[samiv]

"The traffic light though is very simple. Yellow means “it was green and will turn red”. Red+yellow means “it was red and will turn green”."

That was not the point, that's the standard way the lights will work.

The point is that sometimes you have a light combination where actual light post only has yellow/red for example (no green light). Sometimes you have a light post that has red only (on, off).

[shizzor]

I have never seen those anywhere in Germany. Are you sure you are talking about traffic lights?