Flashing yellow arrow signals prevent crashes, reduce fatalities

During the past few years, drivers throughout Illinois may have noticed a fourth light on certain traffic signals—a flashing yellow arrow (FYA). The purpose of this arrow is to signal to motorists that a left turn is permissible—but they should enter the intersection with caution. This change was implemented based on a 2006 Federal Highway Administration study that indicated FYAs are the clearest way to communicate left turns are permitted as long as there are no oncoming motorists or pedestrians.

The Illinois Department of Transportation (IDOT) began employing FYA signals in 2010. In order to identify and quantify the benefits of this technology, IDOT requested that ICT launch project R27-097, “Evaluation of Flashing Yellow Arrows (FYA) for Protected/Permissive Left-Turn (PPLT) Control.”

In Phase 1 of the project, the research team, headed by Professor Kerrie Schattler of Bradley University, conducted a driver comprehension survey in which participants were presented with seven left-turn scenarios. The survey results showed that the FYA signals heightened driver understanding of the correct action to take, especially if supplemental signage (e.g., “Left Turn Yield on Flashing Arrow”) is used.

The Phase 1 report and a separate literature review are available on ICT’s website.

In 2013, the study was expanded to include additional research and analysis, including examination of three years’ worth of crash data after the FYA signals had been installed, development of crash modification factors, and quantification of the cost effectiveness of FYA signals.

Schattler says, “Although our data is preliminary, we have found that there is a significant reduction in the number of left-turn-related crashes at intersections where the FYAs are present.”

Randall Laninga, traffic safety engineer for IDOT District 4 and Technical Review Panel chair for the project states, “The use of flashing yellow arrows for permissive left turns has been spreading throughout the country to improve safety. Our study of the FYA installations in the Peoria area plans to show how beneficial they will be for Illinois by calculating the crash reduction we can expect from these signals. We also want to examine the best techniques of getting drivers to understand FYAs and the best practices for installation. With the conclusion of this project, we hope to have guidelines covering planning through installation of FYAs. “

In June, IDOT installed FYA traffic signals at six intersections in Springfield where 40 severe-injury crashes occurred over a five-year period.  With the new traffic signals, motorists have less time to wait and have more opportunities to make a left turn. When the FYA is displayed, motorists may turn left—after yielding to oncoming traffic and pedestrians. In addition, turn lanes have been shifted to provide better sight distances for motorists.

For a closer look at how these signals work, please watch this short video.

This project is scheduled to be completed in late 2015.