In a number of cases, it might be due to accumulation of dust and dirt. However, for majority of this phenomenon, it is because of fungus or algae growth on concrete bridges. After rainfall, bridge surface absorbs water and retains it for certain period of time. Hence, this provides a habitat for fungus or algae to produce. Moreover, atmospheric pollution and nearness of plants provide nutrients for their development. Development in drainage facts and application of painting and coating to bridges help to solve this problem. Reference is completed to Sandberg Consulting Engineers Report 18380/X/01.