The art does have a practical purpose: the material help protect the houses from heavy rain:
Today, after more than a year of planning, 2000 square meters of rooftops have been covered with photos of the eyes and faces of the women of Kibera. The material used is water resistant so that the photo itself will protect the fragile houses in the heavy rain season. The train that passes on this line through Kibera at least twice a day has also been covered with eyes from the women that live below it. With the eyes on the train, the bottom half of the their faces have be pasted on corrugated sheets on the slope that leads down from the tracks to the rooftops. The idea being that for the split second the train passes, their eyes will match their smiles and their faces will be complete.