Abstract
This paper presents a functional model of river-sea ships (shortly called: SRM) operating in European system of transport corridors. It is composed of two parts: Part I contains a descriptive model of functioning the SRM fleet with taking into account various shipping tasks as well as impact factors (external and internal factors, limitations and criteria). Also, a mathematical model of functioning the SRM fleet, including choice of relevant economic criteria (e.g. profit maximization, capital return period minimization etc), is presented. Results achieved on the basis of the functional model are presented in Part II of the paper.