The objective of the project is to improve energy efficiency of traction vehicles, reducing the fuel consumption and the production of polluting emissions. The main principle is the use of hybrid technology, the use of which is particularly appropriate for certain traction vehicles. This is in particular due to mode of their operation and that the space and weight problems are significantly smaller than in the case of application of hybrid drives for cars. Besides this main objective, attention is paid to other ways to improve energy efficiency, such as improved utilisation of waste heat of internal combustion engines. The possibility of using alternative fuels and alternative sources of primary energy will also be assessed. A substantial reduction in installed primary energy source power output (to 25 - 50 %) compared to the conventional traction vehicles can be expected. Another important part of the project is the analysis of real operational modes of traction vehicles and a method of the hybrid drive controll.