<p>Using the traveler response function to operational feature of transport means, this paper aims to propose a model of departure time decision. The disutility functions relating to the earliness of departure time and lateness of arrival are established here to understand traveler behavior. The model is then applied to identify the morning commute behavior of student in a case study. In particular, it is applied for students using public transports. The numerical result shows that the model well predicts the departure time decision related to travel mode. By 7:15 a.m. as the designated start time at school, an average of 6:14 a.m. with a standard deviation of 10.2 minutes was recognized as the departure time choice for student using public transports.</p>