The paper presents the results and conclusions of the field tests under service loads that were conducted on a soil-steel composite (SSC) railway bridge. Inductive gauges, extensometers and accelerometers were used to monitor displacements, strains and accelerations of this bridge, respectively. The maximum displacement and strain of the SSC bridge was –0.61×10-3 m and –54×10-6, respectively. The maximum SSC bridge and ballast accelerations were equal to 0.67 and 1.23 m/s2, respectively, and they did not exceed the Eurocode limit of 3.5 m/s2. On the basis of the measured displacements, a Discrete Fourier Transform (DFT) method was implemented to determine the frequencies of SSC bridge (dominant frequencies were 0.1 (or 0.2) and 1.2 Hz). The natural frequencies of the bridge were 0.25 and 1.3 Hz, and they corresponded to approximately two first dominant frequencies extracted from the forced vibration tests.