The first frequency of the own bending vibrations of the car body of the EMU train is one of the main normalized parameters associated with smooth running. Estimation of this parameter at the design stage allows to accelerate the process of development of design documentation and to reduce further number of tests. Rigidity of the undercarriage and roof equipment of the EMU train cars contributes to the overall rigidity of the body. When simulating the equipment with concentrated masses at the attachment points, underestimating the rigidity of the body results in underestimated values of the first natural frequency of bending vibrations of the body. It is shown that modeling the equipment with a rigid area with subordinate nodes at the attachment points makes it possible to simplify the process of constructing the model and adequately take into account the rigidity of the equipment not only in determining the static characteristics of body deflections, but also in calculating the dynamic characteristic and the first natural frequency. Using subordinate nodes of a rigid area on the surfaces of the fixing holes leads to a reassessment of the natural frequency. Value of the first natural frequency of the body oscillations is linearly dependent on the specific weight of the undercarriage equipment. When designing the bodies of EMU train cars (especially motor cars), in order to increase the frequency value, the equipment boxes should be located, taking into account the compatibility of the deformations of the box frames and the loadbearing structure of the body. Massive boxes for small equipment should be placed as close to the bolster beams as possible. If it is necessary to place largesize boxes under the car equipment, one should consider variants of its location in the central part of the body to include the box frames in the bend of the transverse beams of the frame.