1. Kiewit/Clyde JV
Diverging Diamond Interchange
I-15/American Fork Main Street
May 2012

2. Diverging Diamond Interchange from ‘Scratch’
 How did UDOT get it’s first DDI?
I-15/American Fork Main Street
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3. Pioneer Crossing Design Build Project
 The RFP
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4. Diverging Diamond Interchange ‘workings’
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5. Pioneer Crossing Design Build Project
 The ATC Process (Alternative Technical Concept)
 ATC #1: Diverging Diamond Interchange
 A little history
 DDI drivers:
 Innovation
 Heavy Left Turn Movements
 Project Savings
 ROW
 Fill/Embankment
 Structure Area (sq. ft.)
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6. Design Build Innovation
 Why ATC # 1
 Allowed interchange to remain at original Skew
 Accommodated the heavy left turn movements
 Provided efficient phased construction of
bridges over I-15
 Construction cost savings
 Reduced Right-of-way (as compared to RFP SPUI)
 Minimized User Costs (delays, detours, etc.)
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7. Do Your Homework
 ATC # 1 Engineering
 Development
 Traffic Modeling
 VISSIM
 Design Issues
 RFP-SPUI layout
 Vineyard Connection (future)
 Construction Quantities
 FHWA; IAJR-Interstate Access Justification Report
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8. Add Value to the Project
 ATC # 1 Approval
 Increased Interchange efficiency
 Better Level of Service
 Decrease congestion and delay
 Smaller bridge footprint
 Faster construction
 Reduced user costs
 MOT benefits during construction
 Traffic maintains existing patterns
 Simple traffic switchovers and phasing
 Reduced construction and user costs
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9. Construction Progress
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10. Design Key
Minimum angle of intersection is 30°
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11. Let’s Compare Facts
DDI vs. SPUI
Signals 2 phase 3 phase
Conflict Points 2 8
Left Turns Free Signalized
Operational Capacity More Less
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12. Benefits
 Reduces conflict points
 Provides free left turns
 Increases left turn capacity
 Improves interchange safety
 Increases Operational Capacity
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13. Don’t forget Pedestrians
 Outside
 Similar to a SPUI
 Center
 Advantages
 Crosswalks controlled by signals
 Disadvantages
 Unfamiliar
 More lanes to cross
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14. Opening a new DDI?—You better have a plan
 Public Information
Fears
 Wrong way vehicles
 Public Acceptance
 Messaging
 Commercials
DDI A dv ertisement.w mv
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15. How much do you know ?
Like all good engineering, the DDI design was
developed by German engineers?
The I-15/American Fork Main Street DDI is the first in
the USA built from the ground up?
A DDI requires less square footage of bridge deck
which will provide project cost savings?
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16. Is it: FACT or CRAP ?
DDI’s accommodate left turn movements while
eliminating the need for left turn signals?
A DDI will increase potential safety conflict points?
Use of a DDI on the Pioneer Crossing provided $20
million in cost savings to the project ?
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17. Questions?
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