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2021 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 968 LED Roadway Lighting IMPACT ON DRIVER SLEEP HEALTH AND ALERTNESS Rajaram Bhagavathula Ronald Gibbons Virginia Tech Transportation Institute Virginia Polytechnic Institute and State University Blacksburg, VA John Hanifin George Brainard Light Research Program Thomas Jefferson University Philadelphia, PA Research sponsored by the American Association of State Highway and Transportation Officials in cooperation with the Federal Highway Administration Subscriber Categories Safety and Human Factors
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 techniquesâthe 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 TRBâs 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; TRBâs 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&Iâs 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.mytrb.org/MyTRB/Store/default.aspx Printed in the United States of America NCHRP RESEARCH REPORT 968 Project 05-23 ISSN 2572-3766 (Print) ISSN 2572-3774 (Online) ISBN 978-0-309-67409-6 Library of Congress Control Number 2021941196 Â© 2021 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 manufacturersâ names or logos 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 Boardâs 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 968 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, Publications Senior Advisor Natalie Barnes, Director of Publications NCHRP PROJECT 05-23 PANEL Field of TrafficâArea of Illumination and Visibility Kristen S. Cetin, Iowa State University, Ames, Iowa (Chair) James G. Jones, Texas Department of Transportation, Austin, TX Alan L. Lewis, New England College of Optometry, Boston, MA Amin Salman, Tennessee Department of Transportation, Nashville, TN Norman P. Schips, New York State Department of Transportation, Colonie, NY Alison Smiley, Human Factors North, Inc., Toronto, ON Michelle Arnold, FHWA Liaison Joseph Y. Cheung, FHWA Liaison Bernardo B. Kleiner, TRB Liaison
This report provides information for state and local transportation agencies on the potential impact of LED roadway lighting on driver health. Thus, the report will be of immediate interest to staff in these agencies with responsibility for the design and operation of roadway lighting. Roadway lighting sources are being converted from high-pressure sodium (HPS) and other high-intensity discharge (HID) luminaires to light-emitting diode (LED, also termed solid-state) luminaires because LEDs are generally more energy-efficient and may offer better visibility. LEDs with a correlated color temperature (CCT) greater than 3000K often have higher blue content in their spectrum than HPS lamps. Light in this wavelength may affect the production of the hormone melatonin, which plays a key role in regulating the human circadian rhythm. Research has also shown that light with a high blue content can increase alertness and enhance cognitive performance in humans. To design LED roadway lighting that minimizes any negative effects on driver health and maximizes alertness, research was needed to understand the relationship between LED roadway lighting and driver sleep health and alertness. Under NCHRP Project 05-23, âEffects of LED Roadway Lighting on Driver Sleep Health and Alertness,â the Virginia Polytechnic Institute and State University was tasked with evaluating the effects of LED roadway lighting on the sleep health and alertness of drivers and comparing these effects to those of HPS lighting and no roadway lighting. In this research, five experimental sessions, each involving one light type and level, were conducted between 1:00 a.m. and 3:00 a.m., including indoors at the university and outdoors on the Virginia Smart Road. Physiological metrics related to sleep health and alertness were determined as well as reaction times for detection of objects and colors on the Virginia Smart Road in realistic conditions. Overall, the research found no statistically significant differences between the physiological metrics and reaction times determined for LED and those for HPS roadway lighting and no roadway lighting. The key outcome of this research is that the experimental results do not support the need to modify NCHRP Research Report 940, Volume 1: Guide for Solid-State Roadway Lighting due to any effects of LED roadway lighting on driver sleep health and alertness. F O R E W O R D By Edward T. Harrigan Staff Officer Transportation Research Board
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. 1 Summary 3 ChapterÂ 1 Introduction 4 ChapterÂ 2 Literature Review 4 Human Vision 6 Purpose of Roadway Lighting 6 Light Sources for Illuminating Roadways 11 Circadian Regulation by Light 11 Circadian, Neuroendocrine, and Neurobehavioral Photoreception 12 Pineal Gland and Melatonin Production 13 Light-Induced Melatonin Suppression 14 Effects of Light on Sleep 15 Direct Alerting Effects of Light at Night 16 Interaction of Alertness and Melatonin 20 Gaps in Research 21 Addressing Gaps in the State of Knowledge 21 Project Objective 22 ChapterÂ 3 Methods 22 Corneal Illuminance Dosage Experiment 26 Driver Sleep Health and Alertness Experiment 36 ChapterÂ 4 Results 36 Corneal Illuminance Dosage ExperimentâNaturalistic Driving Exposure 39 Driver Sleep Health and Alertness Experiment 48 ChapterÂ 5 Discussion 53 ChapterÂ 6 Conclusions 54 Abbreviations 55 References C O N T E N T S