Environmental Protection Agency
The U.S. Environmental Protection Agency (EPA) is reconsidering the Tier 4 criteria pollutant standards for new motor vehicles promulgated within the final rule entitled "Multi-Pollutant Emissions Standards for Model Years 2027 and Later Light-Duty and Medium-Duty Vehicles." This reconsideration will occur in two separate, but coordinated, rulemakings. In this Part 1 rulemaking, the EPA is proposing to amend the phase-in schedule for the Tier 4 criteria pollutant standards for certain vehicles to address changing circumstances and feasibility concerns. These amendments, if finalized, would extend the Tier 3 standards for certain vehicles to model years (MYs) 2027 and 2028 such that the Tier 4 standards for these vehicles would phase in starting with MY 2029. The EPA is also proposing other changes to the test protocols used to evaluate emissions performance for certification and related regulatory issues. Potential amendments to the Tier 4 standards and other program elements will be proposed separately in a future Part 2 rulemaking.
Document Headings Document headings vary by document type but may contain the following: the agency or agencies that issued and signed a document the number of the CFR title and the number of each part the document amends, proposes to amend, or is directly related to the agency docket number / agency internal file number the RIN which identifies each regulatory action listed in the Unified Agenda of Federal Regulatory and Deregulatory Actions See the Document Drafting Handbook for more details. Environmental Protection Agency 40 CFR Parts 85, 86, and 1066 [EPA-HQ-OAR-2025-3297; FRL-13030-01-OAR] RIN 2060-AW96 AGENCY: Environmental Protection Agency (EPA). ACTION: Proposed rule. SUMMARY: The U.S. Environmental Protection Agency (EPA) is reconsidering the Tier 4 criteria pollutant standards for new motor vehicles promulgated within the final rule entitled “Multi-Pollutant Emissions Standards for Model Years 2027 and Later Light-Duty and Medium-Duty Vehicles.” This reconsideration will occur in two separate, but coordinated, rulemakings. In this Part 1 rulemaking, the EPA is proposing to amend the phase-in schedule for the Tier 4 criteria pollutant standards for certain vehicles to address changing circumstances and feasibility concerns. These amendments, if finalized, would extend the Tier 3 standards for certain vehicles to model years (MYs) 2027 and 2028 such that the Tier 4 standards for these vehicles would phase in starting with MY 2029. The EPA is also proposing other changes to the test protocols used to evaluate emissions performance for certification and related regulatory issues. Potential amendments to the Tier 4 standards and other program elements will be proposed separately in a future Part 2 rulemaking. DATES: Comments. Comments must be received on or before July 6, 2026, at 11:59 p.m. Eastern Time. Comments on the information collection provisions submitted to the Office of Management and Budget (OMB) under the Paperwork Reduction Act (PRA)…
Citation: 91 FR 28463
