Scenarios and forecasts for the development of large socio-economic systems (for example, Russia) are developed regularly. But for the development of transport, more detailed scenarios and forecasts for the development of their transport subsystems (for example, railway transport in Russia) are required. The article discusses the method and technique for solving this problem based on a linear discrete model of the socio-economic system, including its transport subsystem. A model-software complex has been developed for the formation of scenarios and forecasting of the states and indicators of this transport subsystem. This complex gives the possibility to use scenarios and forecasts developed by reputable international and state organizations, regional authorities, as well as large corporations. The results of using this complex concerning the railway transport of Russia show the possibility of forecasting freight traffic on the railways of Russia.