The recent spread of the internet and mobile phones has developed information service in various fields. In the field of transportation，ITS (Intelligent Transport Systems) has began to provide information on the timetables of railroad and bus service for the purpose of enhancing navigation systems and improving the convenience of public transportations. The information service through ITS primarily aims at improving the safety and comfort of land transportation by providing passengers with information necessary to travel safely，comfortably，and efficiently. But from the viewpoint of research of traffic flow，the service enables researchers to obtain a large amount of data on traffic flow at the researcher's office. This study examines from the viewpoint of researching traffic flow to what extent information service through ITS can be utilized，and to what extent the inspection of traffic flow based on the data can be validated.