Hybrid traction systems of lithium-ion batteries with fuel cells or diesel engines are the one of the effective measures to reduce the emission of railcars for nonelectrified lines. Some of challenges, including the revenue services, of the hybrid systems have been recently addressed in Japan. In this paper, the evolution of the hybrid traction systems and features of the diesel hybrid systems and the fuel cell hybrid systems are discussed with the examples of the challenges. In addition, the technical trend of the applications of the storage batteries for the hybrid traction systems is summarized with perspectives of the future hybrid traction systems. Copyright © 2010 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.