Abstract: A linear mass-spring system model of a tractor-semitrailer together with driver body parts and sprung seat is presented. Natural frequencies of the system are calculated and response of components in the system to road roughness is completed by means of computer simulation and power spectral density (PSD) approach in all of road conditions and loading cases. The results show that the severest situation of response of the system occurs when the road in rough condition and vehicle unladen. The most sensitive frequency to human body parts is around 0.9Hz, and model types of a human body seem to be not significant tothe response of a heavy tractor-semitrailer system, including to the response of the driver himself.