virginia’s diverging diamond interchanges -...
TRANSCRIPT
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)
5
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
6
• 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
7
Virginia’s DDI’s
• I-64 Exit 136 – Zions Crossroads• Improve capacity at interchange
• Retain existing bridge structure
8
Virginia’s DDI’s
• Route 460 – Southgate Connector near Virginia Tech• Event traffic
• Smaller footprint
• Conversion from an at-grade intersection
• Future expansion opportunities
9
Virginia’s DDI’s
• I-581 – Valley View Boulevard interchange
10
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
12
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
13
Valley View DDI Design Features
• Close proximity of signal to east
• Future development on the west
• Separate pedestrian bridge
14
Public Outreach
• Beyond our normal public involvement
• Movie clip advertising in adjacent theater
• Cost effective
• Capitalized on a popular theme
• Insert video clip
15
Public Outreach
16
Safety Experience
• Accident history at Zion Crossroads DDI
50%
Reduction in
85%
Reduction in
fatal & injury
18
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
20