Bridges are among the most important and costliest elements of roads and rail-roads. Inopportune maintenance programs spill over damages during the operation period and natural disasters. This paper proposes a method for planning bridge investigation and maintenance projects according to the risks that influence bridges. At first, the main risks have been recognized and they have been classified in 6 groups. 1) Earthquake risks and their effect on the sphere, 2) design and traffic insufficiency risks, 3) flood risks, 4) structural system risks, 5) structural resistance against earthquake risks and 6) different designing, building or maintenance problems risks. These recognized risks have been assessed based on a multiple criteria decision making (MCDM) method known as TOPSIS in fuzzy environment. So the weights of these risks have been determined according to four criteria: safety, functionality, cost and environment. Further in a case study, repair and maintenance projects of bridges have been prioritized using a fuzzy TOPSIS method. Analyzing the results presents that the proposed method is efficiently applicable for bridge prioritization and decision making about allocation of funds and performing maintenance projects. There is not limitation for number of bridges or risks in the proposed method and it can be applied in different conditions or regions
