In this presentation, a simple formula is derived for the modal damping ratio of the bridge using the correlation between the instantaneous amplitudes of the related front and rear contact responses of a two-axle test vehicle by the Hilbert transform (HT). To start, closed-form solutions were derived for the dynamic response of the damped bridge and vehicle-bridge contact responses. Next, the HT was employed to generate the instanta- neous amplitudes of the two contact points. Based on their correlation, a simple formula is derived for the bridge damping ratio. Finally, the reliability of the derived formula was verified in the numerical study. It was demonstrated that the proposed formula can be successfully used to determine the first bridge damping ratio, even in the presence of rough pavement, but with the aid of random traffic. This presentation was based primarily on the paper given in Ref. [1]. REFERENCES [1] Yang, Y.B., Yang, M., Liu, D.H., Liu, Y.H., Xu, H., Bridge damping formula based on instantaneous amplitudes of vehicle's front and rear contact responses by Hilbert transform, Int. J. Struct. Stab. & Dyn., 2024, 2471006.