Abstract: A portable, foldable step ladder in a deployed configuration straddles a tire of a truck, tractor or other heavy vehicle, allowing an operator and mechanic to easily climb toward the engine compartment. A top step rests on the uppermost portion of the tire tread. A middle step and a bottom step are suspended from the top step and, together with their suspensory structure, are foldable into proximity with the bottom surface of the top step. On each side of the top step, a hand rail has a lower portion rotatably connected to the side of the top step near the front thereof. Each hand rail has a transverse portion extending toward the rear of the top step and, attached to the transverse portion, a rear portion extending downward and connected to the sides of the top step near the rear thereof. The hand rail assembly engages the side walls of the tire in hook-like fashion, stabilizing the top step, while the top step supports the hand rail assembly at four points.