Transient dynamic analysis of vehicles riding pavements has became a reliable and important tool - whenever well carried out, in the durability and fatigue life evaluation of mechanical sub-components. Since a given vehicle or accessory is designed to operate on distinct types of terrain/roads, a detailed knowledge of these excitations is necessary for a realistic characterization of its effects over the structural parts. The most common form to obtain terrain profile is throughout profilometers installed on special vehicles. The amplitude vs. time signature of any terrain could then be used directly as the excitation applied to dynamic models, but this would restrict the analysis only to those terrains already measured and catalogued.The objective of the present work is to revist the generation of power spectrum density (PSD) functions aiming their usage as excitation on numerical dynamic models of vehicles. If specially catalogued for dedicated use as source of vibration on vehicles, PSD functions can provide significant resource savings for the developing part. For instance, they can be combined to generate new, intermediary terrains, thus avoiding new measurements. It is important, however, to asses show much information of the original sign is lost due to its transformation to a PSD or, conversely, how realistic a terrain is when reconstructed from its PSD.