Flashing Yellow Arrows for Permissive Left Turns

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Flashing Yellow Arrows for Permissive Left Turns
Is It for You?
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• Presented by
• Bruce E. Friedman, P.E., PTOE
• Kimley-Horn and Associates
• Cary, NC

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Flashing Yellow LT Arrows

• What is its history?
• How does it operate?
• What is its current status?
• What are its advantages?

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• What is the history of the flashing yellow
  left-turn arrow?

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Traffic Signal Displays

• Innovations are rare in vehicular signal
  displays
• Pedestrian signal innovations
• Solid symbol messages
• Countdown displays
• Accessible ped signals

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Traffic Signal Displays

• The last significant innovation in vehicular
  signal displays was the red left-turn arrow that
  was introduced in the 1971 MUTCD

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(No Transcript)
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Research Project Requested

• The Signals Technical Committee (STC) of the
  NCUTCD had concerns in the mid-1990s about the
  effectiveness of the circular green as the
  indication for permissive left turns

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Research Project Requested

• The STC was also concerned about the wide variety
  of permissive left turn displays being used
  around the nation, such as the flashing circular
  red in Michigan or the flashing circular yellow
  in Washington State

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Shared Face Permissive Only LTs
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Shared Face Permissive Only LTs
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Shared Face Protected/Permissive LTs
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Shared Face (with sign) Protected/Permissive LTs
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Shared Face Permissive Only LTs
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Separate Face Protected Only LTs
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Research Project Requested

• Left-turning driver confusion about the meaning
  of circular green led the STC to request a
  research project to take a new look at
  protected/permissive LT displays

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Research Project

• NCHRP Report 493 documents a comprehensive,
  national research study to evaluate operational
  advantages and safety aspects of various
  left-turn displays at signalized intersections

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Research Process

• Studied a wide variety of types of left-turn
  displays, including
• Flashing circular yellow
• Flashing yellow arrow
• Flashing circular red
• Flashing red arrow
• Flashing green arrow (Canada)
• Steady circular green

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Research Process

• Still Photograph and Video Studies
  (approximately 2,500 drivers)
• Driver Simulation (more than 400 drivers)
• Field Implementation in 4 States

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Research Results

• NCHRP Report 493 found that the flashing yellow
  arrow permissive left-turn indication had
  significantly more correct responses than the
  steady circular green permissive left-turn
  indication

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Research Results

• NCHRP Report 493 found that a flashing yellow
  arrow (FYA) permissive indication is
  well-understood by drivers and recommended its
  application for permissive left turns

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Other NCHRP Report 493 Recommendations

• A 4-section, all-arrow signal face should be the
  only FYA display allowed
• The FYA left-turn signal face should be placed
  over the left-turn lane

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Other NCHRP Report 493 Recommendations

• A supplemental sign is not needed with the FYA
  display
• The FYA should be tied to the opposing through
  green indication

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• What does the new FYA operation look like and how
  does it work?

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Shared Face Sequence Leading Protected/Permissiv
e LT
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Shared Face Sequence Leading Protected/Permissiv
e LT
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Shared Face Sequence Leading Protected/Permissiv
e LT
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Shared Face Sequence Leading Protected/Permissiv
e LT
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Shared Face Sequence Leading Protected/Permissiv
e LT
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Shared Face Sequence Leading Protected/Permissiv
e LT
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Left Turn Trap with Shared Faces
Protected/Permissive LTs
Northbound
Southbound
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Left Turn Trap with Shared Faces
Protected/Permissive LTs
Northbound
Southbound
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Left Turn Trap with Shared Faces
Protected/Permissive LTs
Northbound
Southbound
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Classic Left Turn Trap with Permissive LTs
Northbound
Southbound
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• The separate signal face (Dallas Phasing)
  solution for the LT trap

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Separate Face (Dallas Phasing) Protected/Permi
ssive LTs
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Separate Face Sequence Leading
Protected/Permissive LT
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Separate Face Sequence Leading
Protected/Permissive LT
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Separate Face Sequence Leading
Protected/Permissive LT
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Separate Face Sequence Leading
Protected/Permissive LT
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Separate Face Sequence Leading
Protected/Permissive LT
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Separate Face Sequence Leading
Protected/Permissive LT
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• The flashing yellow arrow signal face solves the
  LT trap problem and offers other advantages as
  well

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A New Idea A Flashing Yellow Arrow (FYA)
Signal Face for LTs
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• Simultaneous leading protected/permissive
• LTs in both directions

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FYA Sequence Simultaneous Leading
Protected/Permissive LTs
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FYA Sequence Simultaneous Leading
Protected/Permissive LTs
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FYA Sequence Simultaneous Leading
Protected/Permissive LTs
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FYA Sequence Simultaneous Leading
Protected/Permissive LTs
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FYA Sequence Simultaneous Leading
Protected/Permissive LTs
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FYA Sequence Simultaneous Leading
Protected/Permissive LTs
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FYA Sequence Simultaneous Leading
Protected/Permissive LTs
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Leading LT Phase with FYA
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• Lagging left-turn when the opposite direction has
  a leading left-turn

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FYA SequenceLagging Permissive/Protected LT
whenOpposite Direction Has a Leading LT
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FYA SequenceLagging Permissive/Protected LT
whenOpposite Direction Has a Leading LT
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FYA SequenceLagging Permissive/Protected LT
whenOpposite Direction Has a Leading LT
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FYA SequenceLagging Permissive/Protected LT
whenOpposite Direction Has a Leading LT
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FYA SequenceLagging Permissive/Protected LT
whenOpposite Direction Has a Leading LT
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FYA SequenceLagging Permissive/Protected LT
whenOpposite Direction Has a Leading LT
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Lagging LT phase with FYA
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• Leading left-turn when the opposite direction has
  a lagging left-turn the solution to the LT trap

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FYA Sequence Leading Protected/Permissive LT
when Opposite Direction Has a Lagging LT
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FYA Sequence Leading Protected/Permissive LT
when Opposite Direction Has a Lagging LT
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FYA Sequence Leading Protected/Permissive LT
when Opposite Direction Has a Lagging LT
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FYA Sequence Leading Protected/Permissive LT
when Opposite Direction Has a Lagging LT
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FYA Sequence Leading Protected/Permissive LT
when Opposite Direction Has a Lagging LT
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FYA Sequence Leading Protected/Permissive LT
when Opposite Direction Has a Lagging LT
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FYA Sequence Leading Protected/Permissive LT
when Opposite Direction Has a Lagging LT
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FYA Sequence Leading Protected/Permissive LT
when Opposite Direction Has a Lagging LT
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FYA Sequence Leading Protected/Permissive LT
when Opposite Direction Has a Lagging LT
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• Permissive only left-turn when the opposite
  direction has a lagging left-turn the solution
  to the LT trap

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FYA Sequence Permissive LT when Opposite
Direction Has a Lagging LT
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FYA Sequence Permissive LT when Opposite
Direction Has a Lagging LT
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FYA Sequence Permissive LT when Opposite
Direction Has a Lagging LT
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FYA Sequence Permissive LT when Opposite
Direction Has a Lagging LT
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FYA Sequence Permissive LT when Opposite
Direction Has a Lagging LT
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FYA Sequence Permissive LT when Opposite
Direction Has a Lagging LT
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• Use of the FYA signal face for permissive only
  left-turns at times of the day when the LT
  volumes are low

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FYA Sequence Permissive Only LT
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FYA Sequence Permissive Only LT
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FYA Sequence Permissive Only LT
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FYA Sequence Permissive Only LT
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• Perhaps the ultimate signal operation during low
  traffic volumes lagging left-turns in both
  directions with set-back detection

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FYA Sequence SimultaneousLagging
Permissive/Protected LTs
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FYA Sequence SimultaneousLagging
Permissive/Protected LTs
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FYA Sequence SimultaneousLagging
Permissive/Protected LTs
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FYA Sequence SimultaneousLagging
Permissive/Protected LTs
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FYA Sequence SimultaneousLagging
Permissive/Protected LTs
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FYA Sequence SimultaneousLagging
Permissive/Protected LTs
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FYA Sequence SimultaneousLagging
Permissive/Protected LTs
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• The flexibility of the
• 4-section FYA signal face
• Protected/permissive operation

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FYA Sequence Protected/Permissive LT
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FYA Sequence Protected/Permissive LT
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FYA Sequence Protected/Permissive LT
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FYA Sequence Protected/Permissive LT
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FYA Sequence Protected/Permissive LT
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FYA Sequence Protected/Permissive LT
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FYA Sequence Protected/Permissive LT
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• The flexibility of the
• 4-section FYA signal face
• Protected only operation

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FYA Sequence Protected Only LT
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FYA Sequence Protected Only LT
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FYA Sequence Protected Only LT
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FYA Sequence Protected Only LT
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• The flexibility of the
• 4-section FYA signal face
• Permissive only operation

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FYA Sequence Permissive Only LT
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FYA Sequence Permissive Only LT
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FYA Sequence Permissive Only LT
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FYA Sequence Permissive Only LT
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3-Section FYA Signal Face Permissive Only LT
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• What is the current status of the flashing yellow
  left-turn arrow?

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MUTCD Revision

• This Standard was deleted in the 2003 MUTCD
• A traffic control signal shall be operated in
  either a steady (stop-and-go) mode or a flashing
  mode at all times.

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Interim Approval Issued 3/20/2006Optional Use
of FYA Display for Permissive LTs
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Interim Approval Status

• The following are among the agencies that have
  received approval to implement FYA under the
  Interim Approval

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Interim Approval Status

• 11 State DOTs
• Colorado, Iowa, Michigan, Minnesota, Missouri,
  New Hampshire, North Carolina, Oregon, Utah,
  Washington, and Wyoming

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Interim Approval Status

• 22 Cities and Counties
• (representing a total of 18 States)

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Current Status

• During experimentation and as a result of the
  Interim Approval, the FYA has now been approved
  for installation and/or installed at
  approximately 500 signalized intersections across
  the U.S.

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Implementation Results

• The FYA display has been successfully
  implemented in the field with relatively little
  or no technical or safety issues
• The field data supports a high level of driver
  understanding of the FYA display

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• What are the advantages of the flashing yellow
  left-turn arrow?

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Advantages of FYA

• The FYA display is better understood by drivers
  than the circular green display
• Allows for the display of different LT modes at
  different times of the day

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Advantages of FYA

• Eliminates the LT trap situation, thus allowing
  the display of leading and lagging LT phases at
  different times of the day to improve signal
  progression, while still providing permissive
  left turns to improve capacity

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Advantages of FYA

• No louvers or other special optical features are
  needed to shield the display from adjacent
  through traffic because the face is comprised of
  arrows only, thus allowing for span-wire mounting
  and eliminating the need for precise aiming

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Advantages of FYA

• No sign is needed as drivers find it easy to
  understand that the FYA display means that
  left-turn drivers must yield to oncoming traffic
• Can be used to prevent a permissive LT movement
  from turning during RR preemption

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One Caution About FYAs

• Steady LT yellow arrow to clear the permissive
  mode is on at the same time as the opposing
  directions circular yellow
• This requires a conflict monitor modification and
  will require revised text in the MUTCD

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One Caution About FYAs

• FHWA has released Official Interpretation
  4-320(I) to cover this situation and has
  recommended that the MUTCD text be changed
  accordingly in the next edition

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Innovative flashing yellow arrows for permissive
left turns are you ready to give them a try in
your jurisdiction?