In places where there is a large number of pedestrians crossing streets and navigating intersections, the amount of time given to pedestrian crossing time on traffic signals exacerbates an already overcrowded transportation system. When you have an area expanding in three dimensions, and a transportation system that is (including subways in with streets for simplicity) fixed in two dimensions, you have a system where the delays and failures can only get worse. Especially in this time where people are moving to cities because they want to be able to walk to where they need to go and not have to own a car, it should be our goal to find a way to make that possible in the safest way we can.
For situations where there is such an overpopulation of pedestrians, I propose to create an elevated pedestrian network. Design cues can be taken from places like Venice, where pedestrians travel above and over top of the canals. A good architect could design a beautiful system that would not only be safer by removing the pedestrian vehicle interactions, but be a tourist draw. He/She would set the standard for city development in the future.
The only potential negative (aside from cost) would be the fact that the current entrances for buildings would now be on a lower level than the pedestrian traffic. This is not a major problem because as people still utilize public transportation and personal vehicles, they will still be using these entrances. And since those same pedestrians will need to move between the street level, subway level and pedestrian network, there will need to be periodic access points between these different levels. This will give those who use the elevated pedestrian network access to all the existing entrances. However, as new buildings are constructed, and old ones are refurbished, they will likely add entrances on this pedestrian level and make it more efficient and more desirable to spend time outdoors at places such as outdoor cafés.
By removing the pedestrian vehicle interactions, the pedestrian crossing time can be removed from traffic signals and they can be move efficient. It will also be safer and faster for people to walk about the area because they will no longer need to wait at traffic signals to cross streets. Between the potential for beautiful architectural outdoor locations, increased safety for pedestrians, and more efficient intersections for the motoring public, there is every reason to invest in this concept.