— For the design of an automated transportation system in an actual seaport container terminal, it is necessary to take into consideration the maintenance of operating robots (AGV: Automated Guided Vehicle and ATC: Automated Transfer Crane). For this purpose, we develop an operation model in which each robot enters a maintenance mode while operating on the basis of its reliability. We also aim to design the mean time between failure (MTBF) which is a kind of a measure of robot performance on the basis of the robots’ reliability as well as the number of robots. However, this is a combinatorial design problem. Therefore, we propose a design methodology in order to derive one combinatorial design solution for a given demand by considering a system management cost that includes a system construction cost and a penalty cost. The designed systems are evaluated on the basis of the system management costs. Finally, we present the validity of the proposed design methodology and designed sys...