This research aims to present a deterministic and probabilistic analysis of the stability in 2D/3D of a road slope, located in the state of São Paulo, Brazil, in the Serra Pelada region, incorporating scenarios with and without surface suction and water level, and predict the movement of the mobilized-mass volume. The results of the stability analysis showed the variability of the safety factor, the probability of failure, and the mobilized-mass volume, in the twenty-six simulated scenarios. The results of the runout analysis of the mobilized-mass volume indicated that any possible landslide would interdict, at least, two of the three lanes of traffic, equivalent to 59.7% of the lanes. Therefore, it can be concluded that a 2D and 3D stability analysis combined with the material point method to predict the post-failure soil displacement provides a better understanding of all processes involved in a landslide, which helps to establish more adequate and effective mitigation and remedial measures for each situation. Finally, in conclusion, the studied slope, with a maximum failure probability of 1.24%, is safe in terms of its overall stability for all twenty-six simulated scenarios.