Innovative IntersectionsLouisiana & Utah
Vaughan W. Inman
SAIC, McLean, VA
Background

Currently Conducting CFI/DDI Evaluation for
FHWA
CFI has been completed in Baton Rouge, La
 CFI is under construction in West Valley City, Utah
 Diverging Diamond Interchange is planned for
Kansas City, MO
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Evaluation Includes Safety and Operational
Effects at All Three Locations
May 10, 2007
58th Annual Missouri Traffic Conference
and Seminars
2
The Continuous Flow Intersection
(CFI)

CFI Design Displaces Left-Turns at Signalized
Intersection to Eliminate Need for Separate
Dedicated Left-Turn Phasing –Two Phase
Signals at Main Intersection
Crossover moves left-turning traffic to left side of
roadway before the main intersection
 Protected Left-turn is Made without Conflict with
the Concurrent Through Movement
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May 10, 2007
58th Annual Missouri Traffic Conference
and Seminars
3
CFI Example
May 10, 2007
58th Annual Missouri Traffic Conference
and Seminars
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Expected CFI Benefits
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Increase Capacity by Eliminating Left-Turn
Signal Phase
Decrease Delay
Increase Safety by Reducing Conflict Points
Reduce Cost Where Grade Separation Can be
Avoided
May 10, 2007
58th Annual Missouri Traffic Conference
and Seminars
5
CFI Reduces Number of CrossingPath Conflicts
Conventional 4-Leg
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Diverging – 8
Merging – 8
Crossing – 16
May 10, 2007
Partial CFI
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Diverging – 8
Merging – 8
Crossing – 12
58th Annual Missouri Traffic Conference
and Seminars
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CFI is New to U.S….
May 10, 2007
58th Annual Missouri Traffic Conference
and Seminars
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The Louisiana CFI
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Completed, March 2006
Partial CFI: Crossovers on Airline Highway, US
61
Cross Street, (Siegen Lane/Sherwood Forest)
has protected left-turn phase
May 10, 2007
58th Annual Missouri Traffic Conference
and Seminars
8
Louisiana CFI
May 10, 2007
58th Annual Missouri Traffic Conference
and Seminars
9
CFI Background
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Level of Service F
US 61 is major north-south corridor
CFI was chosen over adding lanes at this
intersection – lanes were added north of this
intersection
May 10, 2007
58th Annual Missouri Traffic Conference
and Seminars
10
The Utah CFI


Intersection of Bangerter Highway (SR 154) and
West 3500 South
Construction Began in February of this year
Major north-south high speed arterial – limited
access between major east-west urban arterials
 Estimated cost: $8M
 Predicted level of service at completion: D

May 10, 2007
58th Annual Missouri Traffic Conference
and Seminars
11
N
Utah CFI
May 10, 2007
58th Annual Missouri Traffic Conference
and Seminars
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Utah CFI Background
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Level of Service F Required Action
Elimination of a signal phase was identified as solution
Alternative Design Considered was Michigan GradeSeparated Turnaround
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Left movement go through main intersection, exit on ramp to
right, and use flyover turnaround to join right turn movement
CFI was superior with: lower cost, better user acceptance,
fewer miles traveled, less delay, lower right-of-way
requirement
If this CFI is a success, additional CFIs will be built on
Bangerter corridor
May 10, 2007
58th Annual Missouri Traffic Conference
and Seminars
13
LA CFI Travel Time & Volume
Results to Date
Travel Times:
Before After Change
AM Peak Southbound
252
270
-7%
Northbound
223
318
-43%
PM Peak Southbound
441
265
40%
Northbound
221
306
-38%
Movement Counts (PM):
After
Before
Airline Northbound
Left
Through
336
1126
216
1174
After
Before
Siegen Lane N/Eastbound
Left
Through Right
557
737
539
549
622
314
May 10, 2007
Right
142
255
Airline Southbound
Total
Left
Through
Right
1604
141
1719
369
1645
121
1622
246
-41
-2%
Sherwood Forest S/Westbound
Total
Left
Through
Right
1833
319
584
75
1485
368
528
83
348
23%
58th Annual Missouri Traffic Conference
and Seminars
Total
2229
1989
240
12%
Total
978
979
-1
0%
14
LA Crash Counts
Four-leg Signalized
Mar. 21-Dec. 31
2003 2004 2005
Type of Collision
CFI
Mar. 21-Dec. 31
2006
Rear End
36
60
71
45
Merging/Diverging/Side
Swiping
10
15
15
12
Crossing(Left Turn)
5
3
9
3
Crossing (angle)
1
3
4
1
Right Angle
30
26
23
17
Total
82
107
122
78
May 10, 2007
58th Annual Missouri Traffic Conference
and Seminars
15
LA: Other Safety Data
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No Head-On Crashes at Crossovers
Police Report Congestion is Reduced
No Fatal Crashes in After Period, One in Three
Years Before
There it Insufficient Data to Evaluate Safety
Effect, But Preliminary Results Indicate No
Increase in Crash Occurrence or Severity
May 10, 2007
58th Annual Missouri Traffic Conference
and Seminars
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Observed Problems At CFI
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Stopping at Inappropriate Location
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58th Annual Missouri Traffic Conference
and Seminars
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Red Light Violation
May 10, 2007
58th Annual Missouri Traffic Conference
and Seminars
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Pedestrian Facilities
May 10, 2007
58th Annual Missouri Traffic Conference
and Seminars
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Red Light Violation
May 10, 2007
58th Annual Missouri Traffic Conference
and Seminars
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Future Work: Simulation
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Utah CFI Modeled in FHWA Highway Driving
Simulator
Signing for crossover
 Markings where vehicle overrun problem has been
identified
 Near-side signal where vehicle at vehicle overrun
location

May 10, 2007
58th Annual Missouri Traffic Conference
and Seminars
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Future Work: Evaluation
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Traffic Operations Analysis
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Crash Safety Analysis – 3 Years Before, 2-3 Years After
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Measuring Safety through Surrogates
Behavioral Analysis
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Accident Reports
Empirical Bayes (EB) before-and-after
Conflict Analysis
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Field Data and Simulation Data
Driver Errors
Lane Keeping, Stop Location, Deceleration Rates, Sudden Lane Changes,
Excessive Speed, Red Light Violations, etc.
Digital Video Analysis

Used to provide conflict, behavioral, and operational data
May 10, 2007
58th Annual Missouri Traffic Conference
and Seminars
22
Early Observations – LA CFI
May 10, 2007
58th Annual Missouri Traffic Conference
and Seminars
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Quad View
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and Seminars
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References
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Chick, M. J. (2001). The Displaced Right Turn Junction. In anonymous (Ed.) (pp.
80). Leeds.
El Asawey, M., & Sayed, T. (2007). Comparison of Two Unconventional Intersection
Schemes: The Crossover Displaced Left-Turn (XDL) Intersection and the Upstream
Signalized Crossover (USC) Intersection. Paper presented at the Transportation
Research Board Annual Meeting, Washington, DC.
Jagannathan, R. (2003). Evaluation of Crossover Displaced Left-turn (XDL)
Intersections and Real-Time Signal Control Strategies with Artificial Intelligence
Techniques. Virginia Tech, Falls Church, VA: ram-thesisaug27final.pdf.
Reid, J. D., & Hummer, J. E. (2001). Travel Time Comparisons Between even
Unconventional Arterial Intersection Designs. Transportation Research Record,
1751(0), 56-66.
Rodegerdts, L. A., Nevers, B., Robinson, B., Ringert, J., Koonce, P., & Bansen,
J., et al. (2004). Signalized Intersections: Informational Guide ( No. FHWA-HRT04-091): Kittelson and Associates, Incorporated; Federal Highway
Administration.
May 10, 2007
58th Annual Missouri Traffic Conference
and Seminars
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Additional Information

Joe Bared – [email protected]
May 10, 2007
58th Annual Missouri Traffic Conference
and Seminars
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Summary

CFI Design is Promising
Increasing intersection capacity
 Low cost relative to alternatives
 Safer

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Safety and Operational Analyses are Ongoing
May 10, 2007
58th Annual Missouri Traffic Conference
and Seminars
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Questions?
May 10, 2007
58th Annual Missouri Traffic Conference
and Seminars
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