Tools for Assuring WIM Data Quality: Practical Guide (2023)

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.

2023 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 1070 Tools for Assuring WIM Data Quality PRACTICAL GUIDE Olga Selezneva Dean Wolf Applied Research Associates, Inc. Elkridge, MD Subscriber Categories Data and Information Technology • Pavements • Research 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 1070 Project 20-50(20) ISSN 2572-3766 (Print) ISSN 2572-3774 (Online) ISBN 978-0-309-69904-4 Library of Congress Control Number 2023943749 © 2023 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 spec- ifications. 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 1070 Waseem Dekelbab, Deputy Director, Cooperative Research Programs, and Manager, National Cooperative Highway Research Program Camille Crichton-Sumners, Senior Program Officer Mazen Alsharif, Senior Program Assistant Natalie Barnes, Director of Publications Heather DiAngelis, Associate Director of Publications NCHRP PROJECT 20-50(20) PANEL Field of Special Projects Tommy E. Nantung, Indiana Department of Transportation, West Lafayette, IN (Chair) Alexander K. Appea, Virginia Department of Transportation, Lynchburg, VA Wiley D. Cunagin, Pavement Analytics, LLC, Tallahassee, FL Yong-Rak Kim, Texas A&M University, College Station, College Station, TX Seungwook “David” Lim, California Department of Transportation (CALTRANS), Rancho Cordova, CA Alejandra L. Medina, Virginia Polytechnic Institute and State University (Virginia Tech), Blacksburg, VA Nusrat Siraj Morshed, New Jersey Department of Transportation, Trenton, NJ Hao Wang, Rutgers University, Piscataway, NJ Deborah Walker, FHWA Liaison

NCHRP Research Report 1070: Tools for Assuring WIM Data Quality: Practical Guide provides state departments of transportation (DOTs) with new procedures to help prac- titioners improve accuracy and increase the reliability of weigh-in-motion (WIM) data through (1) more appropriate site selection; (2) WIM system selection, installation, calibra- tion, and maintenance; (3) data analysis methods; and (4) quality control/quality assurance (QC/QA) procedures. The report, practical guide, and WIM tools should be useful to practitioners in state, regional, and local transportation agencies interested in improving the quality of traffic loading and truck weight data collected by WIM systems. WIM systems provide an estimate of the static weight of moving vehicles. WIM data is used for transportation and freight planning, pavement and bridge design, and highway safety investigations. The Federal Highway Administration (FHWA) Long-Term Pavement Performance (LTPP) program, formed in 1991, has collected truck weight and axle load- ing data using WIM systems installed at LTPP Specific Pavement Studies test sites across North America for almost two decades. In addition, the LTPP program has collected WIM performance validation and calibration data, including test truck data for quantifying WIM measurement precision and bias. This and other data sets were used to inform the state of practice. There are potential sources of error in WIM measurement that affect WIM data accuracy and consistency. WIM systems are subject to specific measurement conditions that have an impact on the quality and reliability of the data they measure and on the durability of the sensors and the WIM system itself. WIM data accuracy and consistency may be improved by considering factors such as sensor technology, temperature and seasonal effects on pavement support and sensor output, vehicle speed, pavement condition, pavement surface smoothness, changes in truck volumes and vehicle configurations, data sampling frequen- cies, and WIM system age. More advanced WIM tools and procedures may consider these factors and help state DOTs with WIM site selection, sensor selection and maintenance, and calibration and data quality acceptance procedures. Under NCHRP Project 20-50(20), “LTPP Data Analysis: Develop Practical Tools and Procedures to Improve WIM Data Quality,” Applied Research Associates (ARA) was asked to review the state of practice for WIM and analyze WIM data to develop the next gen- eration of tools and procedures to improve accuracy and increase the reliability of WIM data through (1) more appropriate site selection; (2) WIM system selection, installation, calibration, and maintenance; (3) updated data analysis methods; and (4) advanced QC/QA procedures. F O R E W O R D By Camille Crichton-Sumners Staff Officer Transportation Research Board

In addition to this report, several supplemental resources are available, including NCHRP Web-Only Document 370: LTPP Data Analysis: Practical Tools and Procedures to Improve WIM Data Quality, four presentations, and six WIM spreadsheet tools: • WIM Site Assessment Tool, • WIM Sensor Selection Tool, • WIM Installation Quality Assurance Tool, • WIM Maintenance Tool, • WIM Calibration Tool, and • WIM Data Quality Assurance Analysis Tool. These materials can be found on the National Academies Press website (nap.national academies.org) by searching for NCHRP Research Report 1070.

1 Chapter 1 Introduction 1 Importance of WIM Data 1 WIM Data Quality Issues 2 Guide Purpose 2 Guide Overview 3 How to Navigate the Guide 3 Accessing the WIM Tools and Support Materials 4 Chapter 2 WIM Equipment Selection 4 Supporting Tools and Reference Documents 4 WIM Equipment Components 5 Selecting WIM Sensor Type and Array Using WIM Sensor Selection Tool 11 Recommended WIM Sensor Layouts 13 WIM Controller 14 Equipment Cabinet 14 Communications Equipment 14 Power Equipment 15 Surge Suppression and Grounding 15 Fans and Environmental Controls 15 Pull Boxes 15 WIM Site Design Plan 16 Chapter 3 WIM Site Assessment 16 Reference Sources 16 Tools and Equipment 17 Supporting Data and Documentation 17 WIM Site Evaluation Criteria Overview 20 WIM Site Assessment Procedure 34 Chapter 4 WIM Installation Quality Assurance 34 Supporting Materials, Tools, and Equipment 35 Project Documentation 35 Reference Documentation 35 WIM Installation QA Inspection Procedure 63 WIM Site Installation Acceptance Report 65 Chapter 5 WIM Equipment Maintenance 65 Equipment and Supplies 66 Supporting Tools and Documentation 66 Safety 66 Routine Preventive Maintenance 72 Corrective Maintenance and Repair 74 WIM System Troubleshooting and Repairs 79 Documenting Maintenance Activities and Outcomes C O N T E N T S

82 Chapter 6 WIM Equipment Calibration 82 Calibration Purpose 82 Initial and Routine WIM System Calibration and WIM System Performance Validation 83 Supporting Tools, Equipment, and Reference Documents 83 Scheduling WIM System Calibration 84 Previsit WIM Operation Checks and Data Analysis 85 On-Site Activities Prior to WIM System Calibration 86 WIM System Calibration Procedure 93 Reports and Other Outcomes 97 Chapter 7 WIM Data Quality Assurance and Analysis 97 Supporting Tools, Software, and Hardware 97 WIM Data Format and Recommended WIM Vendor Software Requirements 98 WIM Data Quality Assurance Analysis Overview 98 Daily Rudimentary Automated WIM Data QC 102 Periodic WIM Data QA Review and Analysis Using WIM Data QA Analysis Tool 125 Real-Time Operational Review 125 Troubleshooting WIM Data Quality Issues 130 Chapter 8 WIM Data Acceptance Considerations and Criteria 130 Specifying WIM Data Accuracy Requirements 131 Quantification of WIM Measurement Errors 132 Methods for Assessing WIM Measurement Accuracy and Acceptance Criteria 135 Specifying WIM Data Availability Requirements 136 Development of Acceptance Criteria for WIM Data Reasonableness and WIM Data Comparison QA Analyses 138 Daily and Monthly WIM Data Acceptance Analysis 139 Appendix A WIM Site Design Catalog 148 Appendix B WIM Site Design Plan and Cabinet Wiring Diagrams 152 Appendix C Weight Record Format from 2016 FHWA Traffic Monitoring Guide 154 References 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 nap.nationalacademies.org) retains the color versions.