You just have to walk down through streets of Barcelona to see that it is one of the European cities with more motorcycles. In fact, only Rome has more of them. When you see how they position themselves in the red crosslights to leave first then you understand that they are the queens of the asphalt.
It's one of the things that often draws attention to people who visit, especially if they have to drive around Barcelona, and they are not used to having to think about having motorbikes everywhere around! Even us, people from Barcelona, who are used to them, find sometimes in tnese situations created between motorbikes and other vehicles.
I am, myself, sometimes a pedestrian, a cyclist, a motorcyclist and motorist in Barcelona, and I also use public transportation. I think we can all live together if we all are willing to cooperate. Actually, problems are caused not by the type of vehicle, but by who and how they are driven it!