This rule makes technical amendments to the recent final rules for heavy-duty engine criteria pollutant standards (2023), light/medium-duty vehicle multipollutant standards (2024), and heavy-duty vehicle greenhouse gas standards (2024). Since the promulgation of these regulations, EPA, manufacturers, and other stakeholders have identified several areas where amending the specified test procedures and other compliance provisions could improve the overall accuracy, repeatability, and clarity of the regulations without changing the stringency of the standards. As such, EPA is proposing amendments which include regulatory corrections, clarifications to test procedures and compliance provisions, and other minor changes to improve clarity and streamline the regulations. In addition, minor technical amendments are included for certain other mobile source sectors.