This paper presents a numerical method for wave transmission through a periodic track having a disturbed region. The infinite track analysis is realized by attaching the transmitting boundaries at both ends of the finite sub-domain. To achieve this, an impedance matrix representing the transmitting boundary is constructed by utilizing eigenmodes for the transfer matrix of a unit cell. The developed method is applied to infinite tracks subjected to incident harmonic waves. Through numerical analyses, the influence of the stiffness of the pads on the wave transmission is examined. The relation between the transmittance and the band structure of track is also discussed.