Revision of Tier 4 Phase-in Schedule for Light-Duty and Medium-Duty Vehicles

The U.S. Environmental Protection Agency (EPA) is proposing to extend the Tier 3 criteria pollutant standards for vehicles up to 6,000 pounds gross vehicle weight rating into model years (MYs) 2027 and 2028, and to delay the start of the phase-in of the Tier 4 criteria pollutant standards until MY 2029.