Modern trains have to fulfil high economical and ecological requirements facing a strong competition of a huge variety of different traffic systems. The rail way industry is enforced to highly optimise all systems and sub-systems of its vehicles. In particular the aerodynamics and the aero-acoustics are playing a major role in the layout process of train configurations. Currently time and cost expensive experiments in wind tunnels with sophisticated models are conducted to measure all significant parameters like drag, lift coefficients and other torques and forces in order to estimate the overall performance trains. In future computational flow simulation shall allow for calculating all aerodynamical and acoustical properties of designed train conceptions for both an early design and a final configuration. This will be part of a sophisticated design and optimisation process chain. At DLR numerical flow simulations of the flow around simplified generic trains on the one hand and highly detailed real train configurations on the other hand are performed. One objective is to capture all significant aspects of the flow physics of trains in order to further develop numerical simulation tools and the optimisation capability, in particular with respect to turbulence, flow separation and vortical flows. Another objective is to improve the performance of existing trains by aerodynamical optimisation of all systems and sub-systems as part of a refurbishing process.