At the maintenance stage of operation of roads for various reasons, it is necessary to carry out major repairs of pavement. The most common way to restore the strength of pavements in practice is to strengthen them: laying new ones or replacing existing upper layers, in most cases of asphalt concrete. The thickness of the reinforcement layers is calculated on the basis of information about the actual and required general elastic moduli of flexible pavements. The article gives an overview of the models for recalculating elastic deflections obtained by the installations of the static and dynamic loading principle. The results of a computational experiment to determine the thicknesses of the gain layers according to an industry normative document based on information on actual dynamic elastic deflections are presented and compared. A proposition has been made and substantiated that the actual durability of flexible pavements is incorrectly estimated by the settings of the static principle of operation, since when designing flexible pavements, the design scheme with dynamic characteristics is.