The expansion of railroads as a feasible form of transportation for inter and intra-city travel has been highly prominent in recent years owing to railway technology advancements, which has led to the never-before-seen demand for urban and high-speed trains. There is a paradigm change in railway infrastructure development, with more developing nations constructing and upgrading existing infrastructure for high-speed trains. However, it becomes crucial to investigate the adverse effect of high speed on the dynamics of railway bridges and passenger ride comfort. The current study focuses on this issue and examines the impact of random track irregularity on passenger ride comfort and bridge dynamics for the high-speed train using an Indian Railways case study. The study uses Linke Hofmann Busch (LHB) rolling stocks and steel–concrete composite girder bridges of the Indian Railways. The simplified two-dimensional model of the train-track-bridge interaction is developed and validated with the published literature. Multibody dynamics is used to model 10 ten degrees of freedoms LHB train. The rail and bridge are simplified and represented as the two-dimensional Euler–Bernoulli beam element using the finite element method. Further, a reduced viscoelastic model of ballasted track structure is defined using the spring analogy. The train, track and bridge are developed as a unified system, and a direct coupling approach is used to solve the integrated train-track-bridge system dynamic equation. The ride comfort is measured using Sperling’s Ride Index, which decreases with increased train speed, surpassing the threshold value of 2. Moreover, long-wavelength track irregularity has a more pronounced effect on ride comfort than short-wavelength track irregularity.