Air pollution from motor vehicle emissions (i.e., exhaust) can lead to negative public health and environmental impacts that disproportionately impact children, seniors, urban residents and people with existing lung and heart problems. The United States Environmental Protection Agency (EPA) sets standards for allowable levels of certain air pollutants (e.g., carbon monoxide, ozone) through the National Ambient Air Quality Standards (NAAQS). When a particular air quality control region exceeds any portion of the NAAQS, the home state must either submit a plan to reduce pollution or accept EPA sanctions such as highway funding restrictions and/or emission offset requirements. In 2007, Missouri established the Gateway Vehicle Inspection Program (GVIP) in response to NAAQS nonattainment in the St. Louis Region (City of St. Louis; St. Louis, St. Charles, Franklin and Jefferson Counties). House Bill 661, passed during the 2021 regular session and vetoed by the Governor, would have removed the GVIP inspection and maintenance requirements for Franklin, Jefferson, and St. Charles Counties.3,4 In October 2021, the Missouri Department of Natural Resources proposed a rule change that would remove Franklin County from GVIP requirements due to emissions reductions in the St. Louis region that offset higher emissions within Franklin County.