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 Idaho, residents are required to title and register their vehicles with the Idaho Transportation Department (ITD). New residents must title and register their vehicles within 90 days of establishing residency. Idaho does not have a statewide vehicle safety inspection program, so vehicles are not required to pass a comprehensive safety inspection for titling or registration purposes. However, Idaho does have an emissions testing program that is required in certain counties. As of the knowledge cutoff date, Ada and Canyon counties require emissions testing for most vehicles to help improve air quality in these more densely populated areas. Vehicles must pass the emissions test every two years, and the results are a prerequisite for registration renewal in the affected counties.