An algorithm for determining the optimal parameters 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. 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. Also, to determine the bearing capacity reserve of the optimal arch, the arch calculations were performed with a gradual increase in the automobile load up to destruction. Three options for the vehicle load location were considered. The optimal parameters of an arched road bridge with a span of 12 meters and its bearing capacity have been determined. It is shown that the arch destruction occurs with an increase in the load from the car by about 1.6 times.