## 4 Summary  
Train impressions and point transfer admittances were measured on two different sections of the same railway line using artificial vibration sources, and subsequently, line transfer admittances and force density spectra were computed for the most common train types in operation, including high-speed and freight trains. A method has been introduced that significantly reduces the effort required for determining the line transfer admittances through the integration of multiple point transfer admittances, which can be estimated from the maximum point transfer admittance measured at a site. This requires the in situ measurement of only one point transfer admittance, rather than dozens over the entire length of the trains of interest. While the same train configurations operated at both locations at similar speeds, the two survey points differed significantly in terms of track alignment (tunnel vs. embankment), track structure (slab track vs. ballasted track) and soil dynamics (Molasse Zone vs. recent river sediments). These differences are reflected in the computed trains' force density spectra. Despite the theoretical considerations in the literature e.g., in [5], the  
Figure 16: Comparison of the average force density spectra measured for different train types on the embankment and tunnel tracks, as well as a spectrum computed in the SILVASTAR project for an ICE on ballasted track. Figure 15: Force density spectra for different trains on the embankment track. empirical force density spectra determined in the course of this study do not eliminate the effect of train-track interaction and thus do not present a site-independent train emission spectrum. The fact that a site-dependent train-track interaction will always occur needs to be taken into account when aiming to use force density spectra for prediction purposes and applying them to geologies or track structures that diverge from the ones they were measured on. The authors therefore want to point out that track stiffness and geological conditions, as shown in [7, 8], do have a relevant influence on the emitted force density spectrum by different trains, but this influence is an order of magnitude smaller than the variance of vibration velocity spectra used as source spectra in conventional prediction procedures according to [1], as illustrated through the impression spectra recorded for over 3000 trains on the tunnel invert over 4 weeks. The experimental results from this study were compared to findings from a theoretical investigation [11], which used numerical simulations to compute site-independent force density spectra for common train categories. As the ICE was available in both studies on ballasted track, this train was used for direct comparison and showed very good agreement over a broad frequency range. The peak in the low frequency bands of 16-20 Hz (attributed to quasi-static effects of the moving loads) as well as the dip in the 32 Hz band were confirmed. Furthermore, the higher force densities in the bands above 40 Hz, attributed to rail roughness, were also visible in both studies. Conceptualization and methodology, B.T. ; writing--original draft preparation, B.T. ; writing--review and editing, K.A. ; visualization, K.A. ; On-site Measurements, All; data processing, K.A., M.L. and M.O. ; validation and review, R.F. ; project administration, M.L. and M.O. All authors have read and agreed to the published version of the manuscript. This research received no external funding. Not applicable. The data presented in this study are available on request from the corresponding author. The authors would like to thank the Austrian Federal Railways (OBB) for providing the opportunity to carry out the surveys presented herein. Author [PERSON], [PERSON] and [PERSON] were employed by the company Benedikt Tappauf GmbH. Author [PERSON] was employed by the company AIT Austrian Institute of Technology GmbH.