Rollover is critical for intercity bus vehicles, as they often carry a large number of passengers while having a relatively high centre of gravity. Utilising the same models for determining the rollover threshold speed (RTS) of different types of vehicles may induce some errors, as most of the existing models do not consider several factors such as vehicle type and dimension, vehicle load, turning radius of the axles, and diversion angle of the curve. This study intends to propose a more accurate relationship for determining the rollover speed of the intercity bus vehicles considering the aforementioned factors. Using the revised model, it was shown that when both the radius of the horizontal curve and the diversion angle are small, the diversion angle plays an important role in determining the RTS. The results also suggest that under the assumptions of this study, the RTS for three-axle buses happens at lower speeds compared to two-axle buses.