From the Kentucky Transportation Cabinet Dept. of Highways District 3:

Flashing Yellow Arrow Traffic Display to be Installed
New signal heads to be installed on Scottsville Road

BOWLING GREEN, Ky. (April 29, 2010) - Motorists will encounter a new type of traffic signal on Scottsville Road beginning next week. The light includes a flashing yellow arrow, which indicates that motorists are allowed to proceed with caution but must yield to oncoming traffic. The Kentucky Transportation Cabinet (KYTC) has implemented this new signal in six other highway districts with success. It is already being used in Colorado, Florida, Michigan, Minnesota, Nevada and Oregon.

"Studies have indicated this signal helps reduce left turn crashes at intersections," said Greg Meredith, chief district engineer for the Bowling Green highway district. "The new light has the potential to improve safety because it more clearly signals to drivers that they can turn only when there’s no oncoming traffic."

The flashing yellow arrow will be installed at three intersections with Scottsville Road.

• Ashley Circle
• Woodhurst
• Wilkenson Trace

Flashing yellows will be installed at each approach for Ashley Circle while Woodhurst and Wilkenson Trace will have it on mainline traffic only.

The new signal display has four intervals:

A steady red arrow means STOP. Drivers turning left must stop.

A steady yellow arrow means the signal is getting ready to turn to red. Drivers turning left should stop if it is safe to do so.

A flashing yellow arrow means left-turns are permitted. Drivers may turn left but must first yield to oncoming traffic and pedestrians and then proceed with caution.

A steady green arrow means left-turns are protected. Drivers may turn left. Conflicting traffic must stop.

The flashing yellow arrow is used to replace the permissive green "ball," traditionally used in left-turn traffic signal configurations. Flashing yellow arrows indicate a permissive move for drivers turning left, meaning they can make a left turn, but they have to yield to oncoming traffic. If the pavement sensor in the left-turn lane detects a constant presence of vehicles unable to turn on flashing yellow, the signal will ultimately display a green arrow, indicating a "protected" turn for the vehicles. More information about the signal, and for a simulation of its operation, visit: http://www.bouldercolorado.gov/flash/departments/Transportation/yel_solution.swf 

Historically, the green ball governing left turns has led some motorists wrongly thinking they have a protected turn. In contrast, highway users seem to intuitively know the flashing yellow is communicating the need for caution during the turn.