Chicago Goes Green in Its Alleys (2/2)

Sunlight bounces off the light-colored surface, so it stays cool on hot days. Densely built areas of cities trap heat. This is known as the urban heat-island effect. The Green Alley program also uses recycled materials. And it uses energy-saving streetlights. These direct light downward to reduce light pollution at night.

Research for the project began in two thousand four. No businesses own any patents on the materials used in the Green Alley program.

Not all Chicago alleys need replacing. Program head Janet Attarian says sixty-two alleys will have been renewed or rebuilt by the end of this year. City officials are also starting to use the environmentally friendly technologies for parking areas and low-traffic roads.

Permeablepavement is not very good for roads with a lot of traffic. Too much weight and travel over the material can damage it. Within six months of pouring Chicago's first permeable concrete" class="hjdict" word="concrete" target=_blank>concrete alley, the cost of the new concrete had dropped more than sixty percent.

Chicago has "more miles of alleyways than any other city in the world," says Mayor Richard M. Daley in the Green Alley Handbook.