The problem is it looks like it doesn't work. It curves around the wrong way, and all you can see is the road dropping down and forming a massive obstacle. There's no visual confirmation that the sidewalk crosses to the other side. So the obvious thought, looking at a map, is "Oh I suppose I have to cross the street here" – the street being four lanes of Mass Ave at its worst. And then you discover you have to cross back the other way on the far side of that mess.
@unlambda
Which depending on how bad the traffic is and how fast you walk, something like a 20 to 30 minute pedestrian detour.
@whitequark