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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?.
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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?
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
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?
Left Turn Trap with Shared Faces: Protected/Permissive LTs Southbound Northbound
Left Turn Trap with Shared Faces: Protected/Permissive LTs Southbound Northbound
Left Turn Trap with Shared Faces: Protected/Permissive LTs Southbound Northbound
Classic Left Turn Trap with Permissive LTs Southbound Northbound
The separate signal face (“Dallas Phasing”) solution for the LT trap
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