National Academies Press: OpenBook
Suggested Citation:"Front Matter." Transportation Research Board and National Research Council. 2013. Overcoming Barriers to Electric-Vehicle Deployment: Interim Report. Washington, DC: The National Academies Press. doi: 10.17226/18320.
×
Page R1
Suggested Citation:"Front Matter." Transportation Research Board and National Research Council. 2013. Overcoming Barriers to Electric-Vehicle Deployment: Interim Report. Washington, DC: The National Academies Press. doi: 10.17226/18320.
×
Page R2
Suggested Citation:"Front Matter." Transportation Research Board and National Research Council. 2013. Overcoming Barriers to Electric-Vehicle Deployment: Interim Report. Washington, DC: The National Academies Press. doi: 10.17226/18320.
×
Page R3
Suggested Citation:"Front Matter." Transportation Research Board and National Research Council. 2013. Overcoming Barriers to Electric-Vehicle Deployment: Interim Report. Washington, DC: The National Academies Press. doi: 10.17226/18320.
×
Page R4
Suggested Citation:"Front Matter." Transportation Research Board and National Research Council. 2013. Overcoming Barriers to Electric-Vehicle Deployment: Interim Report. Washington, DC: The National Academies Press. doi: 10.17226/18320.
×
Page R5
Suggested Citation:"Front Matter." Transportation Research Board and National Research Council. 2013. Overcoming Barriers to Electric-Vehicle Deployment: Interim Report. Washington, DC: The National Academies Press. doi: 10.17226/18320.
×
Page R6
Suggested Citation:"Front Matter." Transportation Research Board and National Research Council. 2013. Overcoming Barriers to Electric-Vehicle Deployment: Interim Report. Washington, DC: The National Academies Press. doi: 10.17226/18320.
×
Page R7
Page viii Cite
Suggested Citation:"Front Matter." Transportation Research Board and National Research Council. 2013. Overcoming Barriers to Electric-Vehicle Deployment: Interim Report. Washington, DC: The National Academies Press. doi: 10.17226/18320.
×
Page R8
Suggested Citation:"Front Matter." Transportation Research Board and National Research Council. 2013. Overcoming Barriers to Electric-Vehicle Deployment: Interim Report. Washington, DC: The National Academies Press. doi: 10.17226/18320.
×
Page R9
Suggested Citation:"Front Matter." Transportation Research Board and National Research Council. 2013. Overcoming Barriers to Electric-Vehicle Deployment: Interim Report. Washington, DC: The National Academies Press. doi: 10.17226/18320.
×
Page R10
Suggested Citation:"Front Matter." Transportation Research Board and National Research Council. 2013. Overcoming Barriers to Electric-Vehicle Deployment: Interim Report. Washington, DC: The National Academies Press. doi: 10.17226/18320.
×
Page R11
Suggested Citation:"Front Matter." Transportation Research Board and National Research Council. 2013. Overcoming Barriers to Electric-Vehicle Deployment: Interim Report. Washington, DC: The National Academies Press. doi: 10.17226/18320.
×
Page R12

Below is the uncorrected machine-read text of this chapter, intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text of each book. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.

Overcoming Barriers to Electric-Vehicle Deployment Interim Report Committee on Overcoming Barriers to Electric-Vehicle Deployment Board on Energy and Environmental Systems Division on Engineering and Physical Sciences Transportation Research Board

THE NATIONAL ACADEMIES PRESS 500 FIFTH STREET, NW WASHINGTON, DC 20001 NOTICE: The project that is the subject of this report was approved by the Governing Board of the National Research Council, whose members are drawn from the councils of the National Academy of Sciences, the National Academy of Engineering, and the Institute of Medicine. The members of the committee responsible for the report were chosen for their special competences and with regard for appropriate balance. This project was supported by Contract DE-EE0004436 between the National Academy of Sciences and the U.S. Department of Energy. Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the authors and do not necessarily reflect the view of the organizations or agencies that provided support for this project. International Standard Book Number-13: 978-0-309-28448-6 International Standard Book Number-10: 0-309-28448-1 Copies of this report are available Additional copies of this report are available in limited supply, free of charge, from: for sale from: Board on Energy and Environmental Systems The National Academies Press National Research Council 500 Fifth Street, NW 500 Fifth Street, NW Keck 360 Keck W934 Washington, DC 20001 Washington, DC 20001 (800) 624-6242 or (202) 334-3313 (202) 334-3344 http://www.nap.edu Copyright 2013 by the National Academy of Sciences. All rights reserved. Printed in the United States of America.

The National Academy of Sciences is a private, nonprofit, self-perpetuating society of distinguished scholars engaged in scientific and engineering research, dedicated to the furtherance of science and technology and to their use for the general welfare. Upon the authority of the charter granted to it by the Congress in 1863, the Academy has a mandate that requires it to advise the federal government on scientific and technical matters. Dr. Ralph J. Cicerone is president of the National Academy of Sciences. The National Academy of Engineering was established in 1964, under the charter of the National Academy of Sciences, as a parallel organization of outstanding engineers. It is autonomous in its administration and in the selection of its members, sharing with the National Academy of Sciences the responsibility for advising the federal government. The National Academy of Engineering also sponsors engineering programs aimed at meeting national needs, encourages education and research, and recognizes the superior achievements of engineers. Dr. Charles M. Vest is president of the National Academy of Engineering. The Institute of Medicine was established in 1970 by the National Academy of Sciences to secure the services of eminent members of appropriate professions in the examination of policy matters pertaining to the health of the public. The Institute acts under the responsibility given to the National Academy of Sciences by its congressional charter to be an adviser to the federal government and, upon its own initiative, to identify issues of medical care, research, and education. Dr. Harvey V. Fineberg is president of the Institute of Medicine. The National Research Council was organized by the National Academy of Sciences in 1916 to associate the broad community of science and technology with the Academy’s purposes of furthering knowledge and advising the federal government. Functioning in accordance with general policies determined by the Academy, the Council has become the principal operating agency of both the National Academy of Sciences and the National Academy of Engineering in providing services to the government, the public, and the scientific and engineering communities. The Council is administered jointly by both Academies and the Institute of Medicine. Dr. Ralph J. Cicerone and Dr. Charles M. Vest are chair and vice chair, respectively, of the National Research Council. www.national-academies.org

COMMITTEE ON OVERCOMING BARRIERS TO ELECTRIC-VEHICLE DEPLOYMENT JOHN G. KASSAKIAN, NAE, 1 Massachusetts Institute of Technology, Cambridge, Chair DAVID L. BODDE, Clemson University, South Carolina JEFF DOYLE, Washington State Department of Transportation GERALD GABRIELSE, NAS, 2 Harvard University, Cambridge, Massachusetts KELLY SIMS GALLAGHER, Tufts University, Medford, Massachusetts ROLAND HWANG, Natural Resources Defense Council, San Francisco, California PETER ISARD, Retired, Washington, D.C. LINOS JACOVIDES, NAE, Paphos Consulting, Grosse Pointe, Michigan ULRIC KWAN, Pacific Gas and Electric Company, San Francisco, California REBECCA LINDLAND, Consultant, Greenwich, Connecticut RALPH D. MASIELLO, NAE, Kema, Inc., Chalfont, Pennsylvania JAKKI MOHR, University of Montana, Missoula MELISSA SCHILLING, New York University Stern School of Business RICHARD TABORS, Across the Charles, Cambridge, Massachusetts THOMAS TURRENTINE, University of California, Davis Staff ELLEN K. MANTUS, Study Co-Director K. JOHN HOLMES, Study Co-Director JAMES ZUCCHETTO, Board Director JOSEPH MORRIS, Senior Program Officer NORMAN GROSSBLATT, Senior Editor MICHELLE SCHWALBE, Program Officer DAVID W. COOKE, Associate Program Officer ALICE V. WILLIAMS, Senior Program Assistant 1 National Academy of Engineering. 2 National Academy of Sciences. v

BOARD ON ENERGY AND ENVIRONMENTAL SYSTEMS ANDREW BROWN, JR., NAE, 1 Delphi Corporation, Troy, Michigan, Chair WILLIAM F. BANHOLZER, NAE, Dow Chemical Company, Midland, Michigan WILLIAM CAVANAUGH III, NAE, Progress Energy (retired), Raleigh, North Carolina PAUL A. DeCOTIS, Long Island Power Authority, Albany, New York CHRISTINE EHLIG-ECONOMIDES, NAE, Texas A&M University, College Station SHERRI GOODMAN, CNA, Alexandria, Virginia NARAIN G. HINGORANI, NAE, Independent Consultant, San Mateo, California ROBERT HUGGETT, Independent Consultant, Seaford, Virginia DEBBIE NIEMEIER, University of California, Davis DANIEL NOCERA, NAS, 2 Massachusetts Institute of Technology, Cambridge MARGO OGE, Environmental Protection Agency (retired), McLean, Virginia MICHAEL OPPENHEIMER, Princeton University, Princeton, New Jersey JACKALYNE PFANNENSTIEL, Independent Consultant, Piedmont, California DAN REICHER, Stanford University, Stanford, California BERNARD ROBERTSON, NAE, Daimler-Chrysler (retired), Bloomfield Hills, Michigan GARY ROGERS, FEV, Inc., Auburn Hills, Michigan ALISON SILVERSTEIN, Consultant, Pflugerville, Texas MARK THIEMENS, NAS, University of California, San Diego RICHARD WHITE, Oppenheimer & Company, New York City ADRIAN ZACCARIA, NAE, Bechtel Group (retired), Frederick, Maryland Staff JAMES ZUCCHETTO, Board Director DANA CAINES, Financial Associate DAVID W. COOKE, Associate Program Officer ALAN CRANE, Senior Scientist K. JOHN HOLMES, Senior Program Officer/Associate Director LaNITA JONES, Administrative Coordinator ALICE V. WILLIAMS, Senior Program Assistant JONATHAN YANGER, Senior Project Assistant 1 National Academy of Engineering. 2 National Academy of Sciences. vi

TRANSPORTATION RESEARCH BOARD 1 Executive Committee DEBORAH H. BUTLER, Executive Vice President, Planning, and CIO, Norfolk Southern Corporation, Norfolk, Virginia, Chair KIRK T. STEUDLE, Director, Michigan Department of Transportation, Lansing, Vice Chair ROBERT E. SKINNER, JR., Transportation Research Board, Executive Director Members VICTORIA A. ARROYO, Executive Director, Georgetown Climate Center, and Visiting Professor, Georgetown University Law Center, Washington, D.C. SCOTT E. BENNETT, Director, Arkansas State Highway and Transportation Department, Little Rock WILLIAM A.V. CLARK, Professor of Geography (emeritus) and Professor of Statistics (emeritus), Department of Geography, University of California, Los Angeles JAMES M. CRITES, Executive Vice President of Operations, Dallas-Fort Worth International Airport, Texas JOHN S. HALIKOWSKI, Director, Arizona Department of Transportation, Phoenix PAULA J. C. HAMMOND, Secretary, Washington State Department of Transportation, Olympia MICHAEL W. HANCOCK, Secretary, Kentucky Transportation Cabinet, Frankfort SUSAN HANSON, Distinguished University Professor Emerita, School of Geography, Clark University, Worcester, Massachusetts STEVE HEMINGER, Executive Director, Metropolitan Transportation Commission, Oakland, California CHRIS T. HENDRICKSON, Duquesne Light Professor of Engineering, Carnegie Mellon University, Pittsburgh, Pennsylvania JEFFREY D. HOLT, Managing Director, Bank of Montreal Capital Markets, and Chairman, Utah Transportation Commission, Huntsville, Utah KEVIN L. KEITH, Missouri Department of Transportation, Jefferson City GARY P. LaGRANGE, President and CEO, Port of New Orleans, Louisiana MICHAEL P. LEWIS, Director, Rhode Island Department of Transportation, Providence JOAN McDONALD, Commissioner, New York State Department of Transportation, Albany DONALD A. OSTERBERG, Senior Vice President, Safety and Security, Schneider National, Inc., Green Bay, Wisconsin STEVE PALMER, Vice President of Transportation, Lowe’s Companies, Inc., Mooresville, North Carolina SANDRA ROSENBLOOM, Director, Innovation in Infrastructure, The Urban Institute, Washington, D.C. HENRY G. (GERRY) SCHWARTZ, JR., Chairman (retired), Jacobs/Sverdrup Civil, Inc., St. Louis, Missouri KUMARES C. SINHA, Olson Distinguished Professor of Civil Engineering, Purdue University, West Lafayette, Indiana DANIEL SPERLING, Professor of Civil Engineering and Environmental Science and Policy; Director, Institute of Transportation Studies; University of California, Davis GARY C. THOMAS, President and Executive Director, Dallas Area Rapid Transit, Dallas, Texas PHILLIP A. WASHINGTON, General Manager, Regional Transportation District, Denver, Colorado 1 Membership as of February 2013. vii

Ex Officio Members REBECCA M. BREWSTER, President and COO, American Transportation Research Institute, Smyrna, Georgia ANNE S. FERRO, Administrator, Federal Motor Carrier Safety Administration, U.S. Department of Transportation LeROY GISHI, Chief, Division of Transportation, Bureau of Indian Affairs, U.S. Department of the Interior, Washington, D.C. JOHN T. GRAY II, Senior Vice President, Policy and Economics, Association of American Railroads, Washington, D.C. MICHAEL P. HUERTA, Administrator, Federal Aviation Administration, U.S. Department of Transportation JOUNG HO LEE, Associate Director for Finance and Business Development, American Association of State Highway and Transportation Officials, and Chair, TRB Young Members Council, Washington, D.C. DAVID T. MATSUDA, Administrator, Maritime Administration, U.S. Department of Transportation MICHAEL P. MELANIPHY, President and CEO, American Public Transportation Association, Washington, D.C VICTOR M. MENDEZ, Administrator, Federal Highway Administration, U.S. Department of Transportation ROBERT J. PAPP (Adm., U.S. Coast Guard), Commandant, U.S. Coast Guard, U.S. Department of Homeland Security CYNTHIA L. QUARTERMAN, Administrator, Pipeline and Hazardous Materials Safety Administration, U.S. Department of Transportation PETER M. ROGOFF, Administrator, Federal Transit Administration, U.S. Department of Transportation DAVID L. STRICKLAND, Administrator, National Highway Traffic Safety Administration, U.S. Department of Transportation JOSEPH C. SZABO, Administrator, Federal Railroad Administration, U.S. Department of Transportation POLLY TROTTENBERG, Under Secretary for Policy, U.S. Department of Transportation ROBERT L. VAN ANTWERP (Lt. General, U.S. Army), Chief of Engineers and Commanding General, U.S. Army Corps of Engineers, Washington, D.C. BARRY R. WALLERSTEIN, Executive Officer, South Coast Air Quality Management District, Diamond Bar, California GREGORY D. WINFREE, Acting Administrator, Research and Innovative Technology Administration, U.S. Department of Transportation FREDERICK G. (BUD) WRIGHT, Executive Director, American Association of State Highway and Transportation Officials, Washington, D.C. viii

Preface Electric vehicles hold many promises—from reducing dependence on imported petroleum to decreasing greenhouse-gas emissions. However, there are many barriers to their mainstream adoption regardless of incentives and enticing promises to solve difficult problems. The vehicles have some technologic limitations, such as restricted electric range and the long time required for battery-charging; they cost more than conventional vehicles; and they require an infrastructure for charging the battery. Given the concerns regarding barriers, Congress asked the Department of Energy to commission a study by the National Research Council (NRC) to investigate the barriers and recommend ways to mitigate them. In this short interim report, the Committee on Overcoming Barriers to Electric-Vehicle Deployment identifies infrastructure needs for electric vehicles, the barriers to deploying that infrastructure, and optional roles for the federal government in overcoming the barriers; it also presents an initial discussion of pros and cons of the optional roles. The committee first addresses needs and barriers associated with the adoption of plug-in electric vehicles from the customer perspective. It then discusses the needs for and barriers to charging and the electric grid. Those issues and many others will be developed further in the committee’s final comprehensive report, which is due in late summer 2014. The present report has been reviewed in draft form by persons chosen for their diverse perspectives and technical expertise in accordance with procedures approved by the NRC Report Review Committee. The purpose of the independent review is to provide candid and critical comments that will assist the institution in making its published report as sound as possible and to ensure that the report meets institutional standards of objectivity, evidence, and responsiveness to the study charge. The review comments and draft manuscript remain confidential to protect the integrity of the deliberative process. We thank the following for their review of this report: Andrew Brown, Jr., NAE, 1 Delphi Corporation, Lawrence D. Burns, NAE, University of Michigan, Doug Chapin, NAE, MPR Associates, Mary English, University of Tennessee, Knoxville, Robert Graham, Southern California Edison, David L. Greene, Oak Ridge National Laboratory, Chris T. Hendrickson, NAE, Carnegie Mellon University, Jeremy J. Michalek, Carnegie Mellon University, John O’Dell, Edmunds.com, and Dan Reicher, Stanford University. Although the reviewers listed above have provided many constructive comments and suggestions, they were not asked to endorse the conclusions or recommendations, nor did they see the final draft of the report before its release. The review of the report was overseen by the review coordinator, Maxine Savitz, NAE, Honeywell Inc. (retired), and the review monitor, Elisabeth Drake, NAE, Massachusetts Institute of Technology (retired). Appointed by NRC, they were responsible for making certain that an independent examination of the report was carried out in accordance with institutional procedures and that all review comments were carefully considered. Responsibility for the final content of the report rests entirely with 1 National Academy of Engineering. ix

the committee and the institution. The committee gratefully acknowledges the following for their presentations: Marcus Alexander, Electric Power Research Institute, Allison Carr, Houston-Galveston Area Council, Patrick Davis, Department of Energy, Rick Durst, Portland General Electric, Jim Francfort, Idaho National Laboratory, Britta Gross, General Motors, Jonna Hamilton, Electrification Coalition, Jack Hidary, Hertz, Don Karner, ECOtality, Ed Kjaer, Southern California Edison, Michael Krauthamer, eVgo, Richard Lowenthal, ChargePoint, Brewster McCracken, Pecan Street, Nick Nigro, Center for Climate and Energy Solutions, Jim Slezak, Department of Energy, Michael Tamor, Ford Motor Company, Joe Thompson, Nissan North America, Jacob Ward, Department of Energy, and Jason Wolf, Better Place. The committee is also grateful for the assistance of the NRC staff in preparing this report. Staff members who contributed to the effort are Ellen Mantus and K. John Holmes, study co-directors; James Zucchetto, board director; Joseph Morris, senior program officer; Norman Grossblatt, senior editor; Michelle Schwalbe, program officer; David Cooke, associate program officer; and Alice Williams, senior program assistant. I especially thank the members of the committee for their efforts throughout the development of this report. John G. Kassakian, Chair Committee on Overcoming Barriers to Electric-Vehicle Deployment x

Contents SUMMARY 1 1 INTRODUCTION 7 Historical and Policy Context, 7 The Plug-in Electric Vehicle and Its Ecosystem, 8 Possible Advantages and Disadvantages of Adoption of Plug-in Electric Vehicles, 11 The Committee and Its Task, 12 The Committee’s Approach to Its Task, 12 Organization of This Report, 12 References, 13 2 THE CUSTOMERS, MANUFACTURERS, AND DEALERS 15 Customer Needs and Barriers, 15 Optional Roles of the Federal Government in Addressing Customer Needs and Barriers, 20 The Automobile Manufacturer, 22 Dealerships and Retail Outlets, 22 References, 24 3 THE CHARGING INFRASTRUCTURE 27 Charging and How It Works, 27 Charging Levels, 30 Charging Locations: Needs, Barriers, and Options, 33 Fleets, 41 Shared-Use Vehicles, 42 Findings and Possible Government Roles in the Charging Infrastructure, 43 References, 46 4 THE ELECTRIC GRID 49 The Electric Grid and Its Interaction with Plug-in Electric Vehicles, 49 Utility Policies that Potentially Affect Adoption of Plug-in Electric Vehicles, 50 Clean Energy, the Electric Grid, and Possible Roles of the Federal Government, 53 Local Electrical Code Requirements, 54 Findings on the Electric Grid, 54 References, 55 APPENDIXES A Committee Biographical Information 57 B Statement of Task 62 C Meetings and Presentations 64 D Technical Specifications 66 xi

Boxes, Figures, and Tables BOXES 4-1 Demand charges, 51 FIGURES 1-1 Plug-in electric vehicle (PEV) sales from December 2010 to March 2013, 9 1-2 The ecosystem of the plug-in electric vehicle, which includes the automobile manufacturer, the car dealer, the customer, the owner, the electric vehicle, the charger, and the electricity system, 10 2-1 Distribution of daily travel distance, 19 3-1 AC Level 1 charging information, 31 3-2 AC Level 2 charging information, 32 3-3 DC fast charging a Nissan Leaf, 33 3-4 The charging pyramid represents the relative importance of residential, workplace, and publicly accessible charging, 34 3-5 Distribution of vehicle locations throughout the week on the basis of data from the 2001 National Household Travel Survey, 35 4-1 Basic diagram of the electric power delivery system, 50 4-2 Aggregate electricity demand from plug-in electric vehicles in (a) San Francisco, California, and (b) Nashville, Tennessee, 52 D-1 The standard connector used for AC Level 1 and Level 2 charging (the J1772 standard of SAE International) allows most plug-in electric vehicles to be charged with chargers built by various manufacturers, 66 D-2 The CHAdeMO plug for DC fast charging is used for most DC fast chargers in the United States, Europe, and Japan and is available on most battery electric vehicles that can accept DC fast charging, 66 D-3 Standard proposed as an alternative to the CHAdeMO connector includes the current plug and socket for AC Level 1 and 2 charging as the upper connector and two lower connectors added for DC fast charging, 67 D-4 The Tesla proprietary plug for DC fast charging that is used for all Tesla DC fast chargers (Superchargers) now available in the United States, 67 D-5 Society of Automotive Engineers charging configurations and ratings terminology, 68 TABLES 3-1 Battery Capacities and All-Electric Ranges for Several Plug-in Electric Vehicles, 28 3-2 Average Costs of Installing Publicly Accessible DC Fast-Charging Stations for the West Coast Electric Highway Project, 39 xii

Next: Summary »
Overcoming Barriers to Electric-Vehicle Deployment: Interim Report Get This Book
×
Buy Paperback | $36.00 Buy Ebook | $28.99
MyNAP members save 10% online.
Login or Register to save!
Download Free PDF

The electric vehicle offers many promises—increasing U.S. energy security by reducing petroleum dependence, contributing to climate-change initiatives by decreasing greenhouse gas (GHG) emissions, stimulating long-term economic growth through the development of new technologies and industries, and improving public health by improving local air quality. There are, however, substantial technical, social, and economic barriers to widespread adoption of electric vehicles, including vehicle cost, small driving range, long charging times, and the need for a charging infrastructure. In addition, people are unfamiliar with electric vehicles, are uncertain about their costs and benefits, and have diverse needs that current electric vehicles might not meet. Although a person might derive some personal benefits from ownership, the costs of achieving the social benefits, such as reduced GHG emissions, are borne largely by the people who purchase the vehicles. Given the recognized barriers to electric-vehicle adoption, Congress asked the Department of Energy (DOE) to commission a study by the National Academies to address market barriers that are slowing the purchase of electric vehicles and hindering the deployment of supporting infrastructure. As a result of the request, the National Research Council (NRC)—a part of the National Academies—appointed the Committee on Overcoming Barriers to Electric-Vehicle Deployment.

This committee documented their findings in two reports—a short interim report focused on near-term options, and a final comprehensive report. Overcoming Barriers to Electric-Vehicle Deployment fulfills the request for the short interim report that addresses specifically the following issues: infrastructure needs for electric vehicles, barriers to deploying the infrastructure, and possible roles of the federal government in overcoming the barriers. This report also includes an initial discussion of the pros and cons of the possible roles. This interim report does not address the committee's full statement of task and does not offer any recommendations because the committee is still in its early stages of data-gathering. The committee will continue to gather and review information and conduct analyses through late spring 2014 and will issue its final report in late summer 2014.

Overcoming Barriers to Electric-Vehicle Deployment focuses on the light-duty vehicle sector in the United States and restricts its discussion of electric vehicles to plug-in electric vehicles (PEVs), which include battery electric vehicles (BEVs) and plug-in hybrid electric vehicles (PHEVs). The common feature of these vehicles is that their batteries are charged by being plugged into the electric grid. BEVs differ from PHEVs because they operate solely on electricity stored in a battery (that is, there is no other power source); PHEVs have internal combustion engines that can supplement the electric power train. Although this report considers PEVs generally, the committee recognizes that there are fundamental differences between PHEVs and BEVs.

  1. ×

    Welcome to OpenBook!

    You're looking at OpenBook, NAP.edu's online reading room since 1999. Based on feedback from you, our users, we've made some improvements that make it easier than ever to read thousands of publications on our website.

    Do you want to take a quick tour of the OpenBook's features?

    No Thanks Take a Tour »
  2. ×

    Show this book's table of contents, where you can jump to any chapter by name.

    « Back Next »
  3. ×

    ...or use these buttons to go back to the previous chapter or skip to the next one.

    « Back Next »
  4. ×

    Jump up to the previous page or down to the next one. Also, you can type in a page number and press Enter to go directly to that page in the book.

    « Back Next »
  5. ×

    To search the entire text of this book, type in your search term here and press Enter.

    « Back Next »
  6. ×

    Share a link to this book page on your preferred social network or via email.

    « Back Next »
  7. ×

    View our suggested citation for this chapter.

    « Back Next »
  8. ×

    Ready to take your reading offline? Click here to buy this book in print or download it as a free PDF, if available.

    « Back Next »
Stay Connected!