In December 2009, after extensive testing, the Federal Highway Administration authorized the use of flashing yellow arrows nationwide. A study conducted by the National Cooperative Highway Research Program determined that drivers had fewer crashes with flashing yellow left-turn arrows than with traditional yield-on-green signal configurations.
Steady yellow arrow: The left-turn signal is about to change to red;
prepare to stop, or prepare to complete your left turn if you are within the intersection.
Flashing yellow arrow: Left turns permitted.
Yield to oncoming traffic and pedestrians. (Oncoming traffic has a green light.)
Green arrow: Safe to turn left.(Oncoming traffic must stop.)