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Presented by:Matt Crim P.E., PTOEStantec Consulting Services Inc.October 29, 2015
Innovative Intersections
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Traditional Intersections
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3 4
Traditional Intersections allow left turns from all approaches.
There are four basic signal phases:
1. Left turns on Major St.
2. Throughs on Major St
3. Left turns on Minor St
4. Throughs on Minor St
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Traditional Intersections…Phase, Phase, Everywhere a Phase
30%
30% 20%
20%
50% 20%
30%
30%70%
4 Phase Signal
3 Phase Signal
2 Phase Signal
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Traditional Intersection Safety
32 Conflict Points
Angle crashes account for 40% of
fatal crashes at intersections
Left turn crashes account for 20%
of fatal crashes at intersections
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What Are Innovative Intersections?
Intersections that:• Improve the way traffic makes certain movements by
eliminating, relocating or modifying conflict points
• Improve the signalization by reducing cycle lengths and the number of phases
• Improve travel time and reduce delay
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Innovative Intersections
• Superstreets
• Continuous Flow Intersection (CFI)
• Diverging Diamond Interchange (DDI)
• Single Point Urban Interchange (SPUI)
• Median U-Turn Crossover
• Roundabouts
• Jughandle
• Quadrant Intersection
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Superstreet Intersections in the U.S.(aka J-Turn, Restricted Crossing U-Turn, Reduced Conflict Intersection)
Source: FHWA Restricted Crossing U‐Turn Informational Guide
States with Superstreet Intersections
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Superstreet Intersection
Traditional Intersection
Superstreet Intersection
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Superstreet Signal Phasing
• Mainline Through and Right-Turn
• Mainline Left-Turn and U-Turn
• Side Street Right-Turn
Side StreetM
ainline
Side Street
Mainline
Phase 1
Phase 2
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Comparison of Conflict Points
Conflict Type Four-Leg Signalized Intersection
Superstreet Intersection
Merging/Diverging 16 12Crossing (left turn) 12 2Crossing (angle) 4 0Total 32 14
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Superstreet Safety Benefits
Collision Type Crash Reduction
Fatal and Injury 63%Angle and Right Turns 75%Left Turns 59%Rear Ends 1%Sideswipes 13%Other 15%Total 46%
Source: N.C. State University Research Project 2009‐06
• Reduced collisionsfor total, angle and right turn, left turn, and fatal and injury
• Total collisions reduced by 46%
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NC 87 @ Peanut Plant Road
• NC 87 Bypass was opened in 1997
• 60 Total Crashes and 5 Fatal Crashes in 8 years after completion
NC 87 at SR 1150-Peanut Plant Rd
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NC 87 @ Peanut Plant RoadCollision Diagram
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NC 87 @ Peanut Plant Road
3 Years Prior to Superstreet:
• 24 Total Crashes• 8 Crashes per Year
• 19 T-Bone Crashes (w/Injury)• 6.33 Crashes per Year
1.5 Years After Superstreet:
• 2 Total Crashes• 1.33 Crashes per Year
• No T-Bone Crashes (w/Injury)• 0 Crashes per Year
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Superstreet Semi-Trailer Accommodations
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Superstreet Pedestrian Accommodations
Source: FHWA Restricted Crossing U‐Turn Informational Guide
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Superstreet Pedestrian Safety
Source: FHWA Restricted Crossing U‐Turn Informational Guide
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Superstreet Feasible Demands
Source: FHWA Restricted Crossing U‐Turn Informational Guide
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Continuous Flow Intersection (CFI)(aka Displaced Left Turn or Crossover Displaced Left)
Minor Street Movements
Major Street Movements
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CFI History• Concept Developed over 30 years ago
• AASHTO’s 2002 National Award for Innovation
• Currently Constructed in• Colorado
• Louisiana
• Maryland
• Mississippi
• Missouri
• Ohio
• Texas
• Utah
• Under Design for Construction• Florida
• Georgia
• North Carolina
• Virginia
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CFI Basics
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CFI Signal PhasingAdvance CFI Traffic SignalAdvance CFI
Traffic Signal
Center CFI Traffic Signal
Advance CFI Traffic SignalAdvance CFI
Traffic Signal
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CFI Efficiency
Conventional 4-lane roadway650 v/l/h x 4 lanes = 2600 v/h
C=150 P.M. Peak
CFI 4-lane roadway850 v/l/h x 4 lanes = 3400 v/h
C=120 P.M. Peak
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Comparison of Conflict Points
Source: FHWA Signalized Intersections: Informational Guide
Conflict Type Four-Leg Signalized Intersection
Partial CFI Intersection
Merging/Diverging 16 14Crossing (left turn) 12 6Crossing (angle) 4 10Total 32 30
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Airline Hwy @ Sherwood Forrest Blvd CFI
Operational Benefits:
Travel Times reduced by 40%Delay reduced by 50%
Crash Rate Reduction:
From 10 per million vehicle miles (MVM) to 4
per MVM
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Public AcceptanceQuestion: Do the improvements make TRAFFIC CONGESTION Better, Worse, or the Same?
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Public AcceptanceQuestion: What is your level of Satisfaction with the current traffic conditions of the intersection?
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Diverging Diamond Interchange (DDI) (aka Double Crossover Diamond)
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Diverging Diamond Interchange (DDI)
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Where did the DDI come from?
Le Perreux sur Marne, France Versailles, France
Seclin, France
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DDI Signal Phasing
Phase 1
Phase 2
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DDI Cost BenefitsInterchange Location DDI Cost
(real or estimated) Alternative Design Cost Cost Savings
I -44/Route 13 Springfield, MO $3.2 Million Over $10 Million $6.8 MillionDiamond: $11.4 MillionSPUI : $25 Million
SR 265/SR 62 Utica, IN $52 Million $118 Million $66 MillionSPUI : $10 MillionTriple Left Diamond: $13.6 Million
$4.7 - 18.3 Million
$6 - 9.6 Million
I -435/Front Street Kansas City, MO $6.7 Million
I -590/Winton Road Brighton, NY $4 Million
Retrofit• Existing Bridge can usually be used
• Additional R/W rarely needed
• Construction time is reduced
• Maintenance of traffic simplified during construction
New Interchange• Fewer lanes than other
interchange forms
• Less bridge structure
• Less R/W than a cloverleaf
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DDI Awards
• Popular Science’s Top 100 Innovations for 2009• AASHTO’s 2010 National Award for Innovation
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US 68 @ Kentucky 4 DDI
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US 68 @ Kentucky 4 DDI
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Comparison of Conflict PointsDDI
• 2 crossing conflict points
Traditional• 4 crossing
conflict points
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US 68 @ Kentucky 4 DDI Safety
Post
DDI
Pre
DDI
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Public Acceptance
Question: Overall, do you think this project was a good transportation solution for this location?
72%
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Public Acceptance
Question: Do you think a DDI should be considered at other locations in Lexington or elsewhere in Kentucky?
72%Yes
No
10. High return on investment
9. Improves quality of life
8. Many designs are aesthetically pleasing
7. Attracts investment to revitalize struggling areas
6. Better access management
5. More feasible to convert general purpose lanesinto other uses such as transit only lanes
4. Reduces right-of-way impacts
3. Avoids street widening and even grade separation
2. Fewer conflicts and less congestion improve safety
1. Better mobility enhances the local economy
