United States. Congress, Energy Independence and Security Act of 2007…
“ In General.— The Secretary of Transportation, in consultation with the Administrator of the Environmental Protection Agency, shall establish and carry out a pilot program for making grants to railroad carriers (as defined in section 20102 of title 49, United States Code) and State and local governments— (1) for assistance in purchasing hybrid or other energy-efficient locomotives, including hybrid switch and generator-set locomotives; and (2) to demonstrate the extent to which such locomotives increase fuel economy, reduce emissions, and lower costs of operation. ”
