The paper presents a comparison of dynamic responses of bridges with different dynamic characteristics to a quasi-real mobile load. Different bridge – track – train (moving at high speed) systems were analyzed. The system is ballasted monotrack. The model of the bridge is a 15-meter beam simple-supported with a steel structure. The load model is represented by the Shinkansen train. The results are compared with very simplified load models, such as streams of concentrated forces, concentrated masses, one-mass oscillators and two-mass oscillators.