In this doctoral thesis the dynamic characteristics of ballasted tracks on railway bridges are studied. Due to increasing train speed in rail network, resonance effects at railway bridges are possible. As a result the ballast may become unstable. Current standards require a dynamic safety analysis for defined given criterions such as the train speed. However, appropriate global mechanical models with corresponding parameters are not available, such as parameters describing the stiffness and damping properties of the ballasted track. As a consequence, detailed studying of the dynamic behaviour of the ballasted track by developing and using a testing facility on full scale has become the aim of this thesis. Furthermore parameters for a mechanical model, describing dynamic properties of the ballasted track are to be determined. For instance, the to date unused damping potential of the ballasted track in dynamic safety analysis will be considerable then. ^Three main sections of the present work are to be emphasized: At first a small scale model (on a scale of 1:5) of the testing facility was built for checking its functionality. The findings led to an essential improvement of the full scale testing facility. Optical measurements on the ballast substructure were also conducted at the scaled model to study the dynamic process in the ballast, in particular the movement of ballast stones. The gained findings verify the developed mechanical model describing the dynamic behaviour of ballasted track. In the second section the development and construction of the testing facility (full scale) as well as the conducted experiments are summarized. Two types of ballast were tested, i.e. a ballast made of unused virgin gravel and a second one made of already used (old) gravel. Comparison of the test results for both types of ballast have been conducted to reveal whether its properties in a life cycle period are changed. ^However, only an insignificant deterioration of the ballast was observed. Furthermore, a significant frequency dependence of the damping properties of the ballasted track was observed, but their dependence on amplitudes is small. The third and last section addresses the determination of parameters for the developed mechanical model of the ballasted track. Some questions have still remained open, which are to be studied in future. Moreover, additional experiments with the developed testing facility need to be done; for example, the effect on changing characteristics induced by loading the ballasted track and by frozen ballasted track in winter. The results and findings of this and future investigations will allow a detailed mechanic description of the ballasted track, and subsequently an accurate dynamic safety analysis of railway bridges.