; (v) motor vehicles acquired and used for military purposes that the Secretary of Defense has certified to the Secretary must be exempt for national security reasons; or (vi) nonroad vehicles, including farm and construction vehicles. (B) Medium duty passenger vehicle The term medium duty passenger vehicle has the meaning given that term in subsection (f)(1). (C) Heavy duty motor vehicle The term heavy duty motor vehicle means a motor vehicle with a gross vehicle weight rating equal to or in excess of 8,501 pounds, but does not include any medium duty passenger vehicle. . 8. Research, development, and demonstration of natural gas vehicles There are authorized to be appropriated to the Secretary of Energy $25,000,000 for fiscal year 2019 through 2023 for research, development, and demonstration activities with respect to natural gas vehicles, including advanced efficiency for natural gas vehicle engines, continuation of ARPA–E Methane Opportunities for Vehicular Energy projects, and development of low nitrogen oxide or advanced high pressure direct injection engines. 9. Clean Cities program deployment grants There is authorized to be appropriated to the Secretary of Energy $50,000,000 for fiscal year 2019 for natural gas vehicle deployment grants under the Clean Cities program. 10. Diesel emissions reduction settlement amounts At least 50 percent of amounts provided for under a settlement agreement regarding alleged violations of environmental law in which a defendant agrees to perform a diesel emissions reduction Supplemental Environmental Project under subtitle G of title VII of the Energy Policy Act of 2005 ( 42 U.S.C. 16131 et seq.) shall be used for alternative fuel vehicle deployment grants. 11. Sense of Congress on the Smartway Program It is the sense of the Congress that— (1) the Smartway Program of the Environmental Protection Agency should include recognition of the energy security, fuel efficiency and environmental benefits of using domestic natural gas, including renewable natural gas