In order to satisfy family daily needs, people will devote their efforts to get wages and exchange them for commodities and services in markets. Consequently, work becomes a primary activity of household heads on weekdays. If the work starting time is fixed, the commuting trips will be concentrated during peak hours, resulting in traffic congestion. Congestion will result in traffic accidents, air pollution, noise, and higher travel cost (time) and will make workersí quality of life worse. This study proposes that a ìflexible time systemî will have strong effects on workersí ìwork starting time choiceî and ìcommuting time choiceî. Furthermore, workersí ìschedule evaluationî will be affected by ìwork starting time choiceî and ìcommuting time choiceî. Therefore, the commuting time will be changed if work starting time becomes flexible. Consequently, traffic congestion at peak hours will be diminished. In other words, workers can arrange their daily time more efficiently and get higher utility from their schedule evaluations under a flexible time system. From the viewpoint of schedule evaluations, the commuting time choice model under a flexible time system will be established. The stated preference method will be used to evaluate the effect of a flexible time system. Finally, the results can be viewed as a practical suggestion concerning travel demand management for planners.