How Effective are "Flashing Yellow Arrow" Signals in Enhancing Safety?

Crashes (in particular, those involving left-turn vehicles) at signalized intersections result in substantial economic losses to the society in terms of death, injury, and property damage. A wide variety of traffic signals are used by the traffic engineers, in the United States, to minimize left-turn crashes and provide maximum safety at signalized intersections. One latest innovation and addition to these traffic signals is the "flashing yellow arrow (FYA)" signal. This paper focuses on safety evaluation of FYA signals "before" and "after" their installation at six selected signalized intersections in the city of Charlotte, North Carolina. Empirical Bayes (EB) technique was used for evaluation. The EB method compares the number of crashes "after" the installation to the estimated number of crashes that would have occurred during the "after" period if the FYA signal had not been installed. Results obtained indicate that the number of crashes would have generally increased if the FYA signals had not been installed at the selected signalized intersections.