Researches were made on tractor drivers in year 2009. Objects were located at the area of Slovenian high carst in GGO Postojna, Novo mesto and Kočevje. Loads were measured by timber harvest on 4 adjusted agricultural tractors and 2 skidders. First part of this gradual thesis presents overall structure of physical loads, loads by vibrations and loads by noise by individual working operations and working procedures. Calculated modular loads by vibrations and by noise were compared with valid standards. The analyzes of results show us that tractor drivers were over loaded physically, by vibrations and by noise. Loads by each tractor are present in the second part. The analyses of results show us that with a current level of knowledge we can not certainly predict which tractor is the best to work within different working environments.