## 1 Introduction  
The demand for public transport is increasing continuously, not only for large, but also for medium and smaller sized cities in order to mitigate congestion and provide flexible mobility. There is still an ongoing cross-disciplinary discussion about costs, flexibility and environmental impacts of tram (Light Rail Transport) versus Bus (Bus Rapid Transport) solutions [1; 2; 3]. Interestingly, potential adverse health effects of noise and especially vibrations are rarely discussed, while effects of air pollution and related climate issues are the central themes [4]. There are a decent number of (older) studies related to tram sound emissions [5; 6], determining factors [6; 7] and about special issues such as squeal noise [8; 9; 10]. However, the current scientific data base regarding tramway immissions is small, most (except [11; 12; 13]) reported sound levels only in dBA, neglecting potential low frequency components and other specific characteristics of tramway sounds, which are produced by the various noise sources of this complex vehicle [7]. Only few studied annoyance responses at the community level [14; 15] and no exposure response data from field studies are available. The majority of publications report results from experimental studies [12; 13; 16]. Often, articles concentrate only on vibration generation and propagation [17; 18], simulation/model validation [19] or strategies for abatement of emissions [20; 21]. Often, the knowledge base stems from railway vehicles or metros [22; 23]. Publications covering both tram noise and vibration measurements in homes are rare [17]. The consideration of potential effects of trans in combination with other sound sources or effects of combined sound and vibration exposure was studied only in the laboratory [12; 24] and is not yet considered in national standards. In contrast, the body of evidence for railway induced vibration [25; 26] and associated health impacts [27; 28; 29; 30; 31; 32; 33] increased substantially during the last decade and changes in policy are addressed [34]. The research on potential adverse health effects of tram noise, vibrations and structure born sounds has never received that level of attention--although the tram pass-by happens closer to residential buildings and national approval procedures for trans apply the same sound criteria as for mainline railways. This is particularly surprising, because the tramway systems and its public use have undergone a profound change in the past two decades in European countries [7]. The typical weight of modern trams in use is now around 40 tons compared with 25 to 30 tons of older trams, as illustrated by the example of Graz, visualized in Figure 1[35; 36; 37]. However, the track systems were often not properly adapted to the new demands. Moreover, the night and morning hours of operation of the tram services were extended (from 11:00 p.m. to 12:00 p.m. and 5:30 a.m. to 04:30 a.m.). These hours are acoustically highly sensitive in terms of the potential for sleep interference, as the background to peak noise ratio increases. Typically, the overall traffic noise decreases and silence is interrupted by passing trams, especially in quieter suburban areas. In addition, sleep research has found these so-called shoulder hours (10:00 p.m. to 12:00 p.m. and 5:00 a.m. to 7:00 a.m.) to be sensitive times for noise exposure and subsequent interference with the sleep and restoration process [38; 39; 40]. Eventually, noise and vibrations show potential for mutual interactive effects on annoyance and sleep disturbance [24; 41; 42; 43; 44; 45; 46]. After the introduction of a new tram system in the city of Graz (2011) several citizen initiatives issued complaints about the new trams regarding both higher noise and vibrations exposure. Figure 1: Tramway fleet in Graz with technical information. The operator commissioned acoustic and vibration measurements. A few measures resulted in improvements at vibration hotspots after two years. However, complaints remained at a high level.