Cars create a lot of pollution, but one in Chicago doesn't just give them free passage; it also cleans up after itself. This street's special pavement actually feeds on smog.
The 3.2 kilometre stretch of Cermak Road and Blue Island Avenue, now being billed as "the greenest street in America," is paved with something called photocatalytic cement. This cement is covered with tiny titanium dioxide particles that can remove nitrogen oxide gases from the air above it. It also works as a permeable filter when it rains, taking a bit of the pressure off of Chicago's sometimes stressed sewer system.
The street that's been treated with this stuff could probably use the help; Cermak Road is a popular route for truckers, and runs through a generally industrial area, past an inactive coal power plant. It's not exactly the kind of neighbourhood you associate with fresh air. It's only a pilot program at the moment, but if the cement lives up to its potential, it could serve as a great, passive way for roads to deal with at least some of the pollution caused by the hulking machines that constantly drive over them. [Grist via Inhabitat]