The growing use of heavier axle loads and faster speeds in railway train operations increases the likelihood of a track support overloading. Using an analytical dynamic wheel/rail and track interaction model, the effects of heavier axle loads and faster speeds on the increase of wheel/rail forces, rail seat loads, and ballast/subgrade pressures are investigated. The axle loads input include those of typical 50-, 70-, 100-, and 125-ton cars complete with unsprung masses. Also included is a projection of what might be expected in the future should 150-ton cars become acceptable. The dynamic loads estimated are for a track composed of RE 136 rail (having a mass of 68.7 kg/m) supported by CN 55A concrete ties at 610 mm center to center and insulated with EVA tie pads and traversed by a truck with the front wheel having a rounded flat (50-mm length x 0.4-mm depth) and a perfectly shaped rear wheel. The theory and concepts are easily extended to dipped rail joints, rail corrugations, random worn wheels of and profile, and other rail or wheel irregularities traversing wood or concrete tie track.