The new signals are intended to help clarify instructions about when motorists can safely turn left across oncoming lanes of traffic.
In the past, motorists turning left had a green arrow, transitioning to a yellow arrow and then to a solid green light. When the signal transitioned to the solid green light, many motorists incorrectly interpreted it as meaning it was safe to go and that oncoming traffic had to stop, which resulted in several T-bone collisions.
Now the left turn signals will be green, flashing yellow, yellow and red arrows. With the flashing yellow arrow, it is safe to turn only if the way is clear, giving motorists some discretion about when to turn. However, the flashing yellow arrow will be turned off during times of heavy traffic, such as afternoon rush hour when the overwhelming majority of the accidents occur at the intersection.
As before, the green arrow means motorists have a dedicated left turn privilege and oncoming traffic must stop, and the yellow arrow signifies motorists should clear the intersection. When the arrow is red, turning is not allowed.