Motivation, the driver of individual behavior, is highly related to what and how people talk and behave. Segmentation is an important marketing concept in business for understanding consumer demand and for formulating marketing strategies to fulfill this demand. From this perspective, the service quality of a city bus is a pull-based motive. Moreover, empirical evidence suggests that higher service quality increases passenger loyalty. Hence, using empirical data, a service quality-based segmentation scheme is developed in this research to help segment city bus passengers on the basis of their perception of service quality. This helps to define a quality improvement strategy for different passenger segments. This study recognizes five segments: 1. a moderate quality disconfirmation segment (21.2%), 2. a slight quality disconfirmation segment (17.6%), 3. a serious quality disconfirmation segment (23.5%), 4. a moderate quality disconfirmation with serious interaction problem segment (12.2%), and 5. a moderate quality disconfirmation with serious management support problem segment (25.5%). All five service quality segments show different patterns of quality disconfirmation, which implies that the service quality of Taipei city buses needs to be improved on the basis of each segment's needs. A service quality improvement strategy is further explored for each segment.