Development of Installation Guidelines for Midwest Guardrail System in Combination with Roadside Curbs for MASH TL-3 Applications (2024)

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2024 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 1089 Development of Installation Guidelines for Midwest Guardrail System in Combination with Roadside Curbs for MASH TL-3 Applications Scott Rosenbaugh Robert Bielenberg Ronald Faller Cody Stolle Jennifer Rasmussen Sina Changizian Joshua Steelman Karla Lechtenberg Chung Song Dan Linzell Midwest Roadside Safety Facility University of Nebraska-Lincoln Lincoln, NE 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). 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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 1089 Waseem Dekelbab, Deputy Director, Cooperative Research Programs, and Manager, National Cooperative Highway Research Program David M. Jared, Senior Program Officer Mazen Alsharif, Senior Program Assistant Natalie Barnes, Director of Publications Heather DiAngelis, Associate Director of Publications NCHRP PROJECT 22-39 PANEL Field of Design—Area of Vehicle Barrier Systems William B. Wilson, Wyoming Department of Transportation, Cheyenne, WY (Chair) Martha Alicia Brown, Illinois Department of Transportation, Springfield, IL Richard M. Dearstyne, New York State Department of Transportation, Albany, NY Ali R. Hangul, Tennessee Department of Transportation, Nashville, TN Samuel Offei-Addo, BSC Group, Inc., Boston, MA Kevin A. Sablan, Idaho Transportation Department, Boise, ID Derwood C. Sheppard, Jr., Florida Department of Transportation, Tallahassee, FL Kathren Zahul, Georgia Department of Transportation, Atlanta, GA Aimee H. Zhang, FHWA Liaison Kelly K. Hardy, AASHTO Liaison ACKNOWLEDGMENTS The authors wish to acknowledge the contributions made by the Midwest Roadside Safety Facility (MwRSF) personnel for conducting the physical tests associated with this research. This work was com- pleted utilizing the Holland Computing Center of the University of Nebraska, which receives support from the Nebraska Research Initiative. The authors would also like to acknowledge Ansys Inc. for supporting this research effort with Ansys LS-DYNA simulation software. Acknowledgment is also given to the following individuals who contributed to the completion of this research project. Midwest Roadside Safety Facility J.C. Holloway, M.S.C.E., Research Engineer and Assistant Director–Physical Testing Division M. Asadollahi Pajouh, PhD, P.E., Research Assistant Professor B.J. Perry, M.E.M.E., Research Associate Engineer A.T. Russell, B.S.B.A., Testing and Maintenance Technician II E.W. Krier, B.S., Engineering Testing Technician II D.S. Charroin, Engineering Testing Technician II R.M. Novak, Engineering Testing Technician II (continued on page vi)

NCHRP Research Report 1089 presents guidelines for the use and placement of the 31-in. Midwest Guardrail System (MGS) adjacent to curbs under the Manual for Assessing Safety Hardware (MASH) Testing Level (TL)-3 impact conditions. The guidelines consider several factors on the performance of guardrail: the effects of curb geometry, fill condition behind the curb, curb termini, blockout depth, barrier offset from the curb, and barrier height relative to the roadway. The new surrogate measures were evaluated against established, crash-based measures and spanned a range of site conditions, crash types, and crash severity. The guidelines describe various types of surrogate measures, offer a framework for organiz- ing the surrogates, outline options for collecting and measuring these surrogates, identify treatments that could benefit from surrogate-based evaluations, and provide case study examples. Curbs are used to control drainage, separate pedestrian facilities, limit right-of-way, pro- vide access control, and limit erosion. However, the need for curbs often competes with guardrail installation. Most research on curb and guardrail has used testing criteria from NCHRP Report 350: Recommended Procedures for the Safety Performance Evaluation of Highway Features. The American Association of State Highway and Transportation Officials’ (AASHTO) and the Federal Highway Administration’s (FHWA) MASH agree- ment requires the use of hardware evaluated with MASH testing conditions. Some crash tests have involved curb placed near guardrail. Many of these tests have failed due to guard- rail rupture, barrier override, or vehicle instability. Traditionally, crash testing focused on the performance of pickup trucks striking guardrail that includes a nearby curb. Some recent crash testing has indicated that research is needed on small cars hitting guardrail near a curb due to the difference in vertical loading on impact when compared to that of a pickup truck. The limitations of using only computer modeling to set guardrail placement recommendations have been shown during crash testing pickup trucks on guardrail that is installed near a curb. More recent crash-testing results, involving the use of a different guardrail and changes in crash-test criteria, call into question how well guardrail performs near a curb. Research was thus needed on the performance of the guardrail system most commonly used, the 31-in. MGS. Under NCHRP Project 22-39, “Guardrail Performance at Various Offsets from Curb MASH TL-3 Applications,” the University of Nebraska–Lincoln was asked to develop instal- lation guidelines for the placement of 31-in.-tall W-beam guardrail in combination with roadside curbs to satisfy MASH TL-3. A 6-in.-tall AASHTO Type B curb was selected as the critical curb, and the steel-post version of the MGS with 8-in.-deep timber blockouts was selected as the critical barrier configuration. Two vehicle trajectory tests were conducted F O R E W O R D By David M. Jared Staff Officer Transportation Research Board

with MASH vehicles (small car and pickup truck) traversing over the curb to evaluate trajec- tories behind the curb. Two full-scale crash tests using the same types of MASH vehicles were also conducted on the MGS offset behind a roadside curb according to MASH TL-3 criteria. Both crash tests resulted in vehicle containment and redirection and passed MASH TL-3 safety performance criteria. Simulations were also conducted to evaluate performance with reduced impact speed or angle. These simulations showed no negative effects on the perfor- mance of the MGS behind curb. Finally, simulations with 4-in.-tall curbs showed significant reductions in the vertical trajectories of the vehicles; thus, the lower-height curbs posed no additional risks to the performance of the MGS placed in combination with curbs. ACKNOWLEDGMENTS (Continued) S.M. Tighe, Engineering Testing Technician I T.C. Donahoo, Engineering Testing Technician I J.T. Jones, Engineering Testing Technician I C. Charroin, Engineering Construction Testing Technician I T. Shapland, Engineering Construction Testing Technician I E.L. Urbank, B.A., Research Communication Specialist Z.Z. Jabr, Engineering Technician J. Oliver, Solidworks Drafting Coordinator Undergraduate and Graduate Research Assistants Uncertainty of Measurement Statement The MwRSF has determined the uncertainty of measurements for several parameters involved in stan- dard full-scale crash testing and nonstandard testing of roadside safety features. Information regarding the uncertainty of measurements for critical parameters is available upon request by the sponsor and the Federal Highway Administration. Independent Approving Authority The Independent Approving Authority for the data contained herein was Mr. Brandon Perry.

1 Chapter 1 Introduction 1 1.1 Background 3 1.2 Objective 3 1.3 Scope 4 Chapter 2 Literature Review 4 2.1 Guardrail-with-Curb Research Prior to MASH 14 2.2 MGS-with-Curb Research 25 2.3 MGS Modeling and Computer Simulation 36 2.4 Discussion 38 Chapter 3 Roadway Agency Survey 38 3.1 Curb Shape and Height 41 3.2 W-Beam Guardrail Characteristics 42 3.3 Soil Backfill Configurations 43 3.4 Sidewalk Configurations 44 3.5 Guardrail Offset from Curb 46 3.6 Critical Curb and Barrier Selection 48 Chapter 4 Curb Traversal Test Setup and Conditions 48 4.1 Scope 48 4.2 Test Facility 49 4.3 Vehicle Tow and Guidance System 49 4.4 Test Vehicles 49 4.5 Data Acquisition Systems 57 4.6 Test Installation Details 65 Chapter 5 Curb Traversal Test 39CT-1 65 5.1 Test Description 69 5.2 Vehicle Trajectory Analysis 71 5.3 Suspension Compression and Wheel Movement 75 Chapter 6 Curb Traversal Test 39CT-2 75 6.1 Test Description 79 6.2 Vehicle Trajectory Analysis 81 6.3 Suspension Compression and Wheel Movement 84 Chapter 7 Analysis of Trajectory Curves 84 7.1 Comparisons to Previous Test Data 87 7.2 Identification of Critical MGS Offsets 93 Chapter 8 Model Validation 93 8.1 Vehicle Model Validation 107 8.2 MGS Model Validation C O N T E N T S

127 Chapter 9 MGS Offset from Curb Simulation Results 127 9.1 MGS Offset from 6-in.-Tall AASHTO Type B Curb—2270P Vehicle 132 9.2 MGS Offset from 6-In.-Tall AASHTO Type B Curb—1100C Vehicle 140 9.3 Discussion 141 Chapter 10 MASH Test Requirements and Evaluation Criteria 141 10.1 Test Requirements 141 10.2 Evaluation Criteria 141 10.3 Soil Strength Requirements 143 Chapter 11 Test Conditions 143 11.1 Test Facility 143 11.2 Vehicle Tow and Guidance System 143 11.3 Test Vehicle 149 11.4 Simulated Occupant 150 11.5 Data Acquisition Systems 153 Chapter 12 System Design Details 153 12.1 Test 2239-1 153 12.2 Test 2239-2 173 Chapter 13 Full-Scale Crash Test No. 2239-1 173 13.1 Static Soil Test 173 13.2 Weather Conditions 173 13.3 Test Description 179 13.4 MGS System Damage 180 13.5 Vehicle Damage 184 13.6 Occupant Risk 185 13.7 Discussion 187 Chapter 14 Full-Scale Crash Test No. 2239-2 187 14.1 Static Soil Test 187 14.2 Weather Conditions 187 14.3 Test Description 193 14.4 MGS System Damage 196 14.5 Vehicle Damage 198 14.6 Occupant Risk 198 14.7 Discussion 201 Chapter 15 Analysis of Various Speeds, Angles, and Curb Shapes 201 15.1 Reduced Speed Vehicle Trajectories 204 15.2 Reduced-Angle Vehicle Trajectories 206 15.3 Reduced-Angle Vehicle Impacts into the MGS 207 15.4 Vehicle Trajectories over Various Curb Shapes 213 Chapter 16 Summary and Conclusions 213 16.1 Summary 214 16.2 Implementation Guidance 219 16.3 Future Research Needs 220 References

224 Appendix A Roadway Agency Survey 231 Appendix B Accelerometer and Rate Transducer Data Plots, Test 39CT-1 235 Appendix C Accelerometer and Rate Transducer Data Plots, Test 39CT-2 239 Appendix D Vehicle Center of Gravity Determination 242 Appendix E Material Specifications 268 Appendix F Static Soil Tests 272 Appendix G Vehicle Deformations, Tests 2239-1 and 2239-2 285 Appendix H Accelerometer and Rate Transducer Data Plots, Test 2239-1 294 Appendix I Accelerometer and Rate Transducer Data Plots, Test 2239-2 303 Appendix J SI Conversion Table