Abstract: Recent remarkable progress of our traffic environments including the increase in cars and improvement of road networks have given us the good results industrially and economically. In another aspect, however, urban traffic problems, including traffic jams and accidents, and environmental problems, including noise and air pollution, have been serious for us. In particular, for traffic jams, which are inveterately happening in urban areas, it can be expected to reduce traffic jams by taking measures to meet the situation. To reduce traffic jams, there can be some effective measures including newly constructing and widening roads, but these cannot be executed easily due to circumstances of the budget or the value of land. On the other hand, due to improvement of the computer performances and technologies, there have been many studies on urban traffic flow simulations within a PC[1, 2, 3, 8], enabling us to try to verify the effective measures for reducing traffic jams in advance.