This new type of signal includes a "flashing yellow arrow,' which is designed to improve pedestrian safety.
According to Traffic Engineer Mike Tassano, the new signal has the usual three lighted turning arrows in red, yellow and green, plus a new flashing yellow arrow.
"The new style four-section signal functions in a similar fashion as the three-section signal, but instead of the circular green indication, a flashing yellow arrow provides a direct message to drivers to cautiously enter the intersection when making a left turn," Tassano said.
In a press release explaining the new signal, Tassano said:
"With this new style head, the red left-turn arrow can be illuminated to restrict left-turn movements while pedestrians are crossing. This option is not available with the standard three-section permissive left-turn signals. The signal will allow left turns to enter the intersection when pedestrians are not present under the 'flashing yellow arrow' which is the same as the 'left turn yield on green ball' operation that currently exists at this location."
"The signal will also have the ability to display a solid green arrow that will provide a protected left turn to improve the efficiency of the signal during the times of the day when this intersection experiences heavy left turn traffic volumes."
It might be clearer after driving over to the intersection and trying it out.