The US EPA issued an Advance Notice of Proposed Rulemaking (ANPR) for the Cleaner Trucks Initiative (CTI). The eventual CTI rulemaking will establish new, more stringent emission standards for NO_x and other pollutants for highway heavy-duty engines. EPA is seeking input from the public and interested stakeholders.

This rulemaking will also offer opportunities to streamline and improve certification procedures to reduce costs for engine manufacturers. This action follows on the petitions from more than 20 organizations, including state and local air agencies, to revise and promulgate more stringent NO_x standards.

In the ANPR, EPA says that it is looking to the following high-level principles to inform the approach to this rulemaking:

• To reduce in-use emissions under a broad range of operating conditions;

• To consider and enable effective technological solutions while carefully considering the cost impacts;

• To develop compliance and enforcement provisions that are be fair and effective;

• To incentivize early compliance and innovation;

• To ensure a coordinated 50-state program; and

• To engage actively with interested stakeholders.

EPA said it is closely following the technical work initiated by the California Air Resources Board (CARB) to update the CARB heavy-duty vehicle and engine programs under a Heavy-Duty NO_x Omnibus proposal. The ANPR provides an opportunity for comment on the extent to which EPA should adopt provisions similar to those expected in the CARB Omnibus proposal.

From 2007 to 2017, US NO_x emissions dropped by more than 40%. However, 100 million people live in areas of nonattainment for ozone and particulate matter (PM), and according to EPA estimates, heavy-duty vehicles will continue to be one of the largest contributors to NO_x emissions—a precursor of ozone and PM formation—from the transportation sector in 2025.

EPA last revised NO_x standards for on-highway heavy-duty trucks and engines in January 2001. The EPA Administrator announced in November 2018 that EPA would pursue the Cleaner Trucks Initiative (CTI) to update NO_x emissions standards for heavy-duty trucks.

EPA intends to publish a proposed rule in early 2020.