The problem: For years, some engineers have had concerns that drivers turning left on a permissive circular green signal indication might inadvertently mistake that indication as implying the left turn has the right of way over opposing traffic, especially under some geometric conditions.
The solution: Replace the old "doghouse" or 5-signal head signals with the 4-head flashing yellow arrow signal.
The operations: The new signal display has four intervals:
§ A steady red arrow means STOP. Drivers turning left must stop.
§ A steady yellow arrow means the signal is getting ready to turn to red. Drivers turning left should stop if it is safe to do so.
§ A flashing yellow arrow means left-turns are permitted. Drivers may turn left but must first yield to oncoming traffic and pedestrians and then proceed with caution.
§ A steady green arrow means left-turns are protected. Drivers may turn left. Conflicting traffic must stop.
The public was made aware of the FYAs through sources such as the KYTC website and LFUCG Division of Traffic Engineering website. In addition, local news agencies published articles on the signals as another method of disseminating information to the public.
To date, flashing yellow arrows have been approved at approximately 100 traffic signals on the state highway system within Kentucky. Within Lexington, there are over 70 intersections that have FYAs installed to date. The LFUCG Division of Traffic Engineering began replacing all 5-section signal heads in May 2009.
Since the FYAs are new, complete conclusions are not known. However, early indications in Lexington have shown a reduction in left turn collisions along the main arterials in which the signals have been installed as compared to prior months before the FYA installation.
Comments from Agencies:
"We are excited about the program and can not upgrade to the FYAs fast enough. The FYA provides us both a safety enhancement, as well as an efficiency improvement at each location they are installed," said Steve Cummins, LFUCG Traffic Signal Manager. He further added that, "Driver's find that the upgrade is beyond intuitive when approaching a FYA at an intersection."
In a statement from Dan O'Dea with Louisville Metro Traffic Engineering Section: "The new 'flashing yellow' arrow is still an experimental display which essentially replaces the standard 5-section signal and is currently being evaluated at various locations statewide. Because the display is more unintuitive, motorists have also adapted quickly. The new 'flashing yellow' arrow is an option in some locations where the traffic volumes and site distance may have been appropriate to allow a permissive left-turn movement, but the intersection's geometry precluded the installation of the standard 5-section display. State and City agencies continue to study the effectiveness of the display particularly as it relates to safety, and initial results are promising."
Jeff Wolfe from the KTYC Division of Traffic Engineering added: "We are pleased with the initial performance of our flashing yellow arrow installations. As suggested by research, drivers appear to have a high-level of comprehension of the new display. While we have not had enough time to conduct a formal before/after study, we feel confident that such studies will ultimately show that the new display improves safety. In addition, the flashing yellow arrow display gives the traffic engineering practitioner more versatile operational features, such as lead-lag protected-permitted phasing, variable left-turn phasing, and a solution to left-turn trap issues."
For more information: Check out more information on KYTC site: