diverging diamond interchange · what is a diverging diamond interchange (ddi)? similar to a...

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Diverging Diamond Interchange M-150/Botts Rd Interchange

Kansas City, MO

Presented by:

Patty Hilderbrand PE MPA

Matt Spencer PE MBA

June 26th, 2012

What is a Diverging Diamond Interchange (DDI)?

Similar to a Standard Diamond Interchange

Signals at each end of the interchange

Traffic crosses to opposite sides at signals

Eliminates left-turn signal phasing

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How a Diverging Diamond Interchange (DDI) Works

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Example of a DDI

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Botts Road at M-150

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Botts Road North of M-150

Interchange at Botts Road and M-

150

Botts Road and M-150 Interchange

Existing Conditions

• At-grade

intersection

• Increased

capacity due to

National Security

Campus and

Centerpoint

Development

• Up to 20% truck

traffic predicted

• 2,000 vehicles

during peak hours

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Goals of the Value Engineering Study

Study Goals:

• Select preferred alternative based on the criteria

• Identify design practical solutions

• Identify Green solutions to apply to final

recommendation.

Screening Criteria:

• Traffic operations (60%)

• Constructability (15%)

• Economic issues (15%)

• Environmental issues (10%)

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Value Engineering Workshop

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Standard Diamond Split Diamond

Continuous Flow Diverging Diamond Michigan U-Turns

Box Diamond

Pros & Cons of a DDI

Pros

Left Turning Movements

Smaller Footprint

Reduces Congestion

Two Phase Operation

Construction Cost Savings

Safety Improvement– Reduces Conflict

Points

Cons

High Through Traffic Volumes

Driver Expectation

Off Ramp Traffic Must Turn

Adjacent Intersections

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Challenges of DDIs – Driver Comfort

Line of sight

Glare screens

Transition angle

Lane widths

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Challenges of DDIs

Public Education

• Drivers

• Bike/Ped

Signing

• Location

• Details

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DDI Structure Benefits

Reduced structure length

• MSE walls

Reduced structure width

• Trail location

Simple, short, cost-effective bridge

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Special Features - Walkway

Allows pedestrian

access

Increases driver

comfort

Decreases

structure width

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Sustainable Infrastructure

Dry detention basin

Planted islands and

medians

Variable flow inlets

Hardscape design

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Sustainable Infrastructure

Native plantings

Bio swale

Low ditch grade

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Sustainable Infrastructure

Consultant selection

Non traditional design

Reduced maintenance

Green Scorecard

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Operating DDI

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Matt Spencer, PE MBA

Project Engineer

HNTB Corporation

mspencer@hntb.com