Solid-State Roadway Lighting Design Guide: Volume 2: Research Overview (2020)

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.

2020 N A T I O N A L C O O P E R A T I V E H I G H W A Y R E S E A R C H P R O G R A M NCHRP RESEARCH REPORT 940 Solid-State Roadway Lighting Design Volume 2: Research Overview Paul Lutkevich WSP Boston, MA Ronald Gibbons Rajaram Bhagavathula Virginia Tech TranSPorTaTion inSTiTuTe Blacksburg, VA Don McLean DMD anD aSSociaTeS LTD. Surrey, British Columbia, Canada Subscriber Categories Design • Maintenance and Preservation • Safety and Human Factors Research sponsored by the American Association of State Highway and Transportation Officials in cooperation with the Federal Highway Administration

NATIONAL COOPERATIVE HIGHWAY RESEARCH PROGRAM Systematic, well-designed, and implementable research is the most effective way to solve many problems facing state departments of transportation (DOTs) administrators and engineers. Often, highway problems are of local or regional interest and can best be studied by state DOTs individually or in cooperation with their state universities and others. However, the accelerating growth of highway transporta- tion results in increasingly complex problems of wide interest to high- way authorities. These problems are best studied through a coordinated program of cooperative research. Recognizing this need, the leadership of the American Association of State Highway and Transportation Officials (AASHTO) in 1962 ini- tiated an objective national highway research program using modern scientific techniques—the National Cooperative Highway Research Program (NCHRP). NCHRP is supported on a continuing basis by funds from participating member states of AASHTO and receives the full cooperation and support of the Federal Highway Administration (FHWA), United States Department of Transportation, under Agree- ment No. 693JJ31950003. The Transportation Research Board (TRB) of the National Academies of Sciences, Engineering, and Medicine was requested by AASHTO to administer the research program because of TRB’s recognized objectivity and understanding of modern research practices. TRB is uniquely suited for this purpose for many reasons: TRB maintains an extensive com- mittee structure from which authorities on any highway transportation subject may be drawn; TRB possesses avenues of communications and cooperation with federal, state, and local governmental agencies, univer- sities, and industry; TRB’s relationship to the National Academies is an insurance of objectivity; and TRB maintains a full-time staff of special- ists in highway transportation matters to bring the findings of research directly to those in a position to use them. The program is developed on the basis of research needs iden- tified by chief administrators and other staff of the highway and transportation departments, by committees of AASHTO, and by the FHWA. Topics of the highest merit are selected by the AASHTO Special Committee on Research and Innovation (R&I), and each year R&I’s recommendations are proposed to the AASHTO Board of Direc- tors and the National Academies. Research projects to address these topics are defined by NCHRP, and qualified research agencies are selected from submitted proposals. Administration and surveillance of research contracts are the responsibilities of the National Academies and TRB. The needs for highway research are many, and NCHRP can make significant contributions to solving highway transportation problems of mutual concern to many responsible groups. The program, however, is intended to complement, rather than to substitute for or duplicate, other highway research programs. Published research reports of the NATIONAL COOPERATIVE HIGHWAY 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 https://www.nationalacademies.org and then searching for TRB Printed in the United States of America NCHRP RESEARCH REPORT 940, VOLUME 2 Project 05-22 ISSN 2572-3766 (Print) ISSN 2572-3774 (Online) ISBN 978-0-309-48153-3 Library of Congress Control Number 2020937449 © 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; the FHWA; or the program sponsors. The Transportation Research Board; the National Academies of Sciences, Engineering, and Medicine; and the sponsors of the National Cooperative Highway 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.

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.nationalacademies.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 NCHRP RESEARCH REPORT 940 Christopher J. Hedges, Director, Cooperative Research Programs Lori L. Sundstrom, Deputy Director, Cooperative Research Programs Edward T. Harrigan, Senior Program Officer Anthony P. Avery, Senior Program Assistant Eileen P. Delaney, Director of Publications Natalie Barnes, Associate Director of Publications Janet M. McNaughton, Senior Editor NCHRP PROJECT 05-22 PANEL Field of Traffic—Area of Illumination and Visibility Sue M. Zarling, Minnesota DOT, Roseville, MN (Chair) Daryl R. St. Clair, Pennsylvania DOT, Harrisburg, PA Anna D. Bosin, Alaska DOT, Anchorage, AK Robert L. Graham, Georgia DOT, Atlanta, GA James G. Jones, Texas DOT, Austin, TX Mark E. Seppelt, Consultant, Springfield, IL Joseph Cheung, FHWA Liaison

F O R E W O R D NCHRP Research Report 940: Solid-State Roadway Lighting Design presents guidelines for the use of solid-state lighting on roadways. Thus, the report will be of immediate interest to engineers in state and local transportation agencies with responsibility for the design, management, and maintenance of roadway lighting. The roadway lighting industry has changed dramatically over the past decade. Trans- portation agencies have moved beyond the use of legacy high-intensity discharge, full- cutoff roadway luminaires by adopting solid-state lighting (SSL) luminaires. SSL luminaires employing light-emitting diode (LED) arrays provide the potential for lower energy usage, reduced maintenance, and improved color as well as a greater ability to control the distri- bution of light on and off the roadway. Under NCHRP Project 05-22, “Guidelines for Solid-State Roadway Lighting,” WSP, in association with the Virginia Tech Transportation-Institute (VTTI) and consultant Don McLean, was tasked with the development of comprehensive guidelines for the application of SSL roadway lighting and the identification of gaps in current knowledge where future research might enhance these guidelines. Their research included a comprehensive litera- ture review and survey of the practices of state and local transportation agencies, which was followed by a field experiment at VTTI’s Virginia Smart Road. The Smart Road experiment was a series of driving tasks in the lighted test environment, where the ability of drivers to detect pedestrians and standard targets in and off the roadway was measured for SSL luminaires equipped with LED arrays of several correlated color temperatures and for high-pressure sodium (HPS) lamps used as a control. The key outcome of this research is a proposed AASHTO guide on solid-state roadway lighting design intended to supplement the AASHTO Roadway Lighting Design Guide, 7th edition. This guide is presented as Volume 1: Guidance. Volume 2: Research Overview is the project final report, which provides experimental data and analysis supporting the contents of the guide. By Edward T. Harrigan Staff Officer Transportation Research Board

1 Chapter 1 Introduction 1 Report Overview and Organization 1 Research Objectives 1 Key Findings 2 Research Approach 4 Chapter 2 Current State of the Adoption of and Guidance for Solid-State Lighting 4 Introduction 4 Survey Methods 4 Survey Results 4 State of Adoption, Construction, and Maintenance of LED Roadway Lighting 5 Design Guidelines and Criteria for LED Roadway Lighting 5 Conclusion 6 Chapter 3 Structure of the Solid-State Lighting Guide 6 AASHTO Roadway Lighting Design Guide 7 Solid-State Lighting Guide 9 Chapter 4 Literature Review and Gap Analysis 9 Differences Between Solid-State Lighting and High-Intensity Discharge Fixtures 14 Off-Roadway Lighting 15 Metrics for Lighting 18 Dirt Depreciation/Light Loss Factor 19 Disability and Discomfort Glare 21 Considerations for Pedestrians, Cyclists, and Motorists 24 Cost–Benefit Methodologies 25 Applications and Obstacles to Adaptive Lighting 28 Impacts of Weather and Climate on Lighting Effectiveness 30 Application to Freeways, Arterials, Intersections, and Interchanges 31 High-Mast Lighting 32 Potential Environmental and Health Effects 35 Aging Drivers 37 Summary 38 Chapter 5 Research and Testing Results 38 Smart Road Testing 38 Experimental Methods 41 Equipment and Facilities 46 Experimental Procedure C O N T E N T S

48 Analyses 51 Results 71 Discussion 74 Conclusion 75 Research Roadmap 77 Abbreviations and Acronyms 79 References 85 Appendix A Survey Results 92 Appendix B DOT Manuals and Specifications 98 Appendix C Illuminance Characterization Tables Note: Photographs, figures, and tables in this report may have been converted from color to grayscale for printing. The electronic version of the report (posted on the web at www.trb.org) retains the color versions.