Assessment of a Flashing Yellow Arrow Signal Implementation Using Gap Acceptance Measures

The use of flashing yellow arrow (FYA) displays for protected permitted left turn (PPTL) operations has been increasing in recent years. With its inclusion in the MUTCD, more traffic agencies will likely adopt FYA for PPTL operations in the future. The intent of FYA is to replace traditional green ball displays to make drivers more cautious when making permissive left turns. In this case study, a before-and-after study of an FYA deployment was performed. The study used gap acceptance as a short-term safety measure to evaluate the FYA deployment under different traffic conditions. It was found that under similar low to moderate traffic conditions, by implementing FYA, most drivers accepted longer gaps to make their permissive left turns, hence improving the safety. No noticeable benefits from FYA were found under heavy opposing traffic conditions when available gaps were short. Opposing traffic volumes also have a significant impact on gap acceptance behaviors