<p>A complementary method to determine the vibration source intensity, defined as the weighted vertical acceleration level at the tunnel wall, is needed urgently when comparable measurements or database predictions are unavailable in empirical predictions. In this study, we present an analytical model designed to quickly and accurately estimate the vibration source intensity produced by moving metro trains, considering both regular and floating slab tracks. The improved periodic pipe-in-pipe (PiP) model with regular or floating slabs affixed to the tunnel invert was developed. The train loads are represented in the frequency-wavenumber domain to apply in the model. Measured track irregularities were applied and the proposed model was validated against the measured results and verified by a tunnel-soil coupled model. The proposed approach effectively and accurately assessed the vibration source intensity generated by underground trains in a prediction time of just 58 s. Track irregularities significantly affect the vibration source intensity, making them a key factor in comparable measurements or database predictions. A floating slab track can reduce the vibration source intensity by about 14 dB. The proposed approach can serve as an additional method to complement comparable measurements or database predictions for determining the vibration source intensity in empirical predictions.</p>