Ballast, a granular material being mainly stones, is used to make a foundation for a railway track. It is the necessary interface for distributing the loads and anchoring the track. Even though ballasted tracks are the most common and cost effective technique for laying tracks, serious degradation problems still occur especially when the track is loaded with high speed or freight trains. The Eurobalt project has set as its goal to determine, model and understand which parameters in the train/track interaction are primarily responsible for such an untimely degradation. The project partners, European railway administrations, universities and railway industries have founded their research on the basic and profound assumption that track geometry deterioration is caused by ballast settlement. An immediate consequence is that track stiffness plays a crucial role and a better understanding of this parameter is of considerable importance. A Track Loading Vehicle was therefore developed, providing a valuable prototype vehicle, which is able to measure track stiffness while moving on the tracks. The experimental results demonstrated strong correlation between track stiffness profile and track geometry quality validating beyond doubt the existence of a relation between the two. Based on the experimental results, advanced parametric models were subsequently proposed in order to optimise track design and maintenance. A set of concluding specifications has also been proposed that will aid the future construction of tracks. Even though the problem of already existing tracks remains open, the Eurobalt project has made considerable advances in understanding ballasted track behaviour and now objective criteria are available for deciding how to construct new railway tracks. Moreover, the establishment of a relation between various vehicle and track parameters to the long-term maintenance requirements will certainly help reduce the current costs.