The U.S. Environmental Protection Agency has proposed delaying compliance deadlines for certain light- and medium-duty vehicle emissions standards by two years, moving the requirements from model year 2027 to model year 2029. The proposal applies to Tier 4 emissions standards for criteria pollutants and would keep manufacturers under the existing Tier 3 standards for model years 2027 and 2028 if finalized.
EPA said the proposal is intended to give vehicle manufacturers additional time to comply while the agency reviews the Tier 4 program. According to the agency, the delay is projected to save more than $1.7 billion, including what EPA described as hundreds of dollars in savings per vehicle for consumers.
The agency said the 2024 Tier 4 standards were based on assumptions about electric vehicle adoption and future fleet mix that it now says have not materialized. EPA stated that the current compliance timeline could increase costs for manufacturers as they work to meet the standards.
If finalized, the proposed rule would allow manufacturers to continue complying with Tier 3 standards for model year 2027 and 2028 vehicles. EPA said Tier 3 standards have already delivered emissions reductions of up to 80% and would remain in effect during the proposed delay period.
EPA described the proposal as the first part of a broader review of Tier 4 standards. A second phase of that review may include proposed changes to the standards themselves, implementation dates, phase-in schedules and test procedures.
The agency will hold a 45-day public comment period on the proposal. EPA said it remains focused on rulemaking that considers public health and environmental protection while also addressing implementation issues for regulated stakeholders.
