Abstract: The field of application of present invention relates to weighing systems of vehicles in motion also called WIM systems (Weigh In Motion). The indicated WIM system foresees the placement of a metal plate to the street level, above which vehicles to be weighed may transit, and this metal plate, which is also called loading plate, is mounted above a cavity obtained on the road surface so that it can flex at the passage of the vehicles above it. The system provides that the measurement of the deflection of said loading plate is carried out with the aid of suitable sensors, and that the estimated weight is obtained through the modeling of the flexing of said loading plate depending on the weight of the vehicle passing over. The invention discloses a particularly advantageous configuration to achieve a weighing system that can be modelled with the required accuracy.