A plurality of power conversion apparatuses disposed in a traveling direction of a plurality of vehicles coupled to one another each includes a conversion unit to convert electric power; a heat dissipation unit to dissipate heat that is generated in the conversion unit to a traveling wind; and a control unit to control the electric power to be converted. The memory control unit may include prioritization logic for selecting access requests in accordance with a priority scheme and bank conflict logic for detecting and handling conflicts between access requests. The present invention is characterized in that each of the tension members is concentrically wound several times, and the wound members are arranged juxtaposedly in the transverse direction of the crawler, thereby forming the tension members in the form of plural layers.