Driving around various parts of Michigan, you may have noticed a new four-light turn signal popping up in more and more places. Eventually, every intersection that allows left turns will have them. The new fourth light is a blinking yellow arrow, and MDOT has released a video explaining how to use them on Youtube.
Basically, the yellow light now acts the same as other yellow lights: Slow down and prepare to stop. The blinking yellow arrow fills the role the blinking red used to: Turn when traffic is clear.
This is a federal mandate, so those who drive in other states will be seeing these everywhere within the next few years.
Michigan.gov has all the information on the new blinking yellow arrow at their website.