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U.S. 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 long-
standing 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 off-
cycle
provisions
C02
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.
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EPA-420-F-18-902
August 2, 2018

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