Just read this great article over at grist.org, where the mayor of Portland OR talks about creating what he calls 20 minute neighborhoods throughout the Portland MSA. His definition of a 20 minute neighborhood is effectively a neighborhood where you can walk or bike to restaurants - they liken it to a "mixed use development."
It would seem Philadelphia is extremely well positioned to leverage this concept as it's a city of neighborhoods. It would be interesting to see this concept made part of the Greenworks Initiative or some other program(s).