As the traffic demand of the Third Square Intersection in Jinhae City reaches the capacity on January, 2007 now and it is forecasted that the traffic demand of the interjection will exceed the capacity greatly at the target year of 2016, the measures to increase the capacity drastically is needed. In order to forecast the traffic demand of the Third Square Intersection at the target year, the traffic demand of the whole Jinhae City was estimated based on the socio-economic forecast of Jinhae City by the 4 steps demand forecast method and the traffic demand of approaching streets of the Third Square Intersection was estimated. Among the measures to improve traffic operation at the Third Square Intersection, the measure of constructing an overpass on the east-west street was evaluated to be the best as maintaining the service level of the intersection at more than the level of C.