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Operational modal analysis is when the modal properties are identified from measured responses only. The modal parameters are: mode shapes (the way the structure moves at a certain resonance frequency), natural frequencies and damping ratios. When modal identification is based on the measured response (output) only, things become more complicated: The excitation (input) is unknown and the measured response (output) is often noisy. In this study, the time domain Stochastic Subspace Identification - Unweighted Principal Components operational modal analysis was applied to the recorded dataset from the durability test conditions of a truck. Using the 40 minutes of road test accelerometer time history in three different road conditions, it was possible to identify the modal parameters and also compare with numerical modal analysis data. Both results presented good correlation.