Re-TiredSounds great. The only problem is that the most common tire on the road today is a steel-belted passenger tire. And those steel wires, once the tire is shredded, will slice the hell out of little tootsies if the rubber is laid down as sidewalk material. To date, they haven't figured a way to separate the steel from the rubber and maintain the integrity of the rubber.
Richmond Times-Dispatch editorial
[Washington DC] is experimenting with rubber sidewalks made of recycled tires. Unlike concrete sidewalks, the rubber ones are easier to work with -- they can be cut and molded and moved with comparative ease and they don't crack or crumble, which lessens the likelihood of lawsuits. They let tree roots breathe, so the roots don't fight upward through the sidewalk for air and water.
Old tires used to present a gawdawful environmental problem. If not used for rope swings or poor-man's planters, they ended up in landfills, collecting water where mosquitoes could breed or catching fire and poisoning the air. More and more, however, they are being ground up and used for a variety of purposes -- from garden mulch to playground cover. Molding them into sidewalk material makes as much sense or more. (link)
What recycling companies are using currently are tractor tires and big-truck tires, neither of which contain steel. And though they work great for the purpose, how many are floating around the marketplace? Probably enough to outfit a few sidewalks in one city.
Now, if they can figure a way to remove those steel wires ...