Two of my favourites were Brownie Distribution Center (there was a Girl Scout symbol there), and Use Stairs Between Floors Only, on the door to a stairwell.
The first one tickled my funny bone (“Can I get a dozen with icing, to go? Whaddya mean, they’re not that kind of brownie?”), the second is still a kinda WTF?
It’s one of those tests that they give you during wartime to prove that you’re a real Canadian and not a spy.
That’s what I thought ordinary merging was. How else can you merge? What would be a NON-alternating merge? Two at once? Speed up and squeeze in two cars ahead?
I suppose you could have one lane always yield to the other, but that would tend to back traffic up in that lane.
There’s one of those in (I think) Elkridge.
Underneath is another sign that says ‘TAKE TURNS’.
I have to admit that I get a bit confused when people ask where the Kiss & Ride is at our local station. There’s an area with signs saying “Passenger Drop-Off”: is that the Kiss & Ride? Or is there another secret drop-off area that I’m not aware of?
I always get a bit neurotic at the idea of giving people bad directions.
Actually I think you are not describing “alternate merge”. I think three cars from one lane are supposed to go, then three from the other, alternating in groups of three. It’s supposed to be more efficient and reduce delays. This is a dim memory of Pennsylvania law I’m working from.
I just looked around for a description of this three car alternation and don’t see it out there, so it looks like I’m mistaken. Carry on.
They’re pretty new to Michigan. At first, as another poster said, I thought it meant stop, then if traffic is clear proceed with your turn, same as what used to be a flashing red at these intersections. Otherwise, a solid red means stop, why complicate it by adding an arrow instead of continuing to use a solid red???
Didn’t help that the first time I came across one was at the exit of a mall parking lot, onto a divided road where you could only turn anyway, not go straight (or turn left for that matter).
Before these started randomly showing up a couple years ago, all I’d ever seen with an arrow was a green arrow, which means, you can go, but only if you’re turning.
There’s some installed at an intersection in my town, OK, it’s basically the only lights in town. 
The right turn arrow’s red if there’s oncoming traffic with a green left turn arrow. If their left turn arrow’s red, then the right turn arrow’s green. However, many folks wait until it’s green and slow everything down.