Effects of Supplemental Traffic Signing at Flashing Yellow Arrow Left-Turn Signal Indications

摘要

In 2010, flashing yellow arrow (FYA) displays were installed at signalized intersections on state routes in the Peoria, Illinois, area. The authors of this paper are involved in funded research to study the safety and effectiveness of the FYA in protected/permissive left-turn control. One objective of this study was to determine whether the addition of supplemental traffic signing with text “Left Turn Yield on Flashing Yellow Arrow” improved driver understanding and safety at the study approaches. This research also investigated the impact of the FYA supplemental sign on older drivers age 65 or greater, recognizing the complex nature of permissive left turns and use of a new traffic control. The results of a driver comprehension survey indicated that drivers had a higher understanding of the FYA if a supplemental sign was present, indicated by both a significant increase in correct responses and a decrease of incorrect “go”, or fail-critical, responses. A crash-based comparison of 164 FYA approaches (including 92 approaches with the sign and 72 approaches without the sign) showed greater crash reductions when the supplemental FYA sign was present. The results also showed that crashes involving older drivers did not experience the same magnitudes of crash reductions as compared to all drivers. Based on the findings of this research, it is recommended that supplemental traffic signing be used when implementing the FYA and that efforts to educate the driving public and older drivers specifically be made to further improve safety for drivers making left turns at signalized intersections.