During the last decades completely new technologies for high speed railway vehicles have been developed. The primary goals have been to increase traction, axle load, and travelling speed, and to guarantee the safety of the passengers. However, new developments have revealed new limitations: settlement and destruction of the ballast and the subgrade lead to deterioration of the track; irregular wear of the wheels causes an increase in overall load and deterioration in passenger comfort; and damage of the running surfaces of the rail and the wheel is becoming more frequent. These problems have been investigated in the Priority Programme SPP 1015 supported by the Deutsche Forschungsgemeinschaft (DFG), with the goal of better understanding of the dynamic interaction of vehicle and track, and the long-term behavior of the components of the system. The book contains the scientific results of the programme as presented at the concluding colloquium held at University of Stuttgart, Germany, 2002.