I guess you have to see it in person to understand how it intuitively feels very clear that it's not a place you want to hang out on. Maybe in the same way that people don't set up picnics on random patches of grass in a traffic triangle. It's immediately obvious that it's a train corridor. Barcelona has them, Toulouse as well and another that comes to mind right away is Bilbao. Nobody is sitting on the grass and even as a newcomer to the city, I could tell without thinking that this wasn't some lounging grass.I just dont see a version of this without some kind of barrier, albeit even a small knee high fence, between the pedestrian area and streetcar tracks, where QQ is safe. Grass will make the situation worse, because pedestrians will want to walk on it.
Here: does this look like a place you'd want to hang out in?
Even this nicer version of that, does this look inviting to a pedestrian?