To analyze such significant indicator of the locomotive industry as the value of import customs payments, the dependence of the volume of import customs payments on weight, cost, weighted average rate and dollar exchange rate is examined. Mathematical modeling was carried out on the basis of monthly data during the period from 2019 up to 2021 of the volumes of customs payments and their parameters of the Group 86 of the Customs nomenclature of EAEU FEA "Railway locomotives or tram motor cars, rolling stock and their parts; track equipment and devices for railways or tram tracks and their parts; mechanical (including electromechanical) signaling equipment of all types". The interrelations of these variables are represented by a system of simultaneous structural equations. The import substitution trend developing in Russia implies strengthening the development of national industries and, accordingly, pursuing a customs policy that implies support for domestic producers and reduction of import supplies. Thus, it is relevant to determine the impact of various factors on the amount of customs duties levied by the customs authorities on foreign economic activity (FEA) participants in operations involving the import of spare parts and other goods for the locomotive building industry to make the right strategic decisions concerning customs restrictions on imports of goods of this industry.

Keywords: locomotive building industry, mathematical modeling, linear multiple regression, multicollinearity, system of simultaneous equations, identification, structural form of the model, reduced form of the model