Parsons DDI

Kiewit/Clyde JVDiverging Diamond Interchange I-15/American Fork Main Street May 2012

Diverging Diamond Interchange from ‘Scratch’ How did UDOT get it’s first DDI? I-15/American Fork Main Street 2

Pioneer Crossing Design Build Project The RFP 3

Diverging Diamond Interchange ‘workings’ 4

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.) 5

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.) 6

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 7

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 8

Construction Progress 9

Design Key Minimum angle of intersection is 30° 10

Let’s Compare Facts DDI vs. SPUISignals 2 phase 3 phaseConflict Points 2 8Left Turns Free SignalizedOperational Capacity More Less 11

Benefits Reduces conflict points Provides free left turns Increases left turn capacity Improves interchange safety Increases Operational Capacity 12

Don’t forget Pedestrians Outside  Similar to a SPUI Center  Advantages  Crosswalks controlled by signals  Disadvantages  Unfamiliar  More lanes to cross 13

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 14

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? 15

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 ? 16

Questions? 17

Parsons DDI

by Utah Department of Transportation

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