Abstract: The present invention relates to a weigh-in-motion system for motor vehicles based on a set consisting of loop sensors and fiber optic sensors mounted on a rigid metal profile. Its technical field of application corresponds to systems for measuring dynamic physical events that are caused directly or indirectly by the passage of a motor vehicle over its sensors. The rigid weighing sensor is made of rigid or semi-rigid metal, plastic, composite or similar material, with a deformation profile optimized for transforming vertical stresses into horizontal stresses and containing damping and protection material to attenuate external horizontal stresses.