Purpose. The possibilities of railway transport for organizing transportation between the countries of the European Union and Ukraine are not fully utilized, since there are a number of technical differences in transport systems, namely: wheel gauge, characteristics of rolling stock, voltage in the contact network, dimensions, etc. One of the options in the organization of goods transportation in international traffic is the use of 1.435/1.520 mm dual gauge. The purpose of this study is to analyze the features of the stress-strain state of the combined construction of the track, first of all the changes in the operation of the under-sleeper base due to the use of a special design of reinforced concrete sleepers with simultaneous fastening of four rails. Methodology. To determine the stresses in the under-sleeper base, a spatial model of dynamic deformations of the railway track was chosen based on the elasticity theory. The movement on a railway track of a conventional construction (with sleepers Ш-1-1), accepted as a reference one, and along the track for combined movement, which differs from a standard using sleepers of type Ш2С-1, was considered. The main results of the calculations were the matrix of stresses in the under-sleeper base. Findings. The analysis of the results of the stresses simulation in the under-sleeper base of the dual gauge did not show their increase in absolute values, but revealed cyclical changes in the possible directions in deviation of ballast particles if there is a propensity for the occurrence of inelastic deformations in the ballast layer. Such a stress-strain state of the under-sleeper base, in turn, can lead to the appearance of deformations in the sleepers and the deterioration of the overall track geometry. Originality. The tasks of simulation got the further development of the track and rolling stock interaction, in particular to determine the stress-strain state of the under-sleeper base of the dual gauge. Practical value. The obtained results can be used to determine the timing of repair work on the sections with a combined track construction, justify the necessary degree of ballast consolidation, the feasibility of using the geogrids or special bonding materials.