Flashing Yellow Arrows for Permissive Left Turns – Is It for You?

Presented by: Bruce E. Friedman, P.E., PTOE Kimley-Horn and Associates Cary, NC

Flashing Yellow LT Arrows What is its history? How does it operate? What is its current status? What are its advantages?

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

Traffic Signal Displays Innovations are rare in vehicular signal displays Pedestrian signal innovations: Solid symbol messages Countdown displays Accessible ped signals

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

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

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

Shared Face: Permissive Only LTs

Shared Face: Permissive Only LTs

Shared Face: Protected/Permissive LTs

Shared Face (with sign): Protected/Permissive LTs

Shared Face: Permissive Only LTs

Separate Face: Protected Only LTs

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

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

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

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

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

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

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

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

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

Shared Face Sequence: Leading Protected/Permissive LT

Shared Face Sequence: Leading Protected/Permissive LT

Shared Face Sequence: Leading Protected/Permissive LT

Shared Face Sequence: Leading Protected/Permissive LT

Shared Face Sequence: Leading Protected/Permissive LT

Shared Face Sequence: Leading Protected/Permissive LT

Left Turn Trap with Shared Faces: Protected/Permissive LTs Northbound Southbound

Left Turn Trap with Shared Faces: Protected/Permissive LTs Northbound Southbound

Left Turn Trap with Shared Faces: Protected/Permissive LTs Northbound Southbound

Classic Left Turn Trap with Permissive LTs Northbound Southbound

The separate signal face (“Dallas Phasing”) solution for the LT trap

Separate Face (“Dallas Phasing”): Protected/Permissive LTs

Separate Face Sequence: Leading Protected/Permissive LT

Separate Face Sequence: Leading Protected/Permissive LT

Separate Face Sequence: Leading Protected/Permissive LT

Separate Face Sequence: Leading Protected/Permissive LT

Separate Face Sequence: Leading Protected/Permissive LT

Separate Face Sequence: Leading Protected/Permissive LT

The flashing yellow arrow signal face solves the LT trap problem and offers other advantages as well

A New Idea: A Flashing Yellow Arrow (FYA) Signal Face for LTs

Simultaneous leading protected/permissive LTs in both directions

FYA Sequence: Simultaneous Leading Protected/Permissive LTs

FYA Sequence: Simultaneous Leading Protected/Permissive LTs

FYA Sequence: Simultaneous Leading Protected/Permissive LTs

FYA Sequence: Simultaneous Leading Protected/Permissive LTs

FYA Sequence: Simultaneous Leading Protected/Permissive LTs

FYA Sequence: Simultaneous Leading Protected/Permissive LTs

FYA Sequence: Simultaneous Leading Protected/Permissive LTs

Leading LT Phase with FYA

Lagging left-turn when the opposite direction has a leading left-turn

FYA Sequence: Lagging Permissive/Protected LT when Opposite Direction Has a Leading LT

FYA Sequence: Lagging Permissive/Protected LT when Opposite Direction Has a Leading LT

FYA Sequence: Lagging Permissive/Protected LT when Opposite Direction Has a Leading LT

FYA Sequence: Lagging Permissive/Protected LT when Opposite Direction Has a Leading LT

FYA Sequence: Lagging Permissive/Protected LT when Opposite Direction Has a Leading LT

FYA Sequence: Lagging Permissive/Protected LT when Opposite Direction Has a Leading LT

Lagging LT phase with FYA

Leading left-turn when the opposite direction has a lagging left-turn – the solution to the LT trap

FYA Sequence:. Leading Protected/Permissive LT when FYA Sequence: Leading Protected/Permissive LT when Opposite Direction Has a Lagging LT

FYA Sequence:. Leading Protected/Permissive LT when FYA Sequence: Leading Protected/Permissive LT when Opposite Direction Has a Lagging LT

FYA Sequence:. Leading Protected/Permissive LT when FYA Sequence: Leading Protected/Permissive LT when Opposite Direction Has a Lagging LT

FYA Sequence:. Leading Protected/Permissive LT when FYA Sequence: Leading Protected/Permissive LT when Opposite Direction Has a Lagging LT

FYA Sequence:. Leading Protected/Permissive LT when FYA Sequence: Leading Protected/Permissive LT when Opposite Direction Has a Lagging LT

FYA Sequence:. Leading Protected/Permissive LT when FYA Sequence: Leading Protected/Permissive LT when Opposite Direction Has a Lagging LT

FYA Sequence:. Leading Protected/Permissive LT when FYA Sequence: Leading Protected/Permissive LT when Opposite Direction Has a Lagging LT

FYA Sequence:. Leading Protected/Permissive LT when FYA Sequence: Leading Protected/Permissive LT when Opposite Direction Has a Lagging LT

FYA Sequence:. Leading Protected/Permissive LT when FYA Sequence: Leading Protected/Permissive LT when Opposite Direction Has a Lagging LT

Permissive only left-turn when the opposite direction has a lagging left-turn – the solution to the LT trap

FYA Sequence: Permissive LT when Opposite Direction Has a Lagging LT

FYA Sequence: Permissive LT when Opposite Direction Has a Lagging LT

FYA Sequence: Permissive LT when Opposite Direction Has a Lagging LT

FYA Sequence: Permissive LT when Opposite Direction Has a Lagging LT

FYA Sequence: Permissive LT when Opposite Direction Has a Lagging LT

FYA Sequence: Permissive LT when Opposite Direction Has a Lagging LT

Use of the FYA signal face for permissive only left-turns at times of the day when the LT volumes are low

FYA Sequence: Permissive Only LT

FYA Sequence: Permissive Only LT

FYA Sequence: Permissive Only LT

FYA Sequence: Permissive Only LT

Perhaps the ultimate signal operation during low traffic volumes – lagging left-turns in both directions with set-back detection

FYA Sequence: Simultaneous Lagging Permissive/Protected LTs

FYA Sequence: Simultaneous Lagging Permissive/Protected LTs

FYA Sequence: Simultaneous Lagging Permissive/Protected LTs

FYA Sequence: Simultaneous Lagging Permissive/Protected LTs

FYA Sequence: Simultaneous Lagging Permissive/Protected LTs

FYA Sequence: Simultaneous Lagging Permissive/Protected LTs

FYA Sequence: Simultaneous Lagging Permissive/Protected LTs

The flexibility of the 4-section FYA signal face: Protected/permissive operation

FYA Sequence: Protected/Permissive LT

FYA Sequence: Protected/Permissive LT

FYA Sequence: Protected/Permissive LT

FYA Sequence: Protected/Permissive LT

FYA Sequence: Protected/Permissive LT

FYA Sequence: Protected/Permissive LT

FYA Sequence: Protected/Permissive LT

The flexibility of the 4-section FYA signal face: Protected only operation

FYA Sequence: Protected Only LT

FYA Sequence: Protected Only LT

FYA Sequence: Protected Only LT

FYA Sequence: Protected Only LT

The flexibility of the 4-section FYA signal face: Permissive only operation

FYA Sequence: Permissive Only LT

FYA Sequence: Permissive Only LT

FYA Sequence: Permissive Only LT

FYA Sequence: Permissive Only LT

3-Section FYA Signal Face: Permissive Only LT

What is the current status of the flashing yellow left-turn arrow?

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.

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

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

Interim Approval Status 11 State DOTs: Colorado, Iowa, Michigan, Minnesota, Missouri, New Hampshire, North Carolina, Oregon, Utah, Washington, and Wyoming

Interim Approval Status 22 Cities and Counties (representing a total of 18 States)

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.

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

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

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

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

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

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

One Caution About FYAs Steady LT yellow arrow to clear the permissive mode is on at the same time as the opposing direction’s circular yellow This requires a conflict monitor modification and will require revised text in the MUTCD

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

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