Download - Quad-Roundabout Double-Diamond Interchange
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Quad-RoundaboutDouble-Diamond Interchange
ITS World Congress 2011Joel K. Marcuson, PEUlteig EngineeringFargo, ND, USA
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Background
Concept Developed for Design/Build I-494/TH 169 ProjectMinneapolis, MN, USA
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3 Traffic Signals Create 3mile Backup Every Morning on TH 169Only Signals on TH 169 Corridor
Project Need
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Remove 3 Signals and Old-Fashioned Cloverleaf/Signalized Intersection Design
Replace with Direct Interchange,Bridges/Roundabouts – Local Traffic6 Roundabouts = MOT Opportunity
Project Description
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Keep Through Traffic on I-494 and TH169 MovingMaintain Access to Local Traffic Around and Through Project
MOT Objective
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Remove Signals QuicklyBuild Bridges Quickly
Run Turning/Local Traffic on Roundabout System
MOT Approach
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Existing Conditions - Current
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Proposed Plan - Ultimate
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MOT Plan – Full Access (Interim)
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Using Permanent Features (Roundabouts) for New PurposeAccommodates all Traffic and Movements
Innovation
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Innovation Description
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Full Access, Improved Traffic EarlyTH 169 Free Flow
I-494 Bottleneck RemovedAvg Speeds Doubled
Unconstrained Flow – During Construction
Benefits of Innovation
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Table 1 - Level of Service*, Average Speeds
Stage ExistingAM/PM 1A AM/PM 1B AM/PM 1C AM/PM 2 AM/PM
Avg Speeds(mph) 13/11 15/10 12/8 14/8 27/27
N TH 169 LOS B/C B/C C/C C/C Free**
S TH 169 LOS A/D D/C A/B C/B Free**
Highwood LOS E/F F/F E/F E/F Free**
Benefits of Innovation
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Current Need - > Service< System Interchange
Quad-Roundabout DD Interchange Fills That Need
Results of Innovation
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Flooding – Closed All Nearby Crossings Except TH 169Volumes Increased on TH 169Restripe 169, Remove Signals
Nature Interfered
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$5B DeficitGovernment Shutdown
Contractor Stopped
Politics Interfered
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Contractor Lost Time, TwiceLost Money, Twice
New Approach – Build Final QuicklyQuad Roundabout DD Abandoned
Result
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One of Best Designs Never ImplementedAn Approach That Will Work
For Right Occasion/ Right Time
Quad-Roundabout DD Interchange
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Are EverythingStill Want to Share Idea
Could be Groundbreaking
Timing/Circumstances
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Between Service and SystemHigh-Performance Service Interchange
Significant Cost SavingsSignficant Benefits
New Category Needed
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System Costs = $250-500MHigh-Performance = $25-50MSimilar Results, 10% of Cost
$$ Impacts Important
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Couldn’t Make it “Not” WorkDoubled Traffic – No Appreciable
Change in Performance
What We Discovered
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Questions?
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