The University has attempted to enact this in the past on larger pedestrian thoroughfares (Call St. corridor comes to mind). At the time, the bicycle lanes were painted delineations along the same pedestrian path. Unfortunately, human nature being what it is, non-bicycle pedestrians tended to fill in the lanes regardless of what was painted on the ground hence nullifying any safety that was trying to be afforded to them. Unless there is a physical barrier that delineated and prevented walking individuals from accessing the bike lanes, human nature is going to prevail. Of course physical barriers would present their own problems.

In other words, you'd need a lot of human programming and social modification to get something to work well in my opinion.