The U.S. Department of Transportation’s Western Uniformity Scenario Analysis A Regional Truck Size and Weight Scenario Requested by the Western Governors’ Association April 2004 i Table of Contents List of Acronyms........................................................................................................... ix Executive Summary Introduction .............................................................................................................. ES-1 Scenario Impacts ...................................................................................................... ES-1 Conclusions .............................................................................................................. ES-9 I Introduction Introduction ..................................................................................................................I-1 Study Purpose...............................................................................................................I-1 Impact Areas.................................................................................................................I-1 Updates and Improvements..........................................................................................I-2 Outreach .......................................................................................................................I-2 Organization of Analysis..............................................................................................I-2 II Scenario Description Introduction ................................................................................................................ II-1 Analysis Year ............................................................................................................. II-3 Base Case 2000 .......................................................................................................... II-4 Analytical Improvements ........................................................................................... II-6 Updated Base and Forecast Years....................................................................... II-6 Scenario Specifications....................................................................................... II-7 The Vehicles............................................................................................................. II-10 The Networks ........................................................................................................... II-11 Western Uniformity Scenario ........................................................................... II-21 Scenario Description......................................................................................... II-22 The Vehicles ..................................................................................................... II-22 The Networks.................................................................................................... II-23 Access Provisions ............................................................................................. II-25 III Freight Distribution and Shipper Costs Introduction ...............................................................................................................III-1 Analytical Approach..................................................................................................III-1 Model and Data Updates....................................................................................III-1 Truck Analysis...................................................................................................III-1 Rail Analysis......................................................................................................III-2 Shipper Cost Analysis........................................................................................III-2 Scenario Impacts .......................................................................................................III-3 Low-Cube Case..................................................................................................III-5 High-Cube Case.................................................................................................III-7 Shipper Cost Impacts .......................................................................................III-10 IV Pavement Introduction ...............................................................................................................IV-1 ii Truck-Pavement Interaction......................................................................................IV-1 Estimates of Pavement Cost – The National Pavement Cost Model ........................IV-3 Scenario Impacts .......................................................................................................IV-4 V Bridge Introduction ................................................................................................................ V-1 Impacts of Truck Loads.............................................................................................. V-1 Stresses................................................................................................................ V-1 Types of Loads.................................................................................................... V-1 Critical Stresses for Analysis.............................................................................. V-2 Design Vehicles, Ratings and the Federal Bridge Formula B.................................... V-2 Design Vehicles .................................................................................................. V-2 Bridge Ratings .................................................................................................... V-3 Federal Bridge Formula B .................................................................................. V-3 Description of Bridges in Western Uniformity Scenario States................................. V-4 Analysis Methodology ............................................................................................... V-4 Analysis Tool...................................................................................................... V-4 Overstress Identification Criterion...................................................................... V-5 Overstress............................................................................................................ V-6 Base Case Vehicles............................................................................................. V-7 Analysis Results ......................................................................................................... V-9 Sensitivity Analysis ............................................................................................ V-9 Analysis Results – Base Case ............................................................................. V-9 Cost of Replaced/Strengthened Bridges ........................................................... V-10 Analysis Results – Western Uniformity Scenario ............................................ V-11 Differential Costs Attributable to the Western Uniformity Scenario Trucks ... V-13 Conclusion................................................................................................................ V-14 VI Roadway Geometry Introduction ...............................................................................................................VI-1 Roadway Geometry and Truck Operating Characteristics........................................VI-1 Offtracking.........................................................................................................VI-1 Analytical Approach..................................................................................................VI-3 Impact Analysis.........................................................................................................VI-4 Geometric...........................................................................................................VI-4 Staging Areas.....................................................................................................VI-5 Scenario Impacts .......................................................................................................VI-7 Geometric Improvements...................................................................................VI-7 VII Safety Introduction ............................................................................................................. VII-1 Vehicle Safety Performance Analysis..................................................................... VII-1 Analyzed Vehicles ........................................................................................... VII-2 Results ..................................................................................................................... VII-3 iii Static Rollover Threshold ................................................................................ VII-3 Rearward Amplification................................................................................... VII-6 Load Transfer Ratio ......................................................................................... VII-8 Crash Database Analysis....................................................................................... VII-10 Previous Research.......................................................................................... VII-11 Summary of Prior Studies.............................................................................