Vertical split rim cracking, rapid unstable propagation of a sub-surface crack parallel to the front rim face, is one of the dominant railroad wheel failure types observed in North America. Wheel impact load is believed to be a trigger for this unstable crack growth. This rapid crack growth rate depends on several factors, such as wheel geometry (wheel diameter and rim thickness), load magnitude, load location, residual stresses in the rim, worn tread profile, and material defects in the rim (size, shape, location, and orientation). This paper investigates the effect of these parameters on vertical split rim cracking, using finite element analysis and fracture mechanics. Vertical split rim cracking is modeled using a three-dimensional, multiresolution, elastic-plastic finite element analysis. Material defects are modeled as mathematically sharp cracks. Wheel impacts are simulated by applying a high axle load on the tread surface. The residual stress and wheel wear effects are also included in modeling vertical split rim cracking.