Abstract
This paper shows three theoretical characteristics of the departure time choice problems. Several theoretical studies related to departure time choice problems on the congested road networks have been done and some of them have shown the solution of equilibrium problems under some conditions of travelers' cost functions. This study shows a solution of the equilibrium without the conditions of cost functions, shows the general relationship between user-equilibrium state and system-optimized state, and derives the condition for the existence of the equilibrium.
