Not only did this recent post from the Infrastructurist make me realize that there are blogs about absolutely everything out there, it got me thinking about what we use to build our sidewalks.
Concrete is the most common choice, as it meets several key criteria for sidewalk design: it's cheap, durable, and slip-resistant. On the other hand, it's pretty boring to look at and--a factor that's becoming increasingly important as stormwater runoff regulations become more stringent--it's impervious.
In the past bricks and similar decorative pavers have been used to spice up the look of sidwalks, but cobbled surfaces can be difficult to navigate for folks with disabilities (not to mention those of us who wear high heels). As an alternative, the FHWA recommends stamped concrete or concrete pathways with brick trim. WALKArlington has been working with that Virginia city on a similar "field and border" design concept that relies entirely on textured concrete slabs with a smooth concrete border.
Then there's the issue of permeability. With pavement covering so much of our urban surfaces, it's important to finds materials that allow water to drain directly into the ground. The City of Olympia in Washington state has been installing pervious pavement in projects throughout the city since 1999. Although pervious concrete sidewalks are more expensive than traditional sidewalks, they can significantly reduce overall construction costs by eliminating the need for expensive "stormawater controls" adjacent to roadways (see the full report on Olympia's pervious sidewalks here).
The uber-green may opt for rubber sidewalks, another porous option, made entirely recycled tires. My knees are particularly intrigued by the proponents' claim that the flexible rubber surface is more comfortable to walk on. Sounds cushy to me.