The Sidewalks of Today and Tomorrow: Is Concrete Our Only Option?

Feb, 23 2010

For most pedestrians, the sidewalk is an unnoticed facet of the everyday streetscape, like a telephone pole, traffic signal, or postal box. But the choices made about the materials to use for building and installing sidewalks can significantly affect the atmosphere of an urban environment.

For most American cities, concrete is the go-to choice for building sidewalks. It's relatively cheap to install — only about $12 per square foot — and it's very solid. Its pale color reflects light, reducing nighttime illumination costs for cities compared to darker-hued alternatives. Plus, if adequately maintained, concrete can last up to eighty years.

Yet concrete also has its downsides: Manufacturing it has a high carbon footprint, since its fabrication requires the energy-intensive heating of limestone; it has a tendency to crack when tree routes grow underneath it; and it has no porosity, depriving the ground under it of essential ground water and increasing runoff problems.

Most importantly for sidewalk users, though, is the fact that concrete rates poorly from an aesthetic perspective — in other words, the older it gets, the uglier it gets.

As a result, cities around the world have invested in a number of alternatives, to varying success. Asphalt — the stuff usually used for the roadbed — is actually a cheaper option, but it's seen as too poorly differentiated from the car path, putting pedestrians in danger. It's also far more susceptible to damage in cold and wet weather.

Brick is a frequent choice in historic neighborhoods, since it gives off the sense of craftsmanship and handiwork. But as a material for the average walker, it's pretty miserable. It becomes incredibly slippery in the rain or snow and it breaks up easily over time. (That said, a broken brick is far less unsightly than a slab of cracked concrete.)

Other urban areas have invested in stone slabs and cobblestones — materials common in European cities like Paris (as shown in the picture above) — where they're praised for their attractive looks and solidity. Toronto iscurrently replacing the sidewalk on one of its major corridors with granite, with the idea that a better looking sidewalk will encourage more people to walk around, and thereby increase area property values.

But heavy stone like granite and marble is expensive to buy. In Beverly Hills, California, installation costs $850 a linear foot – far more than other materials. Some stones can even be a liability, since they become slippery more easily than concrete. And they trip up the movement of people who rely on mobility aids like walkers and wheelchairs, and need more even surfaces.

For now, then, concrete remains the most reliable option — and a relatively cheap one at that. Yet there may be a better future, and it's made out of rubber. Several companies have developed sidewalk panels recycled from used automobile tires, saving material costs and reducing ecological impact. They have a high amount of porosity, limiting runoff and preventing area flooding.

Per square foot, they're just a bit more expensive than concrete. and they've already been installed in several American cities, including Seattle. Yet, they're just as sad looking as a common concrete panel, doing nothing to enliven the street.

In the end, there may be nothing better than the textured, high-quality feel of the sidewalk stone so noticeable in European cities. It's just so darned expensive!

Source: http://www.infrastructurist.com/2010/02/22/the-sidewalks-of-today-and-tomorrow-is-concrete-our-only-option/