Flashing Yellow Arrows

1
Flashing Yellow Arrows

• Joel McCarroll, Region 4 Traffic Manageron
  behalf of
• Edward L. Fischer
• State Traffic Engineer
• Oregon Department of Transportation

2
History of Flashing Yellow Arrows

• NCHRP 493 (2003) Evaluation of Traffic Signal
  Displays for Protected/Permissive Left Turn
  Control
• FHWA Interim Approval for Optional Use of
  Flashing Yellow Arrow for Permissive Left Turns
  (March 2006)
• NCHRP Web-Only Document 123 (2007) Evaluation of
  FYA

3
Background

• Concerns with permissive circular green.
• Concern with circular green in doghouse.
• NCHRP 493 studied a wide variety of potential
  displays.
• Study included driver comprehension studies,
  video conflict studies, and crash analyses.

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Traditional Five-Section Doghouse
Courtesy of ODOT Photo and Video Services
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Intersection with a FYA Head
Courtesy of ODOT Photo and Video Services
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Flashing Yellow Arrow Head
Courtesy of ODOT Photo and Video Services
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Comparison of Conversions
Before
After
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FYA Head Configuration

• Separate signal face for the left turn signal
  face.
• Standard FYA head has four sections, all arrows.
• A three-section signal face with bimodal section
  (green arrow and yellow flashing arrow) may be
  used where impractical to use four-section head.

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Meaning of Indications

• The steady red, yellow and green indications have
  the usual meanings
• Steady Red Arrow means stop
• Steady Green Arrow means protected turn
• Steady Yellow Arrow means the phase is changing
• The flashing yellow allows you to turn left when
  oncoming traffic is clear (oncoming traffic has a
  green light).

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Summary of Research

• NCHRP 493 found that displays with exclusive
  heads were found to offer the higher ratings in
  terms of safety, operations, human factors, and
  versatility.
• The FYA was found to be more intuitive and had
  fewer false positive reactions as compared to
  the green ball.
• NCHRP Web-Only Document 123 follow-up study
  indicated significant safety benefits of the FYA.
  

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Crash Reductions Found in NCHRP 123

• 12 intersections studied (3 in Oregon)
• Conversions from doghouses to FYAs
• Limited before/after data sets
• 74 percent reduction in left-turn related
  crashes.

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Benefits of FYA

• High level of understanding
• Best overall alternative to circular green
• More versatility in field operation
• Lead/lag and left turn re-service
• Time of day flexibility to run protected only,
  PPLT, or permissive only.

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FYA Animation

• Click to start animation

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Implementation

• Oregon, Florida, and Maryland were among the
  first few states with the FYA under the FHWA
  Experimental status.
• After FHWA Interim Approval, many other
  jurisdictions across the country are now using
  the FYA.
• Draft MUTCD includes the FYA.

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ODOT Evaluation of FYA

• Data available for 5 conversions from Doghouses
  to FYA before 2008
• Annual average left-turn-related crashes reduced
  from 1.1 crashes/yr/intersection to 0.35.
  (Reduction of 67)
• Calculated Benefit/Cost Ratio from crash
  reductions is approximately 81
• More comparable crash data will be available
  starting in 2010. (30 recent conversions from
  Doghouse to FYA).

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Operation of FYAs in Oregon

• Delay of Flashing Yellow Arrow allows opposing
  traffic to get started while the FYA head remains
  red. (3 seconds)
• Minimum 3 second red indication during transition
  from protected to permissive operation.
• Seems to be some reluctance among signal timers
  to run coordinated lead/lag operation.

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FYA Operation
Courtesy of ODOT Photo and Video Services
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FYAs in Oregon

• Flashing Yellow Arrow is the ODOT standard for
  Protected/Permissive Phasing.
• We are systematically replacing doghouses with
  FYA. We are about 1/3 complete.
• 49 installations on ODOT highways
• 183 installations on city streets and/or county
  roads
• 46 cities now have at least one FYA within their
  city limits

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46 Cities with FYA in Oregon
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Installation Details

• All ODOT installations had engineered signal
  plans prepared.
• Evaluation of loading changes alleviated
  structural concerns.
• Requires one more conductor than protected-only
  head.
• FYA monitored through conflict monitor.
• All 30 conversions in 2008/2009 were completed by
  ODOT electrical crews

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Signal Timing

• ODOT currently using Wapitis W4IKS, W4HC11, or
  Voyage
• W4IKS requires command-box logic of approximately
  200 lines of code. Necessitates use of laptop to
  download timing to controller.
• W4HC11 has new tables for FYA without command
  box.
• Voyage software for the 2070L controller runs the
  FYA without command box.

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Costs of Conversion

• 30 intersections were converted from doghouse
  left turn heads to the FYA head.
• Most conversions involved 2 doghouse heads
• Average cost was 9,100 per intersection
  including
• Site assessment and engineering
• Hardware
• Installation labor
• Temporary traffic control

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Custom Bracket for Spanwire Installations
24
Custom Bracket for Spanwire Installations(Region
2 Electrical Crew Design)
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Custom Bracket for Spanwire Installations
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Other Issues

• Oregon has a few bi-modal heads.
• 20-7 Project to compare the approved 4 section
  head with a three section bi-modal head.
• Jackson County in southern Oregon has
  experimental approval for FYAs that operate
  differently from the interim approval.

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Summary

• In Oregon, the FYA has proven to be
• Significant safety improvement over the doghouse
• Easily understood by drivers
• Versatile
• Easy to install, operate, maintain
• Popular in many jurisdictions

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More Information

• Contact
• Ed Fischer
• (Ed.L.Fischer_at_odot.state.or.us)
• Or
• Gary Obery
• (Gary.R.Obery_at_odot.state.or.us)

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Questions