Cities that clean themselves

"A new type of concrete can clear the air by dissolving pollutants. Using light and air, photocatalytic concrete breaks down organic and inorganic substances responsible for air pollution," reports Concrete Monthly (my latest cure for insomnia).
In 2003, as Wired tells us, the Italian firm Italcementi "coated 75,000 square feet of road surface on the outskirts of Milan with photocatalytic cement. It found nitrogen oxide levels were reduced by up to 60 percent, depending on weather conditions. A similar experiment in France found nitrogen oxide levels were 20 percent to 80 percent lower in a wall plastered with photocatalytic cement than one with regular cement."
Let's just hope they use that on the new Asian Highway project...