PURPOSE: To make alternative plans for an optimum traffic schedule through traffic flow management so that the delay behind a current traffic schedule is made as small as possible and excesses of capacity in all sectors that the traffic schedule passes through are eliminated.

CONSTITUTION: On the basis of the current traffic schedule, the volumes of traffic are predicted for every sector, (2) and it is checked whether or not they exceed the capacities of the sectors (3 and 4). If there is a sector whose capacity is exceeded, alternative schedule plans for the traffic schedule passing through the sector is made and evaluated in consideration of three points which are start delay, route alteration, and speed adjustment (8), and the alternative schedule plan having the highest evaluation is selected out of the alternative schedule planes and decided as a final traffic plan.