Pollutant emission standards for light-duty and medium-duty vehicles; Product and company certification. Conformity assessment (ICS code(s): 03.120.20); Environmental protection (ICS code(s): 13.020); Air quality (ICS code(s): 13.040); Road vehicle systems (ICS code(s): 43.040)

Revision of Tier 4 Criteria Pollutant Standards, Part 1: Amendments to Phase-In Schedule for Light-Duty and Medium-Duty Vehicles; (25 page(s), in English)

Proposed rule - 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" (notified as G/TBT/N/USA/1991/Add.1). 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. The EPA plans to hold a public hearing for this proposal on 3 June and 4 June 2026. If there is sufficient interest, an additional day of hearings will be held on the subsequent day. Information on the public hearing is available at https://www.epa.gov/regulations-emissions-vehicles-and-engines/revision-tier-4-phase-schedule-light-duty-and-medium. Please also refer to this website for any updates regarding the hearings. The EPA does not intend to publish additional documents in the Federal Register announcing updates. Please sign up for a speaking slot by emailing EPA-LD-MobileSource-Hearings@epa.gov. Note that each speaker will get three (3) minutes to speak.