Several large cities in China that I've been to tend to use pedestrian tunnels at many large intersections. It works pretty well - subway-like staircases at each corner, and nice wide hallway/tunnels going around the whole intersection. Occasionally with some shops.
It has the advantage of being easy on the eyes above-ground. I can imagine in places with serious homelessness issues there could be problems, but the ones I experienced were fairly nice - some more plain than others, but generally graffiti free, well lit, and well used.
