Design Guidelines for Mitigating Collisions with Trees and Utility Poles (2022)

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2022 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 1016 Design Guidelines for Mitigating Collisions with Trees and Utility Poles Ingrid B. Potts Douglas W. Harwood MRIGlobal Kansas City, MO Subscriber Categories Design • Operations and Trafc Management • Safety and Human Factors Research sponsored by the American Association of State Highway and Transportation Ofcials 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.mytrb.org/MyTRB/Store/default.aspx Printed in the United States of America NCHRP RESEARCH REPORT 1016 Project 17-82 ISSN 2572-3766 (Print) ISSN 2572-3774 (Online) ISBN 978-0-309-68744-7 Library of Congress Control Number 2022946394 © 2022 by the National Academy of Sciences. National Academies of Sciences, Engineering, and Medicine and the graphical logo are trade- marks of the 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, APTA, FAA, FHWA, FTA, GHSA, or NHTSA 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 does not develop, issue, or publish standards or speci- fications. The Transportation Research Board manages applied research projects which provide the scientific foundation that may be used by Transportation Research Board sponsors, industry associations, or other organizations as the basis for revised practices, procedures, or specifications. 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 or logos appear herein solely because they are considered essential to the object of the report.

e 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. e 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. e 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. e 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. e 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. e Transportation Research Board is one of seven major programs of the National Academies of Sciences, Engineering, and Medicine. e 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. e 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. e 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 1016 Christopher J. Hedges, Director, Cooperative Research Programs Waseem Dekelbab, Deputy Director, Cooperative Research Programs, and Manager, National Cooperative Highway Research Program Sid Mohan, Associate Program Manager, Implementation and Technology Transfer, National Cooperative Highway Research Program David M. Jared, Senior Program Officer Traci Caldwell, Senior Program Assistant Natalie Barnes, Director of Publications Heather DiAngelis, Associate Director of Publications NCHRP PROJECT 17-82 PANEL Field of Traffic—Area of Safety Tobey Reynolds, New Hampshire Department of Transportation, Concord, NH (Chair) David R. Bizuga, New Jersey Department of Transportation, Trenton, NJ Stephen David Hall, Connecticut Department of Transportation, Newington, CT Jane C. Lundquist, Texas Department of Transportation, Austin, TX Filiberto Sotelo, Illinois Department of Transportation, Springfield, IL Richard Storm, HDR, Minneapolis, MN Scott Zeller, Washington State Department of Transportation, Olympia, WA Richard B. Albin, FHWA Liaison Kelly K. Hardy, AASHTO Liaison Stephen F. Maher, TRB Liaison

NCHRP Research Report 1016: Design Guidelines for Mitigating Collisions with Trees and Utility Poles presents guidelines to quantitatively determine the safety risks posed by fixed objects placed in close proximity to roadways. These guidelines will be of interest to trans- portation agencies seeking to balance safety with roadside design factors and better commu- nicate to decision makers and the public the safety risks posed by fixed objects. The research results are intended for consideration by AASHTO as a new chapter or as a supplement in a future edition of the AASHTO Roadside Design Guide. Each year, roadway departure crashes in the United States result in serious injuries and fatalities. An estimated over 1 in 3 fatalities are associated with impacting fixed objects such as trees and utility poles. Current guidelines advise transportation agencies to remove or avoid placing fixed objects within regions close to the traveled way; however, agencies must often consider numerous competing interests. Furthermore, overhead utilities located along the right-of-way provide essential services to residential and commercial customers, but reloca- tion of utility poles is often costly. As transportation agencies continue to expand the use of data-driven decision-making processes and performance-based design decisions, it is necessary to quantitatively evaluate the safety risks posed by fixed objects located near the traveled way, as well as the benefits of implementing various safety treatments within the clear zone. Transportation practitioners needed a risk-based approach to help mitigate fatal and serious injury crashes with fixed objects within the right-of-way. Under NCHRP Project 17-82, “Proposed Guidance for Fixed Objects in the Roadside Design Guide,” MRIGlobal was asked to develop an evaluation methodology and guidelines to quantify the relative risk of collisions with roadside fixed objects within the right-of-way. This risk-based approach to help mitigate fatal and serious injury crashes with fixed objects is consistent with development of other guidelines for AASHTO to consider for inclusion in the next version of the AASHTO Roadside Design Guide. In addition to the guidelines published as NCHRP Research Report 1016, four deliverables are available on the National Academies Press website (www.nap.edu) by searching for NCHRP Research Report 1016. The deliverables are as follows: • NCHRP Web-Only Document 336: Proposed Guidelines for Fixed Objects in the Roadside Design Guide, which is the research agency’s report documenting the development of the guidelines and the entire research effort; • A slide summary that is a presentation introducing NCHRP Research Report 1016; • A plan for implementation of the research deliverables; and • A spreadsheet tool for calculating predicted crash frequencies, potential number of injured persons by severity level, and benefit-cost ratios for roadside improvements to mitigate crashes involving trees and utility poles. F O R E W O R D By David M. Jared Staff Officer Transportation Research Board

1 Summary 2 Chapter 1 Introduction 2 1.1 Background 3 1.2 Organization of This Guide 4 Chapter 2 Design Criteria for Roadside Clear Zones 4 2.1 Design Criteria for Clear Zone Distance 5 2.2 Adjustment Factors for Clear Zones on Horizontal Curves 7 Chapter 3 Crash Reduction Programs for Removing or Relocating Roadside Trees and Utility Poles 7 3.1 Roadside Trees 9 3.2 Roadside Utility Poles 12 Chapter 4 Relationship of Presence of Roadside Trees and Utility Poles to Crash Frequency and Severity 12 4.1 Existing Roadside Design Models 12 4.2 Recommended Crash Prediction Method Based on Existing Crash Prediction Models 20 Chapter 5 Recommended Benefit-Cost Analysis Method 20 5.1 Computation of Benefit-Cost Ratio and Net Benefits 21 5.2 Annual Number of Crashes Reduced 21 5.3 Crash Costs by Crash Severity Level 21 5.4 Improvement Service Life 22 5.5 Discount Rate or Minimum Attractive Rate of Return 22 5.6 Present Value of Crash Reduction Benefits 22 5.7 Implementation Cost for Removing/Relocating Roadside Trees and Utility Poles 24 Chapter 6 Benefit-Cost Analysis Examples 24 6.1 Benefit-Cost Example 1—Removal of an Isolated Roadside Tree 27 6.2 Benefit-Cost Example 2—Removal of a Continuous Group of Roadside Trees 29 6.3 Benefit-Cost Example 3—Relocation of a Single Utility Pole 31 6.4 Benefit-Cost Example 4—Relocation of an Extended Series of Utility Poles 33 6.5 Benefit-Cost Example 5—Removal of an Extended Series of Utility Poles and Replacement with Underground Utilities C O N T E N T S

35 References and Bibliography 37 Appendix A Current iRAP Model for Predicting Run-Off-Road Crashes 65 Appendix B Predicting the Frequency and Severity of Tree- and Utility-Pole-Related Crashes with the Accompanying Spreadsheet Tool 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.nap.edu) retains the color versions.