Three- or Four-Section Displays for Permissive Left Turns?

Abstract

Many jurisdictions are using the flashing yellow arrow (FYA) to control protected and permissive left turns. For cost and other reasons, some jurisdictions have or are considering implementing FYA with a three-section vertical head, displaying the flashing yellow indication in the same signal face as the protected green arrow. The current Manual on Uniform Traffic Control Devices permits the operation of a three-section vertical head only for permissive turns in locations where heights are restricted. This paper summarizes a comparison of driver performance with three- and four-section FYA signal configurations gathered in a high-fidelity, motion-based driving simulator with mobile eye-tracking equipment. The experiment controlled for the effects of the opposing traffic, the presence and walking direction of pedestrians, and the signal head arrangement. A 24-intersection simulated environment was created, and 27 subjects completed the course, producing 620 permissive left-turn maneuvers for further analysis. Driver performance was measured from the (a) average total eye glance durations at specific areas of interest and (b) the position of the pedestrian in the crosswalk when the driver initiated the left turn. No statistically significant differences between the average fixation duration when the FYA was presented with a three- or four-section signal head were identified. The pedestrian's position in the crosswalk when the driver began the left turn was not statistically significantly different for three of the four pedestrian walking directions presented. Overall, measurable driver performance does not seem to be sensitive to the vertical positioning of the FYA display in the permissive interval.