Roughness measurements—Have the necessities changed?

Roughness of the running surfaces is the predominant source of noise of rail bound transport systems today. Reliable measurements of the roughness of rails and wheels are crucial for noise reduction purposes. In the past, the main purpose of measurements was the understanding of corrugation growth and rolling noise generation. Meanwhile, quantitative descriptions have gained considerable importance. Initiated by Deutsche Bahn, the RM1200E rail roughness measurement device became available in the early nineties of the last century and has since gained a good reputation in the scientific community.Recently standards for measuring sound levels inside rail vehicles and pass-by levels of rail vehicles at a reference distance have been issued on a European level. They require that the level of roughness of the test track is known. Furthermore, Trans European rail networks have been defined, requiring technical specifications for interoperable, border-crossing vehicles, running in several countries. These specifications include noise limits, referring to the methods defined in the new standards. To allow for unambiguous results, the knowledge of the roughness of the rolling surfaces is essential.In view of these developments in standards and specifications, the paper addresses the requirements for roughness measurements and for the data evaluation involved. It focuses on the scientific and practical experience of the past as well as on the present necessities, specifically those derived from regulations on a European scale and describes practical consequences for roughness measuring devices.