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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 REPORT 720 Estimating the Effects of Pavement Condition on Vehicle Operating Costs Karim Chatti Imen Zaabar Michigan State UniverSity East Lansing, MI Subscriber Categories Energyâ â¢â Financeâ â¢â Pavements TRANSPORTAT ION RESEARCH BOARD WASHINGTON, D.C. 2012 www.TRB.org 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 research provides the most effective approach to the solution of many problems facing highway administrators and engineers. Often, highway problems are of local interest and can best be studied by highway departments individually or in cooperation with their state universities and others. However, the accelerating growth of highway transportation develops increasingly complex problems of wide interest to highway authorities. These problems are best studied through a coordinated program of cooperative research. In recognition of these needs, the highway administrators of the American Association of State Highway and Transportation Officials initiated in 1962 an objective national highway research program employing modern scientific techniques. This program is supported on a continuing basis by funds from participating member states of the Association and it receives the full cooperation and support of the Federal Highway Administration, United States Department of Transportation. The Transportation Research Board of the National Academies was requested by the Association to administer the research program because of the Boardâs recognized objectivity and understanding of modern research practices. The Board is uniquely suited for this purpose as it maintains an extensive committee structure from which authorities on any highway transportation subject may be drawn; it possesses avenues of communications and cooperation with federal, state and local governmental agencies, universities, and industry; its relationship to the National Research Council is an insurance of objectivity; it maintains a full-time research correlation staff of specialists in highway transportation matters to bring the findings of research directly to those who are in a position to use them. The program is developed on the basis of research needs identified by chief administrators of the highway and transportation departments and by committees of AASHTO. Each year, specific areas of research needs to be included in the program are proposed to the National Research Council and the Board by the American Association of State Highway and Transportation Officials. Research projects to fulfill these needs are defined by the Board, and qualified research agencies are selected from those that have submitted proposals. Administration and surveillance of research contracts are the responsibilities of the National Research Council and the Transportation Research Board. The needs for highway research are many, and the National Cooperative Highway Research Program can make significant contributions to the solution of 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 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 at: http://www.national-academies.org/trb/bookstore Printed in the United States of America NCHRP REPORT 720 Project 1-45 ISSN 0077-5614 ISBN 978-0-309-25821-0 Library of Congress Control Number 2012939367 Â© 2012 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, FMCSA, FTA, or Transit Development Corporation 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 project that is the subject of this report was a part of the National Cooperative Highway Research Program, conducted by the Transportation Research Board with the approval of the Governing Board of the National Research Council. The members of the technical panel selected to monitor this project and to review this report were chosen for their special competencies and with regard for appropriate balance. The 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 Governing Board of the National Research Council. 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 Research Council, or the program sponsors. The Transportation Research Board of the National Academies, the National Research Council, and the sponsors of the National Cooperative Highway Research Program do not endorse products or manufacturers. Trade or manufacturersâ names appear herein solely because they are considered essential to the object of the report.
The National Academy of Sciences is a private, nonprofit, self-perpetuating society of distinguished scholars engaged in scientific and engineering research, dedicated to the furtherance of science and technology and to their use for the general welfare. On the authority of the charter granted to it by the Congress in 1863, the Academy has a mandate that requires it to advise the federal government on scientific and technical matters. Dr. Ralph J. Cicerone is president of the National Academy of Sciences. The National Academy of Engineering was established in 1964, under the charter of the National Academy of Sciences, as a parallel organization of outstanding engineers. It is autonomous in its administration and in the selection of its members, sharing with the National Academy of Sciences the responsibility for advising the federal government. The National Academy of Engineering also sponsors engineering programs aimed at meeting national needs, encourages education and research, and recognizes the superior achievements of engineers. Dr. Charles M. Vest is president of the National Academy of Engineering. The Institute of Medicine was established in 1970 by the National Academy of Sciences to secure the services of eminent members of appropriate professions in the examination of policy matters pertaining to the health of the public. The Institute acts under the responsibility given to the National Academy of Sciences by its congressional charter to be an adviser to the federal government and, on its own initiative, to identify issues of medical care, research, and education. Dr. Harvey V. Fineberg is president of the Institute of Medicine. The National Research Council was organized by the National Academy of Sciences in 1916 to associate the broad community of science and technology with the Academyâs purposes of furthering knowledge and advising the federal government. Functioning in accordance with general policies determined by the Academy, the Council has become the principal operating agency of both the National Academy of Sciences and the National Academy of Engineering in providing services to the government, the public, and the scientific and engineering communities. The Council is administered jointly by both Academies and the Institute of Medicine. Dr. Ralph J. Cicerone and Dr. Charles M. Vest are chair and vice chair, respectively, of the National Research Council. The Transportation Research Board is one of six major divisions of the National Research Council. The mission of the Transporta- tion Research Board is to provide leadership in transportation innovation and progress through research and information exchange, conducted within a setting that is objective, interdisciplinary, and multimodal. The Boardâs varied activities annually engage about 7,000 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 individu- als interested in the development of transportation. www.TRB.org www.national-academies.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 AUTHOR ACKNOWLEDGMENTS The research reported herein was performed under NCHRP Project 1-45 by the Department of Civil and Environmental Engineering at Michigan State University (MSU). Dr. Karim Chatti, Professor of Civil Engineering at MSU, is the principal investigator. The other author of this report is Dr. Imen Zaabar, Research Associate at MSU. Dr Tom Papagiannakis, University of Texas at San Antonio, also helped in editing this final report. The work was done under the general supervision of Dr. Chatti. The identification, the evaluation, and the calibration/validation of the vehicle operating cost models were done by Dr. Imen Zaabar. Dr. Jorje Prozzi and Mrs. Jolanda Prozzi, University of Texas at Austin, assisted with the repair and maintenance cost data collection effort. The information regarding applicability of the model to the emerging technolo- gies was provided by Dr. Oliver Page, University of Michigan Transportation Research Institute. The authors also would like to thank the technical support staff from the Texas Department of Trans- portation (DOT) for providing the repair and maintenance data of their fleet and the technical support from Michigan DOT for providing repair and maintenance data of their fleet and conducting pavement condition testing, coordinated by Mr. Tom Hynes. The authors also acknowledge the help received by several MSU postdoctoral, graduate, and undergraduate students in conducting the field tests. CRP STAFF FOR NCHRP REPORT 720 Christopher W. Jenks, Director, Cooperative Research Programs Crawford F. Jencks, Deputy Director, Cooperative Research Programs Amir N. Hanna, Senior Program Officer Jeff Oser, Senior Program Assistant Eileen P. Delaney, Director of Publications Natalie Barnes, Senior Editor NCHRP PROJECT 1-45 PANEL Area of DesignâField of Pavements James N. Lee, California DOT, Sacramento, CA (Chair) John Svadlenak, Oregon DOT, Salem, OR Gary E. Elkins, AMEC E&I, Inc., Reno, NV James Selywn Gillespie, Virginia DOT, Charlottesville, VA Kimberly Ann Johnson, Delaware DOT, Dover, DE Michael J. Markow, Teaticket, MA Jerry E. Stephens, Montana State University, Bozeman, MT Matt W. Webb, Michigan DOT (formerly), East Lansing, MI Nadarajah Sivaneswaran, FHWA Liaison Stephen F. Maher, TRB Liaison
F O R E W O R D This report presents models for estimating the effects of pavement condition on vehicle operating costs. These models address fuel consumption, tire wear, and repair and mainte- nance costs and are presented as computational software on the accompanying CD-ROM to facilitate use. The material contained in the report should be of immediate interest to state pavement, construction, and maintenance engineers; vehicle fleet managers; and those involved in pavement-investment decision processes and financial aspects of highway trans- portation. Vehicle operating costs are part of the costs that highway agencies must consider when evaluating pavement-investment strategies. For conventional vehicles, these costs are related to fuel and oil consumption, tire wear, repair and maintenance, and depreciation; emerg- ing vehicle technologies may involve other cost items. These costs depend on the vehicle class and are influenced by vehicle technology, pavement-surface type, pavement condition, roadway geometrics, environment, speed of operation, and other factors. A large body of research is available on the effects of pavement condition on vehicle operating costs and on models used to estimate these effects. Much of this information and many of the models were developed on the basis of data generated more than 30 years ago in other countries for vehicle fleets that vary substantially from those used currently in the United States and for roadways that differ from those built in the United States. However, some relevant infor- mation was collected in the United States in recent years that could help in refining these models or developing models that would better apply to current and future US conditions. Inadequate models for estimating the effects of pavement condition on vehicle operat- ing costs make it difficult to conduct a rational economic analysis. Research was needed to review available information and to develop models applicable to traffic and environmental conditions encountered in the United States. Such models will provide highway agencies with the tools necessary for considering vehicle operating costs in evaluating pavement- investment strategies and identifying options that yield economic and other benefits. Under NCHRP Project 1-45, âModels for Estimating the Effects of Pavement Condition on Vehicle Operating Costs,â Michigan State University worked with the objective of rec- ommending models for estimating the effects of pavement condition on vehicle operating costs that reflect current vehicle technology in the United States. To accomplish this objec- tive, the researchers identified the factors affecting vehicle operating costs, reviewed avail- able models for estimating these costs, and identified those models that could be refined and made applicable to current US conditions. The research also included a field investigation of fuel consumption and tire wear, and the collection and review of data on the repair and maintenance of state departments of transportation vehicle fleets. Using this information, ByâAmirâN.âHanna StaffâOfficer TransportationâResearchâBoard
the researchers calibrated available fuel consumption and tire wear models and developed improved repair and maintenance models. These models are presented as computational software on the accompanying CD-ROM to facilitate use. Appendixes A through D contained in the research agencyâs final report provide further elaboration on the work performed in this project. These appendixes are not published herein, but they are available online at http://www.trb.org/Main/Blurbs/166904.aspx. These appendixes are titled as follows: â¢ Appendix A: Fuel Consumption Models, â¢ Appendix B: Tire Wear Models, â¢ Appendix C: Repair and Maintenance Models, and â¢ Appendix D: An Overview of Emerging Technologies.
C O N T E N T S ixâ Acronyms xiâ Notations 1 Chapter 1â Introduction 1 Background 1 Description of the Problem 1 Project Objective and Scope 1 Research Approach 2 Report Organization 3 Chapter 2â VehicleâOperatingâCostâModels 3 Overview of Existing VOC Models 5 Evaluation of the Existing Models 6 Empirical and Mechanistic VOC Models 7 Selection of Appropriate VOC Models 8 Chapter 3â FuelâConsumptionâModel 8 HDM 4 Fuel Consumption Model 8 Field Trials and Data Collection 11 Testing of the Accuracy and Precision of Test Equipment 12 Field Trials 15 Calibration of the HDM 4 Model 15 Calibration of the HDM 4 Engine Speed Model 18 Calibration of HDM 4 Fuel Consumption Model 19 Effect of Roughness and Texture on Fuel Consumption 21 Roughness 23 Texture 23 Summary 27 Chapter 4â TireâWearâModel 27 HDM 4 Tire Wear Model 27 Data Collection 27 Articulated Truck Tire Wear: NCAT Test Track Data 28 Passenger Cars: Field Trials 30 Calibration of the HDM 4 Tire Wear Model 36 Effect of Roughness on Tire Wear 36 Summary 40 Chapter 5â RepairâandâMaintenanceâCostsâModel 40 Repair and Maintenance Models 40 HDM 4 Model 40 TRDF Study 41 Collection and Assessment of Data Applicability
43 Updating Results of TRDF Study 44 MechanisticâEmpirical Approach 44 Artificial Generation of Road Surface Profiles 45 Dynamic Vehicle Simulation 46 Vehicle Fatigue Damage Analysis 46 Suspension Failure Threshold 48 Mechanistic versus Empirical Approach 49 Effect of Roughness on Repair and Maintenance Costs 49 Summary 51 Chapter 6â ApplicabilityâtoâEmergingâTechnologies 51 New Engine and Alternative Fuel Technology 52 Vehicle Design 53 Automatic Gear Shift for Heavy Trucks 53 New Tire Technology 53 Summary 55 Chapter 7â SummaryâandâSuggestedâResearch 55 Summary 55 Fuel Consumption 56 Tire Wear 56 Repair and Maintenance 58 Applicability to Emerging Technologies 59 Suggested Research 60â References 62 Attachmentâ âUserâGuideâforâVehicleâOperatingâ CostâModel 76 Appendixes Note: Many of the photographs, figures, and tables in this report 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.
AAA American Automobile Association AASHTO American Association of State Highways and Transportation Officials ACC adaptive cruise control AMT automated manual transmission BTS Bureau of Transportation Statistics CCS cruise control systems CNG compressed natural gas COBA Cost Benefit Analysis Program of the United Kingdom CRRI Central Road Research Institute in India CVT continuously variable transmissions DOT Department of Transportation ECU engine control unit EMD electric motor drive/assist EPA Environmental Protection Agency ETSAP Energy Technology System Analysis Program EV electric vehicle FC fuel consumption FE fuel economy FHWA Federal Highway Administration FFV flex fuel vehicles GAO Government Accountability Office GDI gasoline direct injection GPS global positioning systems HCCI homogeneous charge compression ignition HDM Highway Development and Management System HERS Highway Economic Requirements HEV hybrid electric vehicle HIAP Highway Investment Analysis Package HPP highway performance predictor HPMS highway performance monitoring system HUBAM Highway User Benefit Assessment Model of Canada HV hydrogen vehicle ICE internal combustion engine IFC instantaneous fuel consumption IRI international roughness index ISG integrated starter/generator systems ITS intelligent transportation systems A c r o n y m s
LCPC Laboratoire Central des Ponts et ChaussÃ©es LF left front LR left rear MDOT Michigan Department of Transportation MIT Massachusetts Institute of Technology MPD mean profile depth MTD mean texture depth NHTSA National Highway Traffic Safety Administration NITRR National Institute for Transport and Road Research NZVOC New Zealand vehicle operating cost OBD on board diagnostic OEM original equipment manufacturer PHEV plug-in hybrid electric vehicle PIARC Permanent International Association of Road Congresses PMIS pavement management information system PTI Pennsylvania Transportation Institute R&D research and development R&M repair and maintenance RBS regenerative braking systems RPM revolution per minute RR right rear SUV sports utility vehicle TPMS tire pressure monitors systems TRB Transportation Research Board TRDF Texas Research and Development Foundation TRIB Tire Retread and Repair Information Bureau TRRL Transport and Road Research Laboratory VCR variable compression ratio VETO Swedish National Road and Transport Research Institute VOC model VKT vehicle kilometers traveled VMT vehicle miles traveled VOC vehicle operating costs VVL variable value lift systems VVT variable valve timing systems
AF Frontal Area (m2) beng Speed dependent engine drag parameter (dimensionless) ceng Speed independent engine drag parameter (dimensionless) C0tc Tread wear rate constant (dm3/1000 km) Ctcte Tread wear coefficient (dm3/MNm) CD Drag Coefficient (dimensionless) CDmult CD multiplier (dimensionless) Cs Tire stiffness (kN/rad) CR1 Rolling resistance tire factor (dimensionless) CR2 Rolling resistance surface factor (dimensionless) Ct Cost per tire ($/tire) CFT Circumferential force on the tire (N) CTCON Incremental change of tire consumption related to congestion (dimensionless) CONFAC Congestion modification factor (dimensionless) DEF Benkelman Beam rebound deflection (mm) dFUEL Incremental change of fuel consumption related to congestion (dimensionless) EALC Accessory load constant (KW) ECFLC Cooling fan constant (dimensionless) ehp Proportionate decrease in efficiency at high output power (dimensionless) e Superelevation (radians) ESLIP Slip energy, (lb-mi; 1 lb-mi = 7,159 N.m) EQNT Number of equivalent new tires consumed per 1000 km (1/1000 km) FCLIM Climatic factor (dimensionless) FC Fuel consumption (mL/s) Fa Aerodynamic forces (N) Fg Gradient forces (N) Fc Curvature forces (N) Fr Rolling resistance forces (N) Fi Inertial forces (N) GR Gradient (radians) g Gravity (m/s2) IFC Instantaneous fuel consumption (mL/s) K0 Calibration factor reflecting pavement properties (dimensionless) KCS Calibration factor (dimensionless) Kcr2 Calibration factor (dimensionless) n o T A T I o n s
Ktr Road roughness coefficient (dimensionless) Ku Road texture coefficient (dimensionless) Lt Life of tire (km) LFT Lateral force on the tire (N) M Vehicle mass (kg) MODFAC Tire life modification factor (dimensionless) Nt Number of tires Nw Number of wheels (dimensionless) NFT Normal force on the tire (N) Ptot Total power requirement (kW) Peng Power required to run the engine and overcome internal engine friction (kW) Pmax Rated power or the maximum power (kW) Pout Total output power of the engine required to provide tractive force and run the accessories (kW) Ptr Power required to overcome traction forces (kW) Paccs Power required for engine accessories (e.g., fan belt, alternator etc.) (kW) Paccs_a0 Ratio of engine and accessories drag to rated engine power when traveling at 100 km/h (dimensionless) PctPeng Percentage of the engine and accessories power used by the engine (Default = 80%) RPM Engine speed (rotation per minute) RPM100 Engine speed at 100 km/h (rev/min) RPMIdle Idle engine speed (rev/min) R Curvature radius (m) RREC Ratio of the cost of retreads to new tires (dimensionless) RTWR Life of a retreaded tire relative to a new tire SWE Slip energy-volume wear coefficient (lb-mi/in3) T Engine torque (N-m) TRPM Load governed maximum engine speed (rotation per minute) Tdsp Texture depth using sand patch method (mm) TWT Total change in tread wear (dm3/1000 km) TE Tire energy (MNm/1000 km) TYREFAC Tire type modification factor (dimensionless) VWR Volume of worn tread rubber (in3; 1 in = 25.4 mm) VOL Tire volume (dm3) VEHFAC Vehicle specific modification factor (dimensionless) a Fuel consumption at Idling (mL/s) ast Steady state fuel consumption (mL/s) b Fuel efficiency factor (mL/kW/s) or (mL/KJ) bst Steady state fuel efficiency parameter (mL/KJm/s) b2 Acceleration fuel efficiency parameter (mL/KJm/s2) bb Base fuel efficiency parameter (mL/KJm/s) DTWT Change in tread wear (mm) l Tire slip coefficient (dimensionless) m Coefficient of friction (dimensionless) u Vehicle velocity (m/s) x Fuel-to-power efficiency factor (mL/KW/s) xb Base fuel-to-power efficiency depends on the technology type (gasoline versus diesel) (mL/kW/s) r Mass density of the air (Kg/m3)