Drive-in steel storage racks represent a popular alternative to the more common selective racks when available space is restricted or when storing the same good. In drive-in racks, the forklift truck drives into the rack and stores the pallets on beam rails on the "first-in last-out" principle. Recent experimental studies have shown that by acting as horizontal ties between uprights, pallets significantly influence the structural behaviour of the rack. However, due to the uncertainty in the degree of friction between the rail beams and the pallets, current industry design practice does not consider this effect. This paper quantifies the influence of the pallets on the bending moment distribution in the uprights using a 3D finite element model calibrated against experimental results on a full scale drive-in rack. Additionally, as 3D models may be computationally intensive when a large number of analyses are required, this paper presents an improved version of the 2D model of drive-in racks introduced by Godley. In the improved 2D model, all possible loading scenarios and the influence of pallets on the structural behaviour of the rack are considered. When compared to advanced 3D finite element analyses, the model is able to accurately reproduce the bending moment distribution in the upright, with and without the presence of pallets.