DEPARTMENT OF TRANSPORTATION 

U.S. ENVIRONMENTAL PROTECTION AGENCY 

NHTSA and EPA Proposed SAFE Vehicle Rule 

Overview of the Alternatives Analyzed 

Today, the U.S. Department of Transportation’s National Highway Traffic Safety Administration 

(NHTSA) and the U.S. Environmental Protection Agency (EPA) released a notice of proposed 

rulemaking, the Safer Affordable Fuel-Efficient (SAFE) Vehicles Rule for Model Years 2021-

2026 Passenger Cars and Light Trucks (SAFE Vehicles Rule). 

Agencies typically consider regulatory alternatives in proposals as a way of evaluating the 

comparative effects of different potential ways of accomplishing their desired goal. To ensure 

robust public comment, NHTSA and EPA are evaluating eight alternatives. 

Alternatives analysis begins with a “no-action” alternative, typically described as what would 

occur in the absence of any regulatory action. Today’s proposal includes a no-action alternative, 

described below, as well as seven “action alternatives” besides the proposal. 

Aside from the no-action alternative, NHTSA and EPA defined the different regulatory 

alternatives in terms of percent-increases in corporate average fuel economy (CAFE) and 

greenhouse gas (GHG) stringency from year to year. Under some alternatives, the rate of 

increase is the same for both passenger cars and light trucks; under others, the rate of increase 

differs. Two alternatives also involve a gradual discontinuation of CAFE and average GHG 

adjustments reflecting the application of technologies that improve air conditioner (A/C) 

efficiency or, in other ways, improve fuel economy under conditions not represented by longstanding fuel economy test procedures. For increased harmonization with NHTSA CAFE 

standards, which cannot account for such issues, under Alternatives 1-8, EPA would regulate 

tailpipe carbon dioxide (CO2) independently of A/C refrigerant leakage, nitrous oxide (N2O) and 

methane (CH4) emissions. 

Under the no-action alternative, EPA would continue to regulate A/C refrigerant leakage, nitrous 

oxide and methane emissions under the overall CO2 standard. Like the baseline no-action 

alternative, all of the alternatives are more stringent than the preferred alternative. 

EPA also seeks public comment on retaining the existing credit program for regulation of A/C 

refrigerant leakage, nitrous oxide, and methane emissions as part of the CO2 standard. 

The agencies have examined these alternatives because the agencies intend to continue 

considering them as options for the final rule. The agencies seek public comment on these 

alternatives and on the analysis presented here, seek any relevant data and information, and will 

review responses. That review could lead the agencies to select one of the other regulatory 

alternatives for the final rule. 

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The table below shows the different alternatives evaluated in this proposal. 

Regulatory Alternatives Currently under Consideration 

Alternative Change in stringency A/C 

efficiency 

and offcycle 

provisions 

CO2 

Equivalent AC 

Refrigerant 

Leakage, 

Nitrous Oxide 

and Methane 

Emissions 

Included for 

Compliance? 

Baseline/ 

No-Action 

MY 2021 standards remain in place; MYs 2022-2025 augural 

CAFE standards are finalized and GHG standards remain 

unchanged; MY 2026 standards are set at MY 2025 levels 

No change Yes, for all 

MYs 1 

1 

(Proposed) 

Existing standards through MY 2020, then 0%/year increases 

for both passenger cars and light trucks, for MYs 2021-2026 

No change No, beginning 

in MY 20212 

2 Existing standards through MY 2020, then 0.5%/year increases 

for both passenger cars and light trucks, for MYs 2021-2026 

No change No, beginning 

in MY 2021 

3 Existing standards through MY 2020, then 0.5%/year increases 

for both passenger cars and light trucks, for MYs 2021-2026 

Phase out 

these 

adjustments 

over MYs 

2022-2026 

No, beginning 

in MY 2021 

4 Existing standards through MY 2020, then 1%/year increases 

for passenger cars and 2%/year increases for light trucks, for 

MYs 2021-2026 

No change No, beginning 

in MY 2021 

5 Existing standards through MY 2021, then 1%/year increases 

for passenger cars and 2%/year increases for light trucks, for 

MYs 2022-2026 

No change No, beginning 

in MY 2022 

6 Existing standards through MY 2020, then 2%/year increases 

for passenger cars and 3%/year increases for light trucks, for 

MYs 2021-2026 

No change No, beginning 

in MY 2021 

7 Existing standards through MY 2020, then 2%/year increases 

for passenger cars and 3%/year increases for light trucks, for 

MYs 2021-2026 

Phase out 

these 

adjustments 

over MYs 

2022-2026 

No, beginning 

in MY 2021 

1 Carbon dioxide equivalent of air conditioning refrigerant leakage, nitrous oxide and methane emissions are 

included for compliance with the EPA standards for all MYs under the baseline/no-action alternative. Carbon 

dioxide equivalent is calculated using the Global Warming Potential (GWP) of each of the emissions.

2 Beginning in MY 2021, air conditioning refrigerant leakage, nitrous oxide, and methane emissions may be 

regulated independently by EPA. The GWP equivalent of each of the emissions would no longer be included with 

the tailpipe CO2 for compliance with tailpipe CO2 standards. 

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8 Existing standards through MY 2021, then 2%/year increases 

for passenger cars and 3%/year increases for light trucks, for 

MYs 2022-2026 

No change No, beginning 

in MY 2022 

Also, EPA seeks public comments on whether to proceed with this proposal to discontinue 

accounting for A/C leakage, methane emissions, and nitrous oxide emissions as part of the CO2 

emissions standards to provide for better harmony with the CAFE program or whether to 

continue to consider these factors toward compliance and retain that as a feature that differs 

between the programs. EPA seeks comment on whether to change existing methane and nitrous 

oxide standards that were finalized in the 2012 rule. Specifically, EPA seeks information from 

the public on whether the existing standards are appropriate, or whether they should be revised to 

be less stringent or more stringent based on any updated data. 

The agencies are providing a short narrative of the alternatives below. 

No-Action Alternative 

The No-Action Alternative applies the augural CAFE and final GHG targets announced 

in 2012 for MYs 2021-2025. For MY 2026, this alternative applies the same targets as for MY 

2025. Carbon dioxide equivalent of air conditioning refrigerant leakage, nitrous oxide, and 

methane emissions are included for compliance with the EPA standards for all model years under 

the baseline/no-action alternative. 

Alternative 1 (Proposed) 

Alternative 1 holds the stringency of targets constant and MY 2020 levels through MY 

2026. Beginning in MY 2021, air conditioning refrigerant leakage, nitrous oxide, and methane 

emissions are no longer included with the tailpipe CO2 for compliance with tailpipe CO2 

standards. 

Alternative 2 

Alternative 2 increases the stringency of targets annually during MYs 2021-2026 (on a 

gallon per mile basis, starting from MY 2020) by 0.5% for passenger cars and 0.5% for light 

trucks. Beginning in MY 2021, air conditioning refrigerant leakage, nitrous oxide, and methane 

emissions are no longer included with the tailpipe CO2 for compliance with tailpipe CO2 

standards. 

Alternative 3 

Alternative 3 phases out A/C and off-cycle adjustments and increases the stringency of 

targets annually during MYs 2021-2026 (on a gallon per mile basis, starting from MY 2020) by 

0.5% for passenger cars and 0.5% for light trucks. Beginning in MY 2021, air conditioning 

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refrigerant leakage, nitrous oxide, and methane emissions are no longer included with the 

tailpipe CO2 for compliance with tailpipe CO2 standards. 

Alternative 4 

Alternative 4 increases the stringency of targets annually during MYs 2021-2026 (on a 

gallon per mile basis, starting from MY 2020) by 1.0% for passenger cars and 2.0% for light 

trucks. Beginning in MY 2021, air conditioning refrigerant leakage, nitrous oxide, and methane 

emissions are no longer included with the tailpipe CO2 for compliance with tailpipe CO2 

standards. 

Alternative 5 

Alternative 5 increases the stringency of targets annually during MYs 2022-2026 (on a 

gallon per mile basis, starting from MY 2021) by 1.0% for passenger cars and 2.0% for light 

trucks. Beginning in MY 2022, air conditioning refrigerant leakage, nitrous oxide, and methane 

emissions are no longer included with the tailpipe CO2 for compliance with tailpipe CO2 

standards. 

Alternative 6 

Alternative 6 increases the stringency of targets annually during MYs 2021-2026 (on a 

gallon per mile basis, starting from MY 2020) by 2.0% for passenger cars and 3.0% for light 

trucks. Beginning in MY 2021, air conditioning refrigerant leakage, nitrous oxide, and methane 

emissions are no longer included with the tailpipe CO2 for compliance with tailpipe CO2 

standards. 

Alternative 7 

Alternative 7 phases out A/C and off-cycle adjustments and increases the stringency of 

targets annually during MYs 2021-2026 (on a gallon per mile basis, starting from MY 2020) by 

1.0% for passenger cars and 2.0% for light trucks. Beginning in MY 2021, air conditioning 

refrigerant leakage, nitrous oxide, and methane emissions are no longer included with the 

tailpipe CO2 for compliance with tailpipe CO2 standards. 

Alternative 8 

Alternative 8 increases the stringency of targets annually during MYs 2022-2026 (on a 

gallon per mile basis, starting from MY 2021) by 2.0% for passenger cars and 3.0% for light 

trucks. Beginning in MY 2022, air conditioning refrigerant leakage, nitrous oxide, and methane 

emissions are no longer included with the tailpipe CO2 for compliance with tailpipe CO2 

standards. 

4 EPA-420-F-18-902 

August 2, 2018