This paper presents the evaluation result of the Namsan 1st tunnel traffic information system, which is providing the real time queue length status and incidence information inside of the Namsan 1st tunnel, 1600meters long in the Seoul metropolitan CBD. This information system plays an important role because of notifying drivers to pay a toll for the tunnel path, the congestion information in advance. According to the analysis, an evident improvement on the tunnel path and its bypass without any conspicious adverse impact. Furthermore, survey analysis found that motorists placed a high value on the provided information. During peak time, the system turned out to help motorists to relax their hasty minds. As well, several performance indices showed the reduction of congestion and travel time variation on both of the tunnel path and its bypass, in spite of no traffic information on the bypass.