Driver comprehension and behavioral analysis of a novel traffic control device: Implementation of the flashing yellow arrow permissive indication
Perhaps the most significant safety and operational element in signalized intersection operation is simultaneous movements which cross paths, specifically, left-turn movements. Protected/permissive left-turn (PPLT) signal phasing was a concept developed to improve operational efficiency at signalized intersections by providing a protected phase for left-turns as well as a permissive phase during which left-turns can be made if gaps in opposing through traffic allow. The recurring major issue with PPLT signal phasing, targeted by traffic engineers and drivers alike, is the permissive indication, which is a circular green (CG) signal indication. As a result of this concern, the CG permissive indication became the primary focus of National Cooperative Highway Research Program (NCHRP) project 3-54. After a series of studies the NCHRP research team concluded that a flashing yellow arrow (FYA) permissive indication provided a better alternative to the CG permissive indication. Therefore the research team recommended that the FYA permissive indication was an acceptable, and perhaps recommended indication, for permissive left-turns, and recommended the FYA permissive indication for inclusion in the Manual on Uniform Traffic Control Devices, which is the national standard for traffic control devices. Detailed review of the NCHRP research recommendations by an MUTCD oversight committee resulted in several questions that needed to be addressed before the FYA could be unconditionally recommended for the MUTCD.
The research described herein formulated these questions into six research hypotheses and used assorted evaluation methodologies to provide quantitative and/or qualitative responses to the developed hypotheses. Specifically, driver comprehension and behavioral analyses were completed using myriad experimental procedures, which included the use of a fixed-base, fully-interactive, dynamic driving simulator and a computer-based static evaluation. In total, four simulator experiments, and 11 static evaluations were completed by a total of over 950 drivers and pedestrians evaluating over 11,600 permissive left-turn scenarios.
The research resulted in direct responses to each of the developed hypotheses and included in several recommendations. The primary recommendation calls for inclusion of the FYA permissive indication in the MUTCD. Additionally, several additional applications of the FYA were evaluated and recommended, and a series of recommendations for future research were included.