would rubber sidewalks even work?

If they can make it so it is resistant to the weather and the elements then it might work. It might also be easier on peoples joints when they walk or run.

I think rubber could be used in many ways and it is better to re-use it rather than burn it or throw it away. Maybe there is some technique to make it resistant to sunshine and cold weather. I just saw on TV they have some material made of rubber that is used to cover playgrounds so that the children don´t hurt themselves so easily. It was still solid enough so that even wheelchairs can move on it without problem.

I'm not 100%, but i think this has been done here in Alberta. Car and truck tires were shredded and mixed with other compounds (don't know). Maybe Philly can contact some Alberta officials to find out more. Forgot to mention, this rubber was used on the highway. Take care Eaforeman.

I think it would be worth investigating, especially if it included use of recycled rubber tires and other products. It has been used for flooring and sports surfaces already, so I imagine figuring out a way to make it withstand the elements is the last battle! Kudos to Philly for taking the bull by the horns!