Track ballast has many functions in the permanent way system. It is, amongst others, responsible for the load transfer into the subgrade, the drainage of the superstructure and the reliable position of the track panel. Even so, ballast is compared to other track components still a relatively unresearched area. With the use of the Discrete Element Method - a numerical calculation method for computing a large number of particles - and powerful computers it has now become possible to reliably determine the path of movement as well as the interaction of particles. Plasser & Theurer utilises this technology to gain new insights into the permanent way and so to optimise its track construction machines even further.