04/25/2023 - Clean Car Rules

Ambitious and Achievable: EPA’s Proposed Multi-Pollutant Emissions Standards for Model Years 2027 and Later Light- and Medium-Duty Vehicles

by Carrie Jenks, Sara Dewey

On April 12, 2023, EPA released a proposal to cut vehicle emissions: a multipollutant emissions standard for light- and medium-duty vehicles. The proposed rule would set more stringent emissions standards for vehicles, grounded in EPA’s statutory authority under the Clean Air Act (CAA) Section 202(a) and its longstanding regulatory approach to vehicle emissions. The rule also builds on investments that the auto industry and Congress have already made to support vehicle electrification.

The transportation sector is the largest domestic source of greenhouse gas (GHG) emissions, contributing nearly 30 percent of total emissions in the U.S. The sector is also a major contributor to ozone, particulate matter (PM), and air toxics that are associated with significant health impacts. For example, EPA states that in 2023, mobile sources will account for 54 percent of anthropogenic nitrogen oxide (NOx) emissions.

To address these emissions, EPA proposes emission reduction standards for light- and medium-duty vehicles that are designed to be achievable with existing technology and follow industry trends toward electrification. While the new standards are ambitious, they are largely consistent with what the industry is projecting for itself. Along with the proposed standards, the agency is taking comments on three alternative standards with different rates of adoption and stringencies. EPA must consider and respond to these comments before promulgating its final rule.

In our analysis of the proposed light- and medium-duty vehicle standards, we provide an overview of the proposed requirements and review the statutory authority, regulatory history, and rapidly evolving legislative and economic context in which EPA developed this proposal. We also look at issues the agency will need to consider in a final rule based on the stakeholder comments EPA is now seeking.

Regardless of its final form, we expect legal challenges to the light- and medium-duty vehicle proposal once it is finalized. Depending on timing, the pending DC Circuit challenge to EPA’s 2021 GHG standards in Texas v. EPA could shape the contours of the rule or future litigation.

Read our analysis of the proposed GHG vehicle standards.