Freight rolling stock of Russian Railways is equipped with automatically operating brake control valves (BCV). BCV is complicated braking device directly engaged in the braking process and thus affecting the safety operation. In this regard the strict requirements established by the relevant normative documents are imposed to work of BCV. The article by the example of selecting perspective brake control valve from several options under consideration shows regular method based on a comparison in a particular case of 13 criteria that characterize the properties of different distributors from functional and economically feasible point of view. Number of criteria, as shown, does not affect the sequence of solutions, therefore, the number is not limited to these criteria. In addition to numeric values, conventional “weight” of criteria is considered reflecting the importance of its relationship with each other for this problem, allowing obtaining a qualitative result of calculation. The method can be successfully applied for an objective selecting of other complex devices of brake system (brake control valves for passenger rolling stock, antiskid devices, etc.), when the number of considered comparing criteria is large enough. Initial data when assigning criteria for the objective selection of the diffuser (a complex device having a mandatory fully determined and specific properties and meet the same specific requirements, including controversial) are applicable regulatory documents, publications, test results and other published materials.