PURPOSE: To provide information to users of the city traffic service in real time and to improve the service for the user by providing information to users and to the transport facilities based on the navigation improvement plan pre pared by a navigation improvement plan preparing means.

CONSTITUTION: An information input means 10 provides road information, waiting information and the congestion information in a vehicle. Based on the information, a traffic information estimating means 30 estimates the travelling state. The result of estimation is evaluated by a traffic index evaluating means 40 and when the result of evaluation is out of an allowable range, a navigation improvement plan preparing means 50 prepares the navigation improvement plan. Based on the navigation improvement plan, an information providing means 60 provides each information to the user and to the transport facilities. Thus, users can be notified of the delay state of transport facilities in real time, the transport facilities side can perform the navigation improvement based on the provided information, and the transport facilities can keep the schedule.