Railway networks have different levels of development, which affects the overall transport process and integrated sustainable development. This paper presents a methodology to assess and classify the railway network performance along the Trans-European Transport Network (TEN-T) core network corridor. The Orient−East Med corridor (OEM) has been examined. Twenty-two infrastructural, economic and technological criteria for assessment of railway transport have been proposed. The countries were ranked used multi-criteria decision making (MCDM), by applying the Sequential Interactive Modelling for Urban Systems (SIMUS). A sensitivity analysis was performed regarding each objective, and then, their allowable range of variation was determined without modifying the whole ranking of countries. The criteria weights have been determined on the basis of the output of using the SIMUS method. It was found that the main criteria for ranking the countries are: length of the connecting railway lines of the corridor in the country, length of the railway lines in the country, number of intermodal terminals, gross domestic product (GDP) per capita, passengers transport performance, freight transport performance for the railway network, corridor freight usage intensity. It was found that the railway transport in the area of the OEM corridor located in Central Europe is better developed than in the Southeast European area. A cluster analysis was performed to classify countries into groups to verify the results. The results show that the eight countries included in the OEM corridor can be classified into three groups. The methodology could be used to make decisions about transport planning and improvement of the connectivity and sustainability of the railway transport, considering their development.