CARB Proposes New Rules To Cut GHG Emissions Following Rescission Of Biden-Era Waivers

The California Air Resources Board (CARB) is exploring regulatory measures aimed at reducing greenhouse gas (GHG) emissions and criteria pollutants from medium- and heavy-duty trucks. These efforts are part of CARB's response to the recent congressional rescission of Biden-era preemption waivers, which previously allowed California to implement stricter vehicle emission standards than those prescribed federally. Lacking these waivers, CARB is now seeking alternative mechanisms to maintain state-level environmental standards for its commercial trucking sector.

Options under consideration include manufacturer standards that likely would mandate lower fleet-wide emissions performance for new medium- and heavy-duty vehicles. CARB is also considering stricter trailer standards—aimed at enhancing aerodynamics and fuel efficiency—as a means to curb CO₂ outputs. In addition, CARB is contemplating regulations focused on non-exhaust emissions, which include particulate matter released through brake wear, tire wear, and road dust. Together, these proposals represent a multi-pronged strategy targeting both engine systems and vehicle design to reduce both exhaust and non-exhaust emissions across the transportation lifecycle.

These proposals reflect California's adaptive regulatory strategy: despite losing the federal waiver authority, CARB intends to pursue integrated, state-level interventions to keep its transportation emissions trending downward. The outcome will depend on forthcoming rulemaking processes, stakeholder engagement and legal viability.

CARB's proposed truck emission measures are currently at the pre-rulemaking stage. The next steps toward enforceable regulations include:

1. Working Papers and Public Workshops: CARB staff will produce detailed staff working papers outlining the technical and policy rationale behind each proposed standard (e.g., engine, trailer, non exhaust emissions). These papers will be released for public workshops, offering stakeholders opportunities to ask questions, provide feedback and suggest alternatives.
2. Release of Proposed Regulations and Formal Comment Period: After workshops and revisions, CARB will publish a formal notice of proposed rulemaking along with the draft regulatory text, a regulatory impact analysis, and supporting documentation. This notice triggers a minimum 45-day public comment period, during which CARB must accept written comments and may hold additional hearings to deliberate stakeholder feedback and technical adjustments.
3. Board Hearing and Final Adoption: CARB staff will synthesize input and issue responses in a final statement of reasons. If the board approves the measures, CARB will adopt them as binding regulations.
4. Implementation, Compliance Timeframes and Enforcement: After adoption, CARB will set an effective date and provide timelines for compliance. Typical provisions include compliance deadlines phased over several model years, tools for compliance demonstration, and schedules for reporting and enforcement. CARB's enforcement may include penalties for non-compliance and follow-up rule refinements.

While no formal timeline has been publicly released, stakeholders can expect each phase to span several months to over a year—meaning regulatory adoption and phased implementation could unfold over the next 12–24 months.

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