Most states have titling and registration laws that require residents to title and register their cars in the state—and for new residents of the state to do so within some period of time, such as 30 days. Some states require titled cars to pass a comprehensive safety inspection. And some states also require cars owned by residents of certain counties to pass an emissions test/inspection designed to improve air quality in more densely populated counties.
In Missouri, residents are required to title and register their vehicles with the Missouri Department of Revenue. New residents must title and register their vehicles within 30 days of establishing residency. The state mandates that vehicles undergo a safety inspection, which is generally required when a used vehicle is being sold or ownership is changing. Additionally, Missouri requires emissions inspections for residents of the St. Louis metropolitan area, which includes St. Louis City and the counties of St. Louis, St. Charles, Franklin, and Jefferson. This emissions test is part of the Missouri Gateway Vehicle Inspection Program and is required for most vehicles every two years or when ownership changes. The purpose of these inspections is to ensure that vehicles meet safety standards and, in the case of emissions testing, to help improve air quality in more densely populated areas.