EVALUATION OF THE IMPACT OF SEPARATE AND SHARED YELLOW SIGNAL SECTIONS AND HEAD ARRANGEMENTS FOR FLASHING YELLOW ARROW LEFT-TURN CONTROL

Abstract

The objective of this research was to analyze the driver comprehension impacts of retrofitting existing traffic signal displays by installing a flashing yellow arrow indication in a bimodal traffic signal section with either the green arrow or yellow arrow indication. This research was completed by developing a computer-based static evaluation that asked participants how they would respond to a given set of signal indications when turning left. The participants were provided four responses, generalized as Go, Yield, Stop, or Don?t Know. Data collection was conducted in Madison, Wisconsin and Amherst, Massachusetts over a three week period in November and December, 2013. After completing the data collection effort, a statistical analysis was completed to determine the impacts of the various traffic signal indication combinations on driver comprehension. The main focus of the analysis was to determine if the flashing yellow arrow was comprehended any differently when being combined with the green arrow (bottom) section compared to being combined with the yellow arrow (middle) section. Findings show that there was not a significant difference in driver comprehension when the flashing yellow arrow was displayed bi-modally in the bottom section or bi-modally in the middle section of a three-section vertical display or five-section clustered display without simultaneous indications. Driver comprehension was significantly lower when the flashing yellow arrow was added bi-modally to the five-section clustered display with simultanoues indications. It is recommended that the flashing yellow arrow is an acceptable retrofit for existing three-section vertical displays, but not for five-section clustered displays.