For many years, engineers, as well as people not involved in vibration propagation issues, have been convinced that in order to reduce the level of vibrations observed on buildings in the vicinity of a tram line, the speed of travel should be reduced and the problem will practically disappear. Road workers and railway workers are also very keen to use such knowledge in practice. Is this belief reflected in reality? The Building Vibration Laboratory of the Cracow University of Technology has been measuring traffic source vibrations for many years. This paper presents unique research results on the impact of tram speed on the level of vibrations generated in buildings in the close neighborhood of the tram line. The researches were conducted on several polygons, recording the impact of vibrations on building ceilings as a function of the speed of several selected types of trams at a dedicated speed in the vicinity of the buildings under study. Building Vibration Laboratory of Cracow University of Technology is international accredited unit with ILAC certification.