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Access Type

Open Access Thesis

Document Type


Degree Program

Civil Engineering

Degree Type

Master of Science in Civil Engineering (M.S.C.E.)

Year Degree Awarded


Month Degree Awarded



With the advancement of implementation for a novel traffic control device, the Flashing Yellow Arrow (FYA), agencies across the country have continually sought strategies to improve intersection operations and safety, specifically with respect to the left-turn application. More so, permissive left-turn intervals have been communicated to drivers using several traffic signal indications; however, most frequently these phases are represented through the circular green (CG) ball and more recently, the FYA. Previous research in this area determined that the FYA indication produced the most effective communication of permissive left-turns. Further, this previous research led to the inclusion of the FYA in the 2009 edition of the Manual on Uniform Traffic Control Devices (MUTCD). In recent years, agencies across the country have embraced the implementation of the FYA for permissive left-turns. However, there remains a lack of national guidance on the definition of change and clearance intervals for transitioning between protected and permissive left-turns. Complicating the matter is the connection between traditional signal phasing/design and human factors. Investigation through driver comprehension and real-world operations will allow us to not only evaluate current conditions, but also experimental and future conditions. Recommendations provided from this research will ultimately offer agencies with the strategies for the most effective transition from a protected left-turn to a permissive left-turn phase.


First Advisor

Michael A. Knodler Jr.

Second Advisor

Eleni Christofa