Diesel-electric traction is a well-established technology in railways systems, mainly for lines with a low traffic potential. In those conditions, the choice of a diesel-powered locomotive is due to the reduced costs compared to the infrastructure cost of a standard electric train. However, thermal engines in a vehicle as main energy and power source leads to difficulty in the optimization of such system, where the working range has to be large. It becomes then difficult to obtain a good efficiency in all the running conditions. By its principle, such a technology does not allow the recovering if energy. This contributes also to a poor efficiency, and does not offer a flexible energy management. It is therefore important to develop new strategies to increase the energy efficiency of a diesel – electric train. To reach that goal, a system with supercapacitive energy storage is proposed. This solution should reduce diesel consumption and therefore also CO2 and other pollutant emissions while being economically viable. It enable also an efficient energy management, while enabling the recovering of energy. This paper is to present a novel solution to increase the energy efficiency of a diesel - electric train without impairing on its dynamic characteristics.