FR8HUB WP6 “freight loco of the future” aims at defining and developing concepts, systems and subsystems of future freight locomotives for a maximum improvement of the energy efficiency of the locomotive alone, in the train consist or within a fleet. Task 6.3 shall evaluate whether a cost-effective energy efficiency improvement is possible with small decentralized ESS, summarizing the results in this deliverable D6.4. In a first step, possible functions & systems that would profit from such concept shall be listed (Chapter 2). The analysis shows that from today’s perspective it is not advantageous to integrate small and decentralized ESS. Therefore, the compilation of the most suitable energy storage system (ESS) and the needs for new rolling stock is not further pursuit (following subtasks). For the interested reader, an extensive overview on ESS is provided in deliverable D6.1. Leader of this Deliverable: Bombardier Transportation GmbH