The proposed legislation seeks to amend the Clean Air Act to restrict state authority over locomotive emissions. Specifically, it prohibits states from setting their own emission control standards for existing locomotives and engines used in locomotives . This prohibition applies to locomotives engaged in common carrier railroad transportation for compensation , effectively preempting state-level regulation in this sector. The bill modifies Section 209(e)(1) of the Clean Air Act, which deals with nonroad engines and vehicles, to explicitly include these commercial locomotives under federal preemption. This change aims to create a uniform regulatory framework by preventing states from imposing additional or different emission requirements on these specific types of locomotives.