Design and function of a driving simulator making use of tractors and forage harvesters in full scale are given. The NORD-20 process computer are used for controlling the functions, programming the simulated operation and for some data processing. Recordings are made of controlling performance, driver's heart rate, sitting posture and judgements. Different steering devices and use of rear view mirrors are studied, using subjects with and without practical experience in operating this equipment. Some examples of results and relations to practical operation are given.