Those 'transforming' arrows are used by ODOT when they install a flashing protective/permissive left turn signal on a span wire. It has a red left arrow on top, a yellow left arrow in the middle, and then the transformer at the bottom. If cross traffic has the right of way, obviously all signals on that approach show red, the left turn signal stays showing red.
If a car is waiting to make a left, the light will change like a standard protected left, going from a red left arrow, to a green one. It will then use the middle yellow indication to return to red for about 5 seconds to allow oncoming traffic to start moving. Then the bottom indication will re-activate but using the amber element instead in a flashing sequence, telling you it's okay to make your turn but you must yield to oncoming traffic.
If no car is waiting to make a left, it simply holds the red left arrow for about 5 seconds to allow oncoming traffic to start moving and then goes into the flashing yellow left.
Bottom indication showing green/protected left movement
Bottom indication showing flashing yellow for permissive left.
And a traditional pole-mounted 4-section flashing left showing permissive left movement
I'll shoot a video of one of these in action when I get home.
You think your car gets bad mileage? SP 4449 consumes 10 gallons of bunker oil and 100 gallons of water every mile.