Regulation Database – Motor Vehicles

Model Year 2012-2016 Light-Duty Vehicle Greenhouse Gas Emission Standards and Corporate Average Fuel Economy Standards

In May 2010, together with the National Highway Traffic Safety Administration (NHTSA), EPA promulgated standards applicable to passenger cars, light-duty trucks, and medium-duty passenger vehicles, covering model years 2012 through 2016. Under the coordinated program, EPA finalized greenhouse gas emissions standards under the Clean Air Act, and NHTSA finalized Corporate Average Fuel Economy (CAFE) standards under the Energy Policy and Conservation Act. The EPA standards were the first-ever national greenhouse gas emission standards under the Clean Air Act, enabled by the endangerment and cause or contribute findings EPA made in 2009 with respect to greenhouse gas emissions from motor vehicles.

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Model Year 2017-2025 Light-Duty Vehicle Greenhouse Gas Emission Standards and Corporate Average Fuel Economy Standards

In October 2012, EPA extended greenhouse gas emission standards for light-duty vehicles to model years 2017-2025, and NHTSA extended CAFE standards for these same model years. The standards are expected to result in an average industry fleetwide level of 163 grams/mile of carbon dioxide in model year 2025, equivalent to 54.5 miles per gallon. Together with the 2012-2016 standard, the program is expected to cut six billion metric tons of greenhouse gases over the lifetimes model year 2012-2025 vehicles.

The rule called for a mid-term evaluation to determine whether the standards should be revised for light duty vehicles MY 2022-2025. In January 2017, EPA issued a final determination on the appropriateness of the emission standards in which it concluded that no change was warranted for the MY 2022-2025 standards.

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On March 15, 2017, EPA and NHTSA announced their intention to reconsider the GHG standards for light duty vehicles model years 2022-2025 (see Notice of Intention to Reconsider the Final Determination of the Mid-Term Evaluation of Greenhouse Gas Emissions Standards for Model Year 2022-2025 Light Duty Vehicles).

EPA and NHTSA issued the notice shortly after the Alliance of Automobile Manufacturers filed a petition for review of the Jan. 17 determination in the D.C. Circuit Court of Appeals. Prior to filing that petition, the Alliance also sent a letter to EPA Administrator Scott Pruitt urging EPA to reconsider the emission standards. The Alliance dropped the lawsuit shortly after EPA and NHTSA announced that they would reconsider the emission standards.

On July 26, 2017, NHTSA announced that it would prepare an environmental impact statement to assess the potential environmental impacts of new Corporate Average Fuel Economy (CAFE) standards it is proposing to adopt for model year 2022-2025 passenger cars and light trucks.

On August 10, 2017, NHTSA and EPA announced that they were opening a public comment period on the reconsideration of the greenhouse gas (GHG) emissions standards for cars and light trucks for model years (MY) 2022-2025. EPA stated that it would also take comment on whether the MY 2021 standards are appropriate.

On April 13, 2018, EPA published a notice stating that it had completed its mid-term evaluation of the GHG standards for light-duty vehicles, that it determined the standards were too stringent, and that it intended to initiate a new notice-and-comment rulemaking proceeding to revise the standards to make them less stringent.

On August 2, 2018, EPA and NHTSA published a proposed rule to weaken the light-duty vehicle emission and fuel economy standards. The proposal – entitled the “Safer Affordable Fuel-Efficient (SAFE) Vehicles Rule" – would freeze the light-duty vehicle standards for MY 2021-2026 at 2020 levels, rather than having the standards become more stringent over time as provided for in the original rule. It would also revoke the waiver allowing California to establish more stringent standards which other states can then adopt.

On September 19, 2019, EPA and NHTSA finalized the portion of the SAFE Rule that revokes the waiver permitting California to establish vehicle standards for greenhouse gases and zero-emission vehicles.  California and twenty-two other states - plus Washington, D.C., New York City and Los Angeles - have challenged the waiver revocation in court. 

On March 31, 2020, EPA and NHTSA finalized the SAFE Rule. Under the final rule, GHG and CAFE standards will become 1.5% more stringent every year from 2020-2026.


On May 27, 2020, a coalition of states and a coalition of environmental groups challenge the SAFE Rule in Court.

Regulations for Greenhouse Gas Emissions from Heavy-Duty Vehicles, Model Years 2014-2018

In August 2011, EPA and NHTSA finalized greenhouse gas emission standards and fuel economy standards for heavy-duty highway vehicles for model years 2014-2018, cutting an estimated 270 million metric tons of carbon dioxide emissions.

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Regulations for Greenhouse Gas Emissions from Heavy-Duty Vehicles, Model Years 2018-2027, 2021-2027

In August 2016, EPA and NHTSA extended GHG and CAFE standards for medium- and heavy-duty vehicles through model years 2018-2027 for certain trailers, and model years 2021-2027 for semi-trucks, large pickup trucks, vans, buses, and work trucks. These new standards are expected to cut 1.1 billion metric tons of carbon dioxide emissions.

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The provisions of the extended GHG and CAFE standards applying to trailers were challenged in Truck Trailer Manufacturers Association, Inc. v. EPA (2016). The Truck Trailer Manufacturers Association has argued that EPA and NHTSA lack authority to regulate GHG emissions from trailers under the Clean Air Act and the Energy Independence and Security Act.

On May 8, 2017, the D.C. Circuit Court of Appeals issued an order to delay oral argument and hold the case in abeyance for 90 days.

On October 27, 2017, the Court issued an order staying implementation of the standards as applied to trailers, pending review by EPA.

As of October 2019, the case remains in abeyance. 

Rule Increasing Penalties

On December 28, 2016, NHTSA published a final rule to increase penalties for automobile manufacturers that fail to meet fuel economy standards. The rule increased the fines from $5.50 to $14 per tenth-of-an-mpg, and allowed for adjustments for inflation between the publication date and the assessment of the violation.

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On July 12, 2018, NHTSA announced that it would indefinitely delay the effective date of the rule. In a separate notice, NHTSA announced that it would reconsider and potentially revise the rule.


On September 8, 2017, five state attorneys general filed a lawsuit alleging that NHTSA’s indefinite delay of the rule was unlawful and should be vacated. On April 23, 2018, the 2nd U.S. Circuit Court of Appeals issued a one-page order vacating the delay, granting petitions by environmental groups and a coalition of state attorneys general.

Deregulatory Action:

On July 26, 2019, NHTSA finalized a rule to freeze civil penalties for violating fuel efficiency standards at $5.50 per ten-of-an-mpg. The rule replaced a 2016 rule that would have increased fines to $14 per ten-of-an-mpg in 2019.


On August 31, 2020, the Second Circuit Court of Appeals vacated NHTSA's rule freezing civil penalties and reinstated the 2016 rule increasing the penalty rate to $14.

Fuel Economy Labeling of Motor Vehicles

In July 2011, EPA and NHTSA finalized a rule to redesign and add information to the fuel economy label that is posted on the window sticker of all new cars and light-duty trucks sold in the U.S. The redesigned label provides new information to American consumers about fuel economy and consumption, fuel costs, and environmental impacts associated with purchasing new vehicles beginning with model year 2013 cars and trucks. The rule also develops new labels for certain advanced technology vehicles poised to enter the U.S. market, including plug-in hybrid electric vehicles and electric vehicles.

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California Greenhouse Gas Regulation Waivers

The Clean Air Act allows California to enact air pollution standards for motor vehicles more stringent than those of federal government. EPA must approve a waiver before California’s rules may go into effect. In December 2005, the California Air Resources Board (CARB) requested a waiver to regulate GHG emissions from new motor vehicles. The request was denied by EPA in March 2008. In January 2009, CARB requested that EPA reconsider its waiver denial, and in June 2009, EPA granted a waiver.

With new federal greenhouse gas standards for vehicles being developed, CARB later requested to align its vehicle-related GHG regulations with the nationwide vehicle standards. In June 2011, EPA published a notice stating that requested revisions made by CARB fall within the scope of the CAA preemption waiver granted to California in 2009.

In January 2013, EPA granted California a waiver to implement the state’s Advanced Clean Car Program. The program includes regulations to phase in stricter fleet average standards for 2015-2025 model year cars  and light-duty trucks. The regulations also set new greenhouse gas emissions limits for 2017-2025 model year cars and light duty trucks, and mandates that a certain percentage of new vehicles produce no carbon dioxide tailpipe emissions. The waiver reaffirms California’s key role under the Clean Air Act as a laboratory for setting new motor vehicle emissions standards.

In August 2014, EPA granted CARB’s request to regulate greenhouse gas emissions for certain model year 2011-2013 tractors, and dry- and refrigerated-van trailers pulled by such tractors. In December 2016, EPA then granted CARB’s request to regulate greenhouse gas emissions for 2014 and subsequent model year on-road medium- and heavy-duty engines and vehicles.

Deregulatory Action:

On September 19, 2019, EPA and NHTSA took final action to revoke California's preemption waiver as applied to the greenhouse gas emissions standards and zero-emission vehicle mandate.  California and twenty-two other states - plus Washington, D.C., New York City and Los Angeles - have challenged the waiver revocation in court. 

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