Emission from road traffic is one of the major sources of air pollution, and provides some undesirable effects on the atmspheric environment and human health. In the city of Seoul, the higher portion of diesel vehicles runs compared with that of other countries. Emission from the diesel vehicles is much higher than that of other vehicles. In this study, the driving pattern of city-bus in Seoul is investigated through on-road vehicle test and compared with the test modes of other countries in order to examine appropriateness of the present test mode that is taken in our country.