designer's own words:we can see a lot of manhole covers on the street at any cities in the world. Also the manhole covers are just heavy metal that is not functional. If so, how is a manhole cover that has information system of air pollution on ? Nowdays many people are concerned about air pollution all over the world. But we don't know exactly that how heavily it's polluted and what state we are living in. So If there is a manhole cover that has a system for information of air pollution on the footway and road, we can see the present state of air pollution any place and any time on walking or driving even in a building. Also if the light color that is name of city on the manhole cover is changed by state of air pollution, we may further realize seriousness of pollution and make efforts as well for decrement of air pollution. In addidtion, the light color on it can give good visual impressions not just a manhole cover that looks dark and dull to us and the city. Once again say, I can say that this is manhole cover for information of air pollution that is functional as well as visual.