The main purpose of this legislative proposal is to change the Clean Air Act by preventing individual states from setting their own emission standards for existing locomotives and the engines used in them. The goal is to create a uniform standard across the country, which supporters argue will help facilitate interstate commerce and reduce regulatory burdens on the railroad industry. Key provisions of this proposal include a specific amendment to the Clean Air Act. It clarifies that states cannot impose their own emission control standards on locomotives and engines that are already in use.