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

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?

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

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

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

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

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

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

  7. 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

  8. 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

  9. Shared Face: Permissive Only LTs

  10. Shared Face: Permissive Only LTs

  11. Shared Face: Protected/Permissive LTs

  12. Shared Face (with sign): Protected/Permissive LTs

  13. Shared Face: Permissive Only LTs

  14. Separate Face: Protected Only LTs

  15. 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

  16. 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

  17. 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

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

  19. 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

  20. 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

  21. 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

  22. 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

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

  24. Shared Face Sequence: Leading Protected/Permissive LT

  25. Shared Face Sequence: Leading Protected/Permissive LT

  26. Shared Face Sequence: Leading Protected/Permissive LT

  27. Shared Face Sequence: Leading Protected/Permissive LT

  28. Shared Face Sequence: Leading Protected/Permissive LT

  29. Shared Face Sequence: Leading Protected/Permissive LT

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

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

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

  33. Classic Left Turn Trap with Permissive LTs Southbound Northbound

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

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

  36. Separate Face Sequence: Leading Protected/Permissive LT

  37. Separate Face Sequence: Leading Protected/Permissive LT

  38. Separate Face Sequence: Leading Protected/Permissive LT

  39. Separate Face Sequence: Leading Protected/Permissive LT

  40. Separate Face Sequence: Leading Protected/Permissive LT

  41. Separate Face Sequence: Leading Protected/Permissive LT

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

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

  44. Simultaneous leading protected/permissive LTs in both directions

  45. FYA Sequence: Simultaneous Leading Protected/Permissive LTs

  46. FYA Sequence: Simultaneous Leading Protected/Permissive LTs

  47. FYA Sequence: Simultaneous Leading Protected/Permissive LTs

  48. FYA Sequence: Simultaneous Leading Protected/Permissive LTs

  49. FYA Sequence: Simultaneous Leading Protected/Permissive LTs

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