The Sidewalk of the Future Is Not So Concrete

Concrete has long been the go-to material for sidewalks because it's strong and cheap. The typical stretch of walkway can last decades; New Jersey sidewalks have an estimated lifespan of 75 years. But concrete has its drawbacks, too, especially for cities intent on improving walkability. Tree roots can crack concrete, creating hazards for pedestrians (especially wheelchair users and parents pushing strollers), and the more a tree grows the more its surrounding sidewalk swells. Frequent replacement can get costly — about $35 per square foot in Los Angeles — and self-healing concrete exists more in theory than in practice.

Some cities have started to rethink the traditional sidewalk as a result. Local governments and technology companies all over the world are considering new ways of building pedestrian pathways that go beyond the common mix of cement and aggregate we know as concrete. These materials have broadened not only how cities construct sidewalks but also the very notion of what a sidewalk can be. They can now enhance walkability, generate renewable energy, and improve public safety, even as they withstand all those tree roots that have been breaking concrete slabs for decades.