In this paper, an analysis of methods for calculating structures from allowable stresses and from limiting states is made. It is shown that when the transition from the longitudinal beam calculation to the allowable stresses to the calculation of the limiting state, the strength limit increases by 1.5 times. A mathematical model of the stress–strain state of a longitudinal beam of metro wagon truck without taking into account the transverse force is developed. The mathematical modeling with the given margin of strength of the power calculation of the longitudinal beam metro wagon track, which is a simple beam of a constant hollow rectangular section, pinched at its ends and loaded along the middle of the span by a concentrated stationary force, is carried out. Thus, the application of the method of calculation for the limiting state makes it possible to identify the resource–saving reserve of the strength characteristics of the longitudinal beam of the metro wagon truck – a 3-fold increase in the maximum permissible load.