The added resistance in waves is one of the important factors for the evaluation of the ship performance in actual seas. As the added resistance in waves is associated with the bow shape above the waterline as well as that below the waterline, the relation between them has been studied, and the bow shapes to reduce the added resistance in waves have been developed and installed to the actual ship. In this paper, the development of the energy saving device STEP that reduces the added resistance in waves due to the wave reflection is described. The optimal shape and the optimal position of STEP were investigated for the 170 meters long pure car and truck carrier in 3 meters height of head waves as the design condition. Through the model tests, STEP has indicated 18% reduction of the added resistance in waves in the design condition. In addition, the effect of STEP under the off-design conditions has been also examined. From the calculation of the ship performance in actual seas, the reduction amount of CO2 emission from the ship has been evaluated as 2% in head waves and winds of Beaufort scale 6.
