Walk-overs are expensive, but yes, at major intersections. What about ziplines? Sounds crazy, but if a company would come in and backed with insurance, then maybe they can get people (mostly the young) across the street.
Problems? Too many come to mine, but cars running into people and the back end of other cars braking are just two. Do you wait for every light to change before crossing the street? Not many people do, but the problem is when there is traffic and someone runs across the street. There isn't really a remedy as some people will do as they please no matter how many PSA's.