Parsons DDI

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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