The presented studies, research and innovation focus in marshalling yards is on providing adequate responses on standard timings or deviations from the normal timetable. To address the possible deviations in the marshalling yard daily operation, the decision support system called SMART Real Time Management System (RTMY) is developed and introduced in this study. In general, Smart RTMY should give real-time responses to deviations, and decrease the time for making an adequate decision by providing a decision support system with optimal solutions based on selected criteria and optimization objectives. The system is based on the optimization function, which calculates the numerical (influence) value for each wagon in the marshalling yard, and on the developed expert system. The application of SMART RTMY in its current state is verified through the developed web application used by experts from universities and railways. This system should bring a novel solution to the marshalling yard classification and deviation response systems, thus providing a powerful software tool for marshalling yard dispatchers and operators.