The object of research is an algorithm for determining the load capacity of an elliptical road bridge made of concrete blocks is proposed. The arch section heights are determined from the condition that the height of the concrete compressed zone should not be less than half the section height at any position of the automobile load. Method. To solve the problem by the finite element method in physically nonlinear formulation, the principle of possible stress states is used. The nodes equilibrium equations of the arch are compiled using the possible displacements principle. The arch internal forces by a finite element length are approximated with linear functions, the concrete deformation diagram is represented in a piecewise-broken curve. Results. To determine the loading capacity reserve of the optimal arch, the arch calculations were performed with a gradual increase in the automobile load up to destruction.