Rail pads are a major component of ballasted railway tracks. It helps attenuate the excessive dynamic stress from wheel/rail impact forces in order to prevent premature breakdown of other track components. Based on numerous analytical and numerical models, rail pad plays a crucial role on the dynamic behaviours of railway track. Over years, the rail pads have been worn by the services to carry either passenger or freight train operations. The characteristics of worn rail pads become imperative to maintenance unit as to plan the renewal schedule. Using methods of modal analysis, this paper adopts an instrumented hammer to excite an innovative rail pad test rig, modelled as an equivalent single degree-of-freedom system (SDOF), incorporating a rail pad as a resilient element. The test rig can allow the static preloads to the worn rail pads through the force sensing bolts up to 400 kN at a railseat. The vibration responses are then recorded using Bruel & Kjar PULSE system. The analytical SDOF dynamic model was applied to best fit the experimental modal measurements that were performed in a frequency range of 0-800 Hz. The curve fitting provides the dynamic parameters as the effective mass, dynamic stiffness, and dynamic damping constant, all of which are required for numerical modelling of a railway track. This would lead to a time-variable dynamic evaluation of dynamic behaviour of railway track.