On March 30, 2023, the Environmental Protection Agency (EPA) proposed to approve revisions to the Idaho State Implementation Plan (SIP) submitted by the State of Idaho (Idaho or the State) on December 29, 2022. The SIP revision, applicable in the Boise-Northern Ada County Carbon Monoxide area (Northern Ada County CO area) in Idaho, removes the Inspection and Maintenance (I/M) program, which was previously approved into the SIP for use as a control measure in the State's plan to address motor vehicle emissions in the nonattainment area.