This, my friends, is called an "Umweltspur" (lit. "environment lane") which is reserved for people on bikes... and buses.
Now, I won't drag it too much, since this road is one of the major roads into my home city and during rush hour it can be clogged up a lot by the sheer amount of cars flowing towards the centre from and to the west in the morning and late afternoon. I had to take it from the west a while back and it's pleasant to be able to take the bus and not having it take forever due to the lane being filled with cars (which usually just transport one person).
So, it's great for public transit and that's good. I love public transit.
But when it comes to bicycles, it's a mixed bag. Yes, it's nice that people who commute by bike have a bit more space and don't need to mix with pedestrians (before this was built, bikes had to share the pavement with pedestrians and since it's rather narrow at times (just shy of one metre between the fences on the other side of the road, barely enough to fit a single person on a wheelchair - knowledgeable locals would take the streets running parallel to this road to make the ride easier)... but now they have to mix with buses, which is just as rubbish an idea.
Adding to that is also the fact that not everyone is following the rules. It turns out that motorists still drive into that lane because... it's free, I guess, thus endangering squishy human bodies with their steel machine. And that points to a major problem with this idea: It's not bad, it's just so severely lacking because one point is completely ignored when it comes to cycling infrastructure:
Paint and signs are not infrastructure.
What that means is pretty obvious hopefully, but let me explain it in the simple most terms: Putting up a sign and painting the lanes differently is not enough to ensure the safety of those using the lane. Enforcing the rules by handing out fines is not enough. The only way to ensure the safety of people on bikes is to build actual, effective, physical barriers - either a green strip or a concrete barrier between them and the path used by motorists.
Places that actually separate bicycles from motor traffic are places where it's much nicer to ride and it will increase both the safety of those already using a bike in their everyday life and the number of people riding in the first place, as it will make it more attractive to people who want to ride more frequently, but are on the fence about it due to the perceived (and real!) lack of rider safety. I hope this is a lesson German cities will learn over time as we will shift away from car-oriented infrastructure towards more people-oriented infrastructure.