Railway lines through mountainous terrain are frequently laid on jointed rock. Loads are transferred to the jointed rock component during the operation of high-axle heavy-haul freight trains, reducing the strength of the intact rock block and improving mobility. When a railway embankment is adjacent to a rock slope, failures in jointed rock mass can be triggered when the train load exceeds a specific level. Therefore, it is essential to investigate the impact of train speed on slope stability as well as the combination of pertinent factors that may cause embankment failure on jointed rock slopes. This research is conducted using the finite element shear strength reduction approach in two-dimensional models to analyze the slope stability of jointed rock and railway embankments under drainage conditions. A practical site is selected and related geomechanical parameters are retrieved from the literature. Various parameters are investigated for the relevant variables, including rock properties and joint characteristics. The crucial value for the factor of safety arising from the maximum safe train speed is set at 1.3 for all cases modeled. The maximum train speed is determined for cases with different joint orientations and joint spatial distributions. Cases for embankments sitting adjacent to slopes with different slope angles are also simulated and the corresponding maximum train speeds are established. Furthermore, this study also provides information on the slow speeds that can be adopted for different conditions to ensure the train safety.