This book proposes a method for the simulation of the dynamic interaction between vehicle and railway track. The model has been designed to take into account the complexity of wheel?rail contact, railpad and ballast, with low computational requirements. A modal description of the rails and the sleepers is presented, imposing the cou- pling between these elements and the vehicle by means of the associated interaction forces. This provides a model with a reduced number of coordinates and therefore a low computational cost is achieved. It is shown that this model also enables to incorporate the associated nonlinear characteristics between the different elements by means of a simple formulation. In the development of the following work several commercial softwares have been used in order to obtain a final program in a modular and user-friendly perspective.