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Diverging Diamond Interchange
May 2012I-15/American Fork Main Street
Kiewit/Clyde JV
Diverging Diamond Interchange from ‘Scratch’
How did UDOT get it’s first DDI?
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I-15/American Fork Main Street
Pioneer Crossing Design Build Project
The RFP
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Diverging Diamond Interchange ‘workings’
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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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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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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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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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Construction Progress
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Design Key
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Minimum angle of intersection is 30°
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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Benefits
Reduces conflict points Provides free left turns Increases left turn capacity Improves interchange safety Increases Operational Capacity
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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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Opening a new DDI?—You better have a plan
Public InformationFears Wrong way vehicles Public Acceptance Messaging Commercials
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DDI Advertisement.wmv
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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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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Questions?
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