Medium- and heavy-duty trucks, motor coaches, and transit buses - collectively, "medium- and heavy-duty vehicles", or MHDVs - are used in every sector of the economy. The fuel consumption and greenhouse gas emissions of MHDVs have become a focus of legislative and regulatory action in the past few years. This study is a follow-on to the National Research Council's 2010 report, Technologies and Approaches to Reducing the Fuel Consumption of Medium-and Heavy-Duty Vehicles. That report provided a series of findings and recommendations on the development of regulations for reducing fuel consumption of MHDVs. On September 15, 2011, NHTSA and EPA finalized joint Phase I rules to establish a comprehensive Heavy-Duty National Program to reduce greenhouse gas emissions and fuel consumption for on-road medium- and heavy-duty vehicles. As NHTSA and EPA began working on a second round of standards, the National Academies issued another report, Reducing the Fuel Consumption and Greenhouse Gas Emissions of Medium- and Heavy-Duty Vehicles, Phase Two: First Report, providing recommendations for the Phase II standards. This third and final report focuses on a possible third phase of regulations to be promulgated by these agencies in the next decade. Table of Contents Front Matter Summary 1 Introduction 2 Setting the Stage: Regulatory Horizons, Challenges, and Influences 3 Certification, Compliance, and Enforcement 4 Powertrain Technologies 5 Technologies for Reducing the Power Demand of MHDVs 6 Projected Benefits of Technologies on Fuel Consumption 7 Hybrid and Electric Powertrain Technologies 8 Battery Technology for Medium- and Heavy-Duty Hybrid and Electric Vehicles 9 Freight Operational Efficiency 10 Intelligent Transportation Systems and Automation 11 Manufacturing Considerations 12 Costs and Benefits 13 Alternative and Complementary Regulatory Approaches Appendix A: Committee Biographies Appendix B: Disclosure of Conflicts of Interest Appendix C: Committee Activities Appendix D: Summary of Analysis of Engine and Vehicle Combinations Appendix E: Description of Drive Cycles Used for Compliance Appendix F: Summary of Committee's First Report: Reducing the Fuel Consumption and Greenhouse Gas Emissions of Medium- and Heavy-Duty Vehicles, Phase Two: First Report Appendix G: Acronyms and Abbreviations

In July 2010, the National Research Council (NRC) appointed the Committee to Review the 21st Century Truck Partnership, Phase 2, to conduct an independent review of the 21st Century Truck Partnership (21CTP). The 21CTP is a cooperative research and development (R&D) partnership including four federal agencies-the U.S. Department of Energy (DOE), U.S. Department of Transportation (DOT), U.S. Department of Defense (DOD), and the U.S. Environmental Protection Agency (EPA)-and 15 industrial partners. The purpose of this Partnership is to reduce fuel consumption and emissions, increase heavy-duty vehicle safety, and support research, development, and demonstration to initiate commercially viable products and systems. This is the NRC's second report on the topic and it includes the committee's review of the Partnership as a whole, its major areas of focus, 21CTP's management and priority setting, efficient operations, and the new SuperTruck program.

Affecting technological systems at a global-scale, space weather can disrupt high-frequency radio signals, satellite-based communications, navigational satellite positioning and timing signals, spacecraft operations, and electric power delivery with cascading socioeconomic effects resulting from these disruptions. Space weather can also present an increased health risk for astronauts, as well as aviation flight crews and passengers on transpolar flights. In 2019, the National Academies was approached by the National Aeronautics and Space Administration, the National Oceanic and Atmospheric Administration, and the National Science Foundation to organize a workshop that would examine the operational and research infrastructure that supports the space weather enterprise, including an analysis of existing and potential future measurement gaps and opportunities for future enhancements. This request was subsequently modified to include two workshops, the first ("Phase I") of which occurred in two parts on June 16-17 and September 9-11, 2020. The Phase II workshop occurred on April 11-14, 2022, with sessions on agency updates, research needs, data science, observational and modeling needs, and emerging architectures relevant to the space weather research community and with ties to operational needs. This publication summarizes the presentation and discussion of that workshop. Table of Contents Front Matter Summary 1 The Space Weather Community 2 Research, Observation, and Modeling Needs: The Sun and Heliosphere 3 Research, Observation, and Modeling Needs: Magnetosphere, Ionosphere, Thermosphere, and Mesosphere 4 Research, Observation, and Modeling Needs: Ground Effects 5 Modeling, Validation, and Data Science 6 Research Infrastructure Appendixes Appendix A: Statement of Task Appendix B: Workshop Agenda Appendix C: Poster Session at the April 1114, 2022, Workshop Appendix D: Acronyms and Abbreviations Appendix E: Biographies of Committee Members and Staff

The light-duty vehicle fleet is expected to undergo substantial technological changes over the next several decades. New powertrain designs, alternative fuels, advanced materials and significant changes to the vehicle body are being driven by increasingly stringent fuel economy and greenhouse gas emission standards. By the end of the next decade, cars and light-duty trucks will be more fuel efficient, weigh less, emit less air pollutants, have more safety features, and will be more expensive to purchase relative to current vehicles. Though the gasoline-powered spark ignition engine will continue to be the dominant powertrain configuration even through 2030, such vehicles will be equipped with advanced technologies, materials, electronics and controls, and aerodynamics. And by 2030, the deployment of alternative methods to propel and fuel vehicles and alternative modes of transportation, including autonomous vehicles, will be well underway. What are these new technologies - how will they work, and will some technologies be more effective than others? Written to inform The United States Department of Transportation's National Highway Traffic Safety Administration (NHTSA) and Environmental Protection Agency (EPA) Corporate Average Fuel Economy (CAFE) and greenhouse gas (GHG) emission standards, this new report from the National Research Council is a technical evaluation of costs, benefits, and implementation issues of fuel reduction technologies for next-generation light-duty vehicles. Cost, Effectiveness, and Deployment of Fuel Economy Technologies for Light-Duty Vehicles estimates the cost, potential efficiency improvements, and barriers to commercial deployment of technologies that might be employed from 2020 to 2030. This report describes these promising technologies and makes recommendations for their inclusion on the list of technologies applicable for the 2017-2025 CAFE standards. Table of Contents Front Matter Summary 1 Introduction 2 Technologies for Reducing Fuel Consumption in Spark-Ignition Engines 3 Technologies for Reducing Fuel Consumption in Compression-Ignition Diesel Engines 4 Electrified Powertrains 5 Transmissions 6 Non-Powertrain Technologies 7 Cost and Manufacturing Considerations for Meeting Fuel Economy Standards 8 Estimates of Technology Costs and Fuel Consumption Reduction Effectiveness 9 Consumer Impacts and Acceptance Issues 10 Overall Assessment of CAFE Program Methodology and Design Appendix A: Statement of Task Appendix B: Committee Biographies Appendix C: Presentations and Committee Meetings Appendix D: Ideal Thermodynamic Cycles for Otto, Diesel, and Atkinson Engines Appendix E: SI Engine Definitions and Efficiency Fundamentals Appendix F: Examples of Friction Reduction Opportunities for Main Engine Components Appendix G: Friction Reduction in Downsized Engines Appendix H: Variable Valve Timing Systems Appendix I: Variable Valve Lift Systems Appendix J: Reasons for Potential Differences from NHTSA Estimates for Fuel Consumption Reduction Effectiveness of Turbocharged, Downsized Engines Appendix K: DOE Research Projects on Turbocharged and Downsized Engines Appendix L: Relationship between Power and Performance Appendix M: HCCI Projects Appendix N: Effect of Compression Ratio of Brake Thermal Efficiency Appendix O: Variable Compression Ratio Engines Appendix P: Fuel Consumption Impact of Tier 3 Emission Standards Appendix Q: Examples of EPA's Standards for Gasoline Appendix R: Impact of Low Carbon Fuels to Achieve Reductions in GHG Emissions (California LCFS 2007 Alternative Fuels and Cleaner Fossil Fuels CNG, LPG) Appendix S: NHTSA's Estimated Fuel Consumption Reduction Effectiveness of Technologies and Estimated Costs of Technologies Appendix T: Derivation of Turbocharged, Downsized Engine Direct Manufacturing Costs Appendix U: SI Engine Pathway NHTSA Estimates Direct Manufacturing Costs and Total Costs Appendix V: SI Engine Pathway NRC Estimates Direct Manufacturing Costs Alternative Pathway, Alternative High CR with Exhaust Scavenging, and Alternative EVAS Supercharger Appendix W: Technologies, Footprints, and Fuel Economy for Example Passenger Cars, Trucks, and Hybrid Passenger Cars Appendix X: Full System Simulation Modeling of Fuel Consumption Reductions Appendix Y: Acronym List