100 percent of each company's U.S. sales by MY 2022.  These US06 standards would apply to the same vehicle models that a manufacture chose to certify to the FTP PM standard during the percent phase in period.  PM levels over the US06 are typically higher than the PM emitted over the FTP due to the increased load on the vehicle.    As in the case of the FTP PM standards, the intent of the proposed 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 with the FTP PM standard, we propose a separate in-use US06 PM standard during the percent phase-in period of 15 and 25 mg/mi for vehicles of 6000 lbs GVWR and less, and for vehicles above 6,000 lbs GVWR, respectively.
The next subsections describe in more detail the proposed standards, how they would be implemented over time, and the technological approaches that we believe will be available to manufacturers in order to comply.
Proposed FTP Standards
As summarized above, we propose 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).
FTP NMOG+NOX Standards
We propose that the Tier 3 NMOG and NOX standards, both of which are important to reduce ambient ozone concentrations, be expressed in terms of the sum of the two pollutants, or as NMOG+NOX in mg/mi.  This approach contrasts with the Tier 2 standards, which were expressed as separate NMOG and NOX standards.  We believe that the combined standard is appropriate for this proposed program for several reasons.  At the stringent proposed emission levels, combining NMOG and NOX would provide a small amount of compliance flexibility, while at the same time significantly reducing both NMOG and NOX emission levels.  For example, the combined standard would allow a gasoline vehicle manufacturer to have slightly higher NMOG if it were offset by lower NOX, or allow a diesel vehicle manufacturer to have slightly higher NOX if offset by lower NMOG.  This approach still ensures major reductions in both pollutants compared to today's levels.  This is because the very stringent level of the fully phased-in proposed combined standard (30 mg/mi NMOG+NOX) means that even with a degree of allowed trading off of one pollutant for the other, the maximum emissions of either pollutant would need to be well below current levels.  The standards of the California LEV III program would also be expressed as NMOG+NOX; aligning Tier 3 with LEV III in this respect would facilitate an important element of a national program.
We believe that a fully phased-in level for the proposed fleet-average standard of 30 mg/mi is the most stringent level that we could reasonably propose in the context of our proposed 10-ppm average standard for gasoline sulfur.  As discussed in the feasibility Section IV.A.5 below, when necessary margins of compliance are considered, this proposed standard is very close to zero.  We request comment on this level for the proposed standard, as well as the declining standards during the transition years (see Table IV-3 below).  EPA is proposing compliance mechanisms for the new Tier 3 FTP standards that are the same in most respects as those of the Tier 2 program.  Using the Tier 2 approaches as much as possible would streamline the implementation of the program by maintaining most of the compliance processes that manufacturers are familiar with today.
A key compliance mechanism adapted from the Tier 2 program is a "bin" structure for the proposed emission standards.  For these purposes, a bin is a set of several standards that are intended to be complied with as a group.  Thus each Tier 3 bin would have an NMOG+NOX standard and a PM standard, as well as CO and HCHO standards.  A manufacturer choosing to certify a vehicle to a certain bin would need to meet each of that bin's standards for the full useful life of the vehicle.  In this approach, manufacturers could certify vehicles to any of the bins, but they would have to ensure that average NMOG+NOX of the bins to which all of its vehicles were certified met the fleet average standard specific to the vehicle category (i.e., LDV/LDT1 and LDT2/3/4/MDPVs) for that model year.  That is, a manufacturer would comply by ensuring that the sales-weighted average of the NMOG+NOX values of the bins to which each of its vehicle models was certified was lower than the fleet average standard that applied for that model year.
For each proposed bin, we are including CO and HCHO standards at levels intended to prevent new engine and emission control designs that would result in increases in today's CO and HCHO emissions.  The standards are based on the comparable current LEV II and Tier 2 bin standards for these pollutants.  The current standards do not appear to be technology-forcing, and we believe that this would continue to be the case as Tier 3 technologies are developed.
The bin structure that we are proposing for light duty vehicles, light-duty trucks, and MDPVs standards is presented in Table IV-1.
Table IV-1 Proposed FTP Standards for LDVs, LDTs and MDPVs (mg/mi)
Bin
                                   NMOG+ NOX
                                    (mg/mi)
                                     PM[a]
                                    (mg/mi)
                                      CO
                                    (g/mi)
                                     HCHO
                                    (mg/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, we are proposing that the same standards apply to LDVs, LDTs, or MDPVs, regardless of the fuel they use.  That is, vehicles certified to operate on any fuel (e.g., gasoline, diesel fuel, E85, CNG, LNG, hydrogen, and methanol) would all be subject to the same standards.
We propose to maintain the fleet-average approach of the Tier 2 standards.  Unlike Tier 2, the proposed Tier 3 fleet-average standards would decline annually to a fully phased-in level of 30 mg/mi NMOG+NOX.  (The Tier 2 program, after a period of transition, established a single fleet average standard for all model years.)  Specifically, we are proposing NMOG+NOX standards as measured on the FTP that would reduce the combined fleet-average emissions gradually from MY 2017 through 2025, as shown in Table IV-2 below.  Beginning in MY 2017, we propose separate fleet average standards for lighter and heavier vehicles that would both decline annually, converging in MY 2025.  These proposed declining average standards are identical to CARB's LEV III standards.
The declining fleet-average NMOG+NOX standard requirement would begin in 2017 for light-duty vehicles and light-duty trucks with a GVWR up to and including 6,000 lbs and in 2018 for all other light-duty vehicles and light-duty trucks (i.e., those with a GVWR greater than 6,000 lbs).  The standards would apply to the heavier vehicles a year later to facilitate the transition to a 50-state program for all manufacturers. During this transition period, there would be two fleet-average NMOG+NOX standards for each model year, one for LDVs and LDT1s and a second fleet-average standard for all other LDTs (LDT2s, LDT3s, and LDT4s) and for MDPVs.  We are proposing that the fleet-average standards decline in a linear way from MY 2017 through MY 2025, at which point the two fleet-average standards would converge and stabilize for later model years at the same level, 30 mg/mi, as shown in Table IV-2.   Note that these fleet average standards are for LDT2 and larger vehicles, and for LDVs and LDT1s that manufacturers certify to the 150,000 mile useful life value.  Section IV.A.7.b discusses how the Clean Air Act defines the useful life values for certification purposes and how EPA proposes to also provide for certification to slightly lower emissions standards to a useful life value of 120,000 miles, representing a level of stringency that is equivalent to that of the emission standards corresponding to the 150,000 mile useful life, for LDVs and LDT1s.
Table IV-2 Proposed LDV, LDT, and MDPV Fleet Average FTP NMOG+NOX Standards (mg/mi)

                                  Model Year

                                    2017[a]
                                     2018
                                     2019
                                     2020
                                     2021
                                     2022
                                     2023
                                     2024
                                2025 and 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
                                      30
[a] For vehicles above 6,000 lbs GVWR, the fleet average standards would apply beginning in MY 2018.
[b] These proposed standards apply for a 150,000 mile useful life.  Manufacturers could choose to certify all of their LDVs and LDV1s to a useful life of 120,000 miles.  If any of these families are certified to the shorter useful life, a proportionally lower numerical fleet average standard would apply, calculated by multiplying the respective 150,000 mile standard by 0.85 and rounding to the nearest mg.

EPA is also proposing an alternative phase-in of the 30 mg/mi FTP NMOG+NOX standard that would be available if a manufacturer prefers a stable standard and four full years of lead time, as specified in the Clean Air Act for vehicles above 6,000 lbs GVWR.   For MYs 2017 and 2018, a manufacturer would certify vehicles up to 6,000 lbs GVWR to the primary declining FTP fleet average standards, as in the primary program.  Then, beginning in MY 2019, a stable fleet average standard of 30 mg/mi would apply to an increasing percentage of a manufacturer's light-duty vehicles, light-duty trucks, and MDPVs, both up to and above 6,000 lbs GVWR.  The percent phase-in would match the proposed PM percent phase-in schedule, as discussed below  -  specifically 40 percent of sales in MY 2019, 70 percent in MY 2020, and 100 percent in MY 2021 and later model years.  A manufacturer choosing to certify any vehicle to this alternative phase-in would need to use this approach for all its models in MYs 2019 and later; certifying part of its fleet to the declining fleet average after MY 2018 would not be permitted, since the structures of the two approaches, including the early credits provisions of the NMOG+NOx fleet average program, would not be consistent.  A manufacturer certifying to this alternative phase-in would also need to comply with the alternative SFTP NMOG+NOx phase-in and the alternative FTP PM and US06 PM phase-ins as described below.  Vehicles covered by the alternative phase-in programs would be considered "final Tier 3" vehicles and thus would also comply with the Tier 3 certification fuel and full useful life provisions.  EPA requests comment on this alternative phase-in approach as well as on the primary option above.
FTP PM Standards
We also propose new FTP standards for PM emissions, as summarized in Table IV-3 below.  For many years, EPA's focus for mobile source PM was on diesel engine emissions.  In recent years, the very effective controls on PM exhaust emissions that manufacturers have developed for heavy-duty diesel engines have been successfully applied to light-duty diesel engines as well.  At the same time, attention to gasoline engine PM emissions has increased as research has demonstrated that the level of PM from gasoline light duty vehicles is more significant than had been previously thought.
Under typical driving, as simulated by the FTP, the PM emissions of most current-technology gasoline vehicles are fairly low, well below the Tier 2 PM standards.  At the same time we see considerable variation in PM emissions among vehicle models not consistently associated with any specific engine or emission control technology (Section 1.5.1 of the draft RIA).  As a result, we are proposing a new FTP PM standard that is set to ensure that all new vehicles would perform at a level representing what is already being achieved by well-designed Tier 2 emission control technologies.
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, PM control via oxidation of semi-volatile organic compounds from the lubricating oil by catalytic converters is less effective.  We believe that the proposed FTP PM standard can be achieved with improvements to the fuel controls during the cold start without the need for any new technology or hardware.  Improvements in cold-start exhaust catalyst performance for NMOG+NOx control will also reduce emissions of semi-volatile organic PM.  As such, cold start PM levels are relatively independent of vehicle application and therefore we are proposing a single FTP PM standard for all light-duty and MDPV vehicles.  The PM standard level we are proposing would ensure that future PM performance is consistent with current well-performing Tier 2 vehicles.  Unlike the NMOG+NOX FTP standard, the PM standard would not decline over time, since most manufacturers are already producing vehicles that would meet the proposed new standards.
Although we believe it is important that the proposed FTP PM standard apply from the beginning of the Tier 3 program, we are proposing several provisions to provide a degree of flexibility for manufacturers in how many vehicle models would need to meet that standard in the early years of the program.  Manufacturers have raised several issues that we believe these provisions would address.
In meetings with EPA, several manufacturers have expressed concerns about how a PM standard in the range of the proposed 3 mg/mi standard would be implemented.  One concern related to the initial uncertainties about PM emissions performance that will accompany the development of new engine technologies, including those that may be introduced to address the GHG emissions/fuel economy standards that EPA and NHTSA recently finalized for these vehicles.  Also, manufacturers expressed concerns related to the testing of PM on the FTP, particularly about potential updates to the test procedures required to accurately measure PM at very low levels.  Finally, related to the concerns about the new test procedures are the current limitations that exist for some manufacturers regarding the capacity of their test facilities to perform a significant volume of gasoline vehicle PM testing.
For these reasons, we are proposing a percent-of-sales phase-in during the first 5 years of the program to address these concerns.  Beginning in MY 2017 (and in MY 2018 for vehicles over 6,000 lbs GVWR), manufacturers would 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 would need to comply would increase each year, reaching 100 percent in MY 2021.  In addition to this percent phase-in, we are proposing a separate PM standard of 6 mg/mi that would 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 would 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 would likely choose a single large-volume durability group to meet the 2017 requirements, we seek comment on an option to comply with the MY 2017 PM requirements by allowing manufactures to certify 10 percent of all their light-duty vehicle sales in MY 2017 to the new PM standards, including light-duty vehicles over 6,000 lbs GVWR and MDPVs. This approach would be consistent with the CARB LEVIII 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 proposing to limit the number of tests using the new procedures that a manufacturer would need to perform at certification and during in-use testing.  Specifically, manufacturers would 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).  Manufacturers could select which durability groups to test, but would 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 could limit their testing to 50 percent of their low- and high-mileage test vehicles.  Again, manufacturers would need to rotate their vehicle models so that each model would be tested every other year. Overall, we believe that the flexibility that these proposed provisions would provide would facilitate the expeditious implementation of the proposed program, with no significant impact on the potential benefits of the program.
The PM standards that we are proposing are the most stringent technically feasible standards within the implementation timeframe of this proposal.  Although the CARB LEV III program includes a 1 mg/mi standard which will begin phasing in starting in MY 2025, they acknowledge that there is a need for continuing PM measurement method development prior to implementing this standard.  In order for EPA to propose a standard at this level, there must be established methods to reliably and consistently measure PM below that standard, for compliance purposes.
We request comment on all of the proposed FTP standards, their structure, and their implementation schedules.
Table IV-3  Summary of Proposed FTP Standards

                                Program Element

                                     Units
                                  Model Year
                                     Notes

2017[a]
2018
2019
2020
2021
2022
2023

NMOG+NOX Standard
(fleet average)
                                     mg/mi
      Per declining fleet average for cars and trucks (see Table IV-2)[b]
PM Standards

Phase-in
                                       %
                                      20
                                      20
                                      40
                                      70
                                      100
                                      100
                                      100

FTP
Certification
                                     mg/mi
                                       3
                                       3
                                       3
                                       3
                                       3
                                       3
                                       3
                                    Note c

In-use
                                     mg/mi
                                       6
                                       6
                                       6
                                       6
                                       6
                                       3
                                       3
                                    Note d
[a] For vehicles above 6,000 lbs GVWR, the proposed FTP PM would apply beginning in MY 2018.
b The percent phase-in would not apply to the declining fleet average standards.
[c] Manufacturers would be required to test 25 percent of each model year's durability groups, minimum of 2.
[d] Manufacturers would be required to test 50 percent of their low and high mileage in-use vehicles.
 As with the proposed FTP NMOG+NOX standards, EPA is also proposing an alternative phase-in of the 3 mg/mi FTP PM standard that would be available if a manufacturer prefers 4 full years of lead time for vehicles above 6,000 lbs GVWR.  A manufacturer that chooses the alternative phase-in for the FTP NMOG+NOX program above could also postpone the beginning of the phase-in for PM compliance for vehicles above 6,000 lbs GVWR until MY 2019.  For MYs 2017 and 2018, a manufacturer would certify vehicles up to 6,000 lbs GVWR to the 3 mg/mi FTP PM standard (and have a 6 mg/mi in-use PM standard) for 20 percent of its sales in each of those years, as with the primary PM percent phase-in schedule.  Then, for MYs 2019 and later, it would comply with the 3 mg/mi (and 6 mg/mi in-use) PM standards for their LDVs, LDTs, and MDPVs, both up to and above 6,000 lbs GVWR.  For MYs 2019 and 2020 (i.e., before the phase-in is fully implemented in MY 2021), manufacturers choosing this alternative would be required to meet the PM standard on the same segment of their fleet vehicles being used to meet the NMOG+ NOX fleet average standard, and at the applicable phase-in percentage of sales for the given model year.  Manufacturers certifying to the alternative PM phase-in standard would also need to comply with the alternative US06 PM phase-in as described below, as well as the NMOG+ NOX FTP and SFTP phase-ins.  EPA requests comment on this alternative phase-in approach as well as on the primary PM phase-in option above.
Proposed SFTP Standards
In addition to the proposed FTP standards, we are proposing NMOG+NOX and PM standards as measured on the SFTP.  The SFTP (and specifically the US06 component of the test) is designed to simulate higher speeds and higher acceleration rates (and thus higher loads) when substantially more heat can be generated during the combustion process.  It is during these kinds of operation that engines can go into a fuel "enrichment" mode, where 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.  To reduce emissions caused by excessive enrichment, we are proposing new SFTP standards.  Further, as described in Section IV.A.4.c below, we are proposing limitations on the magnitude of enrichment that could be commanded by the vehicle operator.  We describe the proposed SFTP standards in the following paragraphs.
We are also proposing an SFTP composite CO standard of 4.2 g/mi for all model years 2017 (or 2018) 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.
SFTP NMOG+NOX Standards
We have reviewed certification and in-use NMOG and NOX data on a wide range of recent vehicles as tested on the US06 cycle.  See Chapter 1 of the draft RIA for an analysis of this data.  It is clear that most current vehicles are generally avoiding significant enrichment events during high-load operation and thus achieve relatively low NMOG+NOX emissions on the US06 test.  The data shows that with minor (if any) improvements to engine calibrations and with no significant loss of performance, manufacturers are able to essentially eliminate enrichment events and their emissions consequences.  Thus, as presented in Table IV-5 below, we are proposing new composite SFTP standards for NMOG+NOX at levels that would be more stringent than those required by the existing Tier 2 program.  We believe that the new standards would require emission performance at levels currently achieved today by most vehicles under high-load operation, and we do not believe that significant additional reductions would result from SFTP standards more stringent than the proposed 50 mg/mi fully phased-in level.  The SFTP emissions value for certification of gaseous pollutants would 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.
We believe that the proposed standards could be more challenging in the early years of the program.  Thus, we propose a declining fleet average standard that would become increasingly stringent from MY 2017 to MY 2025.  Manufacturers would comply with a declining NMOG+NOX fleet-average SFTP standard for each year beginning in MY 2017 (MY 2018 for vehicles over 6000 lbs GVWR) and culminating for MY 2025 and later with a fleet-average standard of 50 mg/mi.
To provide flexibility in meeting the fleet-average standards, manufacturers would determine for themselves what the specific SFTP composite standard would be for an 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 would choose any composite NMOG+NOX standard, up to 180 mg/mi, in even 10 mg/mi increments.  The manufacturer would 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 proposed declining fleet-average SFTP NMOG+NOX standards.
 As with the proposed FTP NMOG+ NOX and PM standards, EPA is also proposing an alternative phase-in of the 50 mg/mi SFTP NMOG+ NOX standard that would be available if a manufacturer prefers a stable standard and four full years of lead time for vehicles above 6,000 lbs GVWR.   For MYs 2017 and 2018, a manufacturer would certify vehicles up to 6,000 lbs GVWR to the primary SFTP declining fleet average standards, as in the primary program.  Then, beginning in MY 2019, a stable fleet average standard of 50 mg/mi would apply to an increasing percentage of a manufacturer's light-duty vehicles, light-duty trucks, and MDPVs, both up to and above 6,000 lbs GVWR.  The percent phase-in would match the proposed PM percent phase-in schedule, as discussed below.  A manufacturer certifying to this alternative phase-in would also need to comply with the alternative FTP NMOG+ NOX phase-in and the alternative FTP PM and US06 PM phase-ins, as described elsewhere in this section.  EPA requests comment on this alternative phase-in approach as well as on the primary option above.
US06 PM Standards
Our proposed approach to addressing PM emissions on the US06 test (a component of the composite SFTP standard) is somewhat different from the SFTP standards that we are proposing for NMOG and NOX emissions.  In the case of PM, US06 data on recent vehicles shows that current gasoline vehicles can have very low PM emissions, but US06 PM emission levels vary depending on many factors.  In some cases, manufacturer emission control strategies that are sensitive to variations in operating conditions (e.g., variation due to driver behavior or automatic transmission shift points) appear to result in very low PM levels during some tests and yet higher PM on other tests on the same vehicle when driven slightly differently.  We also believe that some of the observed high PM emissions may be partly due to increasing oil consumption in vehicles as they age, especially under higher-load conditions or hard closed-throttle deceleration conditions.  Thus, we now believe that more focus on vehicles as they age is important.
We have designed the proposed US06 PM standards in light of all of these factors, which relate to PM emission formation under relatively extreme driving conditions.  For these standards, we are proposing to focus on the US06 cycle component of the composite SFTP, since most of our concern about PM formation and sensitivity of engine controls arises from high-speed, high-load driving conditions.  Similarly, the quantity of PM emissions from warmed-up engines is closely related to engine load, since the higher rate of fuel consumption results in more opportunities for PM to form.  For this reason, we propose that heavier vehicles, which face high-load conditions more frequently than lighter vehicles, comply with a higher US06 standard and lighter vehicles comply with a lower standard.  The proposed US06 PM standard would be 10 mg/mi for vehicles at or below 6,000 lbs GVWR and 20 mg/mi for heavier vehicles.
EPA is seeking comment on the use of vehicle weight to establish separate US06 PM standards for cars and trucks.  The data presented in Chapter 1 of the draft RIA demonstrate that today's heavier vehicles are already achieving PM emission levels well below our proposed 20 mg/mi standard and are approximately equivalent to the performance of lighter vehicles.  According to our data, manufacturers appear to be controlling PM emissions in heavier vehicles over severe duty cycles.  Thus, EPA seeks comment on the proposed US06 PM standards in general, including whether EPA should adopt a common US06 standard of 10 mg/mi for all light-duty vehicles.
As is the case for the proposed FTP PM standards, we are proposing a single per-vehicle maximum standard to apply in each model year, with an allowable percentage phase-in schedule identical to the FTP PM phase-in.
Finally, as with the FTP PM standard (and for the same reasons), we propose a slightly less stringent in-use US06 PM standard that would apply during the percent phase-in period only.  The proposed in-use SFTP PM standards would be 15 mg/mi for vehicles at or below 6,000 lbs GVWR and 25 mg/mi for heavier vehicles.
As with the proposed FTP and SFTP NMOG+ NOX standards and FTP PM standards, EPA is also proposing an alternative phase-in of the 20 mg/mi PM standard as measured on the US06 cycle, that would be available if a manufacturer prefers 4 full years of lead time for vehicles above 6,000 lbs GVWR.  A manufacturer that chooses the alternative phase-in for the FTP NMOG+ NOX program above could also postpone the beginning of the phase-in for US06 PM compliance for vehicles above 6,000 lbs GVWR until MY 2019.  For MYs 2017 and 2018, a manufacturer would certify vehicles up to 6,000 lbs GVWR to the 10 mg/mi FTP PM standard (and have a 15 mg/mi in-use standard) for 20 percent of its sales in each of those years, as with the primary PM percent phase-in schedule.  Then, for MYs 2019 and later, it would comply with the respective standards for vehicles up to and above 6,000 lbs GVWR for their LDVs, LDTs, and MDPVs (i.e., 10 mg/mi and 15 mg/mi (in-use) for vehicles up to 6,000 lbs GVWR, and 20 mg/mi and 25 mg/mi (in-use) for vehicles above 6,000 lbs GVWR.)  For MYs 2019 and 2020, manufacturers choosing this alternative would be required to meet both the FTP PM and the US06 PM standards on the same segment of their fleet vehicles being used to meet the 30 mg/mi fleet average NMOG+ NOX standards, at the applicable percent phase-in requirement for the given model year.  Manufacturers certifying to the alternative US06 PM phase-in standard would also need to comply with the alternative FTP PM phase-in as described above, as well as the NMOG+ NOX FTP and SFTP phase-ins.  EPA requests comment on this alternative phase-in approach as well as on the primary US06 phase-in option above.
All of the proposed SFTP/US06 standards are shown in Table IV-4 and Table IV-5.
Table IV-4 Proposed LD and MDPV SFTP Composite Fleet Average Standards

                                  Model Year

                                     2017
                                     2018
                                     2019
                                     2020
                                     2021
                                     2022
                                     2023
                                     2024
                                2025 and later
                              NMOG + NOX (mg/mi)
                                    103[a]
                                      97
                                      90
                                      83
                                      77
                                      70
                                      63
                                      57
                                      50
                                   CO (g/mi)
                                     4.2 a
[a] For vehicles above 6,000 lbs GVWR, the NMOG+NOX and CO standards would apply beginning in MY 2018.
Table IV-5 Summary of Proposed SFTP Standards

                                Program Element

Units
                                  Model Year
                                     Notes

2017[a]
2018
2019
2020
2021
2022
2023

NMOG+NOX Standard
(fleet average)
                                     mg/mi
      Per declining fleet average for cars and trucks (see Table IV-4)[b]
PM Standards

Phase-in
                                       %