The Environmental Protection Agency (EPA) is amending the test procedures for heavy-duty engines and vehicles to improve accuracy and reduce testing burden. EPA is also making other regulatory amendments concerning light-duty vehicles, heavy-duty vehicles, highway motorcycles, locomotives, marine engines, other nonroad engines and vehicles, and stationary engines. These amendments affect the certification procedures for exhaust emission standards and related requirements. EPA is finalizing similar amendments for evaporative emission standards for nonroad equipment and portable fuel containers. The amendments increase compliance flexibility, harmonize with other requirements, add clarity, correct errors, and streamline the regulations. Given the nature of the amendments, they will have neither significant environmental impacts nor significant economic impacts for any sector.