When they're essentially sharing the same spaces, then you need to think about how to deal with that.
One of the great amusing mysteries to me since I've lived here is how the powers that be are always wondering why Broad St. - the main central vehicle artery through the city - isn't some beautiful grand boulevard filled with people. The answer is rather simple. It's the main central vehicle artery through the city. It's never going to be that appealing to pedestrians as long as maximizing vehicle flow is high on the priority list.
The busiest intersections in Center City should probably have "Barnes Dance" pedestrian signals, basically stop all traffic at the intersection and let pedestrians cross every which way for a period, and then give the streets back the cars. The crush of people crossing the street with the light isn't compatible with the number of drivers trying to make turns.
