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1-5:Aurora Donald Interchange(Exit 278) Interchange Area Management Plan for Marion County Approval ODOT KN19062 Oregon Department of Transportation—Region 2 TABLE OF CONTENTS (CONTINUED) 3.2.1 2018 (Existing)Traffic Volumes 3-2 3.2.2 Intersection Traffic Operations 3-5 3.2.3 Freeway Ramp Merge/Diverge Operations 3-6 3.2.4 Crash History and Trends 3-6 3.2.5 Pedestrian and Bicycle Travel Conditions 3-8 3.3 Future No-Build Conditions 3-9 3.3.1 2042 Traffic Volumes 3-9 3.3.2 Intersection Traffic Operations 3-9 3.3.3 Freeway Ramp Merge/Diverge Operations 3-12 3.3.4 Safety 3-13 3.3.5 Pedestrian and Bicycle Travel Conditions 3-13 4. CONCEPT AND ALTERNATIVES DEVELOPMENT 4-1 4.1 Process Overview 4-1 4.2 Concept Evaluation Framework 4-3 4.2.1 Construction Cost 4-3 4.2.2 Traffic Performance 4-4 4.2.3 Right-of-Way Impacts 4-4 4.2.4 Land Use and Business Impacts 4-4 4.2.5 Specific Business and Farm Impacts 4-4 4.3 Concept Screening 4-5 4.3.1 TDI—Tight Diamond Interchange 4-5 4.3.2 Central Roundabout Interchanges 4-8 4.3.3 DIR—Diamond Interchange with Roundabout Ramp Terminals 4-12 4.3.4 FDR—Folded Diamond Interchange with Roundabout Ramp Terminals 4-15 4.3.5 FDS—Folded Diamond Interchange with Signalized Ramp Terminals 4-18 4.3.6 DGR—Diamond Interchange with Gullwing West and Roundabout Ramp Terminals 4-21 4.3.7 SPI—Single Point Interchange 4-24 4.3.8 DDI—Diverging Diamond Interchange 4-26 4.4 Selecting the Preferred Alternative 4-29 4.4.1 Refinement of Alternatives 4-29 4.4.2 Preferred Alternative 4-34 5. PREFERRED ALTERNATIVE 5-1 5.1 The Diverging Diamond Interchange 5-2 5.2 Preferred Alternative Refinement 5-4 5.2.1 Value Engineering(VE) Process 5-4 5.3 Preferred Alternative 5-4 July 2020 1274-3012-031