Abstract
Experts from various fields of study make tremendous efforts to reduce ever-growing traffic congestion. It is no exaggeration to say that the role of transportation manager, who takes the responsibility for overall situation, is of great importance. Nowadays, it becomes possible to collect real-time traffic data due to the advances in technology, but there is still no powerful decision making supporting system using those data. A method, providing realistic image of depicting overall congested area, is needed for network manager to make a proper decision efficiently, especially in metropolitan area. A method supporting network manager's policy making will be provided in this paper.