Additional EPA Response to February 13 Comments from Interagency Review

EPA Proposed Rule, “Control of Air Pollution from Motor Vehicles:

Tier 3 Motor Vehicle Emission and Fuel Standards,” RIN 2060-AQ86

The February 13 comments asked about what analysis could be done in the short term to 

address OMB’s interest in better understanding the effects of the proposed Tier 3 fuel sulfur 

standards in isolation of the proposed Tier 3 vehicle standards.

As we noted in our prior response, we analyzed the combined fuel and vehicle program, 

in keeping with the fundamental principles of the Tier 3 program: that vehicles and fuels should 

be analyzed as an integrated system, as has been successfully done in the mobile source emission 

control program for over a decade; and there should be a harmonized national vehicle program 

that establishes a comprehensive approach to regulating motor vehicles (both greenhouse gases 

and non-greenhouse gases), as requested by the Presidential Memo of May 2010.

As described in detail in the draft proposal and in the scientific literature, there is a firstorder relationship between fuel sulfur content and the efficiency of modern three-way catalytic 

converters. The Tier 3 proposal addresses the stringency of exhaust gas standards and fuel sulfur 

level as a system because that is what the scientific literature tells us—the two are strongly 

linked.

With respect to the harmonized national program goal, the Administration has informed 

EPA in the past several years that development of federal vehicle standards that are closely

coordinated with standards adopted by the States is critically important for the automotive 

industry to provide the opportunity for a nationally harmonized set of standards. The proposed 

Tier 3 combined fuel sulfur and vehicle standards are designed to both significantly reduce 

emissions to protect public health and welfare and to enable closely coordinated national and 

state vehicle standards.

While it is not possible to identify the air quality impacts, health effects, or benefits of a 

fuel sulfur program that would be independent of a vehicle program, the proposal contains a 

significant amount of analysis that distinguishes the impacts of fuel sulfur on the existing fleet 

(pre-Tier 3) from the impacts of the vehicle and fuel sulfur standards for new Tier 3 vehicles.

For example, Section III.B. of the preamble presents these emission impacts both in total and 

separately, as excerpted below.

Table III-2 Projected NOX Reductions from Tier 3 Program (Annual U.S. Tons)

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%

Table III-3 Projected VOC Reductions from Tier 3 Program (Annual U.S. Tons)

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%

Tables III-2 and III-3 from the preamble show that in 2017, the impact of fuel sulfur standards on 

the existing fleet of Tier 2 and pre-Tier 2 vehicles is quite significant in terms of NOx and VOC 

reductions. These same tables show that when combined with the proposed Tier 3 vehicle 

standards and significant vehicle fleet turn-over to Tier 3 vehicles by 2030, the impact of both 

Tier 3 fuel sulfur standards and Tier 3 vehicle standards is also significant in terms of actual 

projected emissions reductions. Table III-4 shows the impacts in 2017 and 2030 on carbon 

monoxide emissions.

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%

In addition to the impacts of fuel sulfur standards alone on the pre-Tier 3 fleet and 

combined fuel sulfur standards and vehicle standards for the Tier 3 fleet presented in Tables III-2 

through III-4 of the preamble, EPA has also conducted air quality modeling for 2017 in order to 

understand the immediate impacts of the Tier 3 proposal. The air quality impacts in 2017 are 

mostly due to the impact of the fuel sulfur program on the existing fleet, reflecting the 

corresponding reduction in emissions. 
The proposal would meaningfully reduce ozone concentrations as early as 2017 (the first 

year of the program), and even more significantly in 2030. We also project that the Tier 3 

standards would reduce ambient PM2.5 concentrations. On a nationwide, population–weighted 

average basis the Tier 3 standards are projected to reduce ozone and 24-hour PM2.5 design values 

by 0.47 ppb and 0.01 ug/m3in 2017 and by 1.55 ppb and 0.14 ug/m3in 2030. These air quality

modeling results are presented in detail in preamble Section III.C. and RIA Chapter 7. Finally, 

we performed an illustrative analysis of monetized impacts associated with the proposal in 2017 

(preamble Section VIII.E and RIA Chapter 8.1.4).

The proposal package also presents the costs of the vehicle and sulfur programs both 

separately and combined, for both 2017 and 2030. For example, the RIA Executive Summary

presents the following tables. (Similar material is also presented in preamble Section VII and 

RIA Chapters 2, 5, and 8).

Table ES-1 Annual Vehicle Technology Costs, 2010$

Year Vehicle Exhaust 

Emission Control 

Costs

($Million)

Vehicle Evaporative 

Emission Control 

Costs

($Million)

Facility Costs 

($Million)

Total Vehicle 

Costs

($Million)

2017 $634 $71 $4 $709

2030 $1,790 $253 $4 $2,047

Table ES-2 Annual Fuel Costs, 2010$

Year Fuel Sulfur Control Costs ($Million)

2017 $1,289

2030 $1,320

Table ES-3: Total Annual Vehicle and Fuel Control Costs, 2010$

Year Total Vehicle and Fuel Control Costs ($Million)

2017 $1,999

2030 $3,367

In these ways, the Tier 3 proposal presents substantial and transparent analysis of the impacts of 

the vehicle and sulfur standards.