Stray Current Control of Direct Current-Powered Rail Transit Systems: A Guidebook (2020)

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2020 T R A N S I T C O O P E R A T I V E R E S E A R C H P R O G R A M TCRP RESEARCH REPORT 212 Research sponsored by the Federal Transit Administration in cooperation with the Transit Development Corporation Subject Areas Public Transportation • Energy • Safety and Human Factors Stray Current Control of Direct Current-Powered Rail Transit Systems: A Guidebook Emer C. Flounders, Jr. CORRPRO COMPANIES, INC. AdvANCEd ENgINEERINg SERvICES gROuP Malvern, PA Saud A. Memon HNTB CORPORATION Houston, TX

TCRP RESEARCH REPORT 212 Project D-16 ISSN 2572-3782 ISBN 978-0-309-48126-7 © 2020 National Academy of Sciences. All rights reserved. COPYRIGHT INFORMATION Authors herein are responsible for the authenticity of their materials and for obtaining written permissions from publishers or persons who own the copyright to any previously published or copyrighted material used herein. Cooperative Research Programs (CRP) grants permission to reproduce material in this publication for classroom and not-for-profit purposes. Permission is given with the understanding that none of the material will be used to imply TRB, AASHTO, FAA, FHWA, FTA, GHSA, NHTSA, or TDC endorsement of a particular product, method, or practice. It is expected that those reproducing the material in this document for educational and not-for-profit uses will give appropriate acknowledgment of the source of any reprinted or reproduced material. For other uses of the material, request permission from CRP. NOTICE The research report was reviewed by the technical panel and accepted for publication according to procedures established and overseen by the Transportation Research Board and approved by the National Academies of Sciences, Engineering, and Medicine. The opinions and conclusions expressed or implied in this report are those of the researchers who performed the research and are not necessarily those of the Transportation Research Board; the National Academies of Sciences, Engineering, and Medicine; or the program sponsors. The Transportation Research Board; the National Academies of Sciences, Engineering, and Medicine; and the sponsors of the Transit Cooperative Research Program do not endorse products or manufacturers. Trade or manufacturers’ names appear herein solely because they are considered essential to the object of the report. TRANSIT COOPERATIVE RESEARCH PROGRAM The nation’s growth and the need to meet mobility, environmental, and energy objectives place demands on public transit systems. Cur- rent systems, some of which are old and in need of upgrading, must expand service area, increase service frequency, and improve efficiency to serve these demands. Research is necessary to solve operating prob- lems, adapt appropriate new technologies from other industries, and introduce innovations into the transit industry. The Transit Coopera- tive Research Program (TCRP) serves as one of the principal means by which the transit industry can develop innovative near-term solutions to meet demands placed on it. The need for TCRP was originally identified in TRB Special Report 213—Research for Public Transit: New Directions, published in 1987 and based on a study sponsored by the Urban Mass Transportation Administration—now the Federal Transit Administration (FTA). A report by the American Public Transportation Association (APTA), Transportation 2000, also recognized the need for local, problem- solving research. TCRP, modeled after the successful National Coop- erative Highway Research Program (NCHRP), undertakes research and other technical activities in response to the needs of transit ser- vice providers. The scope of TCRP includes various transit research fields including planning, service configuration, equipment, facilities, operations, human resources, maintenance, policy, and administrative practices. TCRP was established under FTA sponsorship in July 1992. Proposed by the U.S. Department of Transportation, TCRP was authorized as part of the Intermodal Surface Transportation Efficiency Act of 1991 (ISTEA). On May 13, 1992, a memorandum agreement outlining TCRP operating procedures was executed by the three cooperating organi- zations: FTA; the National Academies of Sciences, Engineering, and Medicine, acting through the Transportation Research Board (TRB); and the Transit Development Corporation, Inc. (TDC), a nonprofit educational and research organization established by APTA. TDC is responsible for forming the independent governing board, designated as the TCRP Oversight and Project Selection (TOPS) Commission. Research problem statements for TCRP are solicited periodically but may be submitted to TRB by anyone at any time. It is the responsibility of the TOPS Commission to formulate the research program by identi- fying the highest priority projects. As part of the evaluation, the TOPS Commission defines funding levels and expected products. Once selected, each project is assigned to an expert panel appointed by TRB. The panels prepare project statements (requests for propos- als), select contractors, and provide technical guidance and counsel throughout the life of the project. The process for developing research problem statements and selecting research agencies has been used by TRB in managing cooperative research programs since 1962. As in other TRB activities, TCRP project panels serve voluntarily without compensation. Because research cannot have the desired effect if products fail to reach the intended audience, special emphasis is placed on disseminat- ing TCRP results to the intended users of the research: transit agen- cies, service providers, and suppliers. TRB provides a series of research reports, syntheses of transit practice, and other supporting material developed by TCRP research. APTA will arrange for workshops, train- ing aids, field visits, and other activities to ensure that results are imple- mented by urban and rural transit industry practitioners. TCRP provides a forum where transit agencies can cooperatively address common operational problems. TCRP results support and complement other ongoing transit research and training programs. Published research reports of the TRANSIT COOPERATIVE RESEARCH PROGRAM are available from Transportation Research Board Business Office 500 Fifth Street, NW Washington, DC 20001 and can be ordered through the Internet by going to http://www.national-academies.org and then searching for TRB Printed in the United States of America

The National Academy of Sciences was established in 1863 by an Act of Congress, signed by President Lincoln, as a private, non- governmental institution to advise the nation on issues related to science and technology. Members are elected by their peers for outstanding contributions to research. Dr. Marcia McNutt is president. The National Academy of Engineering was established in 1964 under the charter of the National Academy of Sciences to bring the practices of engineering to advising the nation. Members are elected by their peers for extraordinary contributions to engineering. Dr. John L. Anderson is president. The National Academy of Medicine (formerly the Institute of Medicine) was established in 1970 under the charter of the National Academy of Sciences to advise the nation on medical and health issues. Members are elected by their peers for distinguished contributions to medicine and health. Dr. Victor J. Dzau is president. The three Academies work together as the National Academies of Sciences, Engineering, and Medicine to provide independent, objective analysis and advice to the nation and conduct other activities to solve complex problems and inform public policy decisions. The National Academies also encourage education and research, recognize outstanding contributions to knowledge, and increase public understanding in matters of science, engineering, and medicine. Learn more about the National Academies of Sciences, Engineering, and Medicine at www.national-academies.org. The Transportation Research Board is one of seven major programs of the National Academies of Sciences, Engineering, and Medicine. The mission of the Transportation Research Board is to provide leadership in transportation improvements and innovation through trusted, timely, impartial, and evidence-based information exchange, research, and advice regarding all modes of transportation. The Board’s varied activities annually engage about 8,000 engineers, scientists, and other transportation researchers and practitioners from the public and private sectors and academia, all of whom contribute their expertise in the public interest. The program is supported by state transportation departments, federal agencies including the component administrations of the U.S. Department of Transportation, and other organizations and individuals interested in the development of transportation. Learn more about the Transportation Research Board at www.TRB.org.

C O O P E R A T I V E R E S E A R C H P R O G R A M S CRP STAFF FOR TCRP RESEARCH REPORT 212 Christopher J. Hedges, Director, Cooperative Research Programs Lori L. Sundstrom, Deputy Director, Cooperative Research Programs Gwen Chisholm Smith, Manager, Transit Cooperative Research Program Stephan A. Parker, Senior Program Officer Stephanie L. Campbell, Senior Program Assistant Eileen P. Delaney, Director of Publications Natalie Barnes, Associate Director of Publications Linda A. Dziobek, Senior Editor TCRP PROJECT D-16 PANEL Field of Engineering of Fixed Facilities Rufus Francis, Fairfield, CA (Chair) Steven D. Bezner, Rockville, MD Donald S. Carnell, Atkins North America, Raleigh, NC Melvin Clark, LTK Engineering Services, Flower Mound, TX Kai A. Looijenga, Tri-County Metropolitan Transportation District of Oregon, Portland, OR William H. Moorhead, TRAMMCO, LLC, Smithfield, VA Gerard J. Ruggiero, Jacobs, Boston, MA Xianming Shi, Washington State University, Pullman, WA Robert S. Vail, AECOM, Atlanta, GA Roy Wei Shun Chen, FTA Liaison Louis F. Sanders, APTA Liaison Scott Babcock, TRB Liaison

TCRP Research Report 212: Stray Current Control of Direct Current-Powered Rail Transit Systems: A Guidebook documents best practices for those seeking guidance on design, main- tenance, and testing of stray current control (SCC) for rail transit systems. TCRP Research Report 212 is based on a study of both national and international transit agencies and is formatted as a reference guide. It not only includes information and resources needed to implement and evaluate SCC and mitigation measures but also lists testing and mainte- nance strategies for transit operators. Stray current is the part of the current caused by a direct current (DC)-traction system that follows paths other than the return circuit. Stray current leakage and the corrosion caused by these currents is more of an issue in low resis- tivity soils and embedded tracks, which typically run through major traffic areas, city centers, and threads between utility lines that require the rail to be continuously isolated to provide superior track-to-earth resistance. Direct current (DC)-powered transit systems have been faced with major repairs and modifications to signal and traction power systems because of ineffective negative return rail isolation. An indication of the magnitude of the financial costs is cited in a comprehensive research report published by the IEEE in the 1990s, which estimated that a major portion of the $500 million per year from stray current corrosion losses was borne by DC-powered transit properties and the surrounding infrastructure assets. This figure does not take into account the costs associated with signal problems and repairs. The cost to DC-powered transit systems has been increasing steadily due to stray current issues. The overall objective of TCRP Project D-16 was to develop a guidebook on design and sustainability of SCC and control of railcar-to-earth and rail-to-earth voltages for DC-powered rail transit systems. This includes (a) a primer that explains all significant issues in readily understandable terms for nontechnical people, (b) guidelines addressed to design and maintenance practitioners, (c) historical performance data (based on agency interviews) of third rail and overhead contact, and (d) recommendations for further research. Led by co-principal investigators Emer Flounders and Saud Memon, the research team began by assembling and undertaking a thorough review of data and current operating practices from • National and international resources; • Technical journals; • Conference papers; • Transit agency design criteria documents; F O R E W O R D By Stephan A. Parker Staff Officer Transportation Research Board

• International standards; • Transit agency test results and maintenance documents; and • Related reports by transit agencies, consultants, and organizations. A mix of 30 transit agencies (21 national and 9 international) that responded to the questionnaires or participated in interviews augmented the literature review effort. This was supplemented with in-person interviews of eight stray current corrosion consultants and face-to-face interviews and testing of selected transit agencies. This guidebook also includes four anonymized case study SCC sites. They are as follows: (a) an agency with relatively newly constructed tracks; (b) an agency with older tracks; (c) an agency with tracks under construction (both light rail transit and heavy rail transit); and (d) an international transit agency with overhead contact systems. Key decision matrices associated with implementing, maintaining, and testing of SCC and safety control of rail-to-earth potentials were developed using the information collected from the literature review, questionnaires, data gathered during the transit agencies’ and corrosion consultants’ interview process, and SCC testing observations. Using these find- ings, proactive sequential steps are presented in the guidebook for stray current isolation and quality control. These steps include measures that need to be taken at the inception of design, at preconstruction, at construction, and at postconstruction, leading into the main- tenance and testing program phase during the revenue service of the transit system. These recommendations, if followed, will help to ensure that uniform stray current isolation and quality control are achieved for a DC-powered transit system. This guidebook and a PowerPoint presentation describing the project are available on the TRB website at www.trb.org by searching on “TCRP Research Report 212”.

1 Summary 3 Chapter 1 Introduction 4 1.1 Research Methodology 5 1.2 Clarification of Terms 8 Chapter 2 Literature Review 9 2.1 Corrosion and Corrosion Rate 11 2.2 Stray Current and Stray Current Corrosion by Transit Systems 13 2.3 Traction Power 14 2.4 Soil Resistance—Corrosion and Earth Conduction 16 2.5 DC Traction System Grounding (Earthing) 19 2.6 Effects of Stray Current on People and Animals 20 2.7 History of Stray Current Corrosion and Methods of Mitigation 30 2.8 Rail Sections and Rail Boot 31 2.9 Design Criteria and Standards 33 2.10 Chapter Summary 34 Chapter 3 Stray Current Control Design, Mitigation, and Testing of DC Rail Transit Systems 34 3.1 Transit Agency Surveys 36 3.2 Transit Agency and Corrosion Consultant Interviews 37 3.3 Transit Agency Essentials and Corrosion Issues (Case Studies) 45 3.4 Chapter Summary 47 Chapter 4 Stray Current Control Provisions for DC Transit Systems 47 4.1 Design Essentials 55 4.2 Stray Current Control 58 4.3 Maintenance and Testing Program 63 4.4 Criteria Document 63 4.5 Chapter Summary 65 Chapter 5 Conclusions 65 5.1 Literature Review 65 5.2 Transit Agency Data Assembly, Studies, and Field Testing 66 5.3 Recommendations and Guidelines 66 5.4 The Potential for Future Work 68 Acronyms 70 References C O N T E N T S

73 Appendix A Short Survey 75 Appendix B Responses from Transit Agencies 80 Appendix C Long Questionnaire 85 Appendix D Summary of Agency Response Findings 100 Appendix E Decision Tree