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Virginia’s Diverging Diamond Virginia’s Diverging Diamond Interchanges May 6, 2016 Anne Booker, PE, PTOE Southwest Regional Traffic Engineer
Virginia’s Diverging Diamond Virginia’s Diverging Diamond
Interchanges
May 6, 2016
Anne Booker, PE, PTOE
Southwest Regional Traffic Engineer
Virginia’s Diverging
Diamond Interchanges
• What is a DDI?
• Why consider a DDI?
• Where are our DDI’s?
• How are we building our DDI’s?
• How are we preparing the public?
• How are they working?
2
What is a DDI?
• An alternative to the conventional diamond
interchange which eliminates the conflicts
between left turn vehicles and opposing through
movements.
3
What is a DDI?
4
What is a DDI?
• Insert simulation video for ramp terminal movements
(Valley View Final DDI.avi)
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Why consider a DDI?
• Efficiencies for high
volumes of turning
traffic
• Shorter cycle length
• Free flow lefts and
right turns onto
ramps in all
directionsdirections
• Efficiency of R/W
footprint
• Efficiencies in structure
construction or reuse
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• Fewer conflict points
• 14 (DDI)
• 26 (Traditional Diamond)
• Severity of crashes lessened
by lower speeds
• Reduces opportunity for
wrong way entry to ramps
Why consider a DDI?
wrong way entry to ramps
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Virginia’s DDI’s
• I-64 Exit 136 – Zions Crossroads• Improve capacity at interchange
• Retain existing bridge structure
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Virginia’s DDI’s
• Route 460 – Southgate Connector near Virginia Tech• Event traffic
• Smaller footprint
• Conversion from an at-grade intersection
• Future expansion opportunities
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Virginia’s DDI’s
• I-581 – Valley View Boulevard interchange
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I-581 at Valley View Boulevard
• Partial diamond interchange
constructed in 1998
• Completion of partial
interchange
• Goals:
• Relieve congestion
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• Relieve congestion
• Improve access
I-581 at Valley View Boulevard
• IMR Completed in 2010
• Multiple interchange types considered
• Alternative recommended - partial cloverleaf
I-581 South to
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I-581 South to
Route 220
I-581 North to
I-81
I-581 at Valley View Boulevard
• Project converted to a design-build opportunity
• D/B proposed a DDI
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Valley View DDI Design Features
• Close proximity of signal to east
• Future development on the west
• Separate pedestrian bridge
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Public Outreach
• Beyond our normal public involvement
• Movie clip advertising in adjacent theater
• Cost effective
• Capitalized on a popular theme
• Insert video clip
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Public Outreach
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Safety Experience
• Accident history at Zion Crossroads DDI
50%
Reduction in
85%
Reduction in
fatal & injury
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Reduction in
crashesfatal & injury
crashes
Pedestrians
• Separate pedestrian facilities
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• Huckleberry Trail underpass
at Route 460 Bypass
What is a DDI?
• x
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