In the sector of railway freight transport is considerable part of performance carried out through the transportation of single wagons from the departure station to the destination station which show decreasing trend in the last period. Currently, the transportation of the single wagons is realized according to long term established procedures, which do not take into account its direction on the basis of the optimal costs for the individual carriers on the network of ŽSR. Transportation of single wagons is realized based on train formation, which is regularly analyzed and adjusted on the basis of strength of wagons lane and requirements of the Business Department. By the application of different optimization methods it is possible to achieve reengineering of these procedures and optimize costs. The paper deals with the reengineering of the single wagons routing by application Critical Path Method (CPM) on the selected particular traffic relation on the network of ŽSR. Through application of CPM method and by reengineering of technological processes it is possible to achieve cost savings for the customer as well as for the carrier for the carriage of goods and truncation the delivery time of shipment to the customer as well as to increase the competitiveness of the railway company.