Heavy-duty highway engines and vehicles; Quality (ICS code(s): 03.120); Transport exhaust emissions (ICS code(s): 13.040.50); Test conditions and procedures in general (ICS code(s): 19.020); Commercial vehicles (ICS code(s): 43.080)

Amendments and Nonconformance Penalties for Model Year 2027 and Later Heavy-Duty Highway Engines and Amendments to Inducement Provisions for SCR-Equipped Diesel Engines; (144 page(s), in English)

Proposed rule - The U.S. Environmental Protection Agency (EPA) is proposing regulatory amendments to certain compliance provisions and test procedures related to model year (MY) 2027 and later heavy-duty highway engines. These amendments would include changes to the regulatory useful life periods and the emission-related warranty periods. The EPA also proposes to add clarity to certain regulatory compliance provisions and correct errors in the regulations to support the MYs 2027 and later program for heavy-duty highway engines and vehicles. This includes certain amendments related to provisions adopted in January 2023 as well as other provisions adopted in earlier rules. The EPA also proposes to make nonconformance penalties (NCPs) available to manufacturers of medium heavy-duty engines (Medium HDE) and heavy heavy-duty engines (Heavy HDE) beginning in MY 2027. In addition, the EPA proposes to amend the requirements for selective catalytic reduction (SCR) system inducement provisions for newly manufactured diesel-fueled highway engines and vehicles (i.e., light- and medium-duty vehicles and heavy-duty engines) and nonroad engines and equipment. The EPA is also considering new inducement guidance for in-use highway and nonroad diesel engines, vehicles, and equipment.

The EPA will hold virtual public hearings on 29 July 2026, starting at 9:00 a.m. Eastern Time and on 30 July 2026, starting at 10:00 a.m. Eastern Time. If there is sufficient interest, an additional day of hearings will be held on the subsequent day. Please refer to the SUPPLEMENTARY INFORMATION section for additional information on the public hearing. Information on the status of the hearing and how to register can be found at https://www.epa.gov/regulations-emissions-vehicles-and-engines/proposed-rule-amendments-and-nonconformance-penalties