The constant spread of commercial trades on railways demand development of alternative diagnostic systems, which are suitable to applications without electric supply and convenient for the industrial development and diffusion, which means low cost, good reliability, and high integrability. Similarly, it is possible to install navigation and traceability systems (for instance, by the use of global positioning systems—GPS—transmitters) to control on demand the travel history of the train and even that of each coach separately. Recent studies demonstrated the possibility to generate directly onboard the electric power needed to the supply of simple diagnostic systems based on low power sensors and integrated wireless transmission modules. The design of this kind of generators is based on the idea of converting the kinetic energy of train vibration to electric energy, through appropriate energy harvesters containing electromechanical transducers dimensioned ad hoc. The goal of this work is to validate the design procedure for energy harvesters addressed to the railway field. The input vibration source of the train has been simulated through numerical modeling of the vehicle and the final harvester prototype has been tested on a scaled roller rig. The innovative configuration of magnetic suspended proof mass is introduced in the design to fit the input vibration spectra of the vehicle. From the coupled study of the harvester generator and the vehicle, the effective output power of the device is predicted by means of a combination of experimental and simulation tests. The generator demonstrated the ability to supply a basic sensing and transceiving node by converting the kinetic energy of a train vibration in normal traveling conditions. The final device package is 150 × 125 × 95 mm, and its output voltage and current are 2.5 V and 50 mA, respectively, when the freight train velocity is 80 km/h. The corresponding output power is almost 100 mW.