EPA Proposes Delay of Tier 4 Vehicle Emissions Standards

The U.S. Environmental Protection Agency released a rulemaking proposal on Friday to delay the adoption of Tier 4 air pollution standards for passenger cars and trucks and to reconsider the standards going forward. The agency stated that the proposed change responds to slowed electric vehicle growth. It said the standards rest on assumptions about EV adoption that have not materialized.

Background on the Tier 4 Standards The Tier 4 Criteria Pollutant Standards were established in April 2024 under the Clean Air Act. They would have set fleet-average limits on volatile organic compounds, oxides of nitrogen, and particulate matter, with phase-in beginning in 2027.

When the standards were adopted, electric vehicles accounted for 8 percent of new light-duty vehicle sales in the United States.

The administration also set a September 2025 expiration date for federal tax credits on new and used electric vehicles. Data from the U.S. Energy Information Administration showed EV sales dropped sharply after the credits ended.

The Alliance for Automotive Innovation said the proposed delay makes sense given current market conditions. John Bozzella, president and CEO of the alliance, stated that the standards would remain unachievable without significant EV sales growth and would raise costs for gas-powered vehicles.

The League of Conservation Voters said the change would increase fuel costs for families and worsen health outcomes. Matthew Davis, the group's vice president of federal policy, noted that gas prices have exceeded $4.50 per gallon. The International Council on Clean Transportation reported that the U.S. share of global EV production fell from 7 percent in 2024 to 5 percent in 2025.

The council linked the decline to policy changes and said automakers have delayed production and reduced investment.