Some issues concerning railway routes are related to avoiding uneven deformations, rail roughness, and increased dynamic loads. Lack of transition zones at the entrance and exit of bridges intensifies the above-mentioned failures due to sudden changes in track stiffness. The main objective of this article is to investigate the effects of approach slab length, thickness, and travel speed on the transition zone. On this basis, one attempts to study the dynamic behavior of a track in a transition zone between a slab track and bridge as well as dynamic responses of sensitivity analysis to the approach slab length and thickness under various vehicle speeds. Dynamic analysis is conducted using a three-dimensional finite element model (FEM) of a track and the China Star train. Results show that an increase in the cruising speed from 120 to 300 km/h exacerbates deformation by 25% and the approach slab thickness reduces the deformation of the transition zone by 42%. Moreover, it is observed that the increase in the length of the transition zone, significantly affects the regulation of deformation intensity and the behavior of the transition zone is a function of the length and thickness of the slab.