Comprehensive Truck Size and Weight Limits Study - Highway Safety and Truck Crash Comparative Analysis Technical Report

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Contact Information: FreightFeedback@dot.gov

June 2015

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Table of Contents

• Executive Summary
• Chapter 1. Introduction
  • 1.1 Goals of the Safety and Truck Crash Comparative Analysis
  • 1.2 Current Truck Size and Weight Limits in the United States
• Chapter 2. Crash Analysis
  • 2.1 Overview
  • 2.2 Preparation and Review of Draft Safety Analysis Plan
  • 2.3 State Data Crash Analyses
  • 2.4 Route-Based Analysis
  • 2.5 Fleet Analysis
  • 2.6 Summary of Crash Data Results
• Chapter 3. Analysis of Safety Vehicle Stability and Control
  • 3.1 Vehicle Stability and Control Scope
  • 3.2 Vehicle Stability and Control Methodology
  • 3.3 Vehicle Stability and Control Simulation Results
  • 3.4 Conclusions
• Chapter 4. Inspection And Violation Analysis
  • 4.1 Overview
  • 4.2 Objectives
  • 4.3 Methodology
  • 4.4 Data Used in Inspection and Violations Analysis
  • 4.5 Data Analysis
  • 4.6 Out-of-service Violations Analysis
  • 4.7 Summary
• Chapter 5. Scenario Analysis
• Chapter 6. Conclusions
• References
• Appendix A. Revised Desk Scan
• Appendix B. Safety Project Plan and Schedule
• Appendix C. Maneuvers for the Vehicle Stability and Control Analysis
• Appendix D. Models for the Vehicle Stability and Control Analysis
• Appendix E. Results of the Vehicle Stability and Control Analysis
• Appendix F. Inspection and Violation Results
• Appendix G. Inspection Level Descriptions

List of Tables

• Table ES1. Truck Configurations and Weight Scenarios Analyzed in the 2014 CTSW Study
• Table 1. States Allowing Tractor Semitrailer Combinations with Maximum GVW Greater than 80,000 lbs
• Table 2. Truck Configurations and Weight Scenarios Analyzed in the 2014 CTSW Study
• Table 3. Criteria for a Preferred Crash Analysis vs. Current Real-World Situation
• Table 4. Crash Involvements and MVMT for Five- and Six-Axle Semitrailer Combinations in Washington, Idaho and Michigan
• Table 5. Crash Involvements and MVMT for Twin and Triple-trailer Configurations (Idaho)
• Table 6. Crash Involvements and MVMT for Semitrailers, Twin, and Triple-trailer Configurations (Kansas Turnpike)
• Table 7. VMT Proportions from Idaho, Michigan, and Washington
• Table 8. Crash Involvement Rates for Five-Axle and Six-Axle Semitrailers
• Table 9. Crash Involvement Rates for Twin Trailer and Triple-trailer Configurations in Idaho (Scenario 5)
• Table 10. Crash Involvement Rates for Semitrailers, Twin Trailer, and Triple-trailer Configurations for the Kansas Turnpike (Scenario 6)
• Table 11. Negative Binomial Models (Five-Axle and Six-Axle Semitrailers)
• Table 12. Severity of Crashes Involving the Five-Axle Single Control and Six-Axle  Scenario 2 Configurations on Interstates in Washington
• Table 13. Severity of Crashes Involving the Five-Axle Single Control and the Six-Axle Scenario 3 Configurations on Interstates in Idaho
• Table 14. Severity of Crashes Involving the Five-Axle Single Control and the Six-Axle Scenario 3 Configurations on Interstates in Michigan
• Table 15. Severity of Crashes Involving the Five-Axle Double Control and the Seven-Axle Scenario 5 Configurations on Interstates in Idaho
• Table 16. Severity of Crashes Involving the Five-Axle Double Control and the Nine-Axle Scenario 6 Configurations on Interstates the Kansas Turnpike
• Table 17. Results of Sequence-of-Events Analyses for Idaho and Michigan
• Table 18. Study Data/Model Accessibility and Data Custody Guidelines
• Table 19. Summary of Fleet Data Request
• Table 20. Severity of Interstate involvements for Twin-trailer and Triple-trailer Configurations from Fleet Data Including All Injury Crashes (Urban and Rural Combined)
• Table 21. Severity of Interstate Involvements for Twin-trailer and Triple-trailer Configurations from Fleet Data Including Crashes with Injuries to Truck Occupants Only (Urban and Rural Combined)
• Table 22. Non-truck Occupant Severity in Interstate Crashes Involving a Twin Trailer or Triple-trailer configuration with a Non-truck (Urban and Rural Combined)
• Table 23. Summary of Crash-Data Analysis Findings Categorized by Scenario, Data Source and Analysis Type
• Table 24. Simulated Vehicle Maneuvers
• Table 25. Low-Speed Off-tracking Results. (All values are toward the inside of the curve)
• Table 26. High-Speed Off-tracking Results
• Table 27. Straight-Line Braking Results
• Table 28. Brake-in-a-Curve Results
• Table 29. Avoidance Maneuver Results
• Table 30. Summary of MCMIS Data From All 19 Study States for 2008 to 2012
• Table 31. 2011 Estimated VMT in Million Miles
• Table 32. Number of Inspected Trucks from 2008 to 2012 for 19 States
• Table 33. Mean Number (Standard Deviation) of Noted Violations per Level 1 Inspection by Weight Threshold for All Truck Configurations
• Table 34. Mean Number (Standard Deviation) of Violations per Inspection by Truck Type
• Table 35. Mean Number (Standard Deviation) of Violations per Inspection by Truck and Weight
• Table 36. Explanatory Variables considered for the Logit models
• Table 37. Likelihood of a Violation Given a Level 1 Inspection – Alternative Tractor Semitrailer Configurations
• Table 38. Mean Number (Standard Deviation) of OOS Violations per Inspection by Weight Threshold for All Truck Configurations
• Table 39. Mean Number (Standard Deviation) of OOS Violations per Inspection by Truck Type
• Table 40. Mean (Standard Deviation) Company-Level Violations per Inspection by Configuration and Weight
• Table 41. Likelihood of OOS Violation given a Level 1 Inspection – Alternative Tractor Semitrailer Configurations
• Table 42. Mean Number (Standard Deviation) of Citations per Inspection by Weight Threshold for All Truck Configurations
• Table 43. Mean Number (Standard Deviation) of Citations per Inspection by Truck Type
• Table 44. Mean Number (Standard Deviation) of Citations per Inspection by Truck Configuration and Weight
• Table 45. Likelihood of a Citation Given a Level 1 Inspection – Alternative Tractor Semitrailer Configurations

List of Figures

• Figure 1. States Allowing the Operation of Longer Combination Vehicles (LCVs) on Some Portion of their Interstate System
• Figure 2. Truck Involvements per Mile versus Truck Volume for Six-Axle Alternative Truck Configurations and Five-Axle Configurations in Michigan
• Figure 3. Truck Involvements per Mile versus Truck Volume for Six-Axle Alternative Truck Configurations and Five-Axle Controls in Washington
• Figure 4. Vehicles Modeled – Single Trailer Combinations
• Figure 5. Vehicles Modeled – Multiple Trailer Combinations
• Figure 6. Low-Speed Off-tracking Maneuver Simulates an Intersection
• Figure 7. Off-tracking of the Drive and Trailer Axles Rises and Falls During the Maneuver
• Figure 8. Trailer Tracks to the Outside of the Curve Centerline in this High-Speed Off-tracking Illustration
• Figure 9. Off-tracking was Calculated by Taking the Difference in the Path Followed by the First and Final Axles
• Figure 10. Simulation of the Straight-line Braking Maneuver
• Figure 11. Position vs. Time (left) and Path Deviation vs. Time (right) of Control Single Vehicle as it Stops with Brake Failure on the Right Ends of the Two Drive Axles
• Figure 12. A Bird’s Eye View of Control Vehicle CS after Coming to Rest in the Brake-in-a-curve Maneuver with the ABS Disabled on the Drive Axles
• Figure 13. Paths of the Axle centerlines of the Control Double as it Executes the 12-ft. Avoidance Maneuver
• Figure 14. Off-tracking was Computed from the Axle Paths in the Previous Figure
• Figure 15. Lateral Acceleration Time Histories of the Three Units of Control Vehicle CD  in the 12-ft Lane Change
• Figure 16. Vertical Tire Forces during the Lane Change Maneuver for the 12-ft Lane Change for Control Vehicle CD
• Figure 17. Tractor Semitrailer Configurations
• Figure 18. Distribution of Driver Age for the 19 States in the Analyses (2008–2012)

List of Acronyms

Acronym	Definition
AASHO	American Association of State Highway Officials
AASHTO	Association of State Highway and Transportation Officials
ABrR	AASHTOWare Bridge Rating®
ABS	anti-lock braking system
AC	asphalt concrete
ADT	average daily traffic
AADTT	annual average daily truck traffic
ADTT	average daily truck traffic
AF	axle factors
AGM	average gross mass
ALF	axle load factors
ARA	Applied Research Associates
ASLRRA	American Short Line and Regional Railroad Association
ASR	allowable stress rating
BTS	Bureau of Transportation Statistics
CAFT	constant-amplitude fatigue threshold
CARB	California Air Resources Board
CBO	Congressional Budget Office
CMV	commercial motor vehicle
CRCP	Continuously Reinforced Concrete Pavement
CRF	Code of Federal Regulations
CTSLW	Comprehensive Truck Size and Weight Limits Study
CTSW	Comprehensive Truck Size and Weight Limits
CVSA	Commercial Vehicle Safety Alliance
DA	data agreement
DOT	Department of Transportation
EDFs	equivalent damage factors
ESALs	equivalent single axle loads
ESAR	equivalent single-axle radius
ESWL	equivalent single-wheel load
FAF	Freight Analysis Framework
FEA	finite element analysis
FHWA	Federal Highway Administration
FMIS	Financial Management Information System
FMVSS	Federal Motor Vehicle Safety Standard
FRA	Federal Railroad Administration
GCW	gross combined weight
GEF	Group Equivalency Factor
GVW	gross vehicle weight
HCA	highway cost allocation
HCAS	Federal Highway Cost Allocation Study
HERS	Highway Economic Requirements Systems
HMA	hot mix asphalt
HPMS	Highway Performance Monitoring System
HV	High-volume
HIS	Interstate Highway System
ITIC	Intermodal Transportation and Inventory Cost Model
IRI	International Roughness Index
IS	Interstate System
ISTEA	Intermodal Surface Transportation Efficiency Act
JPCP	jointed plain concrete pavement
LCC	life cycle cost
LCV	longer combination vehicles
LEF	load equivalence factors
LFR	load factor rating
LRFD	load and resistance factor design
LRFR	load resistance factor rating
LTBP	Long-Term Bridge Performance Program
LTL	less than truckload
LTPP	Long-Term Pavement Performance
LV	Low-volume
MARAD	Maritime Administration
MATLAB	Matrix Laboratory
MCMIS	Motor Carrier Management Information System
MDDs	multidepth deflectometers
MEPDG	Mechanistic Empirical Pavement Design Guide
MV	Medium-volume
NAPCOM	National Pavement Cost Model
NAS	National Academy of Sciences
NATS	National Truck Stop Survey
NBI	National Bridge Inventory
NBMD	National Bridge Management Database
NCHRP	National Cooperative Highway Research Program
NDA	non-disclosure agreement
NESCCAF	Northeast States Center for a Clean Air Future
NHS	National Highway System
NHTSA	National Highway Traffic Safety Administration
NN	National Network
NREL	National Renewable Energy Lab
NSIs	normalized sensitivity indices
OMB	Office of Management and Budget
OGW	operating gross weight
ORNL	Oak Ridge National Laboratories
OOS	out-of-service
OS/OW	oversize/overweight
PBBT	Performance Based Brake Tests
PAS	Pavement Analysis Software
PBS	Performance-based standards
PCC	Portland Cement Concrete
PCE	passenger car equivalents
PCU	passenger car units
POG	Policy Oversight Group
PSI	Pounds per square inch
RC	reinforced concrete
RF	rating factor
SISSI	Superpave Instrumented Stress-Strain Investigation
SPS	Special Pavement Sections
STAA	Surface Transportation Authorization Act
STB	Surface Transportation Board
STCC	Standard Transportation Commodity Code
SwRI	Southwest Research Institute
TF	truck factor
TMG	Traffic Monitoring Guidelines
TOC	Technical Oversight Committee
TRB	Transportation Research Board
TSW	truck size and weight
TTCGS	truck traffic classification groups
USC	United States Code
USDOT	US Department of Transportation
VMT	vehicle miles traveled
VIUS	Vehicle Inventory and Use Survey
VSC	vehicle stability and control
WHVC	World Harmonized Vehicle Cycle
WIM	weigh-in-motion
WIMPI	Weigh-in-Motion Pavement Investigation

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